JP2663369B2 - Lead frame partial plating equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a partial plating apparatus for an IC lead frame, and more particularly to a partial plating apparatus for an IC lead frame by a vertically upward jet.

[0002]

2. Description of the Related Art A lead frame has a mounting base on which an IC element is mounted in a central portion, and a plurality of lead portions formed around the periphery thereof at the front end thereof to be wire-bonded to electrodes on the IC element. In addition, a noble metal plating such as gold or silver is applied to the tip of the lead. Conventionally, such a lead frame is made of a thin plate or a strip of iron, iron alloy, copper, copper alloy, or the like, and after performing photoetching or press punching on the material to cut out unnecessary portions, at least a lead end is formed. It is manufactured by performing a noble metal plating treatment of gold, silver, or the like using a mask that exposes the metal. When performing partial plating of the lead frame, a soft body mask (hereinafter abbreviated as a rubber plate) such as rubber, which has an opening at the portion to be plated (hereinafter abbreviated as the surface to be plated), is attached to the surface to be plated. Is fixed with an upper plate, etc., and a nozzle plate, sparger, slit plate, etc. for spraying the plating solution are set toward the surface to be plated, and a vertical upward jet of the plating solution is blown, and the lead frame and the electrode are This is performed by applying a DC voltage during the period.

In the plating method using a vertically upward jet of a plating solution, the biggest problem is how to treat bubbles on the surface to be plated which are inevitably generated during the jet. For example, if air bubbles are stagnant so that they stick to a part of the plating surface of the lead frame, current does not flow through only that part and electrodeposition does not occur, which is a cause of plating failure called `` no plating '' Become. In addition, when microbubbles move around the surface to be plated, a portion where current does not flow partially occurs, so that the plating thickness changes partially, and further, the crystal structure of the plating portion changes due to a change in overvoltage during plating. This causes plating defects called “plating unevenness”. In this way, the portion where the air bubbles on the surface to be plated are hard to escape and stagnant in the system is a place where the plating solution is liable to stagnate, the old plating solution remains, and based on that, the metal ions in the plating solution, Plating quality tends to fluctuate due to uneven concentration of free CN, additives, and the like.

[0004] As one of the methods for addressing the above problems, conventionally, there has been a method of increasing the pressure of a liquid feed pump in order to increase the flow rate of a plating solution in a plating apparatus and increasing the current density accordingly. Has been taken. At this time, if the pressure of the liquid feed pump is too high, the plating solution penetrates into various parts of the lead frame through the gap of the rubber plate made of rubber etc., and the side and back surfaces of the lead part of the lead frame which should not be plated Phenomenon occurs.
This phenomenon is called side leakage or back leakage. In order to avoid the occurrence of such a phenomenon, the pressure of the liquid feed pump cannot be increased to 3 kg / cm ² or more with the conventional apparatus, and therefore, there is a limit to the increase in current density. Could not be a fundamental solution.

On the other hand, there are various attempts to prevent the retention of bubbles on the surface to be plated or to shorten the retention time of the bubbles by installing a drainage passage for the used plating solution or improving the shape and structure thereof. It has been implemented. That is,
Conventionally, a plating solution drain passage is configured to discharge a used plating solution from a gap between a support plate that supports a rubber plate abutting on the lower surface of a lead frame and a slit plate. The resistance is large and the residence time of air bubbles is prolonged.

On the other hand, as shown in FIG. 2, the lead frame 1 mounted on the support plate 10 and the rubber plate 2 is held down by the holding metal 4 and the holding rubber 5, so that the support plate 10 and the slit plate 3 The shape of the joints is modified to provide horizontal drainage passages 9a and 9b for draining the used plating solution in both right and left directions, or plating as shown in FIG. Nozzle plate 7
And a stepped drain passage 9 for draining a used plating solution on one side of the nozzle plate. All of these devices have a certain effect on the reduction of air bubbles and the residence time of the plating solution on the surface to be plated, but still have a large drainage resistance and a fundamental solution. Couldn't be. In FIGS. 2 and 3, reference numeral 8 denotes a plating solution blowing cell, and reference numeral 6 denotes a rectifying plate installed therein. Also,
The arrows indicate the flow direction of the plating solution, and the electrodes are not shown.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and in a partial plating apparatus using a vertically upward jet of a plating solution, it is unavoidable that the plating solution will The present invention has been made to provide a partial plating apparatus for a lead frame that can significantly reduce the residence time of generated bubbles.

[0008]

SUMMARY OF THE INVENTION The present invention provides a pressing member 20 for a lead frame 1 and a lower surface of the pressing member 20, the upper surface of which is in contact with the lower surface of the lead frame 1 and the lower surface of the lead frame 1 is covered. A rubber plate 2 having an opening corresponding to a plating surface; a support plate 10 for supporting the rubber plate 2; a slit plate 3 provided below the support plate 10 for spraying a plating solution; 3
And a plating solution pumping cell 8 provided at a lower portion of the lead plate, and a partial plating apparatus for a lead frame by a vertically upward jet, wherein the support plate 10 is vertically opposed to an opening of the rubber plate 2. The plating solution flow path 30 provided in the direction, the two provided in the plate thickness portion of the support plate 10 in a horizontal direction and provided with openings facing each other in the plating solution flow path 30 part A plating solution drainage passage 9a, 9b; and a distance H between a vertical upper end of the opening of the plating solution drainage passage 9a, 9b and the upper surface of the rubber plate 2.
Is 1 mm or more and 3 mm or less.

[0009]

As a result of repeated experiments, the inventors have found that the vertical distance between the surface to be plated such as a lead frame and the drainage channel and the shape and structure of the drainage channel are improved to improve the plating surface. It has succeeded in significantly reducing the residence time of bubbles. In the present invention, since two vertical drainage paths are provided at a position in the vertical direction H between the plating surface of the lead frame and the drainage paths of 1 mm or more and 3 mm or less, the flow resistance of the drainage paths is reduced. It can be significantly reduced as compared with the conventional example.

FIG. 1 is a sectional view of a main part of an example of a lead frame partial plating apparatus used in an embodiment of the present invention. 2 and 3 are sectional views of a main part of a conventional partial plating apparatus for a lead frame. 1 and 2
And in FIG. 3, 1 is a lead frame, 2 is a rubber plate, 3 is a slit plate, 6 is a rectifying plate, 7 is a nozzle plate, 8 is a plating solution blast cell, 9, 9a and 9b are drainage paths,
Reference numeral 10 denotes a support plate for supporting the rubber plate 2, reference numeral 20 denotes a lead frame holding member constituted by the holding metal 4 and holding rubber 5, reference numeral 30 denotes a plating solution flow path provided in a vertical direction, and reference numerals 40a and 40b denote plating solutions. The openings of the drainage channels 9a and 9b with respect to the plating solution channel 30 are shown. H indicates the vertical distance between the upper ends of the openings 40a and 40b of the plating solution drainage passages 9a and 9b in the vertical direction and the upper surface of the rubber plate 2, and H is hereinafter referred to as an outlet head difference. The inventors have shown in FIGS.
Using the apparatus of the embodiment of the present invention and the conventional apparatus shown in FIG.
Was made as a prototype, the behavior of bubbles on the surface to be plated was observed, and the relationship between the flow rate of the plating solution and the residence time of the bubbles on the surface to be plated was investigated. The results shown in Table 1 were obtained. That is, when the apparatus of FIG. 1 according to the present invention is used, 0.4
The residence time of bubbles on the surface to be plated could be shortened within the target of 1 sec over the entire flow rate range of 1.0 m ³ / hr. On the other hand, when the conventional apparatus shown in FIGS. 2 and 3 was used, the time could not be shorter than 1 second, and the residence time was remarkably prolonged especially in a low flow rate range.

Normally, the support plate 10 is made of an acrylic resin or the like. If the difference H in the outlet head is extremely reduced, problems occur in the strength and processing of the support plate 10. Therefore, the exit head difference H needs to be at least 1 mm or more. On the other hand, if the outlet head difference H exceeds 3 mm, the effect of shortening the residence time of the air bubbles is significantly reduced, which is not preferable. The apparatus of the embodiment of FIG. 1 used in this experiment has a slit width S = 2 mm of the slit plate and a support plate 10 having a thickness of 15 mm.
And an outlet head difference H between the plating surface of the lead frame and the drainage path was 3 mm, and drainage paths 9 were provided at two locations in the horizontal direction. As experimental conditions at this time, the flow rate of the plating solution was targeted at 1 m / sec, and the calculated value of the Reynolds number was about 3000-9000.

