Lead frame and method for manufacturing the same

Abstract

A metal plate 1 to be a lead frame has a plating with Sn or Zn or a plating with various alloys containing these metals only on the side faces and half-etched faces 6, and a noble metal plating layer formed on the front surface as a surface on which a semiconductor device is to be mounted.

Description

TECHNICAL FIELD[0001]The present invention relates to a lead frame and a method for manufacturing the same, and more particularly to a lead frame good in adhesion to resin.BACKGROUND ART[0002]Metallic lead frames and sealing resins are mainly used for semiconductor packages, where copper alloys are frequently used for the lead frames and epoxy resins are the mainstream of the sealing resins.[0003]In addition, for heat dissipation of a semiconductor package, a copper plate or a copper alloy plate is sometimes used as a material of a component called a heat spreader, and the lead frame and the heat spreader are fixed with a sealing resin.[0004]In a product in which metal materials using copper and a copper alloy and a resin are joined in such a way, the adhesion often comes to be an issue, and as measures for improving the resin adhesion, methods for roughening treatment of the surfaces of the lead frame and the heat spreader are adopted for attaining the anchor effect.[0005]However, ...

AI Technical Summary

Benefits of technology

The present invention provides a method for improving the adhesion between a lead frame and resin by applying local plating with Sn, Zn, or various alloys containing these metals only on etching-dissolved faces (product-side surface and half-etched portions) of the material surface. This method ensures a surface gloss and wire bondability, without affecting the gloss after plating. Additionally, the method improves resin adhesion by increasing the area of plating with Sn, Zn, or various alloys containing these metals, either by plating the product-side surface or adding half-etched faces in the front surface or existing half-etched faces. The method also prevents copper oxidation and improves adhesion to the resin by using oxide films of Sn, Zn, or various alloys containing these metals. Furthermore, the method allows for the use of the same mask for etching and plating, reducing the cost of production. The shape and design of the lead frame can also be improved by adding half-etched portions or increasing the area of existing half-etched portions.

Problems solved by technology

However, the problem in these methods is in that, in a semiconductor package of the QFN (Quad Flat Non-Lead) type for example, the connection terminals are uncovered on the lower surface of the sealing resin, and roughening treatment of the lower surface of the metallic material may cause leakage of the resin, whereas the roughening treatment makes it difficult to peel off the leaked resin.

Therefore, conventionally, there have been proposed methods for making roughening treatment locally, but these processing methods involve the problem of increased cost.

Further, since high-temperature heating of the copper material progresses copper oxidation on the roughened surface to easily cause the oxide film to peel off and decreases the resin adhesion as compared with before heating, the roughening treatment of the copper material therefore has not yet obtained sufficient reliability for a semiconductor package.

The surface treatment of copper and copper alloy strips by these conventional chemical method makes it difficult to sufficiently improve the adhesion to the resin, and a technique for improving the adhesion between the lead frame and the resin is still required.

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