JPH0352552B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for partially plating a metal plate such as a lead frame.

In lead frames for semiconductor devices, it has become common to plate only the semiconductor element bonding portions and inner lead portions with gold, silver, or the like. FIG. 1 shows a sectional view of a main part of a conventional device used for such partial plating. As shown in the figure, a nozzle 2 that injects plating liquid from below onto the material 1 to be plated, a mask plate 3 having an opening 3a shaped to closely contact the material 1 to be plated and define a plating area, and this mask plate 3. Opening 4 with approximately the same shape as the supporting plating area
The mask supporting plate 4 has a shape of 1.a, and a pressing plate 5 that presses the material 1 to be plated from above.An elastic plate 6 is usually attached to the lower surface of the pressing plate 5. Then, the material 1 to be plated is accurately placed on the mask plate 3 using the guide pin 7, the press plate 5 is lowered to press the material 1 to be plated against the mask plate 3, and the plating liquid is sprayed from the nozzle 3 at the same time (not shown). Plating is performed by passing electricity between the insoluble anode and the material 1 to be plated. However, in such a configuration, if the amount of plating liquid injected from the nozzle is small, the plating thickness within the plating area may become uneven. The reason for this is that the plating liquid injected from the nozzle 2 forms a liquid column that collides with the material to be plated and spreads in all directions, but when current flows through this liquid column, the electrical resistance increases in the vicinity of the plating area where it spreads towards the end. This is considered to be because the amount of electrodeposition decreases. If the plating thickness is too thin, it will interfere with use, so this part will be plated to the required thickness, but other parts will be plated to a thickness greater than necessary, wasting precious metals and This will result in an increase in the price of metsuki. It is thought that this cause can be solved by filling the space between the nozzle tip and the material to be plated with plating liquid, but this would require a larger plating liquid supply pump, which would increase the equipment cost. This also has disadvantages such as increased electricity costs.

In order to ensure a uniform plating thickness and reduce the plating price without increasing the size of the plating liquid supply pump, the present invention provides an opening around the nozzle tip and an opening in the mask support plate as a plating liquid discharge port. A narrow annular gap is formed by bringing the inner surface of the nozzle close to the inner surface of the nozzle, so that the space between the nozzle tip and the material to be plated is filled with plating liquid. An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 2 is a cross-sectional view of a main part of an embodiment of the partial plating apparatus of the present invention, which is particularly adapted to be modified from the apparatus shown in FIG. 1. As shown in FIG. 2, an adjustment plate 8 having a circular opening is fitted into the opening 4a of the mask support plate 4, and an auxiliary cylinder 9 is inserted into the tip of the nozzle 2 to adjust the height of the nozzle 2. , and an annular gap 10, ie, an outlet, is formed between the cylinder 9 and the adjustment plate 8 when viewed from above.

In this way, the plating liquid injected from the tip of the cylinder 9 fills the space between the cylinder 9 and the material to be plated 1, and then is discharged from the annular gap 10. As a result of the experiment, the variation in plating thickness was significantly improved, and it was confirmed that there was no need to increase the size of the plating liquid supply pump. As a result of experiments with various opening dimensions of the adjusting plate 8, it was confirmed that the plane area of the gap 10 should be about 0.5 to 10 times the discharge area of the nozzle tip. If this ratio is too small, the amount of plating liquid discharged will be too small, and the amount of plating liquid injected will be reduced, resulting in a reduced stirring effect of the full plating liquid, resulting in burnt plating or uneven plating.
Needless to say, if this ratio is too large, it will not be possible to fully fill the plating solution. Practically speaking, it is better to increase it by 1 to 5 times.

The partial plating device of the present invention is not limited to the embodiment shown in FIG. 2. For example, as shown in FIG. 3, the adjustment plate 8 shown in FIG. Alternatively, as shown in FIG. 4, a mask support plate 4 may be provided with a nozzle 2, a gap 10, and a discharge passage 11.

In short, the present invention brings the circumference of the nozzle tip close to the inner surface of the opening of the mask support plate to form a narrow annular gap 10, so that the gap between the nozzle tip and the material to be plated is filled with plating liquid. It's enough. Note that the annular gap 10 is not limited to an annular shape, and may be formed into a rectangular annular shape if the nozzle tip is a rectangular tube. Also, the gap 10 serving as the plating liquid outlet must be annular, thereby ensuring that the plating liquid flows uniformly over the surface of the plating area.

As described above in detail, the present invention has the effect of almost completely eliminating the problem of non-uniform plating thickness.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a main part of a conventional partial plating apparatus, and FIGS. 2, 3, and 4 are sectional views of main parts of an embodiment of the partial plating apparatus of the present invention. DESCRIPTION OF SYMBOLS 1... Material to be plated, 2... Nozzle, 3... Mask plate, 4... Mask support plate, 5... Pressing plate, 8...
...adjustment plate, 9... cylinder, 10... void.

Claims (1)

[Claims] 1. A nozzle that sprays plating liquid onto the material to be plated from below, a mask plate that closely contacts the material to be plated and defines the plating area, a mask support plate that supports this mask plate, and a pressure plate that presses the material to be plated from above. In a partial plating device equipped with a nozzle liquid discharge port, the periphery of the nozzle tip and the inner surface of the opening of the mask support plate are brought close together to form a narrow annular space, and the space between the nozzle tip and the material to be plated is A partial plating device characterized in that the area is filled with plating liquid.