JP4648953B2 - Lead frame manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a lead frame for a semiconductor device in which an electroplating or electroless plating line is passed and Pd plating is applied to the surface thereof.

  As a lead frame for a semiconductor device, for example, as described in Japanese Patent Publication No. 63-49382 and Japanese Patent No. 2746840, die bonding property for mounting a semiconductor element, and wire between the semiconductor element and the lead There are some which have bonding properties, corrosion resistance of the lead frame itself, and the like, and the plating process and the plating layer itself are made of environmentally friendly Pd plating.

  In this Pd plating, in order to improve corrosion resistance and productivity, a lead frame is formed in a single row or a plurality of rows by pressing or etching from a band-shaped metal plate such as Cu, Ni is underplated, and a Pd plating line is passed through. Or a lead frame of a predetermined length arranged in a strip shape is passed through a plating line to form a uniform Pd plating layer with a thickness of, for example, 25 nm or more over the entire width of the lead frame passed through. is there.

  However, in the electroplating line, the Pd nuclei deposited by energization tend to concentrate at both ends in the width direction of the threading plate, and therefore, an unnecessarily plated layer is formed at both ends in the width direction of the threaded lead frame. The intermediate plating layer tends to be partially thinned. Such a tendency also occurs in the electroless plating line.

  This concentrated precipitation at the width end of the lead frame that has been passed through not only wastes Pd, but also causes non-uniformity in the thickness of the Pd plating layer in the width direction, which also affects solder wettability. For example, when applying ultra-thin plating with a thickness of 0.02 μm or less, the thickness of the Pd plating layer in the middle in the width direction is insufficient depending on the location, solder wettability during assembly work is deteriorated, wire bonding failure, Or, there is a risk of lowering the reliability of bonding.

  The problem to be solved in the present invention is that, in a lead frame subjected to Pd plating by passing through an electroplating or electroless plating line, even if the Pd plating is extremely thin plating, it is uniform in the intermediate portion in the width direction. The purpose is to obtain a Pd plating having a thickness.

  The present invention eliminates the precipitation Pd at both ends in the width direction of the lead frame that passed through the electroplating or electroless plating line and produced the lead frame subjected to Pd plating, or By making it extremely small, the thickness of the Pd plating at the intermediate portion in the width direction is made uniform.

  Even if the Pd plating thickness in the width direction intermediate portion is made as thin as about 25 nm by setting the thickness of the Pd plating at both ends in the width direction of the lead frame to 25% or less of the thickness of the intermediate portion in the width direction, the lead Pd plating with a uniform thickness can be obtained at the intermediate part in the width direction of the frame without causing defective portions, and the amount of deposited Pd is reduced, contributing to cost reduction.

  In order to eliminate the amount of deposited Pd at both ends in the width direction or to obtain a lead frame with a very small amount, an edge mask is provided at both ends of the electroplating or electroless plating line, or the lead frame itself is masked. Or the lead frame is placed in the width direction, the lower end passing through the plating solution is passed through the edge mask, the upper end is passed through the plating solution upper surface, etc. Adopt means.

  Both end portions in the width direction can have a width corresponding to a guide rail portion when assembling the semiconductor device. Since both end portions do not function as a semiconductor device, no trouble is caused.

1. The Pd plating thickness at the intermediate portion in the width direction has little variation even if it is extremely thin, and the plating is performed uniformly without causing defective plating.

2. By eliminating or reducing the Pd plating layers at both ends in the width direction of the lead frame, there is no inconvenience, and the cost is reduced by saving at least 5% of the Pd weight.

3. When Au plating is applied to the Pd surface, the same mask is used to reduce costs by saving Au.

  Hereinafter, embodiments of the present invention will be described by examples in which lead frames are continuously applied to an electroplating line.

  FIG. 1 shows a form of a lead plate 1 for threading plates according to the present invention. The lead frame 1 for threading plates according to the present invention includes a pad 2, a lead 3, and a dam bar on which Pd plating with a uniform thickness is applied. 4. An intermediate portion including a section bar 5 is provided, and Pd plating is hardly applied to both end portions 6 in the width direction.

