JP2003249587A - Method and structure of nickel/gold electroplating for contact pad of chip package substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a structure for nickel/gold electroplating a contact pad of a chip package substrate. <P>SOLUTION: The surface of a substrate patterned to demarcate a circuit layer is covered with a conductive film. Then, a photoresist layer is formed on the surface of the substrate to cover the substrate. A hole is formed in the photoresist layer to expose the circuit layer to allow the circuit layer to serve as a contact pad region. Part of the conductive film not covered by the photoresist layer is removed. Another photoresist layer is formed on the surface of the substrate to cover the remaining part of the conductive film exposed from the previously formed photoresist layer. Then, nickel/gold electroplating is conducted on the contact pad of the substrate to form a nickel/gold electroplating layer on the entire surface of the contact pad. Then, the photoresist layer and the conductive film covered by the photoresist layer are removed. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nickel / gold electroplating method and structure for contact pads of a chip package substrate, and more particularly to a bonding pad (or bonding finger) or a solder ball pad of a semiconductor chip package substrate. The present invention relates to a contact pad, and a method and a structure for performing nickel / gold electroplating on the outer surface of the contact pad.

[0002]

2. Description of the Related Art With the progress of electronic industry related technology and the trend toward miniaturization of electronic products, manufacturers of semiconductor chip package substrates (or IC carriers) have come to encounter many process bottlenecks. Among them, a contact pad extended from a conductive circuit is formed on the surface of the substrate to serve as a transmission means for electronic signals or power.
The upper surface of the contact pad is nickel / gold (Ni / A
u) layer. Such contact pads are
If it is a bonding pad of a semiconductor chip package substrate, that is, the pad surface is covered with a nickel / gold layer, and at the time of chip package wire bonding, both the gold wire and the bonding pad of the substrate are made of gold, and both are electrically connected. Considered to be advantageous. Also, when these contact pads are used as solder ball pads on the package substrate,
The surface of the pad is coated with a nickel / gold layer to prevent the conductive pad body (usually copper) of the solder ball pad from being easily oxidized by the influence of the external environment, thus improving the electrical connection quality of the solder ball implantation.

FIG. 1 is a view showing a structure in which a nickel / gold layer is electroplated on a contact pad of a semiconductor chip package substrate which is generally used in the industry. The substrate 1 that has been subjected to the previous process and is to be used for a chip package has already patterned upper and lower circuit layers 11 and 12, and some conductive holes 13 (P.
TH) or blind holes (Blind via) are formed,
In addition, the substrate 1 is formed by a method such as lithography and etching.
A small number of contact pads 10 (bonding pads or solder ball pads) are defined, and the outer surface of the substrate 1 is covered with a solder prevention layer 14.

The contact pad 10 provided on the substrate 1 shown in FIG.
The gold layer 16 is electroplated. However, in order to form this structure, it is necessary to lay out many electroplating conductive wires 15 on the substrate 1 and electroplat the nickel / gold layer 16 on the contact pads 10 using the electroplating conductive wires. Therefore, although the nickel / gold structure is formed on the contact pad 10, many electroplated conductors laid out must be electroplated, which occupies the area on the substrate 1 and reduces the circuit layout area. Not only that, when using high frequency, noise is likely to occur due to the antenna effect of the extra electroplating conductor. Even if the electroplating 15 is cut off by the etch back method, the rear end portion of the conductor remains. Therefore, although the structure of the nickel / gold layer is formed on the contact pad 10 on the substrate, there is also a disordered structure at the rear end of the conductor. Naturally, there was still a problem that the circuit layout area was reduced and noise was likely to be generated when high frequency was used.

The industry provides another improvement technique for this problem. So-called GPP (Gold
Pattern Plating) step. See Figures 2-5. Some through holes (PTH) or blind holes may be formed in the substrate (not shown).

Subsequently, the conductive layer 21 of the substrate 2 is covered with a photoresist layer 22, respectively. This photoresist layer 2
2 exposes the area of the circuit to be formed having holes, and the nickel / gold layer 23 is electroplated on the portion of the conductive layer 21 not covered by the photoresist 22. This is as shown in FIG.

The photoresist layer 22 is then removed, leaving the nickel / gold layer 23 as shown in FIG.

Finally, using the nickel / gold layer 23 as a photoresist agent, the conductive layer 21 is patterned into a circuit pattern by using a method such as lithography and etching to define the circuit layer 25, and the nickel / gold layer is formed on the upper surface of the circuit layer 25. Layer 23 is plated and as shown in FIG. 5, its implementation on a semiconductor chip package substrate is as shown in FIG.

