JPH02240955A - Lead frame for semiconductor device - Google Patents

Abstract

PURPOSE:To alleviate stress concentration and to control the occurrence of cracks by performing corner chamfering on the rear surface side of the outer edge part of a substrate supporting part. CONSTITUTION:Corner chamfering 1b is performed to the corner of the rear surface side of the outer edge of a substrate supporting part 1. The corner chamfering 1b of the rear surface of the substrate supporting part 1 is achieved only by changing the mask pattern of the rear surface forming a lead frame into the size smaller than the mask pattern of the upper surface by etching effect. Even if residual tensile stress due to the difference in thermal expansion coefficients of the a resin 4 and the substrate supporting part 1 is generated in the resin 4 in the vicinity of the rear surface of the substrate supporting part 1 at the trim of resin sealing, the stress concentration at the outer surface part is alleviated. Thus, the occurrence of cracks can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a lead frame used in a resin-sealed semiconductor device.

(Prior Art) Generally, a sealing method using a resin material is used for semiconductor chips in terms of mass productivity and cost performance.

A conventional resin-sealed semiconductor device will be explained with reference to a cross-sectional view of a main part in FIG.

In a conventional resin-sealed semiconductor device, a lead frame having a substrate support part l and a lead terminal part 2 is formed by pressing or etching a steel plate, and the substrate support part 1 is coated with silver paste or gold eutectic. Semiconductor chip 3
After mounting, the end portion of the lead terminal portion 2 is sealed with a resin 4, and the lead terminal portion 2 protruding from the resin 4 is bent into a predetermined shape.

(Problem M to be Solved by the Invention) However, in the above configuration, since the lead frame is formed by punching with a press or etching using a mold, the outer peripheral edge of the substrate support portion 1 has an acute angle 1 without a chamfer.
It is a.

Furthermore, when comparing the thermal expansion coefficients of the lead frame, semiconductor chip 3, and resin 4, the lead frame using 42-alloy has a coefficient of 4.14 x 10-", and the semiconductor chip using a silicon substrate has a coefficient of 2.4 x 10". -', the resin is extremely large at approximately 170 X tG"', so tensile residual stress is generated in the peripheral area that contacts the back surface of the substrate support part 1 during the resin sealing process, and the acute angle of the outer peripheral edge mentioned above is generated. There was a problem in that stress was concentrated due to the edge effect caused by la and cracks were generated, and in severe cases, gaps were generated, significantly reducing the moisture resistance of the semiconductor device.Furthermore, as the semiconductor chip 3 becomes larger, There was a problem in that the occurrence of cracks and gaps became noticeable.

The present invention solves the above problems and provides a lead frame for a semiconductor device in which stress concentration does not occur.

(Means for Solving the Problems) In order to solve the above problems, one aspect of the present invention is to chamfer a corner on the back side of the outer peripheral portion of the substrate support portion.

(Function) With the above configuration, the back side of the outer periphery of the substrate support part where residual tensile stress is concentrated due to the edge effect is chamfered, so the stress concentration is significantly alleviated and the occurrence of cracks is suppressed. Ru.

(Example) An example of the present invention will be described with reference to a sectional view of the main part in FIG.

The present embodiment shown in the same figure differs from the conventional example shown in FIG. 2 in that corner chamfers 1b are applied to the outer circumferential edge of the substrate support portion and the corners of the back surface. Since the rest is the same as the conventional example, the same components are given the same reference numerals and their explanations will be omitted.

Note that the corner chamfer 1b on the back surface of the substrate support portion 1 may be changed only by making the mask pattern on the back surface, on which the lead frame is formed by etching, smaller than the mask pattern on the front surface.

With the above configuration, even if residual tensile stress occurs in the resin 4 near the back surface of the substrate support part 1, the stress concentration is significantly alleviated because the outer peripheral part is chamfered 1b. Therefore, cracks will not occur.

(Effects of the Invention) As explained above, in the lead frame of the present invention, since the outer periphery of the back surface of the substrate support portion is chamfered, there is a difference in the coefficient of thermal expansion between the resin and the substrate support portion during resin sealing. Even if residual tensile stress is generated due to this, a large concentrated stress will not be generated at the outer periphery of the back surface of the substrate support portion. Therefore, a highly reliable resin-sealed semiconductor device can be obtained since moisture resistance does not deteriorate due to cracks in the resin.

[Brief explanation of drawings]

1 and 2 are sectional views of essential parts of resin-sealed semiconductor devices showing an embodiment of the present invention and a conventional example, respectively. 1... Board support part, la... Acute angle, 1b...
Corner chamfer, 2... Lead terminal portion, 3... Semiconductor chip, 4... Resin. No. 1 Cause 4 Resin patent applicant Matsushita Electronics Co., Ltd.

Claims (1)

[Claims] A lead frame for a semiconductor device, characterized in that the outer periphery of the back surface of the substrate support part is chamfered.