JP2002164493A - Lead frame - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the thickness of a Pd plated film in an intermediate portion in a widthwise direction on a lead frame on which the Pd plated film is formed by passing through an electro plating or an electroless plating line. SOLUTION: In a lead frame on which a Pd plating film is formed by passing through the electro plating or the electroless plating line, the uniformity of the thickness of Pd plated film in the intermediate portion in the widthwise direction is obtained by making the amount of Pd to zero or significantly reducing the amount of Pd in both ends in the widthwise direction of the lead frame. Even if the thickness of the Pd plated film in the intermediate portion in the widthwise direction is ultra-thin, the intermediate portion in the widthwise direction of the lead frame chain where the uniform thickness of the Pd plated film is required can be plated uniformly without defective spots by forming the thickness of Pd plated film in both ends in the widthwise direction of the lead frame becomes less than the thickness of that in the intermediate portion in the widthwise direction by 25% maximum. In addition, reducing the Pd precipitation contributes to cost reduction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for a semiconductor device which has been passed through an electroplating or electroless plating line, and has its surface plated with Pd.

[0002]

2. Description of the Related Art As a lead frame for a semiconductor device, for example, Japanese Patent Publication No. Sho 63-49382, Japanese Patent No. 2746.
As described in Japanese Patent No. 840, the die bonding property for mounting the semiconductor element, the wire bonding property between the semiconductor element and the lead, the corrosion resistance of the lead frame itself, and the like are ensured, and the plating process and the plating layer itself are performed. Is an environmentally friendly Pd plating.

In such Pd plating, in order to enhance corrosion resistance and productivity, a lead frame is formed in a single row or a plurality of rows from a strip-shaped metal plate such as Cu by pressing or etching, Ni is plated as a base, and then electroplating or plating is performed. A method of passing an electroless plating line, or a lead frame of a predetermined length arranged in a strip shape is passed through an electroplating or electroless plating line, over the entire width of the lead frame, for example, a thickness of 25 nm or more. To form a uniform plating layer.

[0004]

However, in an electroplating line, Pd nuclei precipitated by energization tend to be concentrated at both ends in the width direction of the passing plate. The plating layer is formed more than necessary, and the plating layer in the middle tends to be partially thin. Such a tendency also occurs in an electroless plating line.

[0005] The concentrated precipitation at the width end of the passing lead frame not only wastes Pd, but also reduces Pd in the width direction.
This leads to uneven thickness of the d-plated layer and adversely affects the wettability of the solder. For example, when an extremely thin plating of 0.02 μm or less is applied, the thickness of the Pd plated layer at the widthwise intermediate portion is reduced. However, there is a danger that the solder wettability at the time of assembling operation will be degraded, resulting in poor wire bonding or reduced bonding reliability.

The problem to be solved in the present invention is that, in a lead frame passed through an electroplating or electroless plating line and subjected to Pd plating, even if the plating is extremely thin, the Pd plating thickness at the middle portion in the width direction is uniform. Is to gain sex.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a lead frame which has been subjected to electroplating or electroless plating and has been subjected to Pd plating. By eliminating or minimizing the amount of Pd, the Pd at the intermediate portion in the width direction is reduced.
This is to make the plating thickness uniform.

By forming the Pd plating at both ends in the width direction of the passing lead frame at 25% or less of the thickness of the middle portion in the width direction, the Pd plating at the middle portion in the width direction is reduced.
Even if the d-plating thickness is as thin as about 25 nm, the intermediate portion in the width direction of the lead-through lead frame that requires Pd plating with a uniform thickness can be plated uniformly without generating defective portions, and the amount of Pd deposited can be reduced. Contributing to cost reduction by reducing.

In order to obtain a lead-through lead frame in which the Pd plating at both ends in the width direction is extremely reduced or the Pd plating is not applied, as shown in FIG. Either a mask E is provided, or as shown in FIG. 4, a mask F is attached to the passing lead frame 1 itself to pass the plate, or as shown in FIG. 5, the passing lead frame 1 is set up in the width direction and passes through the plating solution. Means can be adopted such that the edge mask E is passed through the lower side, and the upper end is pulled out from the plating solution upper surface G and passed through.

As described above, the both ends in the width direction of the lead-through lead frame in which the Pd plating at both ends is extremely reduced or not formed are used as the guide rails when assembling the semiconductor device. Therefore, even if the Pd plating is not provided or hardly provided, the assembly as a semiconductor device does not cause any trouble.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below with reference to an embodiment in which a lead frame of the present invention is obtained by continuously applying a passing lead frame to an electroplating line.

FIG. 1 shows a form of a lead frame 1 for threading according to the present invention. The lead frame 1 for threading according to the present invention comprises a pad 2 and a lead 3 on which Pd plating having a uniform thickness is applied. , A dam bar 4 and a section bar 5, and Pd plating is hardly or not applied to both ends 6 in the width direction.

FIG. 2 shows a plating line for continuously electroplating Pd on the lead frame 1 for threading shown in FIG. This plating line cleans the lead frame 1 for passing through, and prepares a pretreatment tank A for activation and a Pd
A Pd plating tank B for performing plating and a post-treatment tank C for post-washing the passing plate after the plating treatment are continuously arranged. In the process of passing the passing lead frame 1 from the pretreatment tank A, the plating tank B, and the post-treatment tank C, a plating solution made of, for example, ammine palladium chloride is passed through the plating tank B, By energizing the plating electrode D, Pd plating is applied to an intermediate portion excluding both end portions of the lead frame 1 for threading. Pd plating on both ends is P
Pd plating is performed by disposing edge masks E at positions corresponding to both ends of the lead frame 1 for passing in the d-plating tank B, and passing both ends of the lead frame 1 for passing through the inside of the edge mask E. Is prevented.

