JPH02115389A - Partial plating device - Google Patents

Abstract

PURPOSE:To form plating films of a uniform thickness on both the front and rear sides of a body to be plated by placing a nozzle opposite to one side of the body having gaps and placing an auxiliary electrode opposite to the other side. CONSTITUTION:A plating soln. is jetted from a nozzle 2 toward the under side of a lead frame 1 for a semiconductor device. The jetted plating soln. passes through the gaps 9 in the lead frame 1, reaches the upper side of the lead frame 1 and is continuously circulated. DC power sources 7, 8 are then switched on to apply separate voltages on the lead frame 1, the nozzle 2 and an auxiliary electrode 5. Plating films of a uniform thickness can be formed on both sides of the lead frame 1 by regulating the quantity of electric current flowing between the lead frame 1 and the electrode 7 to 20-50% of that of electric current flowing between the lead frame 1 and the nozzle 2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a partial plating apparatus, and more specifically, it is capable of simultaneously partial plating both the front and back surfaces of an object to be plated having a gap, such as a lead frame for a semiconductor device. The present invention relates to a partial plating device for performing plating.

[Prior art] Conventionally, C has been used as a lead frame material for semiconductor devices.
U alloy, Fe-Ni alloy, etc. are used in lead frames for semiconductor devices, and Ag plating is applied at least to the semiconductor element joints and inner leads, and in some cases, Ag plating is applied to the entire surface of the lead frame. It had been.

In contrast, the inventors of the present application partially plated both the front and back surfaces of the actor lead portion with Sn or Sn alloy, and partially plated the front and back surfaces of the semiconductor element portion and the wiring portion with Ag, and Between the Sn alloy plated part and the Ag plated part (
We proposed a lead frame for semiconductor devices in which Cu plating containing Ag was applied to the discontinuous portions (Japanese Patent Application No. 63-1).
36863), l Conventionally, the following 2 fI methods have been common as methods for selectively plating Sn or Sn alloy on both surfaces of the outer lead portion.

The first method is to use the semiconductor device lead frame 1 as a cathode, the nozzle as an anode, and plate the back surface by passing the plating solution sprayed from the nozzle through the gap of the semiconductor device lead frame.

The second method is a method in which a single-sided partial plating device is used, and both sides are plated through two steps for each side.

However, each of these methods had the following problems.6 Regarding the first method, the side of the object to be plated (lead frame for semiconductor device) that faces the nozzle is There is a large difference in the plating thickness on the opposite side (i.e., the plating on the facing side is thicker, and the plating on the non-facing side is thinner)
There was a problem with that. For this reason, the yield of manufactured lead frames for semiconductor devices is low, causing high costs.

Regarding the second method, the problem is that productivity is low because each side goes through the process twice, and the sheared surface of the object to be plated is double plated, resulting in thicker plating, resulting in poor yield. The problem of becoming one has been solved. These are both
This was a cause of high costs.

[Problems to be Solved by the Invention] The present invention provides a partial plating device that can make the thickness of the plating on both the front and back sides uniform and can perform partial plating on both the front and back sides at the same time. .

[Means for Solving the Problems] A first gist of the present invention is to provide: means for holding an object to be plated; a nozzle located for spouting a plating solution; and an electric circuit for applying different potentials to the object to be plated and the nozzle; partial plating is applied to both the front and back surfaces of the object to be plated having a gap; A partial-plating device for use in plating, the device having an electrode facing the opposite side of the surface of the object to be plated that faces the nozzle, and applying a different potential to the electrode than that of the object to be plated. A partial plating apparatus is characterized in that it has an electric circuit.

The second gist of the present invention is that in the above partial plating apparatus,
During plating, the ratio of the current value flowing between the electrode and the object to be plated to the value of the current flowing between the nozzle and the object to be plated is 0.2 to 0.5. exists in

[Function] According to the present invention, the nozzle is provided facing one surface of the object to be plated having a gap, and the electrode 8i (hereinafter referred to as auxiliary electrode) is provided facing the surface opposite to the surface facing the nozzle. ), plating can be promoted. In addition, by setting the ratio of the current value flowing between the nozzle and the object to be plated to the current value of the current flowing between the auxiliary electrode and the object to be plated to 0.2 to 0.5, it is possible to The thickness of the plating on both the front and back sides of the plated object can be made uniform.

The inventor of the present application has developed a partial plating device that can simultaneously perform partial plating on both the front and back surfaces of the object to be plated, which has a gap, and that makes the thickness of the plating uniform on both the front and back surfaces. We carried out intensive studies from the aspects of surface and electrolytic conditions.

First, in order to equalize the thickness of the plating on both the front and back surfaces of lead frames for semiconductor devices, etc., we changed the shape of the nozzle and the volume of the gap between the holding plate and the object to be plated. attempted to improve the first method of the conventional partial plating method described above, but concluded that it was difficult to make the thickness of the plating uniform by these improvements.

Next, the inventor of the present application provided an auxiliary electrode facing the surface opposite to the nozzle, and attempted to promote the cleaning of the surface opposite to the nozzle.

The inventor of the present invention initially attempted to accelerate plating by connecting an auxiliary electrode to an electric circuit for applying voltage to the nozzle and the object to be plated. However, in this case, abnormal precipitation occurred in the plating on the side facing the auxiliary electrode, and the thickness of the plating on the side facing the auxiliary electrode became significantly non-uniform.

As a result of repeated studies based on this result, the present inventors found that the thickness of the plating on the side facing the auxiliary electrode can be controlled by the current value of the current flowing between the auxiliary electrode and the object to be plated. It was found that abnormal deposition of plating can be prevented by reducing the current value.

