Method of manufacturing substrate for flip chip and substrate for flip chip manufactured using the same

There is provided a method of manufacturing a substrate for flip chip, and a substrate for flip chip manufactured using the same. The method includes providing a base substrate including at least one conductive pad, forming a solder resist layer on the base substrate, the solder resist layer including a first opening exposing the conductive pad, forming a dry film on the solder resist layer, the dry film including a second opening connected with the first opening, forming a metal post in the first opening and a part of the second opening, filling the second opening above the metal post with solder paste, forming a solder cap by performing a reflow process on the filled solder paste, planarizing a surface of the solder cap, and removing the dry film. Accordingly, fine pitches and improve reliability can be achieved.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority of Korean Patent Application No. 10-2009-0094119 filed on Oct. 1, 2009, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a substrate for flip chip, and a substrate for flip chip manufactured using the same, and more particularly, to a substrate for flip chip, capable of realizing fine pitches and ensuring improved reliability, and a method of manufacturing the same.

2. Description of the Related Art

The recent development of the electronic industries has increased the demand for smaller electronic components capable of implementing higher performance and having higher functionality. In this respect, even substrates for surface-mounting components, such as System In Package (SIP) and 3-dimensional (3D) packages, have been required to meet the conditions of high integration, slimness and fine circuit patterns.

Notably, as to surface-mounting on substrates for electronic products, a wire bonding or flip-chip bonding method is in use for an electrical connection between semiconductor chips and printed circuit boards. Here, the flip chip bonding method is considered advantageous over the wire bonding method that brings about an increase in module size, requires additional processes and has limitations in implementing fine pitches in circuit patterns due to the use of wires for a connection with printed circuit boards.

As for the flip-chip bonding method, external connection terminals (i.e., bumps) of tens to hundreds of micrometers in size are formed on a semiconductor chip by using gold, solder, other metallic materials or the like. The semiconductor chip, provided with these bumps, is then flipped over such that its surface faces a substrate, contrary to a mounting method adopting the existing wire bonding technique.

This flip-chip bonding method has evolved from a connection process using existing solder into a connection process using conductive adhesives. Here, the connection process using conductive adhesives desirably requires low costs, and allows for the formation of ultra-fine pitches and the execution of fluxless eco-friendly processes and low-temperature processes.

The flip-chip bonding method using conductive adhesives includes forming bumps, having a uniform height, on a pad, applying an adhesive that contains conductive particles, and bonding a chip with a substrate.

However, among the above-described processes of the flip-chip method, the bump forming technique is disadvantageous in that bumps with desired height need to be selectively formed on each fine pad.

Furthermore, process-wise, the flip-chip bonding method causes inconvenience since bumps need to be formed on both a chip and a substrate for bonding therebetween.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method of manufacturing a substrate for flip chip, capable of realizing fine pitches and ensuring improved reliability, and a substrate for flip chip manufactured using the same.

An aspect of the present invention also provides a method of manufacturing a substrate for flip chip, including a metal post applicable to a package substrate as well as a semiconductor substrate, and a substrate for flip chip manufactured using the same.

According to an aspect of the present invention, there is provided a method of manufacturing a substrate for flip chip, the method including: providing a base substrate including at least one conductive pad; forming a solder resist layer on the base substrate, the solder resist layer including a first opening exposing the conductive pad; forming a dry film on the solder resist layer, the dry film including a second opening connected with the first opening; forming a metal post in the first opening and a part of the second opening; filling the second opening above the metal post with solder paste; forming a solder cap by performing a reflow process on the filled solder paste; planarizing a surface of the solder cap; and removing the dry film.

The metal post may be formed to satisfy a condition of H/D>1 where H denotes a height of the metal post and D denotes a diameter of the metal post.

The metal post may be formed to have a height of 50 μm or greater.

The metal post may be formed by using electroless plating.

The method may further include forming a seed layer for plating on the solder resist layer after the forming of the solder resist layer.

