Source: http://www.google.com/patents/US8076782?dq=6650327
Timestamp: 2015-11-29 03:55:06
Document Index: 285462003

Matched Legal Cases: ['art\n4138', 'arts 1144', 'art 1138', 'art 1139', 'arts 1143', 'art 1138', 'arts 1143', 'arts 1143', 'art 1139']

Patent US8076782 - Substrate for mounting IC chip - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsAn object of the present invention is to provide a substrate for mounting an IC chip which is a component for optical communication having an IC chip and an optical component integrally provided thereon, which can ensure a short distance between the IC chip and the optical component, which is excellent...http://www.google.com/patents/US8076782?utm_source=gb-gplus-sharePatent US8076782 - Substrate for mounting IC chipAdvanced Patent SearchPublication numberUS8076782 B2Publication typeGrantApplication numberUS 10/509,899PCT numberPCT/JP2003/003932Publication dateDec 13, 2011Filing dateMar 28, 2003Priority dateApr 1, 2002Fee statusPaidAlso published asEP1491927A1, EP1491927A4, EP1491927B1, EP1754986A1, EP1754986B1, EP1980886A2, EP1980886A3, US8120040, US20060012967, US20100232744, WO2003083543A1Publication number10509899, 509899, PCT/2003/3932, PCT/JP/2003/003932, PCT/JP/2003/03932, PCT/JP/3/003932, PCT/JP/3/03932, PCT/JP2003/003932, PCT/JP2003/03932, PCT/JP2003003932, PCT/JP200303932, PCT/JP3/003932, PCT/JP3/03932, PCT/JP3003932, PCT/JP303932, US 8076782 B2, US 8076782B2, US-B2-8076782, US8076782 B2, US8076782B2InventorsMotoo Asai, Hiroaki Kodama, Toyoaki TanakaOriginal AssigneeIbiden Co., Ltd.Export CitationBiBTeX, EndNote, RefManPatent Citations (81), Non-Patent Citations (3), Referenced by (12), Classifications (58), Legal Events (2) External Links: USPTO, USPTO Assignment, EspacenetSubstrate for mounting IC chip
US 8076782 B2Abstract
An object of the present invention is to provide a substrate for mounting an IC chip which is a component for optical communication having an IC chip and an optical component integrally provided thereon, which can ensure a short distance between the IC chip and the optical component, which is excellent in electric signal transmission reliability and which can transmit optical signal through an optical path for transmitting optical signal.
The substrate for mounting an IC chip of the present invention is a substrate for mounting an IC chip comprising: a substrate and, as serially built up on both faces thereof, a conductor circuit and an interlaminar insulating layer in an alternate fashion and in repetition; a solder resist layer formed as an outermost layer; and an optical element mounted thereto, wherein an optical path for transmitting optical signal, which penetrates the substrate for mounting an IC chip, is disposed.
1. A substrate for mounting an IC chip comprising:
an insulating substrate having a first surface and a second surface on an opposite side of the first surface;
a first built-up structure formed on the first surface of the insulating substrate and comprising a conductor circuit and an interlaminar insulating layer;
a second built-up structure formed on the second surface of the insulating substrate and comprising a conductor circuit and an interlaminar insulating layer;
a solder resist layer formed as an outermost layer over the first built-up structure;
an optical element mounted over the solder resist layer;
a resin layer formed between the solder resist layer and the optical element; and
an optical path for transmitting optical signal to or from the optical element and penetrating though the insulating substrate, first built-up structure, second built-up structure and solder resist layer.
2. The substrate for mounting an IC chip according to claim 1, wherein the optical element is mounted on the solder resist layer.
3. The substrate for mounting an IC chip according to claim 2, wherein said optical element is at least one of a light receiving element and a light emitting element.
4. The substrate for mounting an IC chip according to claim 1, further comprising an electronic component mounted on a surface of one of the solder resist layer.
5. The substrate for mounting an IC chip according to claim 1, further comprising a micro lens disposed on an end portion of the optical path for transmitting optical signal.
6. The substrate for mounting an IC chip according to claim 1, wherein the optical path for transmitting optical signal has a cross-sectional diameter which is 100 to 500 μm.
7. The substrate for mounting an IC chip according to claim 1, further comprising a plated-through hole connecting the conductor circuit of the first built-up structure and the conductor circuit of the second built-up structure through the insulating substrate and a via-hole connecting the conductor circuit in the first built-up structure and another conductor circuit in the first-built-up structure through the interlaminar insulating layer in the first built-up structure.
The present invention relates to a substrate for mounting an IC chip, a manufacturing method of a substrate for mounting an IC chip, a device for optical communication, and a manufacturing method of a device for optical communication.
Recently, attention has been focused on optical fibers mainly in communication fields. Particularly in the IT (Information Technology) field, a communication technique which employs the optical fibers is necessary to provide a high speed Internet network.
The optical fiber has features of (1) low loss, (2) high band, (3) small diameter and light weight, (4) non-induction, (5) resource saving, and the like. A communication system which employs the optical fibers having these features can considerably decrease the number of relays as compared with a communication system which employs conventional metallic cables, can be easily constructed and maintained, and can improve its economical efficiency and reliability.
Further, since the optical fiber can transmit not only light having a single wavelength but also light having a number of different wavelengths simultaneously, i.e., only one optical fiber can provide multiple transmission of light having a number of different wavelengths, it is possible to realize a large capacity of a transmission line capable of dealing with diversified purposes and deal with picture service and the like.
Therefore, in the field of the network communication such as the Internet, it is proposed that the use of optical transmission using optical fibers not only for the communication of a basic network but also the communication between the basic network and terminal device (a personal computer, a mobile, a game machine or the like) and the communication between the terminal devices.
When the optical communication is used for the communication between the basic network and the terminal device, an IC which processes information (signals) in the terminal device operates at an electric signal; therefore, the terminal device is required to include a unit that converts optical signal into an electric signal or vice versa such as an optical-to-electric converter or an electric-to-optical converter (which device will also be referred to as “optical/electric converter”, hereinafter).
For this reason, the conventional terminal device has mounted thereon separately, a package substrate on which an IC chip is mounted, and optical elements such as a light receiving element and a light emitting element which process optical signal, and electric wirings and the optical waveguide are connected to these elements, thereby performing signal transmission and signal processing.
When the package substrate having an IC chip mounted thereon, optical elements, such as a light receiving element and a light emitting element, which process optical signal, and the like are mounted separately on such a conventional terminal device, the size of a device itself becomes large, making it difficult to make the terminal device small in size.
Further, there has been also proposed a technique of internalizing optical elements such as a light receiving element and the like inside the package substrate on which an IC chip is mounted, and performing the optical communication of the terminal device using this package substrate with the optical elements included therein (hereinafter, also referred to as “optical element-internalizing package substrate”). Although such an optical element-internalizing package substrate can solve the problem in that the device itself becomes large in size, this package substrate has the following problems.
In the optical element-internalizng package substrate, since the optical elements are completely internalized inside the substrate, it is difficult to make a fine adjustment for alignment upon connection of the package substrate to an external optical element (e.g., an optical fiber or an optical waveguide). Besides, since the optical elements are included in the package substrate in advance at the time of producing the substrate, the positional deviation of the optical elements tends to occur. The reason is considered as follows. In a manufacturing process of the package substrate, it is necessary to apply a heat treatment and the like. When the optical elements are included in a resin layer, it is considered that the positional deviation of the optical elements occurs during the heat treatment.
As can be seen, when positional deviation occurs to the included optical elements, connection loss generated at the time of connecting the package substrate to the external optical component (e.g., an optical waveguide) is large, which deteriorates connection reliability in optical communication.
Further, in this optical element-internalizing package substrate, when a problem occurs to one of the included optical elements, it is impossible to replace only the defective optical element; therefore, the optical element-internalizing package substrate itself is regarded as a defective product, which is economically disadvantageous.
In addition, the positions at which the optical elements are mounted are limited due to the need to secure an optical path for transmitting optical signal and the positional relationship between the optical element and the optical component (such as an optical waveguide) attached to the external substrate. As a result, it is difficult to realize the high density of the substrate for mounting an IC chip in some cases.
Thus, the present inventors has made eager study to a substrate for mounting an IC chip capable of achieving optical communication excellent in connection reliability and, also, contributing to making a terminal device small in size. As a result, the present inventors reached the conclusion that the above-described problems can be solved by providing an optical path for transmitting optical signal that penetrates the substrate for mounting an IC chip, on the substrate for mounting an IC chip, and completed a substrate for mounting an IC chip, having the following configurations, according to a first aspect of a first group of the present invention and a manufacturing method of a substrate for mounting an IC chip according to a second aspect of the first group of the present invention.
Further, in a device for optical communication comprising a substrate for mounting an IC chip and a multilayered printed circuit board, the present inventors found that it is possible to secure excellent optical signal transmission characteristic and achieve high-density wiring by forming an optical path for transmitting optical signal in a predetermined manner in at least one of the substrate for mounting an IC chip and the multilayered printed circuit board, and completed devices for optical communication according to third to fifth aspects of the first group of the present invention.
That is, a substrate for mounting an IC chip according to the first aspect of the first group of the present invention is a substrate for mounting an IC chip comprising: a substrate and, as serially built up on both faces thereof, a conductor circuit and an interlaminar insulating layer in an alternate fashion and in repetition; a solder resist layer formed as an outermost layer; and an optical element mounted thereto, wherein an optical path for transmitting optical signal, which penetrates the substrate for mounting an IC chip, is disposed.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is desirable that the optical path for transmitting optical signal is constituted by a vacancy or constituted by a resin composition and a vacancy.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is also desirable that the optical path for transmitting optical signal is constituted by a vacancy and a conductor layer around the vacancy, or constituted by a resin composition, a vacancy and a conductor layer around these.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is desirable that a position at which the optical element is mounted is on a surface of the substrate for mounting an IC chip and that the optical element is a light receiving element and/or a light emitting element.
It is desirable that an electronic component is mounted on a surface of the substrate for mounting an IC chip according to the first aspect of the first group of the present invention.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is desirable that a micro lens is disposed on an end portion of the optical path for transmitting optical signal and that a cross-sectional diameter of the optical path for transmitting optical signal is 100 to 500 μm.
Further, in the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is desirable that the conductor circuits with the substrate interposed therebetween are connected to each other through a plated-through hole, and the conductor circuits with the interlaminar insulating layers interposed therebetween are connected to each other through a via-hole.
The manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention, comprises:
(a) a multilayered circuit board manufacturing step of serially building up a conductor circuit and an interlaminar insulating layer on both faces of a substrate in an alternate fashion and in repetition to provide a multilayered circuit board;
(b) a through hole formation step of forming a through hole in the multilayered circuit board; and
(c) a solder resist layer formation step of forming a solder resist layer having an opening communicating with the through hole formed in the step (b).
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention comprises a roughened face formation step of forming a roughened face on a wall face of the through hole formed in the step (b).
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention comprises a conductor layer formation step of forming a conductor layer on a wall face of the through hole formed in the step (b).
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention is constituted by a resin composition filling step of filling an uncured resin composition into the through hole formed in the step (b).
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention comprises a micro lens disposition step of disposing a micro lens on an end portion of the opening formed in the step (c).
A device for optical communication according to the third aspect of the first group of the present invention is a device for optical communication comprising a substrate for mounting an IC chip and a multilayered printed circuit board, wherein an optical path for transmitting optical signal which penetrates the substrate for mounting an IC chip is formed in the substrate for mounting an IC chip.
A device for optical communication according to the fourth aspect of the first group of the present invention is a device for optical communication comprising a substrate for mounting an IC chip and a multilayered printed circuit board, wherein the multilayered printed circuit board includes a substrate and a conductor circuit, and an optical path for transmitting optical signal which penetrates at least the substrate is formed in the multilayered printed circuit board.
A device for optical communication according to the fifth aspect of the first group of the present invention is a device for optical communication comprising a substrate for mounting an IC chip and a multilayered printed circuit board, wherein an optical path for transmitting optical signal which penetrates the substrate for mounting an IC chip is formed in the substrate for mounting an IC chip, the multilayered printed circuit board includes a substrate and a conductor circuit, and an optical path for transmitting optical signal which penetrates at least the substrate is formed in the multilayered printed circuit board.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is desirable that the optical path for transmitting optical signal is constituted by a cavity or constituted by a resin composition and a cavity.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is also desirable that the optical path for transmitting optical signal is constituted by a cavity and a conductor layer around the cavity or is constituted by a resin composition, a cavity, and a conductor layer around the resin composition and the cavity.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is desirable that a micro lens is disposed on an end portion of the optical path for transmitting optical signal.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is desirable that a cross-sectional diameter of the optical path for transmitting optical signal is 100 to 500 μm.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is desirable that an optical element is mounted on the substrate for mounting an IC chip and that a position at which the optical element is mounted is on a surface of the substrate for mounting an IC chip.
It is desirable that the optical element is a light receiving element and/or a light emitting element.
In the devices for optical communication according to the third to fifth aspects of the first group of the present invention, it is desirable that the substrate for mounting an IC chip includes conductor circuits, interlaminar insulating layers, and a via-hole connecting the conductor circuits across the interlaminar insulating layers.
Furthermore, in the conventional terminal device, since the distance between the IC mounting package substrate and the optical component is large, an electric wiring length is large and signal error or the like due to cross-talk noise or the like tend to occur during the transmission of a signal.
Further, in the conventional device for optical communication, the area between an optical waveguide and an optical element such as a light receiving element or a light emitting element is normally a cavity. When dust, foreign matters and the like floating in the air enters into this part, the optical signal transmission is often hampered by the foreign matters and the like, thereby often increasing the connection loss between the optical components.
Therefore, as a result of dedicated study, the present inventors found that by mounting various types of optical components on the substrate for mounting an IC chip, it is possible to realize optical communication excellent in connection reliability and contribute to making the terminal device small in size. In addition, the present inventors found that by disposing the substrate for mounting an IC chip and the multilayered printed circuit board to be opposed to each other and forming a sealing resin layer between them, it is possible to prevent the foreign matters and the like floating in the air from entering between the respective optical components and moderate the stress generated between the substrate for mounting an IC chip and the multilayered printed circuit board, thereby ensuring a device for optical communication excellent in reliability, and completed a device for optical communication according to the first aspect of the second group of the present invention and a manufacturing method of a device for optical communication according to the second aspect of the second group of the present invention.
That is, a device for optical communication according to the first aspect of the second group of the present invention is a device for optical communication comprising: a substrate for mounting an IC chip on which at least an optical element is mounted; and a multilayered printed circuit board on which at least an optical waveguide is formed, the device for optical communication being constituted to be able to transmit optical signal between the optical waveguide and the optical element, wherein a sealing resin layer is formed between the substrate for mounting an IC chip and the multilayered printed circuit board.
In the device for optical communication according to the first aspect of the second group of the present invention, it is desirable that the sealing resin layer has a transmissivity of 70%/mm or more for communication wavelength light.
It is also desirable that the sealing resin layer contains particles.
In the device for optical communication according to the first aspect of the second group of the present invention, it is desirable that the sealing resin layer contains particles.
In the device for optical communication according to the first aspect of the second group of the present invention, it is desirable that the optical element is a light receiving element and/or a light emitting element.
Further, a manufacturing method of a device for optical communication according to the second aspect of the second group of the present invention is a manufacturing method of a device for optical communication, wherein after separately manufacturing a substrate for mounting an IC chip on which at least an optical element is mounted, and a multilayered printed circuit board on which at least an optical waveguide is formed, the substrate for mounting an IC chip and the multilayered printed circuit board are disposed at and fixed to such respective positions as to be able to transmit optical signal between the optical element of the substrate for mounting an IC chip and the optical waveguide of the multilayered printed circuit board, and further, a resin composition for sealing is caused to flow between the substrate for mounting an IC chip and the multilayered printed circuit board and then a curing treatment is conducted, thereby forming a sealing resin layer.
Further, as a result of the dedicated study, the present inventors found that by disposing the substrate for mounting an IC chip on which various optical components are mounted and the multilayered printed circuit board to be confronting each other, it is possible to realize optical communication excellent in connection reliability and contribute to making the terminal device small in size, and completed a device for optical communication having the following configuration according to the first aspect of the third group of the present invention, a device for optical communication having the following configuration according to the first aspect of the fourth group of the present invention and also completed manufacturing methods of the devices for optical communication.
Moreover, the present inventors found that when a sealing resin layer is formed between the substrate for mounting an IC chip and the multilayered printed circuit board that are disposed to be confronting each other in the device for optical communication, it is possible to prevent the foreign matters and the like floating in the air from entering between the respective optical components and moderate the stress generated between the substrate for mounting an IC chip and the multilayered printed circuit board, thereby ensuring a device for optical communication excellent in reliability.
That is, a device for optical communication according to the first aspect of the third group of the present invention is a device for optical communication comprising: a substrate for mounting an IC chip having at least an area for mounting an optical element in which an optical element is mounted and a resin filled layer for an optical path is formed; and a multilayered printed circuit board at which at least an optical waveguide is formed, said device for optical communication is constituted such that optical signal can be transmitted between the optical waveguide and the optical element through the resin filled layer for an optical path.
In the device for optical communication according to the first aspect of the third group of the present invention, it is desirable that a sealing resin layer is formed between the substrate for mounting an IC chip and the multilayered printed circuit board. In this case, it is desirable that the sealing resin layer has a transmissivity of 70%/mm or more for communication wavelength light.
Further, it is desirable that the sealing resin layer contains particles.
In addition, in the device for optical communication according to the first aspect of the third group of the present invention, it is desirable that: at least one micro lens is disposed on a face of the resin filled layer for an optical path, said face confronting the multilayered printed circuit board; and that, when at least one micro lens is disposed on the face of the resin filled layer for an optical path, said face confronting the multilayered printed circuit board and the sealing resin is formed between the substrate for mounting an IC chip and the multilayered printed circuit board, the micro lens has a refractive index higher than that of the sealing resin layer.
Furthermore, in the device for optical communication according to the first aspect of the third group of the present invention, it is desirable that the optical element is a light receiving element and/or a light emitting element.
In a manufacturing method of a device for optical communication according to the second aspect of the third group of the present invention, after separately manufacturing: a substrate for mounting an IC chip having at least an area for mounting an optical element in which an optical element is mounted and a resin filled layer for an optical path is formed; and a multilayered printed circuit board at which at least an optical waveguide is formed, the substrate for mounting an IC chip and the multilayered printed circuit board are disposed at and fixed to such respective positions as to be able to transmit optical signal between the optical element of the substrate for mounting an IC chip and the optical waveguide of the multilayered printed circuit board, and further, a resin composition for sealing is made to flow between the substrate for mounting an IC chip and the multilayered printed circuit board and a curing treatment is conducted, thereby forming a sealing resin layer.
Moreover, a device for optical communication according to the first aspect of the fourth group of the present invention is a device for optical communication comprising: a substrate for mounting an IC chip at which an optical path for transmitting optical signal is formed, and on one face of said substrate an optical element is mounted; and a multilayered printed circuit board at which at least an optical waveguide is formed, said device for optical communication is constituted such that optical signal can be transmitted between the optical waveguide and the optical element through the optical path for transmitting optical signal.
In the device for optical communication according to the first aspect of the fourth group of the present invention, it is desirable that a sealing resin layer is formed between the substrate for mounting an IC chip and the multilayered printed circuit board, and that the sealing resin layer has a transmissivity of 70%/mm or more for communication wavelength light.
Further, in the device for optical communication according to the first aspect of the fourth group of the present invention, it is desirable that: a micro lens is disposed on an end portion on at least a multilayered printed circuit board side of the optical path for transmitting optical signal; and that, in case the micro lens is disposed on the end portion on at least a multilayered printed circuit board side of the optical path for transmitting optical signal and the sealing resin layer is formed between the substrate for mounting an IC chip and the multilayered printed circuit board, the micro lens has a refractive index higher than that of the sealing resin layer.
In the device for optical communication according to the first aspect of the fourth group of the present invention, it is desirable that the optical element is a light receiving element and/or a light emitting element.
It is also desirable that a resin layer for an optical path is formed inside the optical path for transmitting optical signal.
In a manufacturing method of a device for optical communication according to the second aspect of the fourth group of the present invention, after separately manufacturing: a substrate for mounting an IC chip at which an optical path for transmitting optical signal is formed, and on one face of said substrate an optical element is mounted; and a multilayered printed circuit board at which at least an optical waveguide is formed, the substrate for mounting an IC chip and the multilayered printed circuit board are disposed at and fixed to such respective positions as to be able to transmit optical signal between the optical element of the substrate for mounting an IC chip and the optical waveguide of the multilayered printed circuit board, and further, a resin composition for sealing is made to flow between the substrate for mounting an IC chip and the multilayered printed circuit board and a curing treatment is conducted, thereby forming a sealing resin layer.
Additionally, the present inventors dedicated themselves to the study of a substrate for mounting an IC chip capable of realizing optical communication excellent in connection reliability and contributing to making the terminal device small in size. As a result, the present inventors also completed a substrate for mounting an IC chip having the following configuration according to the fifth group of the present invention.
That is, a substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention is a substrate for mounting an IC chip comprising: a substrate, as serially built up on both faces thereof, a conductor circuit and an interlaminar insulating layer in an alternate fashion and in repetition; a solder resist layer formed as an outermost layer; and an optical element mounted thereto, wherein an optical waveguide is formed inside the substrate for mounting an IC chip, and an optical path for transmitting optical signal which connects the optical element to the optical waveguide is formed.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is desirable that the optical waveguide is an organic optical waveguide.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is desirable that the optical path for transmitting optical signal comprises a cavity, comprises a resin composition and a cavity or comprises a resin composition.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is also desirable that the optical path for transmitting optical signal comprises a cavity and a conductor layer around the cavity, comprises a resin composition, a cavity, and a conductor layer around the resin composition and the cavity or comprises a resin composition and a conductor layer around the resin composition.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is desirable that a position at which the optical element is mounted is on a surface of the substrate for mounting an IC chip and that the optical element is a light receiving element and/or a light emitting element.
It is also desirable that an electronic component is mounted on a surface of the substrate for mounting an IC chip.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is desirable that a micro lens is formed on an end portion of the optical path for transmitting optical signal or in the optical path for transmitting optical signal and that a cross-sectional diameter of the optical path for transmitting optical signal is 100 to 500 μm.
In the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention, it is desirable that the conductor circuits across the substrate are connected to each other through a plated-through hole, and the conductor circuits across the interlaminar insulating layers are connected to each other through a via-hole.
In a manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention, a substrate, an optical waveguide, and a lamination manufactured through at least the following steps (a) to (c) are built up in this order: (a) a conductor circuit lamination formation step of serially building up conductor circuits and interlaminar insulating layers on a base material layer in an alternate fashion and in repetition to provide a conductor circuit lamination; (b) an opening formation step of forming an opening which becomes an optical path for transmitting optical signal in the conductor circuit lamination; and (c) a solder resist layer formation step of forming a solder resist layer having an opening communicating with the opening formed in the step (b), on one face of the conductor circuit lamination.
A manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention comprises: (a) an optical waveguide formation step of forming an optical waveguide on a substrate on which conductor circuits are formed; (b) a multilayered circuit board manufacturing step of serially building up interlaminar insulating layers and conductor circuits on the substrate, on which the optical waveguide is formed, in an alternate fashion and in repetition to provide a multilayered circuit board; (c) an opening formation step of forming an opening which becomes an optical path for transmitting optical signal in the multilayered circuit board; and (d) a solder resist layer formation step of forming a solder resist layer having an opening communicating with the opening formed in the step (c) on one face of the multilayered circuit board.
