Wiring Substrate Terminal with Graded Crystal Structure
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Solution Overview
Problem
Wiring substrates face issues with thermal stress due to differences in thermal expansion coefficients between insulation layers and connection terminals, leading to crack formation during reliability tests.
Innovation Solution
A wiring substrate design featuring a protective insulation layer that covers the connection terminals, with a lower portion having smaller crystal grains and higher roughness, and an upper portion with larger crystal grains, improving adhesiveness and reducing thermal stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection terminals are formed with uniform crystal grain size, then manufacturing is simpler, but thermal stress concentration occurs at the interface with insulation layer causing cracks
Solution Approach 1:
The connection terminal is designed with different crystal grain sizes in different regions: the lower portion (near insulation layer interface) has smaller crystal grains to reduce thermal stress concentration and prevent cracks, while the upper portion has larger crystal grains. This local differentiation resolves the contradiction by optimizing each region for its specific functional requirements.
Solution Approach 2:
The connection terminal is segmented into multiple portions (lower portion with smaller crystal grains and upper portion with larger crystal grains) rather than being uniform throughout. This segmentation allows each portion to have optimized properties for its specific location, improving overall reliability while managing the complexity through functional分区.
2Strength
If connection terminals are directly exposed without protective coating, then manufacturing is easier, but adhesiveness between connection terminal and insulation layer is insufficient
Solution Approach 1:
The connection terminal features a lower portion with smaller crystal grains located near the insulation layer interface, which provides enhanced adhesiveness. This local structural optimization improves the bonding strength at the critical interface without requiring additional protective coatings, thereby resolving the contradiction between adhesiveness and manufacturing complexity.
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
The design effectively disperses thermal stress, limits crack formation, and enhances the adhesiveness between the connection terminals and insulation layers, ensuring reliable mounting of semiconductor chips.
Implementation Method 1
the insulation layer and the connection terminals have different thermal expansion coefficients. Thus, when a reliability test is performed on the wiring substrate through a heating cycle, thermal stress is generated by the difference in thermal expansion coefficient
Implementation Method 2
A side surface of the lower portion is set to have a higher roughness degree than a side surface of the upper portion
Data Source
AI summary
A wiring substrate includes a first connection terminal and a protective insulation layer. The first connection terminal is electrically connected to a wiring layer by a via wiring and projects upward from an upper surface of an insulation layer. The protective insulation layer is located on the upper surface of the insulation layer to contact and cover a portion of a side surface of the first connection terminal. The first connection terminal includes a lower portion that is continuous with the via wiring and an upper portion that is continuous with the lower portion. The lower portion is smaller in crystal grain size than the upper portion. The lower portion and the upper portion are formed from the same metal material. The side surface of the lower portion has a higher roughness degree than the side surface of the upper portion.