JPS6059307B2 - Partial plating device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a partial plating apparatus for plating a plating area thickly at the center and thinly at the periphery.

In a lead frame for a resin-sealed semiconductor device, the semiconductor element mounting part and the wire bonding part are plated with Au or Ag.

An example of an apparatus for performing such partial plating is the apparatus described in Japanese Patent Publication No. 49-24775. FIG. 1 shows an enlarged view of the main parts of such a conventional plating apparatus. That is, in FIG. 1, the material to be plated 1 is placed in close contact with a mask 2, the material to be plated 1 is held down by a pressing plate 3, and the plating solution is supplied from a nozzle 4 which also serves as an anode placed below the material to be plated. At the same time, the material to be plated 1
Plating is performed by passing a direct current through the nozzle 4. In such a plating apparatus, the semiconductor element mounting part 1a and the plurality of wire bonding parts 1b of the material to be plated 1 are damaged.
can be plated with almost uniform thickness. However, in recent years, the prices of Au, Ag, etc. have increased, and the plating thickness has been reviewed due to the need to reduce costs, and it has been confirmed that there is no problem with the plating thickness of the wire bonding part being about half of the conventional plating thickness. However, as shown in FIG. 2, in order to apply plating with different thicknesses to the semiconductor element mounting part 1a and the wire bonding lb of the material 1 to be plated, the conventional partial plating apparatus requires two types with different plating areas. The plating operation must be performed twice: first, the plating area including the wire bonding part lb is thinly plated, and then only the semiconductor element mounting part 1a is plated, which reduces the overall cost. The disadvantage is that it is expensive. The present invention solves these problems by providing a mask plate close to the material to be plated, which has an opening smaller than the plating area in the center and at least one small hole in each of the four corners of the plating area. By arranging the plates so that the plating area is thick, the semiconductor element mounting area can be thickly plated, and the wire bonding area can be plated thinly, in one plating operation. An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 3 is an enlarged view of essential parts showing an embodiment of the partial plating apparatus of the present invention, and the same parts as in FIG. 1 are given the same reference numerals. In the figure, a mask plate 5 is held between a mask 2a and a mask 2b that define a plating area. An opening 5a is provided in the center of the mask plate 5, and the size of the opening 5a is approximately matched to the size of the semiconductor element mounting portion 1a, and a small hole 5b is formed around the opening 5a. is provided so that the air that existed before the plating solution was sprayed can be smoothly discharged from this small hole 5b.

Regarding the distance between the mask plate and the plated material 1, if the distance is too small, the plating thickness of the wire bonding part 1b will be too thin, and if it is too large, the plating thickness of the semiconductor element mounting part 1a will be too thin.
The difference in the plating thickness between the wire bonding portion 1b and the wire bonding portion 1b becomes small, and the effect of material saving is not fully exhibited. Therefore, taking this point into account, they should be placed appropriately close to each other. The result of the experiment is about 1T.
It is appropriate to make it close to about W1. Also, small hole 5
b becomes the outlet for the plating solution after exhausting the air, so
This affects the plating thickness of the wire bonding portion 1b.
Therefore, in order to vent air, it is necessary to provide at least one small hole 5b at a location corresponding to the four corners of the plating area, but if the small hole 5b is made too large, a large amount of plating solution will be supplied to the wire bonding part 1b. Therefore, the plating thickness becomes thicker in the area along the flow of the plating solution. Therefore, variations in the plating thickness of the wire bonding portion 1b become large.
Taking this point into consideration, small holes 5b are appropriately provided at the four corners. As a result of experiments, it was found that the appropriate size of each small hole 5b was approximately one screen in diameter. Note that if the number of small holes 5b of this size is further increased, the plating thickness of the wire bonding part 1b will become thicker, so when increasing the number of small holes 5b, the total opening area of the small holes 5b is four. Almost. It is necessary to make it smaller so that it does not change. Mask plate 5 as above
By providing this, the semiconductor element mounting portion 1a can be plated thickly, and the wire bonding portion 1b can be plated to a thickness of about 112 mm. In this embodiment, a case has been described in which the nozzle 4 is also used as an anode.

In this case, the nozzle 4 is usually made of platinum or titanium coated with platinum, but the nozzle 4 may also be made of a non-conductive material and provided with a separate anode. The anode is indicated by a broken line in FIG. 3, and is made of platinum wire mesh. The platinum mesh for the anode 6 is suitably about 30 mesh; if the opening is too large, the plating surface will become grid-like; if the opening is too small, passage of the plating solution will be hindered. However, by providing the anode separately in this way, the nozzle 4 can be manufactured in any shape. That is, the nozzle 4 may be constructed of a non-conductive material with the conventional shape, or may be simply a non-conductive plate with plating solution ejection holes. Although the above description is about a lead frame, the partial plating apparatus of the present invention is not limited to this, and can be widely applied to the production of materials that need to have a thick plating layer in the center and a thin plating layer in the periphery. It is something. If the plating area is nearly circular, the small holes in the mask plate may be provided at at least four locations at approximately equal intervals around the periphery of the plating area. As described in detail above, according to the present invention, it is possible to plate thickly at the center and thinly at the outer periphery in one plating operation, which has the effect of reducing overall lead frame manufacturing costs, for example.

[Brief explanation of the drawing]

Figure 1 is an enlarged cross-sectional view of the main parts of a conventional partial plating device;
The figures are cross-sectional views of partial plating with different thicknesses, and FIG. 3 is an enlarged cross-sectional view of essential parts showing one embodiment of the partial plating apparatus of the present invention. 1... Material to be plated, 1a... Semiconductor element mounting part, 1b... Wire bonding part, 2, 2
a, 2b...Mask, 3...Press plate,
4...Nozzle, 5...Mask plate, 5a.
...Opening, 5b...Small hole.

Claims (1)

[Claims] 1. In a partial plating device equipped with a nozzle that sprays plating solution from below onto the material to be plated, a mask that closely contacts the material to be plated to define the plating area, and a press plate that presses the material to be plated from above, A partial plating apparatus characterized in that a mask plate having an opening smaller than the plating area in the center and at least one small hole in each of the four corners of the plating area is arranged close to a material to be plated.