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second or third aspect of the fifth group of the present invention comprises: a roughened face formation step of forming a roughened face on a wall face of the opening which becomes the optical path for transmitting optical signal.
Further, it is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second or third aspect of the fifth group of the present invention comprises: a conductor layer formation step of forming a conductor layer on a wall face of the opening which becomes the optical path for transmitting optical signal.
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second or third aspect of the fifth group of the present invention comprises: a resin composition filling step of filling an uncured resin composition into the opening which becomes the optical path for transmitting optical signal.
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second or third aspect of the fifth group of the present invention comprises: a micro lens formation step of forming a micro lens on an end portion of the opening which becomes the optical path for transmitting optical signal.
It is desirable that the manufacturing method of a substrate for mounting an IC chip according to the second or third aspect of the fifth group of the present invention comprises: a micro lens formation step of forming a micro lens in the opening which becomes the optical path for transmitting optical signal.
FIG. 2 is a cross-sectional view schematically showing another embodiment of the substrate for mounting an IC chip according to the first aspect of the first group of the present invention.
FIG. 3 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the third aspect of the first group of the present invention.
FIG. 4 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the fourth aspect of the first group of the present invention.
FIG. 5 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the fifth aspect of the first group of the present invention.
FIG. 6 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the fifth aspect of the first group of the present invention.
FIG. 7 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the fifth aspect of the first group of the present invention.
FIG. 8 is a cross-sectional view schematically showing part of a manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 9 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 10 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 11 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 12 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 13 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention.
FIG. 14 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the first aspect of the second group of the present invention.
FIG. 15 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 16 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 17 is a cross-sectional view schematically showing part of steps of manufacturing a substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 18 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 19 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 20 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 21 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 22 is a cross-sectional view schematically showing part of steps of manufacturing a multilayered circuit board that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 23 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 24 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 25 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 26 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 27 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 28 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the second group of the present invention.
FIG. 29 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the first aspect of the third group of the present invention.
FIG. 30 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 31 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 32 is a cross-sectional view schematically showing part of steps of manufacturing a substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 33 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 34 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 35 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 36 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 37 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 38 is a cross-sectional view schematically showing part of steps of manufacturing a multilayered circuit board that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 39 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 40 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 41 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 42 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 43 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 44 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 45 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 46 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 47 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 48 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the third group of the present invention.
FIG. 49 is a cross-sectional view schematically showing one embodiment of a device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 50 is a cross-sectional view schematically showing another embodiment of the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 51 is a cross-sectional view schematically showing still another embodiment of the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 52 is a cross-sectional view schematically showing part of steps of manufacturing a substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 53 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 54 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 55 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 56 is a cross-sectional view schematically showing part of the steps of manufacturing the substrate for mounting an IC chip that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 57 is a cross-sectional view schematically showing part of steps of manufacturing a multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 58 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 59 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 60 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 61 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 62 is a cross-sectional view schematically showing part of the steps of manufacturing the multilayered circuit board that constitutes the device for optical communication according to the first aspect of the fourth group of the present invention.
FIG. 63 is a cross-sectional view schematically showing one embodiment of a substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention.
FIG. 64 is a cross-sectional view schematically showing another embodiment of the substrate for mounting an IC chip according to the first aspect of the fifth group of the present invention.
FIG. 65 is a cross-sectional view schematically showing part of a manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 66 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 67 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 68 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 69 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 70 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 71 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the fifth group of the present invention.
FIG. 72 is a cross-sectional view schematically showing part of a manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 73 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 74 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 75 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 76 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 77 is a cross-sectional view schematically showing part of the manufacturing method of a substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 78 is a cross-sectional view schematically showing another embodiment of the substrate for mounting an IC chip according to the third aspect of the fifth group of the present invention.
FIG. 79 is a cross-sectional view schematically showing a device for optical communication manufactured in a comparative example.
1020 substrate for mounting IC chip
1120, 1120′ substrate for mounting IC chip
1121 substrate
1122 interlaminar insulating layer
1124 conductor circuit
1127 via-hole
1129 plated-through hole
1134 solder resist layer
1138 light receiving element
1139 light emitting element
1140 IC chip
1142 optical path for transmitting optical signal
1145 conductor layer
30100, 30200, 30300 multilayered printed circuit board
30101, 30201, 30301 substrate
30102, 30202, 30302 interlaminar insulating layer
30104, 30204, 30304 conductor circuit
30107, 30207, 30307 via-hole
30109, 30209, 30309 plated-through hole
30111, 30211, 30311 opening for optical path
30114, 30214, 30314 solder resist layer
30118, 30218, 30318 optical waveguide
30119, 30219, 30319 optical path conversion mirror
30120, 30220, 30320 substrate for mounting IC chip
31120, 32120, 33120 package substrate
31100, 32100, 33100 substrate for inserting optical element
31121, 32121, 33121 substrate
31122, 32122, 33122 interlaminar insulating layer
31124, 32124, 33124 conductor circuit
31127, 32127, 33127 via-hole
31129, 32129, 33129 plated-through hole
31134, 32134, 33134 solder resist layer
31138, 32138, 33138 light receiving element
31139, 32139, 33139 light emitting element
30140, 30240 IC chip
31141, 32141 resin filled layer for optical path
30150, 30250, 30350 device for optical communication
30160, 30260, 30360 sealing resin layer
4100, 4200, 4300 multilayered printed circuit board
4101, 4201, 4301 substrate
4102, 4202, 4302 interlaminar insulating layer
4104, 4204, 4304 conductor circuit
4107, 4207, 4307 via-hole
4109, 4209, 4309 plated-through hole
4111, 4211 opening for optical path
4114, 4214, 4314 solder resist layer
4118, 4218, 4318 optical waveguide
4119, 4219, 4319 optical path conversion mirror
4120, 4220, 4320 substrate for mounting IC chip
4121, 4221, 4321 substrate
4122, 4222, 4322 interlaminar insulating layer
4124, 4224, 4324 conductor circuit
4127, 4227, 4327 via-hole
4129, 4229, 4329 plated-through hole
4134, 4234, 4334 solder resist layer
4137, 4237, 4337 solder connection part
4138, 4238, 4338 light receiving element
4139, 4239, 4339 light emitting element
4140 IC chip
4141, 4241, 4341, 4351 optical path for transmitting optical signal
4142, 4242, 4342, 4352 resin layer for optical path
4145, 4245, 4345, 4355 conductor layer
4150, 4250, 4350 device for optical communication
4160, 4260, 4360 sealing resin layer
5020, 5120, 5220, 5320 substrate for mounting IC chip
5021, 5121, 5221, 5321 substrate
5022, 5122, 5222, 5322 interlaminar insulating layer
5024, 5124, 5224, 5324 conductor circuit
5027, 5127, 5227, 5327 via-hole
5029, 5129, 5229, 5329 plated-through hole
5031 base material layer
5034, 5134, 5234, 5334 solder resist layer
5038, 5138, 5238, 5338 light receiving element
5039, 5139, 5239, 5339 light emitting element
5240, 5340 IC chip
5242, 5342 optical path for transmitting optical signal
5045, 5245, 5345 conductor layer
5050, 5150, 5250, 5350 optical waveguide
First, a substrate for mounting an IC chip according to the first aspect of the first group of the present invention will be described.
The substrate for mounting an IC chip according to the first aspect of the first group of the present invention is a substrate for mounting an IC chip comprising: a substrate and, as serially built up on both faces thereof, a conductor circuit and an interlaminar insulating layer in an alternate fashion and in repetition; a solder resist layer formed as an outermost layer; and an optical element mounted thereto, wherein an optical path for transmitting optical signal, which penetrates the substrate for mounting an IC chip, is disposed.