  FIG. 2 shows a plating line for continuously performing electroplating with Pd on the lead plate 1 for threading shown in FIG. This plating line is for cleaning the lead plate 1 for passing plates, and for pre-cleaning the pretreatment bath A for activation, the Pd plating bath B for applying Pd plating, and the passing plates after plating treatment. The post-treatment tank C is continuously arranged. In the process of passing the lead frame 1 for passing plates from the pretreatment tank A to the plating tank B and further to the post-treatment tank C, the plating tank B is passed through a plating solution made of, for example, ammonium chloride, and plated. By energizing the electrode D, Pd plating is applied to an intermediate portion excluding both end portions of the lead frame 1 for passing plates. For Pd plating on both ends, an edge mask E is disposed at positions corresponding to both ends of the lead frame 1 for passing the plate in the Pd plating tank B, and both ends of the lead frame 1 are passed through the edge mask E. Prevents Pd plating.

  FIG. 3 shows the edge mask E as viewed from the plate side. This edge mask E is composed of a U-shaped mask material E1 made of a vinyl chloride material and a slip material E2 made of Teflon (registered trademark) for preventing scouring at both ends of the lead frame 1 for passing plates. Yes. The slip material E2 and the both end portions 6 of the lead frame 1 have a minimum gap between them to prevent adhesion or slipping. Both end portions 6 covered by the edge mask E of the lead frame 1 for passing plates are used as guide parts for continuous work in assembly work of semiconductor devices such as die bonding on which the lead frame after plating is mounted with semiconductor elements. It is the length corresponding to the width.

  With this plating line, the length of the intermediate portion including, for example, the lead frame pad 2, lead 3, and dam bar 4 shown in FIG. 1 is about 30 mm, and one end of both end portions 5 covered by the edge mask E in the width direction. Pb plating thickness in the intermediate part of the lead frame subjected to Pd plating with a Pd plating thickness of 0.01 μm at both ends and a Pd plating thickness of 0.05 μm at the middle part in the lead plate 1 for passing plate having a width of 2 mm The variation was only ± 0.01 μm. Sn-37Pb was used as the solder in the middle part of the lead frame that had been subjected to this uniform Pd plating and heated at 400 ° C. for 30 seconds, the soldering temperature was 235 ° C., the immersion depth was 2 mm, and the flux was an inert R-type. In the solder wettability test, the zero cross time was 0.5 seconds or less. On the other hand, in the comparative example in which the end portion was subjected to Pd plating with the same thickness as the intermediate portion, the variation in the plating thickness of the intermediate portion was ± 0.03 μm, and the solder wettability test was not good. It was.

  In this embodiment, Pd plating has been described. However, Pd alloy plating, for example, Pd—Ni alloy plating, Pd—Co alloy plating, Pd—Cu alloy plating, and the like can be similarly applied. Further, not only Ni plating but also Ni alloy plating can be applied as the base plating for Pd plating.

  Further, after the Pd plating or Pd alloy plating is performed, Au plating can be applied thereon.

It shows the lead frame through a plate used to make the lead frame of the present invention. 1 shows an electroplating line used to manufacture the lead frame of the present invention. The edge mask used for reducing the Pd plating amount of the both ends of the lead frame of this invention is shown. The method of attaching a mask to the lead frame itself of the present invention and passing it through is shown. The method of taking out the upper end part of the lead frame of the present invention from the plating solution surface and passing it through is shown.

Explanation of symbols

Lead frame 2 pad 3 leads 4 dam bars 5 section bar 6 the width direction of the both end portions A pretreatment tank B plating tank C aftertreatment bath D plating electrode for 1 copy plate
E Edge mask
E1 Mask material E2 Slip material F Mask G Plating solution upper surface H Lead frame upper surface

Claims (3)

An edge mask is arranged at a position corresponding to both ends of a lead frame for passing a Pd plating tank, and a plating line passing through the edge mask through both ends of the lead frame is passed,
Attach an edge mask only to both ends of the lead frame and pass through the plating line,
Or
With the lead frame standing in the width direction, the lower end passing through the plating solution is passed through the edge mask, and the upper end is taken out of the plating solution upper surface by any means of the plate passing through,
Pass through the electroplating or electroless plating line, apply Pd plating to the middle part in the width direction to a uniform thickness,
and,
A method of manufacturing a lead frame for a semiconductor device in which Pd plating is applied to both ends in the width direction to be thinner than an intermediate portion or Pd plating is not applied. The lead frame manufacturing method according to claim 1, wherein both end portions in the width direction of the lead frame are portions corresponding to guide rail portions when a semiconductor device is assembled using the lead frame. The lead frame manufacturing method according to claim 1 , wherein the Pd plating thickness is 25% or less of the thickness of the intermediate portion at both ends in the width direction of the lead frame.

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