FIG. 3 shows a state in which the edge mask E is viewed from the plate side. This edge mask E is composed of a U-shaped mask material E1 made of a PVC material at both ends of a lead frame 1 for threading, and a slip material E2 made of Teflon (registered trademark) for preventing scratches. I have. And
The slip material E2 and both ends 6 of the lead frame 1 have a minimum gap between them to prevent intimate contact or to prevent abrasion. Both ends 6 covered with the edge mask E of the lead frame 1 for the passing plate are the lead frame after plating.
In assembly work of a semiconductor device such as die bonding on which a semiconductor element is mounted, the length corresponds to the width of a guide portion for continuous work.

By this plating line, for example, the pad 2, the lead 3 and the dam bar 4 of the lead frame shown in FIG.
In a lead-through frame 1 having a length of about 30 mm and a width of one end of both ends 5 covered by the edge mask E in the width direction of 2 mm, the Pd plating thickness of both ends is The variation in the thickness of the Pd plating in the middle part of the lead frame on which the Pd plating having a thickness of 0.01 μm and the middle part having a Pd plating thickness of 0.05 μm is ± 0.
It was only 01 μm. This uniform Pd plating was applied, and Sn-37Pd was used as the solder in the middle part of the lead frame heated at 400 ° C. for 30 seconds. The solder 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 portions were also 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.
m, and the solder wettability test was not good.

In this embodiment, Pd plating is described, but Pd alloy plating, for example, Pd-Ni alloy plating, Pd plating
The present invention is similarly applicable to d-Co alloy plating, Pd-Cu alloy plating, and the like. Also, Nd is used as a base plating for Pd plating.
Not only i plating but also Ni alloy plating can be applied.

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

[0018]

According to the present invention, the following effects can be obtained.

1. The thickness of the Pd plating in the middle part in the width direction is small even if it is extremely thin, and the plating is performed uniformly without generating a defective plating portion.

2. By forming both ends in the width direction of the lead-through lead frame as guide rails for assembly, the Pd
There is no inconvenience caused by making the plating layer extremely thin, and the cost is reduced by saving at least 5% of the Pd weight.

3. When applying Au plating to the Pd surface, the same mask is used, so that the cost is reduced due to saving of Au.

[Brief description of the drawings]

FIG. 1 shows a threading lead frame used to manufacture the lead frame of the present invention.

FIG. 2 shows an electroplating line used to manufacture the lead frame of the present invention.

FIG. 3 shows an edge mask used to reduce the amount of Pd plating at both ends of the lead frame of the present invention.

FIG. 4 shows a method of attaching a lead frame itself with a mask and passing the lead frame.

FIG. 5 shows a method of passing the upper end of the lead frame of the present invention out of the plating solution surface and passing the plate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lead frame for passing board 2 Pad 3 Lead 4 Dam bar 5 Section bar 6 Both ends in width direction A Pretreatment tank B Plating tank C Posttreatment tank D Plating electrode E Edge mask E1 Mask material E2 Slip material F Mask G Plating solution upper surface H Lead frame top surface

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[Procedure amendment]

[Submission date] December 6, 2000 (200.12.
6)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

By this plating line, for example, the pad 2, the lead 3 and the dam bar 4 of the lead frame shown in FIG.
In a lead-through frame 1 having a length of about 30 mm and a width of one end of both ends 5 covered by the edge mask E in the width direction of 2 mm, the Pd plating thickness of both ends is The variation in the thickness of the Pd plating in the middle part of the lead frame on which the Pd plating having a thickness of 0.01 μm and the middle part having a Pd plating thickness of 0.05 μm is ± 0.
It was only 01 μm. Subjecting this homogeneous Pd plating, as the solder in the intermediate portion of the lead frame was heated for 30 seconds at 400 ° C., using a Sn-37P b, at a temperature 235 ° C. of the solder, inert R- type immersion depth 2 mm, as a flux 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 portions were also 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.
m, and the solder wettability test was not good.

Continuation of front page (71) Applicant 391003015 Noge Electric Industry Co., Ltd. 2-10-1 Fukuura, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture (72) Inventor Daigo Yamaura 2-10-1, Komine, Yawatanishi-ku, Kitakyushu-shi Mitsui High-Tech Co., Ltd. (72) Inventor Kazuo Tachihara 528-5, Shin-Hosao-cho, Nikko-shi, Tochigi Pref. Furukawa Precision Metal Industry Co., Ltd. (72) Inventor Shigeharu Tanaka 1-6-1, Suehirocho, Ome-shi, Tokyo Sumitomo Metal Mining Co., Ltd. (72) Inventor Katsuhiro Iwadari 2-10-1, Fukuura, Kanazawa-ku, Yokohama-shi F-term in Noge Electric Industry Co., Ltd. 4K022 AA02 AA05 AA42 BA03 BA18 BA36 DA03 DB01 4K024 AA12 AB01 AB02 BA01 BB11 BB12 BB13 BC01 CA01 EA01 5F067 DC12 DC13 DC14 DC17

Claims (4)

[Claims] 1. A lead frame which has been subjected to Pd plating by passing through an electroplating or electroless plating line,
A lead frame in which the thickness of the Pd plating is extremely thinner at both ends in the width direction of the passing lead frame than at the intermediate portion, or Pd plating is not applied at both ends. 2. The lead frame according to claim 1, wherein both end portions in the width direction of the passing plate lead frame are portions corresponding to guide rail portions when assembling the passing plate lead frame. 3. The lead frame according to claim 1, wherein the thickness of the Pd plating is not more than 25% of the thickness of the intermediate portion at both ends in the width direction of the passing lead frame. 4. The lead frame according to claim 1, wherein Ni or a Ni alloy is plated as a base plating of Pd or Pd alloy plating.