JP2001237337A - Plastic package and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A through-hole is filled with a conductive paste,
Provided are a plastic package in which Ni plating and Au plating are directly provided on a conductive paste, and a method of manufacturing the same. A solder ball connection pad (28) is provided at an opening position of a through hole (22) in a copper-clad resin substrate (11).
Is formed, and the through-hole 22 is filled with a conductive paste 25 inside the through-hole 22 in which a Cu plating layer composed of electroless Cu plating 23 and electrolytic Cu plating 24 is formed on the wall surface. The solder ball connection pad 28 is formed by filling the solder ball connection pad 28 with an exposed surface of the conductive paste 25 and a part of a wiring pattern formed therearound. And Au plating 30 is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic package for forming a solder ball connection pad at an opening position of a through hole filled in a hole in a copper-clad resin substrate, and a method of manufacturing the same. The present invention relates to a plastic package formed by filling a conductive paste and applying a metal film directly to an exposed surface of the conductive paste and the periphery thereof, and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, as semiconductor devices have become higher in performance and smaller in size, plastic packages for mounting semiconductor devices have increased the number of external connection terminals, mountability of semiconductor devices, lower cost, and heat dissipation. A ball grid array type plastic package (PBGA) is often used from the viewpoints of characteristics and low impedance. This PBGA is a single-layer or multi-layer highly heat-resistant copper made of BT resin (resin containing bismaileimide triazine as a main component) or polyimide resin having a conductor layer formed by thermocompression bonding of Cu foil on both surfaces. There are a cavity-down type in which a heat slug is bonded to the copper-clad resin substrate using a resin-clad substrate as a substrate, and a direct molding type. A conductor pattern is formed on the surface layer by etching or the like, a through-hole conductor is formed to establish conduction with the conductor pattern on both surface layers, and a solder ball connection pad is formed on the back surface. To various wiring boards through In some cases, the solder ball connection pads are formed on the front side. Here, the solder ball connection pad may be formed at the position of the opening of the through hole of the copper-clad resin substrate. In general, the method of forming the through-hole is to first form a through-hole in the copper-clad resin substrate with a multi-axis drill or the like. And electroless Cu plating is performed after a catalyst such as palladium is applied. Thick plating of electrolytic Cu plating is performed on the electroless Cu plating. Then, the through-hole is filled with a hole filling paste made of insulating resin by printing,
After hardening, it is smoothed with a belt sander or the like in order to remove the filling paste protruding from the through holes. Next, the electroless C
After performing u plating and electrolytic Cu plating, a wiring pattern and a solder ball connection pad are formed by etching a Cu layer using a photolithography method, and after a solder resist is printed and formed, Ni plating and Au plating are performed. (See FIG. 3). Further, as another forming method, an insulating resin substrate to which no Cu foil is stuck is used, and a conductive paste is filled as a paste for filling the through-holes, heat-cured, and then the holes of the through-holes are filled. The Cu foil is thermocompression bonded to the surface of the insulating resin substrate including the filling paste portion, and the Cu foil is etched using a photolithography method to form a wiring pattern and a solder ball connection pad,
After printing and forming the solder resist, Ni plating and Au plating are performed (see FIG. 4).

[0003]

However, the conventional plastic package in which the solder ball connection pad is formed on the through hole as described above has the following problems to be solved. (1) When performing the electroless Cu plating and the electrolytic Cu plating twice, the thickness of the Cu layer becomes too thick, and the pattern resolution of the wiring pattern and the solder ball connection pad in the etching of the Cu layer is reduced. Elaborate patterns cannot be obtained. Therefore, it cannot cope with high performance and miniaturization of a semiconductor element which requires a high density wiring pattern. (2) Further, if the thickness of the Cu layer is too large, a precise pattern cannot be obtained, so that a disconnection or short circuit occurs in the wiring pattern, resulting in a decrease in yield. (3) Therefore, as a countermeasure against this, Cu is formed before pattern formation.
Although an elaborate pattern is obtained by thinning the layer, the work of thinning the Cu layer requires polishing, which lowers the production efficiency. (4) When using an insulating resin substrate to which the Cu foil is not attached, there is a step of attaching the Cu foil in an intermediate step.
The work requires skill. The present invention has been made in view of such circumstances, and fills a conductive paste into a through-hole, is thermally cured, and then forms a metal film such as Ni plating and Au plating on the conductive paste. An object of the present invention is to provide a plastic package capable of coping with high performance and miniaturization of a semiconductor element requiring a high-density wiring pattern and a method of manufacturing the same.