[0012]

[Table 1]

[0013]

Embodiment 1 (Embodiment 1) The difference between the outlet heads H, that is, the vertical upper ends of the openings 40a and 40b of the plating solution drainage passages 9a and 9b and the upper surface of the rubber plate 2 (= lead frame 1 in FIG. 1). An experiment was conducted under the following conditions in order to investigate the effect of the vertical distance H to the surface to be plated) on the residence time of bubbles. That is, the thickness of the support plate 10 is 15 mm, the slit width of the slit plate 3 is 1 and 2 mm (s = 1, 2), and the outlet head difference H is 2 and 3 mm (H = 2, 3). Was changed to investigate the change in the residence time of bubbles on the surface to be plated. As a result, as shown in Table 2, according to the apparatus according to the embodiment of the present invention shown in FIG. 1, the residence time was able to be set within 1 sec as the target in all flow ranges.
Also, the residence time was shorter when the exit head difference H was 2 mm than when it was 3 mm. On the other hand, in Comparative Examples 1 and 2 using the conventional apparatus, the residence time of the bubbles cannot be made within 1 sec, and the residence time of the bubbles is further prolonged, especially in the region where the amount of squirting is small. did.

[0014]

[Table 2]

(Example 2) Using the apparatus of the embodiment of the present invention shown in FIG. 1 and the conventional apparatus shown in FIGS. 2 and 3, a lead frame of a predetermined size was subjected to partial plating under the following conditions. a) Copper strike plating conditions Plating bath composition Cu: 68 g / l Free CN: 6.2 g / l Plating bath temperature Room temperature Current waveform Single-phase full wave Ejected liquid volume 1.1 m ³ / h b) Silver plating conditions Plating bath composition Ag: 73 g / l pH: 7.7 Plating bath temperature 60 ° C. Current density 74 A / dm ² Current waveform Six-phase single-wave pulse Ejected liquid amount 1.1 m ³ / h The lead frame obtained by the above method was 450
A heating test was performed at 3 ° C. for 3 minutes, and the presence or absence of blisters and black spots was investigated. As a result, in the apparatus according to the conventional example of FIGS. 2 and 3, abnormalities such as heating blisters and black spots occurred frequently.
No abnormalities such as black spots were observed at all.

[0016]

As described above, when the partial plating apparatus according to the present invention is used, it is possible to manufacture a lead frame which is free from plating defects such as heat blisters and black spots and is partially plated.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing an example of a partial plating apparatus for a lead frame according to the present invention.

FIG. 2 is a sectional view of a main part of a conventional lead frame partial plating apparatus.

FIG. 3 is a sectional view of a main part of a conventional lead frame partial plating apparatus.

[Explanation of Signs] 1 Lead frame 2 Rubber plate 3 Slit plate 4 Holder 5 Pressing rubber 6 Rectifier plate 7 Nozzle plate 8 Plating solution blow-up cell 9 Drainage channel 9a Drainage channel 9b Drainage channel 10 Support plate 20 Holding member 30 Plating solution flow paths 40a, 40b provided in the vertical direction. Openings of plating solution drainage paths for plating solution flow paths. H Vertically upper ends of plating solution drainage path openings and upper surfaces of rubber plates. Distance (: Exit head difference)

Claims (1)

(57) [Claims] 1. A holding member (20) for a lead frame (1).
And a lower surface of the pressing member (20), the upper surface of which is in contact with the lower surface of the lead frame (1), and
(1) A rubber plate (2) having an opening corresponding to the lower surface to be plated, a support plate (10) for supporting the rubber plate (2), and a plating provided below the support plate (10). A slit plate for liquid jetting (3), and the slit plate (3)
And a plating solution blowing cell (8) provided at the lower part of the lead frame, and a partial plating apparatus for the lead frame by a vertically upward jet, wherein the support plate (10) is provided with an opening of the rubber plate (2). The plating solution flow path (30) provided in the vertical direction relative to the portion, the plating solution flow path (30) portion provided horizontally in the inner plate thick portion of the support plate (10) and the plating solution flow path (30) And two plating solution drain passages (9a, 9b) provided with openings facing each other, and further, the plating solution drain passages (9a, 9a, 9b).
9b) A partial plating apparatus for a lead frame, wherein a distance H between a vertical upper end of the opening and an upper surface of the rubber plate (2) is 1 mm or more and 3 mm or less.