The metal post may be formed by using an electro-plating method.

The method may further include removing the seed layer for plating after the removing of the dry film.

The method may further include performing a deflux process on the solder cap after the forming of the solder cap.

According to another aspect of the present invention, there is provided a substrate for flip chip, the substrate including: a base substrate including at least one conductive pad; a solder resist layer formed on the base substrate and having an opening exposing the conductive pad; a metal post filling at least a part of the opening; and a solder cap formed on the metal post and having a planarized surface.

The metal post may satisfy a condition of H/D>1 where H denotes a height of the metal post and D denotes a diameter of the metal post.

The metal post may have a height of 50 μm or greater.

The metal post may be formed by an electroless plating method.

The substrate may further include a seed layer for plating on an interface between the opening and the metal post within the opening.

The metal post may be formed by using an electro-plating method.

According to another aspect of the present invention, there is provided a method of manufacturing a package substrate, the method including: providing a base substrate including at least one conductive pad; forming a solder resist layer on the base substrate, the solder resist layer including a first opening exposing the conductive pad; forming a dry film on the solder resist layer, the dry film including a second opening connected with the first opening; forming a metal post in the first opening and a part of the second opening; filling the second opening above the metal post with solder paste; forming a solder cap by performing a reflow process on the filled solder paste; planarizing a surface of the solder cap; removing the dry film; providing a chip substrate including at least one metal pad; and bonding the base substrate with the chip substrate such that the solder cap having the planarized surface corresponds to the metal pad.

The metal post may be formed to satisfy a condition H/D>1 where H denotes a height of the metal post and D denotes a diameter of the metal post.

The metal post may be formed to have a height of 50 μm or greater.

According to another aspect of the present invention, there is provided a package substrate including: a base substrate including at least one conductive pad; a solder resist layer formed on the base substrate and having an opening exposing the conductive pad; a metal post filling at least a part of the opening; a solder cap formed on the metal post and having a planarized surface; and a chip substrate including at least one metal pad and bonded with the base substrate such that the metal pad corresponds to the solder cap having the planarized surface.

The metal post may satisfy a condition of H/D>1 where H denotes a height of the metal post and D denotes a diameter of the metal post.

The metal post may have a height of 50 μm or greater.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Hereinafter, the process of manufacturing a substrate for flip chip including a metal post, according to an exemplary embodiment of the present invention, will be described.

FIGS. 1A through 1Iare schematic cross-sectional views illustrating the process of manufacturing a substrate for flip chip, according to an exemplary embodiment of the present invention.

As shown inFIG. 1A, at least one conductive pad2is formed on a prepared base substrate1. Here, the conductive pad2may be formed by using a photolithography process. The base substrate1may utilize a semiconductor substrate or a package substrate.

A photosensitive resin layer (not shown) is applied on the base substrate1including a conductive pad material (not shown) applied thereon. Subsequently, the conductive pad2may be formed by using the photolithography process for exposing and developing the applied photosensitive resin layer using a mask (not shown) having a predetermined pattern.

Thereafter, a solder resist layer3, having a first opening V1(not shown) exposing the conductive pad2, is formed on the base substrate1including the conductive pad2.

Here, the first opening V1may be formed by exposing and developing a solder resist layer3, applied on the base substrate1, by using a predetermined mask pattern (not shown).

Also, an opening “O”, corresponding to a solder pad connected to a mother board or the like, may be then formed.

Subsequently, as shown inFIG. 1B, a seed layer4for plating may be formed on the solder resist layer3. The seed layer4for plating may be formed in the case that a metal post6, depicted inFIG. 1E, is formed using an electro-plating method. The formation method for the metal post6is not limited thereto, and an electroless plating method may be used to form the metal post6. As described above, if the metal post6is formed using the electroless plating method, the seed layer4for plating may not be formed.

Thereafter, as shown inFIG. 1C, a dry film5′ is applied to the seed layer4for plating.

Here, the dry film5′ utilizes a high heat resistant film in order to endure a reflow process performed at a high temperature of 260° C. or higher. In addition, the dry film5′ may have a thickness of 60 μm or greater for the purpose of forming a post bump with an appropriate height.

Thereafter, as shown inFIG. 1D, the dry film5′, depicted inFIG. 1C, is subjected to exposing and developing processes, thereby forming a dry film5having a second opening V2communicating (i.e., connected) with the first opening V1.

The second opening V2may be formed by exposing and developing the photosensitive dry film5′, applied on the seed layer4for plating, by using a predetermined mask pattern (not shown), in the same manner as the first opening V1is formed.

Thereafter, as shown inFIG. 1E, the metal post6is formed in the first opening V1and at least a part of the second opening V2.

At this time, the metal post6may be formed by using an electro-plating method or an electroless plating method.

The metal post6fills the first opening V1and a part of the second opening V2in order to cause wiring patterns to have fine pitches, enable high-speed signal transmissions between a substrate and a semiconductor chip, ensure a sufficient interval between chips, and perform a heat dissipation function. In this case, the metal post6may have a cylindrical structure. Also, the metal post6may be formed of a conductive material such as copper (Cu). However, the material of the metal post6is not limited to the material described, and may utilize nickel (Ni), tin (Sn), gold (Au) or the like.

Here, the metal post6, when formed of copper, can lower the overall electrical resistance of the substrate1for flip chip due to the low resistance of copper, and can also enhance heat dissipation characteristics. Furthermore, the flexural deformation of the substrate10for flip chip can be prevented since copper is a metal with a relatively high level of rigidity and thus can retain its rigidity even after undergoing a plurality of high-temperature processes for forming the substrate10for flip chip.

In this case, the height of the metal post6is not limited specifically, but may satisfy the condition of H/D>1 where H denotes the height of the metal post and D denotes the diameter of the metal post. The metal post6may be formed to have a height of 50 μm or greater. Also, the metal post6may be formed to have a diameter of 30 μm or greater.

Thereafter, as shown inFIG. 1F, the second opening V2above the metal post6is filled with solder paste. The solder paste is then subject to a reflow processes, thereby forming a solder cap7a.

In this case, the solder paste may be filled up to a level higher than the second opening V2.

Subsequently, as shown inFIG. 1G, the surface of the solder cap7ais mechanically or chemically polished to thereby form a planarized solder cap7b.

Accordingly, the overall height of the metal post6and the solder cap7bcan attain uniformity even if the metal post6itself has a non-uniform height due to a variation in plating thickness occurring in the previous process of forming the metal post6.

Namely, the solder cap7bserves to ensure uniformity in height, as well as to perform a buffering function during a packaging process for the substrate10for flip chip.

Thereafter, a typical deflux process is carried out to remove flux remaining on the planarized solder cap7b.

Here, the dry film5may be removed by causing the dry film5on the surface of the base substrate1to contact a solvent. As for this contact method, the base substrate1may be immersed in a solvent, or a solvent may be sprayed onto the base substrate1. In addition, the dry film5may be removed by controlling the temperature and contact duration with a solvent. Alternatively, the base substrate1may be cleaned using ultrasonic waves while being immersed in a solvent. In this case, the time it takes to remove the dry film5can be shortened as compared to when the dry film5on the surface of the base substrate1simply comes in contact with a solvent.

Thereafter, as shown inFIG. 1I, the seed layer4for plating is removed to thereby manufacture a substrate10for flip chip.

The substrate10for flip chip, manufactured according to the process of manufacturing the substrate10for flip chip according to an exemplary embodiment of the present invention, includes a base substrate1including at least one conductive pad2, a solder resist layer3formed on the base substrate1and having a first opening V1exposing the conductive pad1, a metal post6filling at least a part of the first opening V1, and a solder cap7bformed on the metal post and having a planarized surface.

