JP2004292944A - Metallic material for electronic component prevented from generation of whisker - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a metallic material of electronic components for a semiconductor prevented from the generation of whiskers. <P>SOLUTION: The metallic material for the electronic components prevented from the generation of the whiskers is plated with Ni at 0.5 to 5 μm as a substrate and with Cu thereon at 0.5 to 5 μm at the time of subjecting the surface of the metallic material for the electronic components to Ni plating of 0.5 to 5 μm, further to Cu plating of 0.5 to 5 μm in thickness and subjecting the surface of the metallic material for the electronic components to Sn plating layer. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１０】
【発明の効果】
以上述べた様に、本発明の電子部品用金属材料は、ウィスカによる短絡不良の問題が解消され、メッキ後の成型加工においても必要な曲げ加工性もあり、また地球環境保全に適した電子部品用金属材料を提供することができる。
【図面の簡単な説明】
【写真１】Ｓｎメッキ表面に発生したウィスカの一例を示す。
【図１】Ｓｎメッキ層を施した時のＮｉ，Ｃｕメッキ層の厚さとウイスカ発生状況との関係を示す。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a metal material for electronic components of a semiconductor device.
[0002]
[Prior art]
A lead frame used for a semiconductor device such as a semiconductor integrated circuit and a high-density integrated circuit is manufactured through the following steps. First, a conductive adhesive is applied to a semiconductor mounting portion of a semiconductor device lead frame, and after the semiconductor element is mounted, the conductive adhesive is cured in a baking furnace. Next, the electrode part on the semiconductor element and the internal lead part in the lead frame are connected by a bonding wire. Next, in order to protect the semiconductor circuit from the external environment, it is sealed with an epoxy resin. Next, exterior plating such as solder plating is applied to an external lead portion protruding outside the sealing resin connected to the internal lead of the lead frame. The exterior plating is performed mainly for improving corrosion resistance, and is generally subjected to solder plating using a Sn-Pb two-element electrolytic plating coating or a molten solder dipping apparatus. It is used more frequently than a molten solder dip device because it has an advantage that a Sn—Pb plating layer having a predetermined thickness can be more uniformly deposited on the external lead surface by a DC power supply. For a metal material such as a chassis, a single plating of Sn has been performed by an electrolytic plating apparatus for a long time. However, internal stress in Sn is relieved and Sn atoms self-diffuse, and the beard crystal shown in Photo 1 is removed. A so-called needle-like single crystal whisker is generated and grows, and an electrical short circuit occurs, so that the reliability cannot be maintained. Therefore, solder plating of two elements in which Pb is added to Sn is performed. Further, after the dam bar holding the resin is cut, it is separated into individual semiconductor device pieces and cut into a predetermined lead length. Finally, the external lead portion is lead-formed into a predetermined shape such as a gull-wing shape or a J-type to complete the semiconductor device.
[0003]
[Problems to be solved by the invention]
Metal materials used for electronic components such as lead frames and chassis used in conventional semiconductor devices include Cu alloys, 42% Ni iron alloys, iron thin plates, and Al alloys, which have been subjected to a solder plating layer. It is used. However, in the last few years, actions to promote global environmental protection have been steadily advancing, and it has become necessary to regulate Pb contained in the solder plating layer. It is an important issue. Two methods are being considered as countermeasures. One of them is a so-called Sn-Bi plating layer using a Bi component instead of Pb. By using Bi, the melting point is lower than that of Sn without using harmful Pb, and plating that does not generate whiskers can be performed. On the other hand, Bi has poor workability as compared with Pb, so that there is a problem that bending workability is restricted in forming after plating. As another countermeasure, there is a diversion technique of a Sn single plating method conventionally used for a metal material such as a chassis. This countermeasure does not have the above-mentioned processing problem due to the soft nature of Sn, but as described above, there has been a problem that reliability of use performance is lacking due to the problem of whisker generation and short circuit accident.
[0004]
In view of the above-described problems, the present inventors have conducted various studies on the Sn plating method for the purpose of providing an electronic component metal material for a semiconductor device in which generation of whiskers has been prevented. It was found that Ni plating further promotes the whisker suppression effect of Cu plating by applying 0.5 to 5 μm of Ni as a base and further applying 0.5 μm to 5 μm of Cu on the Sn plating layer when applying a Sn plating layer. . It was also found that there was no problem with the molding after plating.
[0005]
[Means for Solving the Problems]