Although this known technique does not require the layout of electroplating conductors separately, it does not require the entire circuit layer 25 of the substrate 2.
Both upper surfaces (including contact pads 26 and all conductive circuitry) were coated with a single nickel / gold layer, and the nickel / gold layer material was quite expensive, apparently wasting large amounts of manufacturing costs. Further, in the above-mentioned portion where the circuit layer 25 is used as the contact pad 26, the contact pad material is copper, which is simply covered with the nickel / gold layer 23 on the upper surface, and the other portion where the contact pad is used as the bonding pad. Is exposed on both side wall surfaces and is nickel /
When the substrate is used for chip package wire bonding, the electrical connection between the gold wire and the bonding pad is easily affected, because the gold surface is not covered with the gold layer and the gold surface is insufficient or oxidizes due to corrosion of the outside. Also, the circuit layer 25
The surface of the conductive circuit of is covered with a nickel / gold layer 23, which does not achieve stable adhesion with the solder prevention layer 27 covering the surface of the substrate due to the difference in material characteristics between the two and forms a defect of poor reliability. It's easy to do.

[0010]

Therefore, the present invention provides a method and structure for nickel / gold electroplating of contact pads of a chip package substrate. The method of the present invention comprises a separate electroplating conductor on the surface of the substrate. No need to lay out, greatly reduce the electroplating conductor layout area and increase the conductive circuit layout area. other than this,
The outer surface of the contact pad of the present invention is completely covered with a nickel / gold layer, and when chip package wire bonding is performed on a substrate, the electrical connection between the gold wire and the contact pad affects the electrical connection quality of the contact pad due to oxidation. It is supposed to be able to prevent giving.

The main object of the present invention is to provide a method of electroplating nickel / gold of a contact pad of a chip package substrate, wherein the nickel / gold electroplating process of the contact pad of the substrate is performed on the surface of the substrate. There is no need to lay out electroplating conductors, which significantly increases the effective layout area and reduces noise interference caused by the electroplating conductor layout.

Another object of the present invention is to provide a nickel / gold electroplating method for a contact pad of a chip package substrate, which is effective without electroplating the nickel / gold layer on the entire circuit layer. Nickel /
The cost of gold layer electroplating can be reduced.

Another object of the present invention is to provide a nickel / gold electroplating structure for a contact pad of a chip package substrate, wherein the outer surface of the contact pad is completely covered with a nickel / gold layer, When the chip package wire bonding is performed on the substrate, the gold wire is electrically coupled to the contact pad, and the contact pad is protected to prevent the electrical connection quality of the contact pad from being affected by three times.

[0014]

SUMMARY OF THE INVENTION The invention of claim 1 provides a nickel / gold electroplating structure for contact pads of a chip package substrate having a substrate with patterned and circuit layers with some contact pads. The outer surface of the contact pad of the substrate is completely covered with a nickel / gold layer, and the substrate is free of electroplated conductors which are separately laid out to be nickel / gold electroplated contact pads. And the nickel / gold electroplating structure of the contact pad of the chip package substrate. The invention of claim 2 provides the nickel / gold electroplating structure of the contact pad of the chip package board according to claim 1, wherein the contact pad is a bonding pad or a solder ball pad of the board. The invention of claim 3 is
(A) providing a substrate on which circuits are patterned to define circuit layers, and the surface of the substrate is covered with a conductive film; (b)
A first photoresist layer is formed on the surface of the substrate covered with the conductive film, and the photoresist layer has openings, and the portion exposed below the openings and covered with the conductive film serves as a partial circuit layer in the contact pad region. Forming step, (c) removing the conductive film not covered with the first photoresist layer, (d) forming a second photoresist layer on the substrate, and leaving the second photoresist layer in the first photoresist layer opening area. Coating a conductive film, (e) performing nickel / gold electroplating on the substrate, and then electroplating a nickel / gold layer on the entire surface of the contact pad, (f) photoresist layer and the conductive film covering the same Removing steps,
(G) A step of coating the surface of the substrate with a solder prevention layer, and the steps (a) to (g) above are included in the nickel / gold electroplating method for contact pads of a chip package substrate. The invention of claim 4 is
The nickel / gold electroplating method for a contact pad of a chip package substrate according to claim 3, wherein the contact pad is a bonding pad or a solder ball pad of the substrate. Claim 5
4. The invention according to claim 3, wherein the conductive film is composed of tin, copper, chromium, palladium, nickel, tin / lead, or an alloy thereof, nickel // of a contact pad of a chip package substrate according to claim 3. The gold electroplating method is used.

[0015]

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a method and structure for nickel / gold electroplating of contact pads of a chip package substrate. The structure described in the present invention is a substrate having a circuit layer with patterned circuits. The circuit layer comprises some contact pads, the outer surface of the contact pads of the substrate is completely covered with a nickel / gold layer, and the substrate is not laid out with the electroplated conductors of the contact pads.

