JP6149268B2 - Lead frame partial plating method - Google Patents

Description

  The present invention relates to a partial plating method for lead frame materials used in transistors and ICs.

  In general lead frames used in transistors and ICs, for example, when silver plating is performed on the lead frame, an elastic sealing material having an opening only at a necessary portion is mechanically pressed onto the lead frame (for example, Patent Document 1), plating is performed.

  However, such a mechanical masking method is practically used for continuous partial plating (stripe plating), intermittent feed partial plating (spot plating), etc., but it is most likely that the finish of the boundary is poor and the apparatus is expensive. It cannot be applied to strips having a complicated punching shape. In addition, the nickel plating used for semiconductor lead frames has a slower deposition rate than silver plating, so that immersion of the plating solution for a long time causes leakage of the plating solution to the seal part, and the non-plated part There was a problem that nickel plating was deposited.

  In addition, there is a method in which a photoresist ink is applied to a part of the lead frame that does not require partial plating (see, for example, Patent Document 2) and plating is performed.

  This photoresist method is a method in which a resist solution is applied to the entire surface of a plating material, exposed through a negative film, and unnecessary resist solution is washed and then partially plated, but the process is long and the amount of chemical used is also large. Since there are many, there exists a fault that a line cost is very high.

  In addition, as a continuous partial plating method, a masking tape is continuously applied to the non-plated portion (see, for example, Patent Document 3). After masking the non-plated portion, continuous partial plating is performed, and then a masking tape is applied. It peeled and the continuous partial plating strip was obtained.

  That is, as shown in FIG. 1, the masking tape 3 is cut with a cutter 4 at a portion where the plating surface is to be formed, and the masking tape 3 with the cut is attached to the surface of the long strip 1. A tape masking method is often employed in which a portion of the masking tape on which a plating surface is to be formed is peeled off, and continuous partial plating 2 is performed on the exposed surface formed by the peeling surface.

  In addition, as shown in FIG. 2, after performing continuous partial nickel plating 2, punching was performed to obtain a lead frame plated at a predetermined position.

  However, in the partial plating method using the masking tape, the plating range can only be continuous in the longitudinal direction of the strip, and it is difficult to perform complicated partial plating.

  In addition, plating is performed using a masking film in which an opening is formed by Thomson processing with a cutter blade when plating is performed selectively on a specific portion such as a connection terminal of a flexible printed circuit board (for example, Patent Documents). 4). However, Thomson processing can only deal with partial plating on terminal shapes that do not require dimensional accuracy, and it has been difficult to perform complex partial plating that requires dimensional accuracy with a lead frame.

JP-A-55-54599 JP-A-57-79194 Japanese Patent Laid-Open No. 3-150867 JP 2008-300441 A JP 56-35792 A

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an opening for partial plating in a masking tape used for partial plating in a method for partially plating a lead frame using a masking tape. Partial plating method that can surely remove tape scraps in minute areas that are cut in order to form slabs, and is capable of nickel plating even on intermittent selective areas with high dimensional accuracy and fine and complex shaped parts. Is to provide.

In order to achieve the above object, according to the lead frame partial plating method of the present invention, an opening of 3 mm square or less is formed using a laser at a position corresponding to a partial plating area of a masking tape having a structure with release paper. Yes and step, a step of attaching to the surface of the masking tape of metal strip material to be plated, and a step of plating through the opening in the surface of the metal strip material pasted the masking tape which In the step of cutting the masking tape using a laser in order to form the opening, only the masking tape is cut, the release paper is not cut, and the masking tape is placed on the surface of the metal strip. When the release paper is peeled off from the masking tape before the pasting step, the masking tape waste together with the release paper Characterized in that so as to removed by.

  According to the present invention, the plating is nickel plating.

According to the present invention, the laser is a CO ₂ laser.

According to the present invention, it is possible to provide a lead frame which has a high dimensional accuracy and is subjected to partial plating with a fine and complicated shape by cutting a masking tape using a laser, particularly a CO ₂ laser.