[0004]

According to the present invention, there is provided a plastic package in which a solder ball connection pad is formed at an opening position of a through hole filled in a hole in a copper-clad resin substrate. The filling of the through-hole is performed by filling a conductive paste into the through-hole in which a Cu plating layer made of electroless Cu plating and electrolytic Cu plating is formed on the wall surface. And a part of a wiring pattern formed on the exposed surface of the conductive paste and the periphery thereof. Further, a metal film is applied to the solder ball connection pad. Thereby, the electroless Cu plating and
The electrolytic Cu plating needs to be performed only once, and the Cu thickness can be set thin, so that a fine pattern can be obtained at the time of etching. Therefore, it is possible to cope with high performance and miniaturization of a semiconductor element requiring a high density wiring pattern. In addition, there is no occurrence of a defect such as disconnection of a wiring pattern or a short circuit due to a failure to obtain a sophisticated pattern. Further, since there is no need to attach a Cu foil in an intermediate step, an inexpensive plastic package can be provided.

[0005] A method of manufacturing a plastic package according to the present invention, which meets the above object, is a method of manufacturing a plastic package in which a solder ball connection pad is formed on a through-hole filled in a hole of a copper-clad resin substrate. A step of forming a through hole, a step of performing electroless Cu plating and an electrolytic Cu plating on the surface of the copper-clad resin substrate and the wall surface of the through hole, and filling a conductive paste into the through hole for the solder ball connection pad, Including a curing step, a step of forming a wiring pattern including solder ball connection pads on the surface of the copper-clad resin substrate, a step of forming a solder resist pattern in necessary places excluding the solder ball connection pads, and including a solder ball connection pad Applying a metal film to a necessary portion. As a result, the electroless Cu plating and the electrolytic Cu plating on the copper-clad resin substrate need only be performed once, so that the thickness of the Cu layer is not excessively increased, and the wiring pattern and the solder ball connection pad in the etching of the Cu layer are eliminated. Does not lower the pattern resolution. Therefore, a fine pattern can be obtained, and a plastic package capable of responding to high performance and miniaturization of a semiconductor element requiring a high density wiring pattern can be manufactured. Further, since no disconnection or short circuit of the wiring pattern occurs, the yield is not reduced. Also, Cu
A plastic package can be manufactured without the necessity of attaching foil in an intermediate step and without requiring any special technique.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. 1A and 1B are a side sectional view of a plastic package according to an embodiment of the present invention, and a partially enlarged side sectional view of a solder ball connection portion.
FIG. 2 is a partially enlarged side sectional view for illustrating a method for manufacturing a plastic package according to one embodiment of the present invention.

First, referring to FIGS. 1A and 1B, a plastic package 10 according to an embodiment of the present invention will be described.
The structure of will be described. As a substrate of the plastic package 10, a copper-clad resin substrate 11 is made of a high-temperature resin such as BT resin (resin containing bismaileimide triazine as a main component) or polyimide resin having a conductor layer formed by bonding Cu foils 21 on both surfaces. It is formed from a single-layer or multi-layer resin substrate made of a resin having excellent heat resistance, dielectric properties, insulation properties, and workability. On both surfaces thereof, a conductor pattern composed of a Cu foil 21, an electroless Cu plating 23, and an electrolytic Cu plating 24, and a Ni plating 29, which is an example of a metal film, and Au
A wiring pattern such as a wire bond pad plated with 30 and a solder ball connection pad 28 is formed. A large number of solder balls 12 as connection terminal electrodes are formed on the lower surface of the copper-clad resin substrate 11 via solder ball connection pads 28.

A conductive paste 25 is filled in a through hole 22 in which a drill is formed and a Cu plating is formed, and a wall is provided with a Cu plating layer of an electroless Cu plating 23 and an electrolytic Cu plating 24. A solder ball connection pad 28 formed of an exposed surface and a part of a wiring pattern formed around the exposed surface (that is, formed at an opening position of the filled through hole 22), and Ni plating applied thereon The wiring patterns on the upper surface of the copper-clad resin substrate 11 and the solder balls 12 on the lower surface of the copper-clad resin substrate 11 are electrically connected to each other via the Au plating 30 and the Au plating 30. In the wiring pattern area on the upper surface of the copper-clad resin substrate 11, a wire bonding pad portion connected by the bonding wire 15, a casting opening portion used when the sealing resin 16 is injected, and the like are provided with Ni plating 29 and A
U plating 30 is applied, and a solder resist 17 is formed in portions other than these patterns. Further, a solder resist 13 is formed on an exposed surface other than the solder ball connection pads 28 on the lower surface of the copper-clad resin substrate 11.

On the solder resist 18 formed in the die bonding region, a semiconductor element 14 is bonded with an Ag paste or the like, and the electrodes of the semiconductor element 14 and the wire bonding pads of the copper-clad resin substrate 11 are connected to an Au wire or the like. Are electrically connected by a bonding wire 15 made of The semiconductor element 14 and the bonding wires 15 are sealed with a sealing resin 16 such as an epoxy resin by transfer molding.

As shown in FIG. 2, the method for manufacturing a plastic package according to an embodiment of the present invention is, as shown in FIG. 2, schematically (1) a drilling step for drilling a through hole in a copper-clad resin substrate, and (2) a drilling step. (3) a hole filling step of filling a conductive paste in a through hole, (4) a patterning step of forming a wiring pattern including solder ball connection pads, (5) And (6) a step of forming a metal film. Hereinafter, each step will be described in detail.

(1) Drilling step for drilling a through hole in a copper-clad resin substrate First, a copper-clad resin substrate 11 is prepared. The copper-clad resin substrate 11 has a single-layer or multi-layer structure made of a BT resin (a resin containing bismaileimide triazine as a main component) or a polyimide resin having a conductor layer formed by bonding Cu foils 21 on both surfaces. It is made of a heat-resistant resin substrate. The thickness of the Cu foil 21 is usually 18 to 70 μm, and the purity of Cu is 9
Use 9.8% or more. Then, using a single-axis drilling machine or a single-axis or multiple-axis numerical control type drilling machine (NC drill machine), a hole drill made of cemented carbide or the like is rotated at high speed on the copper-clad resin substrate 11 (for example, 150 mm).
(About 00 rpm to about 100000 rpm) to form the through hole 22.

(2) Cu plating step of applying electroless Cu plating and electrolytic Cu plating A catalyst such as palladium is applied to the copper-clad resin substrate 11 in which the through holes 22 are formed, and the copper plating resin substrate is placed in a strong alkaline bath using formalin as a reducing agent. To form an electroless Cu plating 23 film. Here, both surface layers of the copper-clad resin substrate 11 are electrically connected via the Cu conductor film formed on the wall surface of the through hole 22. Next, an electrolytic Cu plating 24 is formed on the copper-clad resin substrate 11 on which the electroless Cu plating 23 has been applied.
The plating bath is filled with a plating bath, for example, a copper sulfate bath, a pyrophosphoric acid bath, and the like.
The u-plate is opposed to each side of the copper-clad resin substrate 11 which is a plating object attached to the cathode (cathode) side.
Arrange them. Then, by applying a voltage to the DC power supply device, the electroless C
Metal copper is deposited on the surface layer provided with the u plating 23 and the wall surface of the through hole 22 to form an electrolytic Cu plating 24 film.