The structure described in the present invention is completed by the following examples. (A) A substrate is provided in which a circuit is patterned to define a circuit layer, and a surface of the substrate is provided with a conductive film (Conductive F).
ilm). (B) A first photoresist layer is formed on the surface of a substrate coated with a conductive film, and the photoresist layer has an opening, and the portion exposed below the opening and covered with the conductive film serves as a partial circuit layer in the contact pad region. Eggplant (C) The uncoated conductive film is removed by the first photoresist layer. (D) A second photoresist layer is formed on the substrate, and the second photoresist layer covers the conductive film remaining in the first photoresist layer open area. (E) Nickel / gold electroplating is performed on the substrate, and a nickel / gold layer is electroplated on the entire surface of the contact pad. (F) The photoresist layer and the conductive film covering it are removed. (G) Cover the substrate surface with a solder prevention layer.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The present invention provides a nickel / gold electroplating method and structure for a contact pad of a chip package substrate. 7 to 14 show a nickel / gold electroplating method and structure of a contact pad of a chip package substrate according to an embodiment of the present invention.

First, a single-layer or multi-layer substrate 100 is provided. The substrate 100 has already undergone the necessary pre-process, and for example, some through holes PTH or blind holes are formed.
In addition, the substrate 1 is formed by a method such as lithography and etching.
00 patterned circuit to define circuit layer 105. This is as shown in FIG.

Subsequently, as shown in FIG.
The surface of is covered with the conductive film 110. The conductive film 110 serves as a current conduction path for the electroplating process described later, and it is composed of a conductive thin film such as tin, copper, chromium, palladium, nickel, tin / lead material or alloy thereof. The conductive film 110 is not limited to the above-mentioned materials, and any metal material having conductivity can be used, and the conductive film 110 is formed by a method such as sputtering, electroless plating, physical or chemical deposition.

A first photoresist layer 115 is formed on the surface of the substrate covered with the conductive film 110. The photoresist layer has an opening 1151 to expose a part of a circuit layer in a contact pad region covered with the conductive film 110, the contact pad region including one or a plurality of contact pads 1051.

The conductive film not covered with the first photoresist layer 115 is removed by an etching technique. At this time, a part of the conductive film 1102 remains on the bottom edge of the opening 1151 area of the photoresist layer. This is as shown in FIG.

Further, a second photoresist layer 120 is formed on the substrate 100. This photoresist layer covers the conductive film 1102 remaining in the first photoresist layer openings 1151 areas, and as shown in FIG. This is to prevent gold from being electroplated and causing a short circuit condition in the circuit of the substrate.

Subsequently, a nickel / gold layer is formed on the substrate 100 by electroplating. The conductive film 110 is formed of a conductive material, and the nickel / gold layer 12 is formed when electroplating.
5 is formed by electroplating the conductive film 110 on the surface of each contact pad 1051.
The outer surface of 051 is electroplated with a nickel / gold layer 125. This is as shown in FIG.

Subsequently, the second photoresist layer 120 and the first photoresist layer 120
The photoresist layer 115 and the conductive film 110 covering it are removed, and the nickel / gold layer 125 electroplating structure of the contact pad 1051 of the substrate 100 is completed. The nickel / gold layer 125 was electroplated on the entire outer surface of the contact pad 1051 of the circuit layer 105, as shown in FIG.

Finally, the surface of the substrate 100 is coated with a solder prevention layer 130, which is used as a solder mask, for example, to complete the surface protection of the substrate 100, as shown in FIG.

In the nickel / gold electroplating method and structure of the contact pad of the chip package substrate of the present invention, the contact pad is, for example, a bonding pad or a solder ball pad in the semiconductor chip package substrate. Contact pad 10
51 is shown, the actual contact pad quantity and photoresist layer are distributed on the substrate according to the process required of the actual product, and the process and structure are performed on a single side of the substrate or both sides of the substrate. It is possible. In addition to the contact pads described in the embodiments of the present invention, the nickel / gold electroplating structure can be formed by the process described in the present invention in any portion where the nickel / gold layer electroplating process needs to be performed on the substrate. In addition, the present invention can be applied to the manufacture of a general pringo board in which electronic components are assembled on the second layer, which can be understood by a person having ordinary knowledge in the field to which the technology of the present invention belongs. , Description is omitted.

