Wiring Substrate Pad Structure for Peeling-Resistant Bonding
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Solution Overview
Problem
Existing wiring substrates face issues with peeling defects and reduced electrical characteristics due to weak bonding between the protective layer and the conductor pad, especially at the interface where the protective layer only covers the side and upper surfaces of the pad without adequate contact with the insulating layer.
Innovation Solution
A wiring substrate design featuring conductor pads with a pad body extending along the insulating layer surface, where a protective layer covers both the upper and side surfaces and includes a notch part at the peripheral edge, filled with the protective layer, ensuring strong bonding and stress dispersion to the insulating layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the protective layer covers only the side and upper surfaces of the conductor pad without extending to the insulating layer interface, then the manufacturing process is simpler, but the bonding strength between the protective layer and conductor pad is weak causing peeling defects
Solution Approach 1:
The protective layer is extended from covering only the upper and side surfaces to also covering the interface region where the conductor pad contacts the insulating layer. This dimensional extension into the interface region creates a multi-dimensional coverage that simultaneously achieves strong bonding and reliable stress dispersion without complicating the manufacturing process.
Solution Approach 2:
The protective layer coverage is segmented into distinct functional zones: one region covering the upper and side surfaces of the conductor pad for protection, and another region extending to the insulating layer interface for enhanced bonding and stress dispersion. This segmentation allows each region to fulfill its specific function optimally.
2Device complexity
If the protective layer has limited contact area with the insulating layer, then the device structure is simpler, but the stress dispersion capability is reduced leading to peeling defects
Solution Approach 1:
The protective layer is designed to extend into the interface region between the conductor pad and insulating layer, adding a new dimensional aspect to its coverage. This extension creates additional contact area with the insulating layer, enabling effective stress dispersion and preventing peeling without significantly increasing structural complexity.
3Ease of manufacture
If the conductor pad interface with insulating layer is not protected, then the manufacturing process is easier, but electrical characteristics deteriorate due to peeling defects
Solution Approach 1:
The protective layer is extended into the interface region where the conductor pad contacts the insulating layer, protecting this previously exposed interface area. This dimensional extension ensures that the conductor pad interface is fully protected, preventing peeling defects that would compromise electrical characteristics while maintaining manufacturing simplicity.
Data Source
AI summary
A wiring substrate includes an insulating layer, a conductor layer formed on the insulating layer and including a conductor pad, and a solder resist layer formed on the insulating layer such that the solder resist layer has an opening entirely exposing an upper surface and a side surface of the conductor pad. The conductor layer is formed such that the conductor pad has a pad body extending along a surface of the insulating layer, and a protective layer covering an upper surface and a side surface of the pad body and including material different from material of the pad body, and the pad body of the conductor pad has a notch part formed at a peripheral edge portion of the pad body such that the notch part separates a lower surface of the pad body and the surface of the insulating layer and is filled with the protective layer.