Therefore, in addition to the circuit for applying voltage to the nozzle and the object to be plated, a circuit is installed between the auxiliary electrode and the object to be plated, and the current value of both is controlled individually. It was concluded that the thickness of the plating on both the front and back sides could be made uniform, and that the occurrence of abnormal precipitation could be prevented.

In the present invention, the ratio of the current value of the current flowing between the auxiliary electrode and the object to be plated to the current value of the current flowing between the nozzle and the object to be plated is 0.2 to 0. It is desirable to set it to 5. This is in order to have a good plating appearance and to obtain uniformity of plating thickness on the front and back surfaces of the object to be plated.

If the ratio of current values is 0.5 or more, abnormal precipitation may occur on the surface of the object to be plated on the auxiliary electrode side, and the thickness of the plating becomes too thick. Furthermore, if the ratio of current values is less than 0.2, the effect of the auxiliary electrode will not be sufficiently obtained, and the thickness of the plating on the side of the auxiliary electrode will not be sufficiently thick. Therefore, the ratio of current values will be 0.2. It is most desirable to set it to 0.5.

Note that the apparatus and method according to the present invention can be applied to Sn or Sn.
Not only alloy plating, but also Ni, Ag.

Needless to say, it can also be applied to double-sided partial plating of Cu and alloys thereof.

It is also clear that the present invention can be applied not only to partial plating of lead frames for semiconductor devices, but also to plating of any object with gaps.

[Example] FIG. 1 shows a schematic configuration diagram of an example of a partial plating apparatus according to the present invention.

In FIG. 1, 1 is a lead frame for a semiconductor device; 2 is a lead frame for a semiconductor device;
3 is a nozzle, 3 is a lower mask, 4 is an upper mask, 5 is an auxiliary electrode, 6 is a holding plate, and 7.8 is a DC power source.

Next, the principle of the partial plating apparatus shown in FIG. 1 will be explained. First, the eyelash solution is injected from the nozzle 2. The plating solution injected from the nozzle 2 passes through the lower surface and the gap of the semiconductor device lead frame 1 and reaches the upper surface, and the plating solution is continuously circulated through the DC power source 7.8. O
N, and voltages are applied to the semiconductor device lead frame 1, nozzle 2, and auxiliary electrode 5. At this time, if the current flowing between the semiconductor device lead frame 1 and the auxiliary electrode 5 is 20 to 50% of the current flowing between the semiconductor device lead frame 1 and the nozzle 2, the semiconductor device The thickness of the plating on both sides of the lead frame 1 for use is made uniform.

Next, using the partial plating apparatus shown in FIG.
A case will be described in which partial plating with Sn alloy (here, 5n-Pb) is performed on both the front and back surfaces of a lead frame for a semiconductor device having a shape as shown in the figure.

First, a lead frame for a semiconductor device before plating was subjected to general plating pretreatment of solvent degreasing, alkaline electrolytic degreasing, and pickling, and then plating was performed under the plating conditions shown below.

Plating conditions> Plating bath: Lead S B-HT solder plating bath (manufactured by Kamizai Kogyo Co., Ltd.) Temperature: 20°C Current value: Listed in Table 1 Plating area: 3 cm Plating thickness: 10 μm (adjusted by plating time) ) Next, the appearance of the plating was observed for each test piece after plating, and the plating thickness on the front and back sides was measured using a fluorescent X-ray film thickness meter manufactured by Seiko Electronics Co., Ltd. These results were Shown in Table 1.

No in Table 1, 1. =No, 10 is a test piece related to this example; No, 11. No. 12 is a test piece related to a comparative example. In addition, No, 1 to No.

Among the 10 test pieces, No. 8 to No. 10 are cases where the current value ratio during plating was outside the range of 0.2 to 0.5.

Comparative example, i.e. No, j,! In No. and No. t2, the plating finish appearance was good, but there was a large difference in the plating thickness between the nozzle side and the opposite side.

On the other hand, for Nos., f to No. 10, the difference in plating thickness is small, and especially for No., 1-No., and 7, the appearance of the plating finish is good, and there is almost no difference in the plating thickness on both sides. I couldn't.

[Effects of the Invention] As explained above, according to the present invention, it is possible to simultaneously perform partial plating on both the front and back sides of the object to be plated, and to make the thickness of the plating uniform on both the front and back sides. As a result, high-quality plating can be performed at low cost.

Table 1

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an embodiment of a partial plating apparatus according to the present invention, and FIG. 2 is a schematic diagram showing a lead frame for a semiconductor neck which has been partially plated in an embodiment of the present invention. DESCRIPTION OF SYMBOLS 1... Lead frame for semiconductor devices, 2... Nozzle, 3... Lower mask, 4... Upper mask, 5...
Auxiliary electrode, 6... Pressing plate, 7.8... DC power supply, 9
...Gap of lead frame for semiconductor device, 10...
Gap 11... Lead frame body for semiconductor device, 12
...A part partially plated with 5n-Pb.

Claims (2)

[Claims] (1) means for holding the object to be plated; a nozzle for spouting a plating solution, located facing one surface of the object to be plated held by the means for holding the object; A partial plating apparatus for selectively plating both the front and back surfaces of the object to be plated having a gap, the device having: means for applying different potentials to the object to be plated and the nozzle; What is claimed is: 1. A partial plating apparatus comprising: an electrode facing the surface opposite to the surface facing the object; and means for applying a potential different from that of the object to be plated to the electrode. (2) During plating, the ratio of the current value flowing between the electrode and the object to be plated to the value of the current flowing between the nozzle and the object to be plated is 0.2 to 0.5. The partial plating apparatus according to claim 1, characterized in that: