Semiconductor Post Protrusion Prevents Stress Concentration
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Solution Overview
Problem
Semiconductor devices using the WL-CSP technique face issues with stress concentration on external connecting terminals and cracking between passivation films and interlayer films due to thermal expansion/shrinkage, leading to potential damage and malfunction.
Innovation Solution
The semiconductor device incorporates a post structure with a protruding portion that is in contact with the sealing resin layer, preventing stress concentration on external connecting terminals and includes a trench for the sealing resin layer to cover side surfaces, thereby preventing cracking between passivation and interlayer films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the post tip end surface is exposed from the epoxy resin by grinding, then the post can be connected to the solder ball, but the metallic material of the post extends and spreads on the surface of the epoxy resin causing short circuit
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on the post before the grinding step. This protrusion is specifically designed to prevent the metallic material from extending and spreading on the epoxy resin surface during the subsequent grinding process. The protrusion acts as a pre-prepared structural feature that anticipates and prevents the harmful spreading effect before it occurs.
Solution Approach 2:
The patent applies preliminary anti-action by creating a protrusion that counteracts the natural tendency of the metallic material to spread. The protrusion's geometry and positioning are designed to oppose the spreading force, effectively preventing the short circuit problem before it can manifest during the grinding and assembly process.
2Device complexity
If the corner of the sealing resin layer contacts the solder ball on the post, then the structure is compact, but stress concentrates on the contact portion causing damage during thermal expansion/shrinkage
Solution Approach 1:
The patent applies beforehand cushioning by designing the post with a protrusion that extends toward the sealing resin layer surface. This protrusion acts as a cushioning element that prevents direct contact between the corner of the sealing resin layer and the solder ball. By providing this intermediate protective structure in advance, the patent eliminates the stress concentration problem that would occur during thermal expansion and shrinkage cycles.
3Ease of manufacture
If the post is made of metallic material with ductility, then the post can be formed by plating, but the tip end of the post sags on the epoxy resin surface during grinding
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on the metallic post during the plating or forming process, before the grinding step. This protrusion is specifically designed to compensate for the expected sagging that will occur during grinding. By pre-shaping the post with this protruding feature, the final post tip position achieves the required precision despite the ductility of the metallic material.
Data Source
AI summary
There is provided a semiconductor device with which stress can be prevented from locally concentrating on an external connecting terminal on a post and thus damages of the external connecting terminal can be prevented. The semiconductor device includes a semiconductor chip, a sealing resin layer stacked on a surface of the semiconductor chip, and the post which penetrates the sealing resin layer in a stacking direction of the semiconductor chip and the sealing resin layer, protrudes from the sealing resin layer, and has a periphery of the protruding portion opposedly in contact with a surface of the sealing resin layer in the stacking direction.