JPS6124476B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for partially plating punched strips used, for example, in lead frames for semiconductors. Conventionally, partial plating of punched strips was performed using the liquid level adjustment method,
This was done using mechanical masking methods. However, in the case of lead frames for semiconductors, the shape of the punched strip is complicated, and in addition, more complicated partial plating is also required. For example, Fig. 1 shows a part of a punched strip used as a lead frame for semiconductors, but partial plating in areas b or c in this figure can also be done by the liquid level adjustment method. It is. However, partial plating in a range limited to the central portion as shown in a in the figure is impossible in principle. This part a can be fixed, for example, by the commonly used masking tape method. In this way, the plating liquid will enter the tube through the punched holes of the punched strip, causing irregularities at the ends. The spread of plating occurs and cannot be prevented. In addition, the mechanical masking method is a method of pressing with soft rubber or the like, but there are limitations when the strip is thick, and the manufacturing equipment is complicated and requires intermittent feeding. Mechanical masking methods are used for stripe plating, intermittent-feed spot plating, etc., but the biggest drawbacks are poor border finish and expensive equipment, and it is not suitable for strips with complex punched shapes. is not applicable. In view of the above, an object of the present invention is to use a heat-fusible plastic tape and embed the heat-fusible layer in the punched hole portion of a punched strip, thereby achieving a simple operation based on the masking tape method. An object of the present invention is to provide a method for partially plating a punched strip material by which a partially plating material with clear plating boundaries can be obtained. That is, the gist of the present invention is to provide a method for partially plating a rectangular portion of a punched strip formed by punching out a long strip into a rectangular shape. Masking is achieved by heat-pressing the plastic tapes, embedding the heat-adhesive layers of each plastic tape into the punched holes of the strip-shaped parts, and at the same time adhering the heat-sealable layers of the plastic tapes to each other through the punched holes. After masking the circumference of the strip-shaped part to be removed and plating it in this state,
The method of partially plating punched strips is characterized in that the plastic tape is finally removed by heating and softening. Regarding heat-compression bonding of heat-adhesive plastic tape, the heat-adhesive layer of the plastic tape should be sufficiently embedded in the punched holes of the punched strip based on the thickness and shape of the punched strip. It is advisable to determine conditions such as the shape of the plastic tape (particularly the thickness of the heat sealing layer), pressure, temperature, etc. This masking method using masking tape can be performed continuously with the plating process,
This is a very advantageous method. Figure 2 shows a continuous partial plating process.
is a delivery roll, 2 is a thermofusible plastic tape, 3 is a thermocompression roll, 4 is a degreasing process, and 5 is a degreasing process.
6 indicates a pickling process, 6 indicates a nickel plating process, and 7 indicates a silver plating process. Further, 8 is a peeling take-up roll for the tape 2;
indicates a hot air drying process; 10 is a winding roll; 11 is a winding roll;
1 shows a punched copper strip used as a semiconductor lead frame having the shape shown in FIG. <Example 1> In the process shown in FIG. 2, a partially plated copper strip was obtained by not plating only the portion (a) in FIG. was produced under the following conditions.

【table】

[Table] As is clear from Table 1, in this example, a laminate tape of polyethylene tape and polyester tape is used as the heat-adhesive plastic tape 2. Here, the heat-fusible plastic is polyethylene, and the polyester tape functions as a carrier for the heat-fusible plastic (adhesive). In FIG. 2, the polyethylene side of such a heat-fusible plastic tape 2 is adhered to a punched copper strip 1 using a thermocompression roll 3. In this case, the punched copper strip 1
As shown in FIG. 3, the two heat-fusible plastic tapes 2, 2 bonded from both sides of the copper strip 1 have their respective heat-fusible layers of polyethylene 13 embedded in the punched holes of the punched copper strip 11. By adhering the heat-sealing layers to each other through the punched holes, the entire circumference of the strip-shaped portion to be masked is masked. The heat-fusible plastic tape 2 has a punched copper strip 1
The thicker the material 1 is, the thicker the material is required in order to sufficiently embed the heat-sealing layer in the punched hole portion.
If the thickness is too thick, the heat-sealing layer will protrude 14 as shown in FIG. 4, and its optimum thickness is shown in Table 2, for example. In other words, the optimum thickness of polyethylene for the punched copper strip is 1/5 to 1/10, and if it exceeds 1/2, it will protrude 14
If it is less than 1/10, the heat-sealing layer will be insufficiently embedded, resulting in poor masking, and the effect of the present invention will not be sufficiently achieved.

[Table] After masking and plating as described above, hot air is applied to the heat-adhesive plastic tapes 2, 2 that are bonded to each other through the punched holes of the punched copper strip 11 to soften the polyethylene and bond it. The tapes 2, 2 can be peeled off from the punched copper strip 11 by pulling the tapes 2, 2 from both sides with a weakened force. <Example 2> A partially plated copper strip with gold plating was produced in the same manner as in Example 1. As described above, according to the method for partially plating a punched strip of the present invention, two pieces of heat-fusible plastic tape are heat-pressed from both sides of the punched strip, and each is attached to the punched hole portion of the punched strip. By embedding the heat-adhesive layer of heat-adhesive plastic tape and adhering each heat-adhesive layer to each other through the punched hole part, it is possible to perform reliable masking even to the punched hole part of the punched strip. As a result, it is possible to easily obtain an excellent partially plated material with clear plating boundaries using masking tape. In addition, this method allows the masking process to be carried out continuously in synchronization with the plating process by using masking tape, and in addition, it is only necessary to install a thermocompression press or the like on the plating line, so the cost is low. This method is industrially very advantageous because it does not require a lot of work, and has effects such as being extremely economical.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a punched copper strip used as a lead frame for semiconductors, Fig. 2 is an explanatory diagram of an embodiment of the partial plating method of the punched strip of the present invention, and Fig. 3 is an illustration of the main part of the masking part. The enlarged sectional view, FIG. 4, is an explanatory diagram showing an example of a masking state. 1; Delivery roll, 2; Heat-adhesive plastic tape, 3; Thermocompression roll, 4; Degreasing process, 5; Pickling process, 6; Nickel plating process, 7; Silver plating process, 8; Peeling take-up roll, 9 ;Hot air drying process;
10: Take-up roll, 11: Punched copper strip, 12: Polyester, 13: Polyethylene.

Claims (1)

[Claims] 1. In a method of partially plating a strip-shaped part of a punched strip formed by punching a long strip into a strip, two pieces of heat-fusible plastic tape are heat-pressed from both sides of the strip-shaped part. By embedding the heat-adhesive layer of each plastic tape into the punched hole portion of the strip-shaped portion, and at the same time, adhere the heat-sealable layer of the plastic tape to each other through the punched hole portion, the strip-shaped portion to be masked is A method for partially plating punched strips, which is characterized in that the circumference is masked, plating is performed in this state, and then the plastic tape is finally removed by heating and softening.