(3) Hole-filling step of filling conductive paste in through-holes Screen-printing method of conductive paste 25 in through-holes 22 of copper-clad resin substrate 11 on which electroless Cu plating 23 and electrolytic Cu plating 24 have been applied. And heat-cured.
As the conductive paste 25, for example, a paste kneaded using 80% of Cu powder and a thermosetting resin as a binder is used. After filling the holes, if necessary, the conductive paste 25 protruding from the surface of the through hole 22 may be removed by polishing, and the surface of the through hole 22 may be smoothed.

(4) A patterning step for forming a wiring pattern including solder ball connection pads A dry film to be an etching resist 26 is subjected to electrolytic C
The coating is applied to the u plating 24 coating and the exposed portion of the conductive paste 25 and the periphery thereof. The dry film made of the photoresist has a three-layer structure of a cover film, a photoresist, and a carrier film.
It is formed on the coating and the conductive paste 25. Next, a pattern mask for forming a wiring pattern including the solder ball connection pads 28 is aligned, and ultraviolet light exposure is performed.
After that, the carrier film is peeled off and development is performed to remove the dry film other than the wiring pattern including the solder ball connection pads 28. The remaining dry film becomes the etching resist 26. Next, using an etching solution such as a ferric chloride solution, a cupric chloride solution, an alkaline etchant, and a hydrogen peroxide-sulfuric acid-based etchant,
The Cu plating layer (electroless Cu plating 23 and electrolytic Cu plating 24) in the opening 27 of the etching resist 26 on the copper-clad resin substrate 11 and the copper foil 21 are etched. Here, Cu etching (electroless Cu plating 23 and electrolytic Cu plating 24) and Cu foil 21
By reducing the thickness of the plating (the number of times of the electroless Cu plating 23 and the electrolytic Cu plating 24 is set to one), the influence of the etching factor is reduced, and a fine pattern is formed. Then, the etching resist 26 made of the photoresist covering the wiring pattern including the solder ball connection pads 28 is sprayed on the surface by spraying a stripping solution, and the photoresist is swollen and washed away.
Peel and remove. Thus, a wiring pattern including the solder ball connection pads 28 is formed.

(5) Printing Step of Printing and Forming a Solder Resist Layer The solder ball connection pads 28 of the copper-clad resin substrate 11 and
A screen printing method of solder resists 13 and 17 is applied to the exposed surface excluding a portion of a wire bonding pad connected to a semiconductor element with a bonding wire in a wiring pattern.
For example, the viscosity of the solder paste is 300 poise, the printing pressure is 3.5 kgf, the screen plate is 150 mesh,
A print thickness (formation of a solder resist pattern) is formed at a print thickness of 40 to 50 μm. Solder resist 13, 17
Are Ni plating 29 and A, which are examples of a metal film in a later process.
It serves as a plating resist when applying u-plating 30, does not solder during the soldering operation, and protects the Cu conductor surface from the external environment. In addition, using a heat-curable epoxy resin or an ultraviolet-curable acrylate-based resin as the polymer of the solder paste, the solder resists 13 and 17 are required for various properties as a permanent mask (adhesion, solder heat resistance, moisture resistance, Chemical resistance, electrical insulation properties, etc.).

(6) Metal film forming step A solder ball connection pad 28 which is an opening of the solder resists 13 and 17 of the copper-clad resin substrate 11 and a portion of a wire bonding pad which is connected to a semiconductor element in a wiring pattern by a bonding wire. For example, the plating wiring pattern is energized and electrolytic Ni plating 29 and Au are applied.
Plating 30 is applied. The Ni plating 29 is a base plating of the Au plating 30 and is formed to a thickness of about 2 to 5 μm.
No. 0 is formed to a thickness of about 0.05 to 0.8 μm by flash plating. As the plating bath, a sulfamic acid bath is used for Ni, and various plating baths of hard gold are used for Au.
When the Ni plating is electroless Ni plating, Ni-P plating using hypophosphorous acid is used. N as a metal film
Various metal films such as NiCo plating and Pt plating can be formed in addition to i-plating and Au plating. It is also possible to perform solder plating on the solder ball connection pads 28.