The gist of the present invention is based on this finding. The gist of the present invention is that when an Sn plating layer is applied to the surface of a metal material for electronic components, Ni plating is applied as 0.5 to 5 μm as a base and Cu plating is further applied thereon. It is a metal material for an electronic component in which generation of whiskers is prevented, characterized in that the metal material is applied in an amount of 0.5 μm to 5 μm.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the gist of the present invention will be described in detail.
The present invention relates to a method of manufacturing a metal material (or substrate) for electronic parts generally used such as a metal material used for a semiconductor device, for example, copper and copper alloy, iron and iron alloy (including 42% Ni iron alloy), and Al alloy. , Ni plating, an underlayer of Cu plating is applied thereon, and Sn plating is applied thereon. The Ni and Cu plating layers exert an effect of suppressing whiskers generated and grown from the surface of the Sn plating layer. FIG. 1 shows the relationship between the thickness of Ni and Cu plating and the occurrence of whiskers when Sn plating is performed. The Ni plating is 0.5 to 5 μm and the Cu plating layer is 0 mm. If the thickness is less than 0.5 μm, the effect of suppressing whisker generation is small. If the thickness is excessively more than 5 μm, the effect of suppressing whisker reaches supersaturation, which is economically unnecessary. The numbers in the drawing of FIG. 1 are the scores indicating the degree of whisker generation, and are the same as the scores in Table 1 shown in the explanation on the next page shown in the examples. In the present invention, the reason why the thickness of the Cu plating layer is limited to 0.5 to 5 μm is determined from such experimental results. The Sn plating of the upper layer is performed for solder wettability and corrosion resistance of the external lead. The reason for suppressing the generation of whiskers between the two plating layers is not clear at present, but according to the present inventors' guess, the Ni or Cu plating is thinly applied to the underlayer of the Sn plating layer. Influences the crystal direction and crystal grain size of the Sn plating layer so that the whisker does not easily grow, or reduces the grain boundary energy by coarsening the crystal grains, or promotes the diffusion of Cu plating metal into the Sn plating layer. There are many possible reasons, such as suppressing the generation and growth of whiskers, or improving the adhesion at the interface with a thin plating layer. By applying a Ni plating layer under the Cu plating layer, the adhesion between the surface of the metal material for electronic parts and the Cu plating layer is increased through the Ni plating layer, and the increased adhesion may cause a problem. Has the effect of maintaining the effect of suppressing the whisker of the Cu plating layer for a long period of time without being easily peeled off even when receiving the impact of
[0007]
【Example】
Next, examples of the present invention will be described.
Table 1 shows the plating layer after repeating a thermal cycle of −40 ° C. to 120 ° C. 1000 times using the electronic component metal material of the present invention and the comparative material in the case where various plating layers are applied to the electronic component metal (substrate). The whisker occurrence on the surface was observed by SEM, and the results of the following evaluation were compared and shown.
1; better than Sn-Pb 2; equivalent to Sn-Pb 3; no practical problem, but worse than conventional materials.
4: Applicable to about 100 pins or less 5: Difficult to apply to any device As a result, the metal material for electronic parts of the present invention, in which the lower layer is plated with Ni or Cu, suppresses generation of whiskers. Further, the comparative material in which Sn alone plating or Cu plating with an excessive thickness was applied to the lower layer could not suppress the generation of whiskers.
[0009]
[Table 1]

[00010]
【The invention's effect】
As described above, the metal material for electronic components of the present invention eliminates the problem of short-circuit defects due to whiskers, has the required bending workability even in molding after plating, and is suitable for electronic components suitable for global environmental protection. Metal material can be provided.
[Brief description of the drawings]
[Photo 1] An example of whiskers generated on the Sn plating surface is shown.
FIG. 1 shows the relationship between the thickness of a Ni or Cu plating layer and the occurrence of whiskers when a Sn plating layer is applied.

Claims (1)

An electronic component that prevents generation of whiskers, characterized in that when a Sn plating layer is applied to the surface of a metal material for an electronic component, Ni is applied as a base layer in an amount of 0.5 to 5 μm and Cu is applied thereon in an amount of 0.5 to 5 μm. For metal material.

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