  In addition, it is possible to supply a lead frame subjected to partial plating, particularly nickel plating with a slow deposition rate, using a conventional continuous partial plating apparatus.

  Furthermore, the tape cutting process is performed with the release paper remaining at the time of masking tape processing, and the tape at the cut part is removed together with the release paper at the time of application, so that the tape scraps in the micro area can be reliably removed. It becomes possible.

  In addition to nickel plating, this tape masking method can be applied to various metal (silver, gold, etc.) plating and roughening treatments.

FIG. 1 is a diagram illustrating an example of a conventional continuous partial plating method. FIG. 2 is a diagram illustrating an example of a nickel plating area of a lead frame according to a conventional method. FIG. 3 is a diagram for explaining a product shape and a plated-up shape, which is an embodiment of the present invention. FIG. 4 is a process diagram illustrating a partial nickel plating method by tape masking, which is an embodiment of the present invention. FIG. 5 is a diagram for explaining a masking tape processing method using a CO ₂ laser.

Hereinafter, a partial nickel plating method to which the present invention is applied will be described. Note that the present invention is not limited to the following detailed description unless otherwise specified.
Embodiments of a partial nickel plating method to which the present invention is applied will be described in detail in the following order.
1. 1. Masking tape material, structure and strip material 2. Masking tape processing process 3. Masking tape application process 4. Plating process 5. Masking tape peeling process Winding process 7. Punching process

  Specifically, the lead frame manufacturing method according to the present invention comprises a masking tape processing step, a masking tape attaching step, a plating step, a masking tape peeling step, and a winding as shown in FIG. A process and a punching process.

1. The material of the masking tape, the structure and the material of the strip material The material of the masking tape used in the present invention is a plastic film such as PET (polyethylene terephthalate), polyester, polypropylene, etc., and an adhesive is applied to these supports. The original masking tape is used. The thickness of the masking tape substrate is usually preferably 4 to 100 μm, and particularly in the range of 10 to 30 μm is excellent in handling properties such as sticking and peeling, especially for the shape of the plating area. Since it is excellent in cut processing, it is preferable.
As the masking tape, a structure with a release paper (separator) attached can be used.

  The material of the base material of the release paper is a plastic film such as PET, polyester, polypropylene, etc., and one surface (peeling surface) of these base materials treated with a silicon-based release agent can be used. The thickness of the substrate is not particularly limited, but is preferably 25 to 100 μm from the viewpoint of handleability.

  As an adhesive for masking tape, for example, a synthetic rubber-based or synthetic resin-based adhesive described in Patent Document 5 can be used, and adhesion that improves adhesive strength by heating to 60 to 180 ° C. The agent can be used.

As the masking tape, a masking tape raw material having a width of the strip-like strip or slightly wider than that is prepared.
Here, the reason why a slightly wider masking tape is used is to cover the side surface of the strip material with the masking tape in order to prevent the side surface of the strip material from being plated.

  Moreover, if the material of the metal strip | belt-shaped base material which affixes these masking tapes is illustrated, a copper strip, a copper alloy strip, an iron-type strip | strand etc. can be mentioned.

2. Masking Tape Processing Step This masking film has an opening at a position corresponding to the partial plating area. As a method for processing the opening, a masking tape can be appropriately selected from punching processing, Thomson processing, cutting processing with a cutter, laser processing, and the like. However, in the punching process, it is not possible to perform a half-cut process in which only the masking tape is cut and the release paper is not cut. Also, in Thomson processing, the base wood board is grooved, and a die with a steel blade (Thomson blade) bent in the same shape as the groove is used, so the dimensional accuracy is poor and cut into a fine shape. I can't.

In laser processing, a semiconductor laser, a YAG laser, or a CO ₂ laser can be used. In particular, the majority of resins have a strong absorption band for CO ₂ laser light (wavelength 10.6 μm), and large thermal damage occurs on the resin surface directly irradiated with CO ₂ laser (uncolored resin). But thermal damage occurs due to strong absorption). For this reason, the CO ₂ laser is effective for cutting a resin film.

Therefore, it is preferable to cut the masking tape using a CO ₂ laser. By using a CO ₂ laser, it is excellent in dimensional accuracy and can be cut into a fine shape. Further, by adjusting the output of the CO ₂ laser, it is possible to perform a half-cut process in which only the masking tape is cut and the release paper is not cut.

As shown in FIG. 5, in the masking tape 3 with release paper that has been half-cut using the CO ₂ laser processing apparatus 9 (see FIG. 4), before the step of attaching the tape to the surface of the metal strip 1, When the release paper 11 is peeled off from the masking tape 3, the tape waste 12 can be removed together with the release paper 11. By using the CO ₂ laser processing apparatus 9, there is no generation of burrs on the punched end face generated by Thomson processing or the like, so that the tape waste 12 can be removed together with the release paper 11. Moreover, when the release paper 11 is peeled off from the masking tape 3 by using an adhesive whose adhesive strength is improved by heating and affixing to 60 to 180 ° C. as the adhesive of the masking tape 3, the adhesive strength is weak. Therefore, the tape scrap 12 can be removed together with the release paper 11 by increasing the adhesive force between the adhesive and the release paper 11 on the release paper 11 side.

In particular, when a shape having a side smaller than 3 mm is processed, the cut tape scrap 12 is scattered and attached to unnecessary portions. In the present invention, the CO ₂ laser processing apparatus 9 is used for this tape cutting processing. By using the masking tape 3 by half-cutting, the tape waste 12 can be reliably removed together when the release paper 11 is peeled off.

3. Masking tape application process (see Fig. 4)
The strip material 1 and the masking tape 3 are heated to 60 to 180 ° C. by a preheater before the attaching process, and then the strip material 1 and the masking tape 3 are aligned by the positioning holes 7. Between the strip material backup roll and the masking tape affixing roll, the masking tape is affixed to the strip material by heating to 40 to 200 ° C. and pressing it.

4). Plating process (see Fig. 4)
After maintaining the wide surface of the strip to be vertical and sliding it in the longitudinal direction, after performing degreasing etching and surface treatment in the pretreatment section, the plating solution stored in the plating solution tank is nozzled by a pump. From the above, silver plating, palladium plating or nickel plating can be performed while being discharged onto the surface to be plated.
Here, nickel plating that requires partial plating of a fine and complicated shape can be performed on the lead frame.
The composition of nickel plating bath used herein, nickel sulfate _{(NiSO 4 · 6H 2 O)} 240g, nickel _{(NiCl 2} · 6H ₂ O) chloride 50 g, boric acid _{(H 3} BO ₃₎ 50g standard watt It is a bath.

5). Masking Tape Peeling Step The masking tape 3 to be peeled off is peeled from the lead frame strip 1 at a predetermined position, and taken up by a winder through a guide roll, a peeling tape entrainment detection device and the like.
Thus, as shown in FIG. 3, a strip for a lead frame on which partial nickel plating 2 has been performed is obtained.

6). Winding process After peeling off the masking tape, it is washed with water and dried to wind up the finished nickel-plated strip.

7). Punching process (see Fig. 4)
Thus, a product is manufactured by punching the strip once wound into a predetermined shape of the lead frame, bending, cutting, and washing.

  Specific examples to which the present invention is applied will be described below, but the present invention is not limited to these examples.

  The strip 1 is made of copper alloy (2ZrOFC) having a width of 70 mm and a thickness of 0.5 mm, and a guide hole 6 and a positioning hole 7 (see FIG. Punching).

  As the masking tape 3, a PET substrate having a width of 80 mm and a thickness of 20 μm coated with an acrylic adhesive was used. Next, as the release paper 11, a PET substrate having a width of 80 mm and a thickness of 50 μm having a release layer made of a silicon-based resin on one side was used. The masking tape with release paper was obtained by pasting the release layer 11 side of the release paper 11 to the adhesive coating surface of the original masking tape.

