Tapered Wiring Substrate Projecting Part for Bonding Reliability
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Solution Overview
Problem
The existing built-up wiring substrates face issues with inconsistent bonding strengths due to varying recess part depths and widths during the formation of electrode pads, leading to degradation in bonding reliability between semiconductor chips and the substrate.
Innovation Solution
A wiring substrate design featuring a tapered projecting part on the insulating layer with a narrower cross-section towards the exposed electrode pad surface, where the plating film is only formed on the lower surface of the electrode pad, reducing the manufacturing cost and enhancing connection reliability by preventing plating on the side surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If recess parts are formed by etching a support body to create protruding electrode pads, then the electrode pads can be formed without forming bumps on the substrate side, but the depths and widths of the recess parts vary causing inconsistent bonding strengths
Solution Approach 1:
The support body is removed before the electrode pad formation process is completed. By removing the support body preliminarily, the recess parts are formed naturally, and then electrode pads are formed in these recess parts. This preliminary removal action allows the electrode pads to take shape conformally without requiring precise control of recess dimensions, thereby achieving consistent electrode pad shapes while simplifying the manufacturing process.
2Reliability
If electrode pads are formed in recess parts of the support body, then protruding electrode pads can be created, but the varying shapes of recess parts lead to degraded bonding reliability
Solution Approach 1:
The support body removal is performed as a preliminary action before electrode pad formation. This timing allows the recess parts to be naturally formed and then filled with electrode pad material that conforms to the recess shape. The electrode pads inherit the recess shape characteristics, ensuring uniform shapes and consistent bonding strengths across all pads, thereby improving bonding reliability.
Solution Approach 2:
The invention changes the timing parameter of support body removal from 'after electrode pad formation' to 'before electrode pad formation'. This parameter change in the process sequence allows the electrode pads to form in a controlled manner within the naturally created recess parts, ensuring uniform electrode pad dimensions and consistent bonding properties.
3Ease of manufacture
If plating is performed on electrode pads with varying shapes, then electrode pads can be formed, but inconsistent bonding strengths result among different electrode pads
Solution Approach 1:
By removing the support body before electrode pad formation, the recess parts are pre-formed with consistent geometries. The electrode pad plating then occurs in these pre-formed recesses, ensuring that all electrode pads achieve uniform shapes and dimensions. This preliminary support body removal action guarantees consistent bonding strengths across all electrode pads while maintaining ease of manufacture.
Data Source
AI summary
A wiring substrate includes an insulating layer having a first surface on which a projecting part is formed, and an electrode pad being formed on the projecting part and including a first electrode pad surface and a second electrode pad surface on a side opposite to the first electrode pad surface. The first electrode pad surface is exposed from the projecting part of the insulating layer. The second electrode pad surface is covered by the insulating layer. A cross-section of the projecting part is a tapered shape. One side of the cross-section toward the first electrode pad surface is narrower than another side of the cross-section toward the first surface of the insulating layer.