[0017]

According to the plastic package of the present invention, the solder ball connection pad is formed by applying a Cu plating layer of electroless Cu plating or electrolytic Cu plating on the wall surface of the through hole, and filling the through hole with a conductive paste. ,
Since the metal film is applied to the position of the opening of the through hole, the electroless Cu plating and the electrolytic Cu plating only need to be performed once, and the Cu thickness can be set thin. Therefore, since a sophisticated pattern can be obtained, it is possible to cope with high performance and miniaturization of a semiconductor element requiring a high density wiring pattern. Further, there is no occurrence of defects such as disconnection of the wiring pattern and short circuit. Furthermore, since there is no need for polishing work for thinning the Cu layer, an inexpensive plastic package can be provided.

According to a second aspect of the present invention, there is provided a method for forming a solder ball connection pad on a through-hole, the method comprising: forming a through-hole in a copper-clad resin substrate; A step of applying electroless Cu plating and electrolytic Cu plating to the surface and the wall surface of the through-hole, a step of filling the through-hole for the solder ball connection pad with a conductive paste and curing, and a step of applying a solder ball to the surface of the copper-clad resin substrate A step of forming a wiring pattern including connection pads, a step of forming a solder resist pattern in necessary locations including solder ball connection pads, and a step of applying a metal film to required locations excluding solder ball connection pads. Therefore, electroless Cu plating and electrolytic Cu plating only need to be performed once, and the thickness of the Cu layer is not increased. There is no reduction in the pattern resolution of over emissions and the solder ball connection pad. Therefore, a fine pattern can be obtained, and a plastic package capable of responding to high performance and miniaturization of a semiconductor element requiring a high density wiring pattern can be manufactured. Further, since no disconnection or short circuit of the wiring pattern occurs, the yield does not decrease. Further, there is no need to polish the Cu layer, and the production efficiency is not reduced. In addition, it is possible to provide a method of manufacturing a plastic package which does not need to attach a Cu foil in an intermediate step and does not require any special technique.

[Brief description of the drawings]

FIGS. 1A and 1B are a side sectional view of a plastic package and a partially enlarged side sectional view of a solder ball connection portion according to an embodiment of the present invention, respectively.

FIG. 2 is a partially enlarged side sectional view for explaining a method of manufacturing a plastic package according to one embodiment of the present invention.

FIG. 3 is a partially enlarged side sectional view for explaining a method of manufacturing a conventional plastic package.

FIG. 4 is a partially enlarged side sectional view for explaining a method of manufacturing another conventional plastic package.

[Explanation of symbols]

10: plastic package, 11: copper-clad resin substrate, 12: solder ball, 13: solder resist, 1
4: semiconductor element, 15: bonding wire, 16: sealing resin, 17: solder resist, 18: solder resist, 21: Cu foil, 22: through hole, 23: electroless Cu plating, 24: electrolytic Cu plating, 25 : Conductive paste, 26: etching resist, 27: opening, 2
8: Solder ball connection pad, 29: Ni plating, 30:
Au plating

Claims (2)

[Claims] 1. A plastic package in which a solder ball connection pad is formed at an opening position of a through hole in a copper-clad resin substrate, wherein the through hole is filled by electroless Cu plating on a wall surface. It is performed by filling a conductive paste into the inside of the through hole where the Cu plating layer made of electrolytic Cu plating is formed,
In addition, the solder ball connection pad is composed of an exposed surface of the conductive paste and a part of a wiring pattern formed therearound, and the solder ball connection pad is further provided with a metal film. And plastic package. 2. A method of manufacturing a plastic package in which a solder ball connection pad is formed on a through-hole filled in a hole of a copper-clad resin substrate, wherein the step of piercing the through-hole in the copper-clad resin substrate includes the steps of: A step of applying electroless Cu plating and an electrolytic Cu plating on the surface of the resin substrate and the wall surfaces of the through holes, a step of filling the through holes for the solder ball connection pads with a conductive paste, and curing, and A step of forming a wiring pattern including the solder ball connection pads on the surface of the resin substrate; a step of forming a solder resist pattern in necessary places excluding the solder ball connection pads; A method for manufacturing a plastic package, comprising: a step of applying a metal film.