JPH0618220B2 - Chip on board - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a chip-on-board for mounting a bare chip semiconductor element and performing wire bonding mounting with a bonding wire made of a material such as gold, aluminum or copper. .

(Prior Art) Generally, there is a gold wire as a metal wire for mounting a bare chip semiconductor element by wire bonding. Gold is, of course, expensive, but gold wire is the mainstream of bonding wire because it is superior to other aluminum and copper in stability and reliability of wire bonding. A purity of 99.99% or higher is required as the gold plating for chip on board when wire bonding is performed with this gold wire, and in order to prevent the copper forming the conductor circuit from diffusing into gold, the gold base is In general, a nickel plating layer is formed, and a nickel plating layer is also formed in order to provide hardness during wire bonding.

By the way, an electrolytic plating method is generally used as the plating method for these nickel and gold. In particular, in the case of electrolytic nickel plating, as shown in FIGS.
It is likely to be deposited in abnormal shapes such as squid shoulders (80) and gold balls (90), and the thickness of the electrolytic nickel plating layer (82) varies greatly due to the wiring shape of the conductor circuit (20), resulting in a step between conductors. Occurrence occurs, and as a result, problems such as disconnection of the bonding wire are likely to occur.

In order to solve problems such as variations in the plating thickness of these electrolytic nickel plating layers (82), good results are likely to be obtained by performing electroless plating of nickel, but a general method, namely, When the desired conductor circuit (20) is formed, the solder resist (30) is applied, and then electroless nickel plating and gold plating are performed, there are the following problems.
That is, electroless nickel plating on copper as the conductor circuit (20)
In order to carry out (32), first, it is necessary to make the copper surface a catalytic surface by using palladium or the like as a pretreatment. However, in this catalytic step, a tens of% hydrochloric acid bath is generally used. The solder resist (30) floats up, resulting in defective peeling.

Chip-on-board, which is receiving high reliability every year
In (100), the general method described above, that is, after forming the desired conductor circuit (20) and applying a solder resist (30), electroless nickel plating (32), gold plating (81) When performing, because the base of the solder resist (30) is copper,
Special attention should be paid to corrosion and copper migration.

Further, in the conventional chip-on-board (100), the through-hole copper plating is thinly formed due to the requirement of high-density wiring, so that the dimensional change in the thickness direction of the substrate during heating such as wire bonding may occur. In order to obtain the strength of the through hole of, the nickel plating layer (82) was used for reinforcement,
As shown in FIG. 4, the solder resist (30) for the chip-on-board (100) often forms the solder resist (30) in the through hole (60) in order to meet various application requirements. There is a concern that the through hole (60) will not be nickel plated (82) and its strength may be insufficient.If it is attempted to maintain the strength by thickening the copper plating, the etching accuracy when forming the conductor circuit (20) will be poor. It deteriorates and hinders high-density wiring.

Furthermore, in the case where the solder resist (30) is appropriately formed after the nickel plating (82) and the gold plating (81) are applied to the entire surface of the conductor circuit (20), the conductor circuit which originally does not require gold is used.
Gold plating (81) will also be applied to the part (20), resulting in a significant cost increase.

Therefore, as a result of intensive research conducted by the present inventors to solve the deficiency of the prior art in this type of chip-on-board, electroless nickel plating (32) is applied to the entire surface of the conductor circuit, and then electroless nickel plating is performed. (32) forms a solder resist (30) at a required location on the surface by a known method,
The present invention has been completed by newly discovering that appropriate gold plating gives good results.

(Problems to be Solved by the Invention) The present invention has been made based on the above circumstances,
The problem to be solved is a poor wire bonding property due to the nickel-plated layer for the chip-on-board (100) when performing wire bonding mounting with the gold wire (40), and the chip-on-board (100) itself. Is unreliable.

And the purpose of the present invention is, of course, that the wire bonding property is good, there is no need to worry about solder resist (30) peeling failure, conductor circuit corrosion, copper migration, and moreover, through holes (60) Even if the solder resist (30) is formed, the reliability of the through hole (60) is high.
It is to provide an inexpensive and highly reliable chip-on-board that can be manufactured by using the equipment as it is.

(Means for Solving the Problems) The means adopted by the present invention for solving the above problems will be described with reference to FIG. 1 corresponding to the embodiment, in which “a conductor circuit (20) is formed. In the chip-on-board (100) on which the bare chip semiconductor element (50) and the like are mounted and mounted, the electroless nickel plating (32) is formed on the entire surface of the conductor circuit (20), and the electroless nickel plating (32) The chip-on-board (100) is characterized in that a solder resist (30) is formed on the surface at a required position.

This configuration will be described in more detail with reference to the specific examples shown in the drawings. FIG. 1 shows the chip-on-board (1
00) is shown in vertical section. This chip on board (10
In 0), the conductor circuit (20) is formed, and the electroless nickel plating layer (32) is provided on the entire surface of the conductor circuit (20). Then, a solder resist (30) is formed on a required portion of the surface of the electroless nickel plating (32), and a gold plating (31) is appropriately applied. Here, the gold plating layer (31) is applied only to the terminal (24) portion for mounting the bare chip semiconductor element (50) or the like or for connection such as wire bonding, and these portions do not form the solder resist (30). Of course, it is a part. And electroless nickel plating layer (32)
Is a through hole (60) in which a solder resist (30) is formed, as well as a terminal (24) part for mounting or connecting the above components.
Is formed on the entire surface of the conductor circuit (20) including.

Note that the chip-on-board (100) thus formed is mounted with a bare chip semiconductor element (50) or the like, and is connected by a bonding wire (40) or the like, and then necessary parts are shown by dotted lines in the drawing. As described above, the resin sealing (70) is appropriately performed.

(Operation of the Invention) The present invention has the following effects by adopting the above means.

That is, first, a conductor circuit (20) is formed at a required position on the surface of the electroless nickel plating (32), the electroless nickel plating (32) is applied to the entire surface of the conductor circuit (20), and then a desired solder resist is formed. When (30) is formed by a known method and is appropriately plated with gold, electroless nickel plating (32) is performed in the step before forming the solder resist (30), and naturally the solder resist is used. (30) is not exposed to several 10% hydrochloric acid in the catalytic step. Therefore, the solder resist (30) is not lifted by the hydrochloric acid and is not peeled off. In this case, the type of the solder resist (30) does not need to be particularly excellent in chemical resistance, and a general resist for gold plating bath can be used. Then, the nickel plating method of the present invention is limited to the electroless plating method using a nickel phosphorus bath, and the produced nickel is in an amorphous deposition state, which is stable and thin unlike other plating, and oxidation progresses. By utilizing the property of the oxide film that does not exist, electroless nickel plating (32) is applied to the entire surface of the conductor circuit, and after the solder resist (30) is formed, gold plating (31) is appropriately applied. Even if there is, peeling of the solder resist (30) or peeling of gold may not occur.

In addition to the base of the solder resist (30) of the conductor circuit (20), the through hole (6) covered with the solder resist (30)
Since the electroless nickel plating (32) layer is applied to the entire surface (0), there is no need to worry about copper corrosion or copper migration, which is the conductor circuit (20), and the reliability of the through hole (60) is high. Is also high.

Further, since the nickel plating method is an electroless plating method, variations in the thickness of the nickel plating due to the wiring shape of the conductor circuit are small, and it is difficult for the nickel plating to deposit in an abnormal shape. Therefore, it goes without saying that the wire bonding property is good.

(Example) Next, a chip on board (100) according to the present invention will be described in detail according to an example shown in the drawings.

FIG. 1 shows a chip on board (1 according to an embodiment of the present invention.
00) is shown in vertical section, and this chip on board (10
The conductor circuit (20) of (0) is a known method, a die pad part (23) for mounting the bare chip semiconductor element (50), and a bonding terminal (23) for performing wire bonding connection with the bare chip semiconductor element (50) by a bonding wire (40). The portion 24) and the conductor circuit (20) as an electric circuit and the through hole (60) are appropriately formed as connected or independent. The solder resist (30), the electroless nickel plating (32) and the gold plating (31) are formed in the following process order. That is, first, electroless nickel plating (32) is applied to the entire surface of the conductor circuit (20). Next, the solder resist (30) is formed on the surface of the electroless nickel plating (32) at a necessary place by a known method. And the gold plating layer (3
1) is applied appropriately.

Therefore, the gold plating layer (31) is only a portion where the solder resist (30) is not formed, and the electroless nickel plating layer (32) is applied on the underlying conductor circuit (20) of the gold plating layer (31). Of course, it is also applied on the underlying conductor circuit (20) and the through hole (60) of the solder resist (30).

Note that the chip-on-board (100) thus formed is mounted with a bare chip semiconductor element (50) or the like, and is connected by a bonding wire (40) or the like, and then necessary parts are shown by dotted lines in the drawing. As described above, the resin sealing (70) is appropriately performed.

(Effects of the Invention) As described in detail above, the present invention, as exemplified in the above-described embodiment, "in a chip on board in which a conductor circuit is formed and a bare chip semiconductor element or the like is mounted and mounted, "Electronic nickel plating is formed on the entire surface, and solder resist is formed on necessary parts on the surface of the electroless nickel plating (32)." As a result, there is no need to worry about wire resisting properties, solder resist (30) peeling defects, corrosion of conductor circuit (20), and copper migration. ) Is formed, the through hole (60) is highly reliable, and it is possible to manufacture using the machinery and equipment that have been conventionally adopted as they are. It is possible to provide an inexpensive, highly reliable chip-on-board.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a chip on board according to an embodiment of the present invention. 2 and 3 are vertical cross-sectional views for explaining the problem of the conventional chip-on-board, that is, the squid shoulder and the gold ball, and FIG. 4 is the conventional chip-on-board and the solder. It is a longitudinal cross-sectional view for explaining that there is no nickel layer in a through hole portion where a resist is formed. Explanation of symbols 20 …… Conductor circuit, 30 …… Solder resist, 31 …… Gold plating layer, 32 …… Electroless nickel plating layer, 40 …… Bonding wire, 50 …… Bare chip semiconductor element, 60 ……
Through hole, 70 ... Resin sealing, 80 ... Squid shoulder, 90 ...
… Gold balls, 100… Chip on board.

Claims (1)

[Claims] 1. In a chip-on-board on which a conductor circuit is formed and a bare chip semiconductor element or the like is mounted and mounted, electroless nickel plating is formed on the entire surface of the conductor circuit, and further, on the surface of the electroless nickel plating. A chip-on-board, characterized in that a solder resist is formed in the required areas of.