PLASTIC MOLDED CHIP CARRIER PACKAGE AND METHOD OF FABRICATING THE SAME

Abstract: A novel plastic molded chip carrier package for an integrated circuit chip has a carrier member 10 molded of a plastic material to which are integrally embeded a plurality of I/O pins 20 and a conductor member 30 for interconnection between the terminals of the chip 5 and the corresponding I/O pins 20 to provide a unitary construction obtained at a single molding process. This plastic molded chip carrier package is preferred to have integral positioning studs 12 which project in the same direction of the I/O pins 20 for abutment against a printed circuit board 1 for mounting the package in a spaced relation thereto with the I/O pins 20 plugged into metallized through holes 2 provided in the board 1. A method of fabricating the plastic chip carrier package is also disclosed to comprise the steps of placing a plurality of I/O pins 20 into corresponding vertical slots 52 formed in a molding die 51 with the top portion of the I/O pins 20 projecting above the molding die surface; supporting a conductor member 30 on the I/O pins 20 with the distal top ends of the I/O pins 20 extending into correspondingly through holes 33 formed in the conductor member 30, the conductor member 30 including a plurality of conductor lines 31 for electrical interconnection between the individual I/O pins 20 and the terminals of the chip 5 ; and filling a molten plastic material at least between the conductor member 30 and the molding die surface and solidifying the same so as to form thereat a plastic carrier member 10 to which the conductor member 30 is integrally embeded together with the top portions of the I/O pins 20.

Description: TECHNICAL FIELD The present invention is directed to a plastic molded chip carrier package and a method of fabricating the same, and more particularly to a plastic package having a plurality of I/O pins and an encapsulated conductor member for electrical interconnection of the chip to the individual I/O pins, and to a method of fabricating such package. BACKGROUND ART Plastic chip carrier packages have been widely accepted in the art to replace ceramic packages for their feasibility of incorporating a plurality of I/O pins at the time of molding the package and for thermal compatibility with a conventional printed-circuit boards on which the packages are frequently required to be directly mounted. Such plastic packages have been proposed, for example, in U.S. Pat. No. 4,618,739 in which a chip carrier is molded from a suitable plastic material to integrally include a plurality of I/O pins. This package requires a separately formed metallized layer which should be bonded onto the molded chip carrier for interconnection of the I/O pins and a chip to be disposed centrally of the carrier, adding the bonding process to the fabrication of the package with accompanied difficulty for secure registration of conductor lines on the metallized layer with the corresponding I/O pins. The employment of the separately formed metallized layer inherently poses a problem that the conductor lines may fail to be securely connected to the respective I/O pins due to possible poor bonding between the metallized layer and the molded chip carrier. In this respect, the prior plastic packages suffer from rather complicated fabrication process as well as reduced reliability in the connection between the conductor lines of the metallized layer and the respective I/O pins. From EP-A-0 218 796, published on April 22, 1987, i.e. after the present application date and thus falling within the terms of Article 54(3)EPC, there is known a semiconductor device wherein one or more chips are housed in a plug-in type package molded with a printed wiring substrate, head portions of terminals, and a heat sink for semiconductor chip attachment as an integral part of the package. DISCLOSURE OF THE INVENTION The present invention provides an advantageous plastic molded chip carrier package and a method of fabricating the same. The chip carrier package in accordance with the present invention comprises a carrier member made of a plastic material for mounting an integrated circuit chip and a plurality of I/O pins each protruding from the carrier member with their tip portions being encapsulated therein. Also encapsulated within the carrier member is a conductor member which has a plurality of conductor lines for interconnection between terminal pads of the chip and the corresponding I/O pins. Accordingly, the chip carrier member can be integrally formed with the conductor member having the plural conductor lines together with the I/O pins so that the package is made into a unitary construction in which the conductor member is securely attached to the carrier member for reliable electrical connection between the chip and the I/O pins. This unitary construction of the package including the conductor member enables the fabrication thereof to be made readily only through a single molding process with enhanced productivity. It is therefore a primary object of the present invention to provide a plastic molded chip carrier package in which the conductor member is