Wiring Substrate Protrusion Design for Solder Entry Prevention
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Solution Overview
Problem
The existing wiring substrates face issues with low adhesion between the surface-processed layer and the resin layer, leading to gaps that allow solder to enter and cause electromigration during flip-chip connections, reducing the reliability of the solder connection with metal posts.
Innovation Solution
A wiring substrate design featuring a protective insulation layer with upwardly bulged protrusions around the connection terminals, where the surface-processed layer covers the protrusions and is shaped to limit solder entry, improving adhesion and reducing electromigration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the adhesion level between the surface-processed layer and resin layer is low, then manufacturing is simpler, but gaps form that allow molten solder to enter during flip-chip connection
Solution Approach 1:
The protrusion with its curved peak and sloped surfaces creates a geometry that naturally prevents solder from entering and accumulating in gap regions. The continuous curved surface eliminates trapped voids while maintaining manufacturing feasibility through standard molding or molding-like processes.
2Device complexity
If a flat upper surface of the resin layer is used, then the structure is simpler, but gaps form between the surface-processed layer and resin layer that reduce connection reliability
Solution Approach 1:
The patent introduces a localized curved protrusion structure on the resin layer upper surface. This adds minimal complexity only where needed around the connection terminal, while the rest of the surface can remain simple and flat, achieving a balance between structural simplicity and reliability enhancement.
Solution Approach 2:
The protrusion structure is applied locally around the connection terminal rather than across the entire surface. This localized approach addresses the specific problem area where gaps and solder entry occur, without unnecessarily complicating the overall structure or requiring complex manufacturing throughout the entire component.
Data Source
AI summary
A wiring substrate including an insulation layer, a connection terminal projecting from an upper surface of the insulation layer, a protective insulation layer formed on the upper surface of the insulation layer covering a lower side surface of the connection terminal, and a cover layer covering an upper side surface and an upper surface of the connection terminal exposed from the protective insulation layer. The protective insulation layer includes an upper surface defining a protrusion bulged upward around the connection terminal. The protrusion includes a peak, a first slope inclined downward from the peak and extending toward the connection terminal, and a second slope inclined downward from the peak and extending away from the connection terminal. The cover layer further covers the first slope, the peak, and a part of the second slope.