Since the optical elements are mounted on the substrate for mounting an IC chip according to the first aspect of the first group of the present invention and the optical paths for transmitting optical signal penetrating the substrate for mounting an IC chip are disposed therein, it is possible to transmit input and output signals for the optical elements through the optical paths for transmitting optical signal.
In addition, when an IC chip is mounted on the substrate for mounting an IC chip, the distance between the IC chip and the optical elements is short and the reliability of the transmission of an electric signal is excellent. Specifically, when the optical element is a light receiving element, it is possible to accurately, swiftly process a large capacity of optical signal. When the optical element is a light emitting element, it is possible to swiftly transmit optical signal to the outside of the substrate for mounting an IC chip.
Further, in the substrate for mounting an IC chip on which the IC chip is mounted according to the first aspect of the first group of the present invention, since electronic components and optical elements necessary for optical communication can be provided integrally, it is possible to contribute to making a terminal device for optical communication small in size.
When the optical elements are to be mounted on the surface of the substrate, the optical elements are mounted thereon after forming conductor circuits and interlaminar insulating layers on the substrate for mounting an IC chip. Due to this, at the time of a heat treatment for forming the conductor circuits, the interlaminar insulating layers and the like, the optical elements are not mounted yet and thus positional deviation which may possibly occur during the heat treatment does not occur.
Moreover, when the optical elements are mounted on the surface of the substrate and a defect occurs to one of the optical elements, it suffices to replace only the defective optical element, thus advantageously ensuring good cost efficiency.
Moreover, in the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, the alignment of the optical elements can be carried out relative to the optical paths for transmitting optical signal by an optical treatment or a mechanical treatment. It is, therefore, possible to accurately mount the optical elements at respective desired positions.
Furthermore, in the substrate for mounting an IC chip on which the optical paths for transmitting optical signal are formed according to the first aspect of the first group of the present invention, when the optical elements are to be mounted, the degree of freedom for the mounting positions of the optical elements is improved to make it possible to realize the high density of wirings for the substrate for mounting an IC chip. This is because the improvement of the degree of freedom for the mounting positions of the optical elements enables widening free space in the design of the substrate for mounting an IC chip.
The free space means a region in which conductor circuits are formed and electronic components such as a capacitor are mounted.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, the optical paths for transmitting optical signal which penetrates the substrate for mounting an IC chip are disposed.
In the substrate for mounting an IC chip on which such optical paths for transmitting optical signal are disposed, information can be exchanged between the optical elements mounted on the both faces of the substrate for mounting an IC chip by optical signal through these optical paths for transmitting optical signal.
In addition, in the substrate for mounting an IC chip, the optical elements are mounted on one surface of the substrate and the other surface thereof is connected to an external substrate having the other optical elements mounted thereon through solders and the like. Due to this, information can be exchanged between the optical elements mounted on the substrate for mounting an IC chip and those mounted on the external substrate through the optical paths for transmitting optical signal.
The optical path for transmitting optical signal desirably is constituted by a vacancy. When the optical path for transmitting optical signal is constituted by a vacancy, it is easy to form the optical path for transmitting optical signal and it is difficult to cause transmission loss to occur in the transmission of optical signal through the optical paths for transmitting optical signal. Whether the optical path for transmitting optical signal is constituted out of a vacancy or not may be appropriately determined based on the thickness of the substrate for mounting an IC chip and the like.
It is also desirable that the optical path for transmitting optical signal is constituted by a resin composition and a vacancy. When the optical path for transmitting optical signal is constituted by a resin composition and a vacancy, it is possible to prevent the deterioration of the strength of the substrate for mounting an IC chip.
When the optical path for transmitting optical signal is constituted by a resin composition and a vacancy, it is desirable that the optical path for transmitting optical signal formed in a portion penetrating the substrate and the interlaminar insulating layers is constituted by the resin composition, and the optical path for transmitting optical signal formed in the solder resist layer is constituted by the vacancy. This is because, normally, the substrate and the interlaminar insulating layers are high in adhesion to resin and the solder resist layer is low in adhesion thereto.
It is also desirable that the optical path for transmitting optical signal is constituted by a resin composition. When the optical path for transmitting optical signal is constituted by a resin composition, it is possible to prevent the deterioration of the strength of the substrate for mounting an IC chip.
When the optical path for transmitting optical signal is constituted by the resin composition, it is possible to prevent dust, foreign matters and the like from entering the optical path for transmitting optical signal. It is, therefore, possible to prevent the transmission of optical signal from being hampered by the presence of the dust, the foreign matters and the like.
In addition, the optical paths for transmitting optical signal constituted as mentioned above, i.e., the optical path for transmitting optical signal constituted by both/either of a vacancy and/or a resin composition is difficult to cause an adverse influence by heat and the like (e.g., the cross-sectional diameter of each optical path for transmitting optical signal is made small) in a heat treatment step or a reliability test.
When a part of or all of the optical path for transmitting optical signal is constituted by a resin composition, the resin component of the resin composition is not limited to specific one as long as the resin component is less absorbed in a communication wavelength band. Examples of the resin component include thermosetting resin, thermoplastic resin, photosensitive resin, resin obtained by photosensitizing a part of thermosetting resin and the like.
Specifically, examples of the resin component include epoxy resin, UV cured-type epoxy resin, polyolefin resin, acrylic resin such as PMMA (polymethyl methacrylate), PMMA deuteride and PMMA deuteride fluoride; polyimide resin such as polyimide fluoride; silicone resin such as silicone resin deuteride; polymer produced from benzocyclobutene and the like.
Further, the resin composition may contain particles such as resin particles, inorganic particles and metal particles in addition to the resin component. By incorporating these particles in the resin composition, it is possible to match the thermal expansion coefficients of the optical waveguide, the substrate, the interlaminar insulating layers, the solder resist layers and the like and impart flame resistance to the resin composition depending on the types of the particles.
When particles are mixed in the resin composition, it is desirable that the refractive index of the particles is almost equal to that of the resin component of the resin composition. Therefore, when two kinds of particles having different refractive index from each other are mixed with each other, it is desirable that the refractive index of the particles is almost equal to that of the resin component of the resin composition.
Specifically, when the resin component is, for example, epoxy resin having a refractive index of 1.53, it is desirable to use a mixture of silica particles having a refractive index of 1.54 and titania particles having a refractive index of 1.52.
Examples of a method of mixing up the particles include a kneading method and a method of dissolving and mixing up two or more kinds of particles and then forming them into particle shape.
Examples of the resin particles include thermosetting resin, thermoplastic resin, photosensitive resin, resin obtained by photosensitizing a part of thermosetting resin, a resin complex composed of thermosetting resin and thermoplastic resin, a complex composed of photosensitive resin and thermoplastic resin and the like.
Specifically, they include thermosetting resin such as epoxy resin, phenol resin, polyimide resin, bismaleimide resin, polyphenylene resin, polyolefin resin and fluororesin; resin obtained by reacting the thermosetting group of thermosetting resin (e.g., the epoxy group of epoxy resin) with an methacrylic acid, an acrylic acid or the like to impart an acrylic group to the resin; thermoplastic resin such as phenoxy resin, polyethersulfone (PES), polysulfone (PSF), polyphenylenesulfone (PPS), polyphenylene sulfide (PPES), polyphenyl ether (PPE) and polyetherimide (PI); photosensitive resin such as acrylic resin and the like.
Further, a resin complex of the thermosetting resin and the thermoplastic resin or a resin complex of the thermoplastic resin with the acrylated resin or the photosensitive resin can be used.
As the resin particles, resin particles of rubber can be also used.
In addition, examples of the inorganic particles include aluminum compounds such as alumina and aluminum hydroxide; calcium compounds such as calcium carbonate and calcium hydroxide; potassium compounds such as potassium carbonate; magnesium compounds such as magnesia, dolomite and basic magnesium carbonate; silicon compounds such as silica and zeolite; titanium compounds such as titania and the like. Further, the inorganic particles comprising a material obtained by mixing silica and titania with a certain rate, dissolving and making them even may be used.
As the inorganic particles, those of phosphorus or phosphorus compounds can be used.
Examples of the metal particles include Au, Ag, Cu, Pd, Ni, Pt, Fe, Zn, Pb, Al, Mg, Ca, Ti and the like.
These resin particles, inorganic particles and metal particles may be used alone or in combination of two or more of them.
The particles are desirably inorganic particles, which is desirably silica, titania or alumina. It is also desirable to use particles having a mixture composition obtained by mixing and dissolving at least two kinds among silica, titania and alumina.
The shape of the particles such as the resin particles is not limited to specific one and examples of the particles include a spherical shape, an elliptic shape, a friable shape, a polygonal shape and the like.
The particle diameter of the particles is desirably smaller than a communication wavelength. When the particle diameter is larger than the communication wavelength, the transmission of optical signal is sometimes hampered.
The lower limit and upper limit of the particle diameter are desirably 0.01 μm and 0.8 μm, respectively. When the particles include those exceeding the range, a particle size distribution becomes too wide. At the time of mixing the particles into the resin composition, the variation of the viscosity of the resin composition grows, thereby deteriorating reproducibility in preparing the resin composition and making it difficult to prepare a resin composition having a predetermined viscosity. The viscosity of the resin composition prepared at the time of forming the optical paths for transmitting optical signal is desirably 100000 to 300000 cps (mP�s).
The lower limit and upper limit of the particle diameter are more desirably 0.1 μm and 0.8 μm, respectively. When the particle diameter falls within the range, the resin composition is ensured to be filled into a through hole at the time of applying and filling the resin composition thereto using a spin coater or a roll coater. In addition, at the time of preparing the resin composition into which particles are mixed, it becomes easier to adjust the resin composition to have a predetermined viscosity.
The lower limit and upper limit of the particle diameter are particularly desirably 0.2 μm and 0.6 μm, respectively. When the particle diameter falls within the range, it becomes easier to fill the resin composition particularly into the through holes. Besides, the variation of the optical waveguides thus formed is minimized, ensuring particularly excellent characteristics of the substrate for mounting an IC chip.
When the particles having particle diameters within this range are used, two or more kinds of particles having different particle diameters may be included.
In this specification, the particle diameter means the length of the longest portion of a particle.
The lower limit of the mixing quantity of the particles is desirably 10% by weight, more desirably 20% by weight. On the other hand, the upper limit thereof is desirably 50% by weight, more desirably 40% by weight.
When the mixing quantity of the particles is less than 10% by weight, the effect of mixing particles cannot be sometimes expected. When it exceeds 50% by weight, the transmission of optical signal is sometimes hampered. When the mixing quantity falls within the range of 20 to 40% by weight, even the occurrence of the aggregation or dispersion of particles does not influence optical signal transmission characteristic.
Further, the shape of the optical paths for transmitting optical signal is not limited to a specific one and examples of the shape include columnar, elliptical columnar, quadrangular columnar, polygonal columnar or the like.
Among them, the columnar shape is desirable. This is because the influence of this shape on the transmission of optical signal is the smallest and it is easy to form the optical path into a columnar shape.
The lower limit and upper limit of the cross-sectional diameter of the optical path for transmitting optical signal are desirably 100 μm and 500 μm, respectively. When the cross-sectional diameter is less than 100 μm, the optical path may possibly be closed. When at least a part of the optical path for transmitting optical signal is constituted by a resin composition, it is difficult to fill the optical path with an uncured resin composition. On the other hand, even when the cross-sectional diameter exceeds 500 μm, the optical signal transmission characteristic does not improve so greatly and such a large cross-sectional diameter often hampers the degree of freedom for the design of conductor circuits and the like that constitute the substrate for mounting an IC chip.
The lower limit and upper limit of the cross-sectional diameter are more desirably 250 μm and 350 μm, respectively. When they fall within this range, both the optical signal transmission characteristic and the degree of freedom for design are excellent and no problem occurs even when the optical path is filled with the uncured resin composition.
The cross-sectional diameter of the optical path for transmitting optical signal means the diameter of a cross section when the optical path for transmitting optical signal is cylindrical, the longer diameter of the cross section when the optical path for transmitting optical signal is elliptic, and the length of the longest portion of the cross section when the optical path for transmitting optical signal is prismatic or polygonal.
It is also desirable that the optical path for transmitting optical signal is constituted by a vacancy and a conductor layer around the vacancy.
It is further desirable that the optical path for transmitting optical signal is constituted by a resin composition and a conductor layer around the resin composition.
In addition, it is desirable that the optical path for transmitting optical signal is constituted by a resin composition, a vacancy and a conductor layer around these.
When the conductor layer is to be formed, the conductor layer may be formed entirely around the resin composition and/or the vacancy or may be formed only partially around the resin composition and/or the vacancy.
In this way, by forming the conductor layer on the optical path for transmitting optical signal, it is possible to decrease the irregular reflection of light on the wall faces of the optical path for transmitting optical signal and improve the optical signal transmission characteristic. The conductor layer may be composed of one layer or two or more layers.
Examples of a material for the conductor layer include copper, nickel, chromium, titanium, noble metal and the like.
Further, the conductor layer can often serve as a plated-through hole, i.e., serve to electrically connect the conductor circuits which interpose the substrate therebetween or the conductor circuits which interpose the substrate and the interlaminar insulating layers therebetween.
The material for the conductor layer is desirably metal having glossiness such as noble metal. When the conductor layer is formed out of metal having glossiness, optical signal loss is less and the transmission of optical signal is less hampered. Due to this, it is possible to further ensure that the optical signal is transmitted through the optical paths for transmitting optical signal.
Furthermore, a covering layer made of tin, titanium, zinc or the like or a roughened layer may be provided on the conductor layer. Depending on the kind (wavelength or the like) of optical signal to be transmitted through the optical paths for transmitting optical signal, it is desirable to suppress the irregular reflection of light on the wall faces of the optical paths for transmitting optical signal. By providing the covering layer or roughened layer and, thereby, decreasing the irregular reflection of light on the wall faces, it is sometimes possible to improve the optical signal transmission characteristic.
Moreover, by forming the roughened layer or the like on the wall faces of each optical path for transmitting optical signal, it is possible to further improve the adhesion between the optical path for transmitting optical signal and the substrate or the interlaminar insulating layer.
In addition, the optical path for transmitting optical signal constituted by the resin composition (including a portion of the optical path for transmitting optical signal constituted by a vacancy and a resin composition, which portion is constituted by the resin composition) or the conductor layer may contact with the substrate or the interlaminar insulating layer through the roughened layer. When the optical path for transmitting optical signal or the like contacts with the substrate or the interlaminar insulating layer through the roughened layer, the adhesion thereof to the substrate or the interlaminar insulating layer is excellent to make it more difficult to cause the optical path for transmitting optical signal or the like to be peeled off.
In the substrate for mounting an IC chip, both an optical path for transmitting optical signal for light reception and an optical path for transmitting optical signal for light emission may be formed as the optical paths for transmitting optical signal or only one of them may be formed. Accordingly, in the substrate for mounting an IC chip, a plurality of optical paths for transmitting optical signal may be formed.
The optical path for transmitting optical signal for light reception is intended to transmit an external optical signal transmitted through an optical fiber, an optical waveguide or the like to the light receiving element, whereas the optical path for transmitting optical signal for light emission is intended to transmit optical signal emitted from the light emitting element to an external optical fiber, optical waveguide or the like.
In the substrate for mounting an IC chip, each optical path for transmitting optical signal may be formed for each communication wavelength.
Furthermore, the optical elements such as the light receiving element or the light emitting element are mounted on the substrate for mounting an IC chip according to the first aspect of the first group of the present invention.
They may be appropriately selected based on the configuration of the substrate for mounting an IC chip, required characteristics and the like.
Examples of a material for the light receiving element include Si, Ge, InGaAs and the like.
