Semiconductor Electrode Assembly for Thermal Stress Relaxation
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Solution Overview
Problem
The miniaturization of semiconductor devices poses challenges in forming convex portions on thick metal frames to relax stress applied to conductive bonding materials, particularly thermal stress, while maintaining a fixed thickness of the bonding material.
Innovation Solution
A semiconductor device design featuring a metal plate with a flat shape between the metal frame and the main electrode, where the metal plate has a thickness smaller than the metal frame and includes convex portions corresponding to the main electrode, forming a stress relaxation structure to absorb and distribute stress effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a convex portion is formed on a thick metal frame to maintain a fixed thickness of conductive bonding material, then stress relaxation is improved, but manufacturing difficulty increases due to the thickness of the metal frame
Solution Approach 1:
The invention divides the metal frame into two functional parts: a thick base portion for current flow and a thin protruding portion for convex portion formation. This segmentation allows the thin protruding portion to be formed with convex portions while the thick base portion maintains its current-carrying capacity, resolving the contradiction between stress relaxation and manufacturing difficulty.
Solution Approach 2:
The invention applies different thickness characteristics to different regions of the metal frame. The protruding portion has a smaller thickness than the base portion, allowing convex portions to be easily formed on the protruding portion while the thick base portion continues to handle large currents. This local differentiation resolves the contradiction between forming convex portions and maintaining adequate current flow capacity.
2Reliability
If the thickness of conductive bonding material is increased to relax stress, then stress relaxation is improved, but the device size increases
Solution Approach 1:
The invention uses convex portions (curved surfaces) on the metal frame's protruding portion to maintain a fixed minimum thickness of the conductive bonding material in critical areas. This curvature approach allows stress relaxation through controlled geometry rather than uniformly increasing bonding material thickness everywhere, thus preventing overall device size increase while still achieving stress relaxation where needed.
3Power
If a relatively thick metal frame is used for power applications, then current flow capability is improved, but stress relaxation becomes difficult due to the thickness
Solution Approach 1:
The metal frame is segmented into a thick base portion for current flow and a thin protruding portion for stress relaxation. The thick base portion maintains excellent current flow capability while the thin protruding portion with convex portions provides effective stress relaxation, thus resolving the contradiction between power capability and stress relaxation.
Solution Approach 2:
Different regions of the metal frame are given different thickness properties: the base portion is thick for high current flow capability, while the protruding portion is thin for easy convex portion formation and stress relaxation. This local quality differentiation allows both high power capability and effective stress relaxation to coexist.
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 allows for the relaxation of thermal stress applied to the conductive bonding material, prevents conductive bonding material collapse, and enhances the reliability of the semiconductor device by maintaining a predetermined distance without excessive thickness, facilitating easier manufacturing and high withstand voltage.
Implementation Method 1
the metal plate and the conductive bonding material are configured to form a stress relaxation structure which relaxes a stress applied to the metal plate and the conductive bonding material between the metal frame and the semiconductor element
Data Source
AI summary
A semiconductor device according to the present invention includes: a circuit board; a semiconductor element having a main electrode; a metal frame; and a metal plate having a flat plate shape, the metal plate being disposed between the metal frame and the main electrode, wherein the metal plate and a conductive bonding material, form a stress relaxation structure which relaxes a stress applied to metal plate and the conductive bonding material, disposed between the metal frame and the semiconductor element, and the stress relaxation structure is configured such that a thickness of the metal plate is smaller than a thickness of the metal frame, and at least one convex portion is formed on the metal plate at a position which corresponds to the main electrode. The semiconductor device according to the present invention can relax a stress applied to a conductive bonding material between a semiconductor element and a metal frame even when a relatively thick metal frame is used.