Hemispheric Post Electrodes for WLCSP Stress Reduction
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Solution Overview
Problem
In semiconductor devices using WLCSP technology, the corner portions of post electrodes can cause intensive stress on solder balls, leading to crack formation during mounting on a print circuit board.
Innovation Solution
The post electrodes are designed with a hemispheric top surface, eliminating corner portions and forming a hemispheric interface with external connecting terminals, which reduces stress and enhances lateral stress resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the post electrode is formed with a flat top surface by grinding, then the manufacturing process is simple and efficient, but corner portions are formed that cause intensive stress on solder balls leading to crack formation
Solution Approach 1:
The top surface of the post electrode is formed with a curved shape (convex in plan view) instead of a flat surface, eliminating corner portions that concentrate stress. This curvature distributes the stress from the solder ball more evenly across the post electrode surface, preventing crack formation while maintaining manufacturing feasibility through controlled formation during plating or molding processes.
2Device complexity
If the post electrode has a flat top surface, then the interface with external connecting terminals is simple, but the lateral stress resistance is insufficient
Solution Approach 1:
The curved top surface of the post electrode creates a dome-like interface with the external connecting terminal (solder ball). This curved geometry provides better mechanical interlocking and distributes lateral stresses more effectively compared to a flat interface, enhancing the strength of the connection without significantly increasing structural complexity.
Data Source
AI summary
A semiconductor device according to the present invention includes: a semiconductor chip; a sealing resin layer formed on the semiconductor chip; and a post electrode formed in a through-hole penetrating through the sealing resin layer in a thickness direction, and having a hemispheric top surface.