Among them, InGaAs is desirable because of its excellent light receiving sensitivity.
Examples of the light emitting element include an LD (semiconductor laser), a DFB-LD (distributed feedback type semiconductor laser), an LED (light emitting diode) and the like.
Examples of a material for the light emitting element include a compound of gallium, arsenic and phosphorus (GaAsP), a compound of gallium, aluminum and arsenic (GaAlAs), a compound of gallium and arsenic (GaAs), a compound of indium, gallium and arsenic (InGaAs), a compound of indium, gallium, arsenic and phosphorus (InGaAsP) and the like.
They may be selected based on the communication wavelength. When the communication wavelength is in a 0.85 μm band, GaAlAs can be used. When the communication wavelength is in a 1.3 μm band or a 1.55 μm band, InGaAs or InGaAsP can be used.
Further, the positions at which the optical elements are mounted are desirably on the surface of the substrate for mounting an IC chip. As mentioned above, when the optical elements are mounted on the surface of the substrate for mounting an IC chip and a defect occurs to one of the optical elements, it suffices to replace only the defective optical element. The optical elements are desirably flip-chip type optical elements. This is because flip-chip type optical elements are easy to be replaced and easy to mount at more desirable positions by the self-alignment function at the time of mounting them.
When the optical elements mounting positions are on the surface of the substrate for mounting an IC chip, it is possible to align each optical element relative to each optical path for transmitting optical signal set as an origin as mentioned above.
Furthermore, when the optical elements mounting positions are on the surface of the substrate for mounting an IC chip, it is possible to avoid a problem that occurs to the conventional optical element-internalizing package substrate, i.e., the positional deviation of the optical elements.
In the conventional substrate for mounting an IC chip, an area for mounting an optical element such as a light receiving element and a light emitting element is formed on the substrate in advance and the optical elements are attached to this substrate. Thereafter, by subjecting embedding-resin to filling, curing and the like, the optical elements are mounted. When the optical elements are mounted in such a manner, the positional deviation of the optical elements tends to occur by the influence of heat applied during: the curing treatment of the interlaminar insulating layers and the solder resist layers; the reflow treatment of the solder paste and the like, a stress derived from the warping of the substrate and the rocking of the substrate during a plating treatment and the like.
Furthermore, when the optical elements are mounted using adhesive or solder, this adhesive or solder is often softened by the heat history in later steps and the positional deviation of the optical elements occur, accordingly.
However, when the optical elements are mounted on the surface of the substrate for mounting an IC chip, it is possible to avoid problems that cause such a stress and a positional deviation. This is because the strength of the substrate for mounting an IC chip is maintained as compared with that of the conventional substrate for mounting an IC chip.
When the optical elements are mounted on the surface of the substrate for mounting an IC chip, the face on which the optical elements are mounted may be the same as the face on which an IC chip is mounted or opposite thereto. In addition, when a plurality of optical elements are mounted on the substrate for mounting an IC chip, all of them may not be mounted on the same face.
Electronic components such as a capacitor and the like may be mounted on the surface of the substrate for mounting an IC chip. This is because it is possible to replace only a defective electronic component similarly to the optical elements.
In the substrate for mounting an IC chip, it is also desirable that the conductor circuits with the substrate interposed therebetween are connected to each other through a plated-through hole and the conductor circuits with the interlaminar insulating layers interposed therebetween are connected to each other through a via-hole.
This is because it is possible to realize the high density of the substrate for mounting an IC chip.
Further, by appropriately selecting the positions at which the conductor circuits and the via-holes are formed, it is possible to moderate a stress generated due to the difference in thermal expansion coefficient among the IC chip, the optical elements and the like.
Next, the embodiments of the substrate for mounting an IC chip according to the first aspect of the first group of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional-view schematically showing one embodiment of the substrate for mounting an IC chip according to the first aspect of the first group of the present invention. FIG. 1 shows the substrate for mounting an IC chip in a state where an IC chip is mounted.
As shown in FIG. 1, the substrate for mounting an IC chip 1120 is constituted such that conductor circuits 1124 and interlaminar insulating layers 1122 are serially built up on both faces of a substrate 1121 in an alternate fashion and in repetition and that the conductor circuits with the substrate 1120 interposed therebetween and the conductor circuits with the interlaminar insulating layers 1122 interposed therebetween are connected to one another by a plated-through hole 1129 and via-holes 1127, respectively. In addition, a solder resist layer 1134 is formed on each outermost layer of the substrate for mounting an IC chip 1120.
Further, optical paths for transmitting optical signal 1142 penetrating the substrate 1121, on which the conductor circuits 1124, the interlaminar insulating layers 1122 and the solder resist layers are formed, are formed in this substrate for mounting an IC chip 1120. The optical path for transmitting optical signal 1142 is constituted by a resin composition 1142 a, a vacancy 1142 b, and a conductor layer 1145 formed around the resin composition 1142 a and the vacancy 1142 b. Input/output signals for optical elements (a light receiving element 1138 and a light emitting element 1139) mounted on the substrate for mounting an IC chip 1120 are transmitted through the optical paths for transmitting optical signal.
It is noted that each optical path for transmitting optical signal may be composed of the vacancy or the resin composition, and the conductor layer may not be formed around the vacancy or the resin composition.
The light receiving element 1138 and the light emitting element 1139 are mounted through solder connection parts 1144 so that a light receiving part 1138 a and a light emitting part 1139 a are confronting the optical paths for transmitting optical signal 1142, respectively, and an IC chip 1140 is mounted through solder connection parts 1143 on one face of the substrate for mounting an IC chip 1120. Further, solder bumps 1137 are formed on the solder resist layer 1134 on the other face of the substrate for mounting an IC chip 1120.
In the substrate for mounting an IC chip 1120 thus constituted, optical signal transmitted from the outside through an optical fiber, an optical waveguide or the like (not shown) is received by the light receiving element 1138 (light receiving part 1138 a) through the optical path for transmitting optical signal 1142, converted into an electric signal by the light receiving element 1138, and then fed to the IC chip 1140 through the solder connection parts 1143 and 1144, the conductor circuits 1124, the via-holes 1127, the plated-through hole 1129 and the like.
An electric signal emitted from the IC chip 1140 is transmitted to the light emitting element 1139 through the solder connection parts 1143 and 1144, the conductor circuits 1124, the via-holes 1127, the plated-through hole 1129 and the like, and converted into optical signal by the light emitting element 1139. The optical signal transmitted from the light emitting element 1139 (light emitting part 1139 a) is transmitted to the external optical component (such as the optical fiber or the optical waveguide) through the optical path for transmitting optical signal 1142.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, the light receiving element and the light emitting element mounted on positions close to the IC chip perform optical/electric signal conversion. Therefore, an electric signal transmission distance is short, the reliability of signal transmission is excellent and it is thereby possible to deal with higher rate communication.
In addition, in the substrate for mounting an IC chip 1120, the solder bumps 1137 are formed on the solder resist layer 1134. Due to this, not only the electric signal emitted from the IC chip is converted into optical signal as mentioned above and transmitted to the outside through the optical path for transmitting optical signal 1142 and the like but also the electric signal is transmitted through the solder bumps.
When the solder bumps are formed as mentioned above, it is possible to connect the substrate for mounting an IC chip to an external substrate through the solder bumps. In this case, it is possible to dispose the substrate for mounting an IC chip at a predetermined position by the self-alignment function of solders.
The self-alignment function means a function that a solder is to be present near the center of an opening for forming a solder bump in a more stable form due to the mobility of the solder itself at the time of the reflow treatment. It is considered that this function is generated because surface tension strongly acts so that the solder wants to be spherical when the solder adheres to metal. In case of utilizing this self-alignment function, even when the positions of the substrate for mounting an IC chip and the external substrate are deviated before reflow at the time of connecting the substrate for mounting an IC chip to the external substrate through the solder bumps, the substrate for mounting an IC chip moves during the reflow and can be attached to an accurate position on the external substrate.