securely incorporated in the chip carrier member without requiring another bonding process. In the meanwhile, there is a growing demand for the chip carrier package to be directly mounted on a conventional printed circuit board with the I/O pins plugged into metallized through holes formed therein. For this application, it is highly required to provide on the side of the package positioning projections which abut against the board for supporting the package in a spaced relation thereto. To this end, the chip carrier member of the present invention includes at least one pair of positioning studs which are integrally molded therewith to project in the same direction of the I/O pins. By the nature of the integral molding of the plastic chip carrier member, the positioning studs can be readily added to the carrier member or package without requiring any other separate parts, in addition to that it is kept intact with any electric circuit on the board and never damages the same. It is therefore another object of the present invention to provide a plastic molded chip carrier package in which positioning studs can be easily formed thereon for permitting direct mounting of the package on a conventional printed circuit board, yet preventing the positioning stud from damaging the electric circuit formed on the board. In preferred embodiments, there is incorporated in the chip carrier member a heat sink member having greater thermal conductivity than the carrier member. The heat sink member is embedded in the carrier member at the time of molding the latter with its heat radiation surface exposed and with the opposite surface defining a chip mounting surface. It is therefore a further object of the present invention to provide a plastic molded chip carrier package in which a heat sink member is embedded in the chip carrier member for enhancing heat radiation capacity. Preferably, the heat sink member is of a flat shape with its side wall being inclined inwardly from the chip mounting surface adjacent the conductor member to the opposed heat radiation surface. Also formed with the heat sink member is an external flange which extends sidewardly from the periphery of the heat radiation surface. With this provision of the inclined sidewall plus the external flange, the heat sink member is firmly embedded within the chip carrier member to increase the bonding strength therebetween, which is a further object of the present invention. In preferred embodiments, each of the conductor lines has a through hole into which the corresponding I/O pin extends with its distal top end projecting above the conductor line. The conductor member encapsulated within the molded plastic carrier member is preferably in the form of a metallized layer having the plural conductor lines formed on a substrate and having a center opening of a size smaller than a center recess formed in the carrier member, which center recess has its bottom defined by the top surface of the heat sink member embedded in the carrier member. The metallized layer is incorporated in the carrier member in such a manner as to extend into the center recess the inner peripheral edge portion including the inner lead ends of the conductor lines arranged on that edge portion. Thus, the inner lead ends of the metallized layer are exposed in the center recess for connection with the chip to be mounted on the top surface of the heat sink member or on the bottom of the center recess. The inner peripheral edge portion of the metallized layer including the inner lead ends of the conductor lines and extending into the center recess is backed up by the peripheral portion of the heat sink member so as to be kept aligned on the plane of heat sink member for easy and reliable connection to the terminal pads of the chip such as by a known wire bonding. It is therefore a further object of the present invention to provide a plastic molded chip carrier package in which the inner lead ends of the conductor lines are kept in aligned positions with the terminal pads of the chip by better utilization of the heat sink member embedded in the package. Further, the chip itself is wholly encapsulated within the carrier member together with the metallized layer and the I/O pins so as to entirely seal off the electrical parts and their connections for protection thereof from the atmospheric environment, which is a still further object of the present invention. Also disclosed in the present invention is an advantageous method of fabricating the molded plastic chip carrier package for an integrated circuit chip having terminal pads on its active surface as given in claims 7-9. With this method, the positioning studs can be easily formed at the time of molding to integrally project from the resulting molded plastic chip carrier member by employing a molding die with a corresponding number of stud-forming recesses. Thus, the positioning studs can be readily obtained without requiring any other separate parts, which is therefore another object of the present invention. In a preferred embodiment of the present invention, the chip carrier package is fabricated to integrally include therein a heat sink member