[0027]

In summary, the nickel / gold electroplating method and structure of the contact pads of the chip package substrate of the present invention makes each contact pad on the substrate conductive by using the conductive film as a current conduction path, which is formed on the surface of the substrate. It is possible to effectively save the electroplating conductor layout area and increase the conductive circuit layout area, and to prevent the noise interference that is likely to occur in the electroplating conductor layout of the substrate, since a separate step of laying out the electroplating conductors is unnecessary. Also, there is no need to electroplate nickel / gold layers over the entire circuit layer, effectively saving nickel / gold costs. In addition, the outer surface of the contact pad is completely covered with a nickel / gold layer, which assists the electrical connection of the gold wire to the contact pad when the chip package wire bonding is performed on the substrate, and improves the electrical connection quality of the contact pad by oxidation. The influence can be prevented.

The above description is for explaining the present invention and does not limit the scope of the present invention, and any modification or alteration of details that can be made based on the present invention belongs to the scope of claims of the present invention. I shall.

[Brief description of drawings]

FIG. 1 is a view showing nickel / gold electroplating of a contact pad of a known chip package substrate.

FIG. 2 is a view showing nickel / gold electroplating of contact pads of another known chip package substrate.

FIG. 3 is a view showing nickel / gold electroplating of contact pads of another known chip package substrate.

FIG. 4 is a view showing nickel / gold electroplating of contact pads of another known chip package substrate.

FIG. 5 is a view showing nickel / gold electroplating of contact pads of another known chip package substrate.

FIG. 6 is a view showing nickel / gold electroplating of contact pads of another known chip package substrate.

FIG. 7 is a schematic view showing the nickel / gold electroplating method of the contact pad of the chip package substrate of the present invention.

FIG. 8 is a schematic view showing the nickel / gold electroplating method of the contact pad of the chip package substrate of the present invention.

FIG. 9 is a schematic view showing the nickel / gold electroplating method of the contact pads of the chip package substrate of the present invention.

FIG. 10 is a schematic view showing the nickel / gold electroplating method of the contact pad of the chip package substrate of the present invention.

FIG. 11 is a schematic view showing the nickel / gold electroplating method of the contact pad of the chip package substrate of the present invention.

FIG. 12 is a schematic view showing the nickel / gold electroplating method of the contact pad of the chip package substrate of the present invention.

FIG. 13 is a schematic view showing the nickel / gold electroplating method of the contact pads of the chip package substrate of the present invention.

FIG. 14 is a schematic view showing the nickel / gold electroplating method of the contact pads of the chip package substrate of the present invention.

[Explanation of symbols]

1,2,100 substrate 10,1051 contact pad 11 Upper circuit layer 12 Lower circuit layer 13 Conduction hole 14, 27, 130 Solder prevention layer 15 Electroplating conductor 16,23,125 Nickel / Gold layer 22 Photoresist layer 25, 105 circuit layers 28 chips installation area 110 conductive film 1102 Conductive film residual exposed portion 115 First Photoresist Layer 1151 Opening of photoresist layer 120 Second photoresist layer

Claims (5)

[Claims] 1. A nickel / gold electroplated structure of a contact pad of a chip package substrate having a substrate which is patterned and comprises a circuit layer with some contact pads, wherein the outer surface of the contact pad of the substrate is completely Nickel in a contact pad of a chip package substrate, characterized in that it is covered with a nickel / gold layer and the substrate is laid out separately without electroplating conductors being nickel / gold electroplated contact pads. / Gold electroplating structure. 2. The nickel / gold electroplating structure of a contact pad of a chip package substrate according to claim 1, wherein the contact pad is a bonding pad or a solder ball pad of the substrate. 3. A step of: (a) providing a substrate on which a circuit is patterned to define a circuit layer, and coating the surface of the substrate with a conductive film; (b) providing a first photoresist layer on the surface of the substrate coated with the conductive film. And forming the photoresist layer with apertures,
Forming a portion of the contact pad region exposed under the opening and covered with a conductive film as a partial circuit layer; (c) removing an uncoated conductive film with a first photoresist layer; (2) forming a photoresist layer and covering the conductive film remaining in the first photoresist layer opening with the second photoresist layer, (e) performing nickel / gold electroplating on the substrate, and covering the entire surface of the contact pad A step of electroplating a nickel / gold layer on the substrate, (f) a step of removing the photoresist layer and a conductive film covering the photoresist layer, (g) a step of coating the substrate surface with a solder prevention layer, and the steps (a) to (g) above. A method of electroplating nickel / gold on a contact pad of a chip package substrate, the method comprising: 4. The method of electroplating nickel / gold of a contact pad of a chip package substrate according to claim 3, wherein the contact pad is a bonding pad or a solder ball pad of the substrate. 5. The nickel of a contact pad of a chip package substrate according to claim 3, wherein the conductive film is composed of tin, copper, chromium, palladium, nickel, tin / lead or an alloy thereof. / Gold electroplating method.