Accordingly, when optical signal is to be transmitted through the light receiving element and the light emitting element mounted on the substrate for mounting an IC chip and optical elements mounted on the external substrate, it is possible to accurately transmit the optical signal between the substrate for mounting an IC chip and the external substrate as long as the positions at which the light receiving element and the light emitting element are mounted on the substrate for mounting an IC chip are accurate.
In the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, it is further desirable that micro lenses are disposed on the end portions of the optical paths for transmitting optical signal, respectively. When the micro lenses are disposed, it is possible to further suppress optical signal transmission loss.
The micro lens is not limited to a specific one and examples of the micro lens include a lens ordinarily used as an optical lens. Specific examples of a material for the micro lens include optical glass, resin for an optical lens and the like.
Examples of the resin for an optical lens include acrylic resin such as PMMA (polymethyl methacrylate), PMMA deuteride and PMMA deuteride fluoride; polyimide resin such as polyimide fluoride; epoxy resin; UV cured-type epoxy resin; silicone resin such as silicone resin deuteride; polymer produced from benzocyclobutene and the like.
The shape of the micro lens is not limited to a specific one but may be appropriately selected based on the design of the substrate for mounting an IC chip. Normally, the micro lens has a diameter of 100 to 500 μm and a thickness of 200 μm or less. Since the micro lens is normally small as mentioned above, no cracks occur to the micro lens even when heat is applied thereto.
Particles may be added to the micro lens and the quantity of the added particles is desirably 60% by weight or less.
When particles are added to the micro lens, it is desirable that the resin for an optical lens is equal in refractive index to the particles. For that reason, when the particles are added to the resin for an optical lens, it is desirable to mix two kinds of particles having different refractive indexes to make the refractive index of the particles almost equal to that of the resin for an optical lens.
Specifically, when the resin for an optical lens is, for example, epoxy resin having a refractive index of 1.53, it is desirable to mix silica particles having a refractive index of 1.54 and titania particles having a refractive index of 1.52.
Specific examples of the particles include the same as those contained in the optical paths for transmitting optical signal.
The substrate for mounting an IC chip having the micro lenses disposed on the end portions of the respective optical paths for transmitting optical signal will be described with reference to the drawings.
FIG. 2 is a cross-sectional view schematically showing another embodiment of the substrate for mounting an IC chip according to the first aspect of the first group of the present invention. It is noted that FIG. 2 shows the substrate for mounting an IC chip in a state where an IC chip is mounted.
The substrate for mounting an IC chip 1120′ shown in FIG. 2 is constituted such that micro lenses 1146 a and 1146 b are disposed on the end portions of the respective optical paths for transmitting optical signal 1142, which are constituted by the resin composition 1142 a, the vacancy 1142 b and the conductor layer 1145, through adhesive layers 1147 a and 1147 b, respectively.
By thus disposing the micro lenses, it is possible to suppress the optical signal transmission loss.
The embodiment of the substrate for mounting an IC chip 1120′ is equal to the substrate for mounting an IC chip 1120 shown in FIG. 1 except that the micro lenses 1146 a and 1146 b are disposed.
Further, in the substrate for mounting an IC chip 1120′, the micro lens 1146 b confronting the light emitting element 1139 is disposed on the light emitting element 1139 side of the optical path for transmitting optical signal 1142. Alternatively, the position at which the micro lens is disposed may be opposite to the light emitting element 1139 side of the optical path for transmitting optical signal 1142.
The micro lens 1146 a confronting the light receiving element 1138 is desirably disposed on the opposite side to the light receiving element 1138 side of the optical path for transmitting optical signal 1142.
The positions at which the micro lenses are disposed are not limited to the end portions of the respective optical paths for transmitting optical signal. When the micro lenses are disposed on the respective optical paths for transmitting optical signal each of which is constituted by the resin composition and the vacancy or is constituted by the resin composition, the vacancy and the conductor layer around these, each micro lens may be disposed on the end portion of the resin composition. In this case, the positions at which the micro lenses are disposed are often within the respective optical paths for transmitting optical signal. Further, the micro-lenses may be formed on the both ends or one ends of the respective optical paths for transmitting optical signal.
The substrate for mounting an IC chip thus constituted according to the first aspect of the first group of the present invention can be manufactured using a manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention or the other method.
Next, the manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention will be described.
The manufacturing method of a substrate for mounting an IC chip according to the second aspect of the first group of the present invention comprises: (a) a multilayered circuit board manufacturing step of serially building up a conductor circuit and an interlaminar insulating layer on both faces of a substrate in an alternate fashion and in repetition to provide a multilayered circuit board; (b) a through hole formation step of forming a through hole in the multilayered circuit board; and (c) a solder resist layer formation step of forming a solder resist layer having an opening communicating with the through hole formed in the step (b).
In the substrate for mounting an IC chip manufactured by the manufacturing method according to the second aspect of the first group of the preset invention, the through holes formed in the step (b) and the openings formed in the step (c) and communicating with the through holes formed in the step (b) serve as the optical paths for transmitting optical signal. Therefore, in this manufacturing method, the substrate for mounting an IC chip according to the first aspect of the first group of the present invention, i.e., the substrate for mounting an IC chip for transmitting input/output signals for the optical elements through the optical paths for transmitting optical signal penetrating the substrate for mounting an IC chip can be suitably manufactured.
The step (a), i.e., the multilayered circuit board manufacturing step of manufacturing a multilayered circuit board will first be described in order of steps. Specifically, the multilayered circuit board can be manufactured through the following steps (1) to (9).
(1) Using an insulating substrate as a starting material, conductor circuits are formed first on the insulating substrate.
Examples of the insulating substrate include a glass epoxy substrate, a polyester substrate, a polyimide substrate, a bismaleimide-triazine (BT) resin substrate, a thermosetting polyphenylene ether resin, a copper-clad laminated board, an RCC substrate and the like.
Alternatively, a ceramic substrate such as an aluminum nitride substrate or a silicon substrate may be used.
The conductor circuits may be formed by forming a conductor layer in a spread state on each surface of the insulating substrate by an electroless plating treatment or the like and then etching the resultant conductor layer. Alternatively, the conductor circuits may be formed by etching the copper-clad laminated board or the RCC substrate.
Further, instead of the method of forming the conductor circuits by conducting the etching treatment, the conductor circuits may be formed by forming a plating resist on a conductor layer in a spread state, forming an electroplating layer on non plating resist formed areas, and then removing the plating resist and the conductor layers under the plating resist.
When the conductor circuits with the insulating substrate interposed therebetween are connected to each other by a plated-through hole, the plated-through hole is formed by forming a through hole for a plated-through hole in the insulating substrate using a drill, a laser or the like and, then, conducting an electroless plating treatment or the like. The diameter of the through hole for a plated-through hole is normally 100 to 300 μm.
It is desirable to fill the plated-through hole with a resin filler when the plated-through hole is formed.
(2) Next, the surfaces of the conductor circuits are subjected to a roughening treatment, based on necessity.
Examples of the roughening treatment include a blackening (oxidizing)-reducing treatment, an etching treatment using an etchant containing a cupric complex and an organic acid salt, a Cu—Ni—P needle-like alloy plating treatment and the like.
When roughened faces are formed, it is desirable that the mean roughness of the roughened faces is normally 0.1 to 5 μm. At the time of considering the adhesion between the conductor circuit and the interlaminar insulating layer, the influence of the conductor circuit on electric signal transmission capability and the like, it is more desirable that the mean roughness of the roughened faces is 2 to 4 μm.
This roughening treatment may be performed before filling the plated-through hole with the resin filler and roughened faces may be formed even on the wall faces of the plated-through hole. This is because the adhesion between the plated-through hole and the resin filler is improved.
(3) Either an uncured resin layer of thermosetting resin, photosensitive resin, resin obtained by acrylating a part of thermosetting resin, an uncured resin layer of a resin complex containing one of these resins and thermoplastic resin, or a resin layer of the