and a metallized layer between a pair of separable upper an, lower molding dice. The metallized layer employed has a plurality of conductor lines formed on a substrate for electrical interconnection between the terminal pads of the chip and the corresponding I/O pins. A center opening is preformed in the metallized layer around the periphery of which are arranged the inner leads ends of the conductor lines for connection to the chip to be located within that opening. The metallized layer is supported on the I/O pins, which are placed in position with its lower portions inserted in the vertical slots in the lower molding die and with its top portions projecting above the molding surface, in such a manner that the distal top ends of the I/O pins extend into corresponding through holes formed in the metallized layer. At this condition, the heat sink member placed on the lower molding die is cooperative with a core projecting on the surface of the upper molding die to hold therebetween the inner peripheral edge portion of the metallized layer on which the inner lead ends of the conductor lines are arranged, while the core has its end face closely fitted within the center opening of the metallized layer for abutment on its entire end face with the heat sink member. The heat sink member is preferably disposed on the lower molding die with its bottom end seated in a concavity formed in that die in order to prevent the mold flow from wrapping around the bottom of the heat sink member, eliminating the formation of undesirable burr thereat, which is a further object of the present invention. The present invention discloses the advantageous method of fabricating a plastic molded chip carrier package in which the chip is encapsulated together with the associated metallized layer and the I/O pins within the plastic package at the time of molding thereof, eliminating further packaging process. These and still other objects and advantageous features of the present invention will be more apparent from the following description of the preferred embodiments when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a metallized layer embedded in the chip carrier package of the invention; FIG. 2 is a cross sectional view of a plastic molded chip carrier package in accordance with an embodiment of the present invention; FIG. 3 is a cross sectional view illustrating a set of upper and lower molding dice utilized for molding the above package and illustrating parts placed between the dice prior to the molding of the above package; and FIG. 4 is a cross sectional view of a modification of the above embodiment. Fig. 2 shows a plastic molded chip carrier package in accordance with the present invention, an integrated circuit chip 5 being wholly encapsulated within a plastic molded carrier member 150 together with a metallized layer 170 and a plurality of I/O pins 160 to form a final package product. The chip 5 is centrally mounted directly on the metallized layer 170 composed of a plurality of conductor lines 171 deposited on a substrate 172 and is connected by means of wires 6 to the individual conductor lines 171 fanning in from the outer edges of the metallized layer 170 toward the center portion adjacent the chip 5. Substrate 172 consists of a glass-cloth resin sheet. Suitable resin sheets may be made of epoxy, polyimide, polyester and tetrafluoroethylen. Alternatively, the substrate 172 may be in the form of a thin film made of the above plastic material. The metallized layer 170 has a number of through holes 173 for receiving the top ends of the I/O pins 160 with upper and lower shoulders 161 and 162. As shown in Fig. 3, the metallized layer 170 thus mounting the chip 5 is placed between a set of upper and lower molding dice 190 and 191 in a spaced relation from the molding surfaces by the I/O pins 160 each having its lower portion inserted in vertical slot 192 in the lower molding die 191, at which condition the lower shoulder 162 of each I/O pin 160 closes the top open end of the vertical slot 192 while the upper shoulder 161 supports the metallized layer 170 at the periphery of each through hole 173. Then, the space or cavity between the upper and lower molding dice 190 and 191 is filled with a molten plastic to form thereat the molded chip carrier member 150 in which the chip 5 and metallized layer 170 are encapsulated together with the top portions of the I/O pins 160. The carrier member 150 also includes integral positioning studs 152 which are formed in recesses 193 in the lower molding die 191 for mounting the chip carrier package in a spaced relation on the conventional circuit board 1 with the I/O pins 160 plugged into the plated through holes 2 provided therein. A modification of the above embodiment is shown in Fig. 4 which is identical thereto except for a heat sink member 180 integrally embeded within the chip carrier member 150. The heat sink member 150 is of the same configuration as employed in the first embodiment to have an inclined sidewall 183 and a sideward extending flange 184, and is firmly embeded in the carrier member 150 with its bottom heat radiation surface 182 exposed on the bottom thereof.

Claims: A plastic molded chip carrier package comprising: a carrier member (150) being made of a plastic material for receiving an integrated circuit chip (5) at its central portion; a plurality of I/0 pins (160) having their top end portions wholly encapsulated within said carrier member (150) and protruding outwardly from the carrier member (150); and a conductor member (170) wholly encapsulated within said carrier member (150) and having a plurality of conductor lines (171) for electrical interconnection between the terminals of said chip (5) and the corresponding I/0 pins (160); said chip (5) being wholly encapsulated together with the conductor member (170) and the top end portions of the I/0 pins (160) within said carrier member (150). A plastic molded chip carrier package as in claim 1 comprising: a heat sink member (180) having greater thermal conductivity than said carrier member (150) and shaped to have a chip mounting surface (181) and an opposed heat radiation surface (182), said heat sink member (180) being embedded centrally in the carrier member (150) with its heat radiation surface exposed on the surface of the carrier member (150), said heat sink member (180) having its heat radiating surface (182) projecting beyond the general surface of the carrier member (150). A plastic molded chip carrier package as set forth in claim 2, wherein said heat sink member (180) is a flat shape member with its side wall (183) being inclined inwardly from the chip mounting surface adjacent the conductor member (170) to the heat radiation surface (182), said heat sink member (180) being provided with an external flange (184) extending sidewardly from the periphery of the heat radiation surface (182) and being engaged in the carrier member (150). A plastic molded chip carrier package as in claim 1 or 2, wherein said carrier member (150) is integrally formed with at least one pair of positioning studs (152) which project. from the carrier member (150) for abutment against a support member (1) on which the package is adapted to be mounted with its I/0 pins (160) plugged into metallized through holes (2) formed therein for positive positioning of said package on the support member (1). A method of fabricating a plastic molded chip carrier package for an integrated circuit chip (5) having terminals with a plastic material by utilisation of separable upper (190) and lower molding dies (191), said method comprising: placing a plurality of I/0 pins (160) into corresponding vertical slots (192) formed in the lower molding die (191) with the top portion of each I/0 pins (160) projecting above the molding surface of the lower molding die (191); supporting on said I/0 pins (160) a metallized layer (170), mounting thereon said chip (5) in spaced relation from the molding surfaces of the upper (190) and lower molding dies (191), said metallized layer (170) being composed of a plurality of conductor lines (171) formed on a substrate (172), each of said conductor lines (171) being connected at its one end to respective I/0 pins (160) and at its other end with respective terminals of the chip (5) mounted centrally on the metallized layer (170); and filling into the space formed between the upper (190) and the lower molding dies (191) a molten plastic and solidifying the same so as to form thereat a plastic carrier member (150) in which the metallized layer (170) and the chip (5) mounted thereon are wholly encapsulated together with the top portions of the I/0 pins (160). A method of fabricating a plastic molded chip carrier package as in claim 7, characterised in that the distal top ends of the I/0 pins (160) are connected to the respective conductor lines (171) so that they extend into corresponding through holes (173) formed in the conductor member (172); said molding die (191) is formed with at least one pair of recesses (193) into which the plastic material is fed so as to form thereat correspondingly shaped positioning studs (152) which integrally protrude from the bottom surface of the carrier member (150). A method of fabricating a plastic molded chip carrier package as in claim 7, characterised by the steps of: forming within said conductor lines (171) through holes (173) and disposing therein the corresponding I/0 pins (160) projecting with their distal top ends beyond the conductor lines (171); and molding said carrier member(150)

Inventors: HIRATA, ATSUOMI, MAMIYA, HIROKUNI
Applicants: MATSUSHITA ELECTRIC WORKS, LTD.
Application year: 1987
Main classification: H01L23
IPC codes: H01L21, H01L23, H05K3