In the masking tape 3 with the release paper 11, as shown in FIG. 5, the masking tape 3 is set on the upper side and the release paper 11 is set on the lower side, and the CO ₂ laser processing device 9 (CO ₂ manufactured by Keyence Corporation) is set from the upper side. A laser beam was used to irradiate a laser beam, and a 1.04 mm × 2.28 mm square opening was cut at a line width of 0.3 mm at a position corresponding to the partial plating area. In this case, by adjusting the output of the CO ₂ laser, only the masking tape 3 was cut, and the release paper 11 was not cut.

  Before affixing the masking tape 3 to the strip 1, the half-cut masking tape 3 is peeled off while the release paper 11 is wound around a subsequent winding roll, and the tape scrap corresponding to the partial plating area 12 was removed together with the release paper 11.

After heating the masking tape 3 from which the strip material and release paper have been removed at 120 ° C. with a preheater, the strip material and the masking tape 3 are aligned with each other through the positioning hole 7, and the adhering pressure is 3 kg / The masking tape 3 was affixed to the strip 1 at cm ² .

  The strip 1 with the masking tape 3 applied thereto was slid in the longitudinal direction while maintaining the wide surface vertical, and in the existing continuous partial plating apparatus 10, degreasing etching and surface treatment were performed in the pretreatment section. Then, nickel plating was performed under the conditions shown in Table 1 while discharging the plating solution stored in the plating apparatus from the nozzle to the surface to be plated.

  After stripping the masking tape 3 from the strip 1 plated with partial nickel, the strip was washed with water and dried, and the completed strip with nickel plated was wound up.

  The wound strip was once cut into a predetermined shape by punching to obtain a lead frame.

From the above results, only the masking tape 3 is cut and peeled off in the process of cutting the shape of the opening of 3 mm square or less at the position corresponding to the partial plating area of the masking tape 3 using the CO ₂ laser processing apparatus 9. The paper 11 is not cut, and the tape waste 12 is removed together with the release paper 11 when the release paper 11 is peeled off from the masking tape 3 before the step of attaching the tape to the surface of the metal strip. There is no removal failure, and there is no penetration into the interface between the strip material and the masking tape in the nickel plating bath. The lead frame 5 can be provided with high dimensional accuracy and nickel plating on a fine and complicated shape. It was.

  Moreover, the lead frame 5 which performed partial plating, especially nickel plating using the conventional continuous partial plating apparatus was able to be provided.

  Further, by performing a half-cut process that leaves the release paper 11 when the masking tape 3 is processed, the tape waste 12 is taken up together with the release paper 11 at the time of release, and the tape waste 12 in a minute area can be reliably removed. It turns out that it is possible.

1: Strip material 2: Nickel plating 3: Masking tape 4: Cutter (for masking tape cutting)
5: Lead frame 6: Guide hole 7: Positioning hole 8: Mold for guide hole 9: CO ₂ laser processing device 10: Continuous partial plating device 11: Release paper 12: Tape scrap (cut-off masking tape)

Claims (3)

A step of forming a 3 mm square or less opening using a laser at a position corresponding to a partial plating area of the masking tape having a structure with a release paper, a step of attaching the masking tape to the surface of the metal strip , possess a step of plating through the opening in the surface of the metal strip material pasted the masking tape,
In the step of cutting the masking tape using a laser to form the opening, only the masking tape is cut, the release paper is not cut, and the masking tape is attached to the surface of the metal strip. A method for partially plating a lead frame, characterized in that when the release paper is peeled off from the masking tape before the process, the scraps of the masking tape are removed together with the release paper .   2. The lead frame partial plating method according to claim 1, wherein the plating is nickel plating. The lead frame partial plating method according to claim 1, wherein the laser is a CO ₂ laser .

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