Here, the metal post6may be formed by an electro-plating method or an electroless plating method.

The metal post6serves to enable wiring patterns to have fine pitches, allow for high-speed signal transmission between a substrate and a semiconductor chip, ensure distances between chips, and perform a heat dissipation function. The metal post6fills at least a part of the first opening V1. In this case, the metal post6may have a cylindrical structure. The metal post6may be formed of a conductive material such as copper (Cu), but is not limited thereto. The metal post6may be formed of a material such as nickel (Ni), tin (Sn), gold (Au) or the like.

Here, the metal post6, when formed of copper, may lower the overall electric resistance of the substrate10for flip chip due to the low resistance characteristic of copper, and may also improve its heat dissipation characteristic. Since copper is a metal with a high level of rigidity, it can retain its rigidity even after a plurality of high-temperature processes for forming the substrate10for flip chip, thereby preventing the flexural deformation of the substrate10for flip chip.

The height of the metal post6is not limited specifically. However, the metal post6may be formed to satisfy the condition of H/D>1 where H denotes the height of the metal post6, and D denotes the diameter of the metal post6. Furthermore, the metal post6may have a height of 50 μm or greater. Also, the metal post6may have a diameter of 30 μm or greater.

The solder cap7bis a planarized version of the solder cap7a, which results from the mechanical or chemical polishing of the surface of the solder cap7a.

Accordingly, even if the height of the metal post6is non-uniform due to a variation in plating thickness caused during the previous process of forming the metal post6, the planarized solder cap7bmay supplement this non-uniformity, and thus allows for the uniformity of the overall height of the metal post6and the solder cap7b.

That is, the solder cap7bserves to ensure height uniformity, as well as to perform a buffering function during the packaging process of the substrate10for flip chip.

According to the present invention, there are provided a substrate for flip chip, enabling the formation of fine pitches and having improved reliability, and a method of manufacturing the same.

Furthermore, the use of the metal post and the solder cap solves the non-uniformity in height and location. Thus, the metal post, capable of providing improved height uniformity and mounting reliability, may be applied not only to a semiconductor substrate but also to a package substrate.

FIGS. 2A and 2Bare schematic cross-sectional views for comparing a bonding part between a substrate for flip chip, formed according to an exemplary embodiment of the present invention, and another substrate with a bonding part between a related art substrate for flip chip and another substrate.

Referring toFIG. 2A, a related art substrate100a, including a solder bump60aconnected with a solder pad20ain a solder resist layer300including an opening, is soldered on a chip substrate100b. In this case, typically, the chip substrate100bincludes, for the enhancement of assemblage, a metal pad20band a solder bump60aformed on the metal pad20b, and the chip substrate100bis then soldered with the substrate100a.

However, as shown inFIG. 2B, the substrate10for flip chip, according to this exemplary embodiment, includes the metal post6and the solder cap7bformed on the metal post6. Accordingly, when the substrate10for flip chip, having the vertically elongated metal post6as compared to the related art, is soldered on the metal pad2′ formed on the chip substrate1′, assembly defects can be reduced even without a solder bump formed on the chip substrate1′.

Accordingly, a defect ratio, involving failed soldering, can be reduced even when solder bumps are not formed on both the substrate10for flip chip and another component or a chip substrate. This is contributive to reducing manufacturing costs.

As set forth above, according to exemplary embodiments of the invention, there can be provided the method of manufacturing a substrate for flip chip, capable of achieving fine pitches and improved reliability, and the substrate for flip chip manufactured using the same.

Furthermore, the metal post and the solder cap are used to reduce non-uniformity in height and location. Thus, a package substrate, as well as a semiconductor substrate, can be provided with a metal post allowing for the enhancement of high uniformity and mounting reliability.

Also, defect generation, involving failed soldering, can be reduced even when solder bumps are not formed on both the substrate for flip chip and another component or a chip substrate. This is contributive to reducing manufacturing costs.