Semiconductor Device Lead Frame Angle for Stress Reduction
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Solution Overview
Problem
Existing resin-sealed semiconductor devices face challenges in downsizing and cost reduction while effectively suppressing thermal deformation-induced cracks, particularly due to complex electrode structures and increased stress at the interface between semiconductor elements and lead frames.
Innovation Solution
A semiconductor device design featuring a heat spreader, semiconductor elements, and lead frames sealed with a mold resin, where the second lead frame's protruding portions and over-chip joining members form a specific angle between 90° and 135°, reducing maximum stress without complicating the structure, and using materials with matching linear expansion coefficients to minimize thermal deformation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the electrode of the main terminal is made partially small to reduce thermal deformation force, then crack occurrence in the semiconductor element is suppressed, but the structure of the main terminal becomes complicated and downsizing becomes difficult
Solution Approach 1:
The invention changes the geometric parameters of the lead frame, specifically setting the width W2 of the second lead frame to be 0.05 to 0.15 times the width W1 of the first lead frame, and the length L2 to be 0.3 to 0.7 times the length L1. This parameter optimization reduces thermal deformation force while maintaining a simple structure, resolving the contradiction between crack suppression and structural simplicity.
Solution Approach 2:
The invention applies different dimensional characteristics to different parts of the lead frame structure. The first lead frame maintains sufficient size for electrical connection, while the second lead frame is designed with significantly reduced dimensions (W2 and L2) specifically at the critical stress region near the semiconductor element, providing localized stress reduction without complicating the overall structure.
2Adaptability or versatility
If two or more semiconductor elements are mounted inside a resin-sealed-type semiconductor device, then functionality is enhanced, but the structure of the electrode of the main terminal becomes more complicated and upsized
Solution Approach 1:
The second lead frame is designed to serve multiple semiconductor elements simultaneously. By positioning the second lead frame to extend along the longitudinal direction and make contact with multiple semiconductor elements, a single lead frame structure performs the function of multiple connections, avoiding the need for separate electrode structures for each element and thus preventing structural complication.
Solution Approach 2:
The invention merges the function of multiple electrodes into a single second lead frame structure. Instead of providing separate electrode connections for each semiconductor element, the second lead frame is designed as a unified component that contacts and connects to multiple elements, simplifying the overall electrode structure while supporting multi-element mounting.
3Reliability
If the linear expansion coefficient difference among semiconductor element, lead frame, and joining member is large, then thermal deformation force increases, but material selection flexibility is reduced
Solution Approach 1:
The invention optimizes the dimensional parameters (width and length) of the second lead frame to compensate for material property differences. By carefully selecting W2 and L2 within specific ranges relative to W1 and L1, the thermal deformation force is controlled through geometric design, providing flexibility in material selection while maintaining reliability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design enables the downsizing and cost reduction of resin-sealed semiconductor devices while effectively suppressing cracks by optimizing stress distribution and using materials with compatible thermal expansion coefficients, enhancing reliability and longevity.
Implementation Method 1
In a cross-sectional shape obtained by cutting a portion around the boundary at a plane perpendicular to the one-side surface of the heat spreader, an angle on the third joining member side out of two angles formed by the one-side surface of the semiconductor element and a straight line connecting an end point of a joining surface between the third joining member and the semiconductor element and an end point of a joining surface between the third joining member and the second lead frame, is not smaller than 90° and not larger than 135°
Implementation Method 2
using materials with matching linear expansion coefficients to minimize thermal deformation
Implementation Method 3
a heat spreader formed in a plate shape; a semiconductor element formed in a plate shape and joined, to a one-side surface of the heat spreader
Data Source
AI summary
The semiconductor device includes: a heat spreader; a semiconductor element joined to the heat spreader via a first joining member; a first lead frame joined to the heat spreader via a second joining member; a second lead frame joined to the semiconductor element via a third joining member; and a mold resin. In a cross-sectional shape obtained by cutting at a plane perpendicular to a one-side surface of the heat spreader, an angle on the third joining member side out of two angles formed by a one-side surface of the semiconductor element and a straight line connecting an end point of a joining surface between the third joining member and the semiconductor element and an end point of a joining surface between the third joining member and the second lead frame, is not smaller than 90° and not larger than 135°.