Wiring Substrate with High-Strength Outer Insulating Layer
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Solution Overview
Problem
Existing multilayer wiring substrates face issues with stress concentration and crack formation near conductor pads due to differences in thermal expansion coefficients and external forces, leading to potential defects in the insulating layers.
Innovation Solution
A wiring substrate design featuring a core substrate with build-up parts having insulating layers and conductor layers, where the outermost insulating layer has a higher tensile strength than inner layers, and a covering insulating layer exposing the entire surface of the conductor pads, dispersing stress and preventing crack formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulating layers are made with uniform tensile strength, then the manufacturing process is simple, but stress concentration and crack formation occur near conductor pads due to thermal expansion differences and external forces
Solution Approach 1:
The patent applies local quality by making the outermost insulating layer (first insulating layer) have different properties from the inner insulating layers. Specifically, the first insulating layer has higher tensile strength than the other insulating layers, creating a gradient structure that provides enhanced crack resistance at the critical outer surface where stress concentration occurs, while maintaining simpler structure for the inner layers
Solution Approach 2:
The patent uses composite materials by combining insulating layers with different tensile strengths in a layered structure. The first insulating layer is made of a material or treated to have higher tensile strength compared to the other insulating layers, creating a composite insulating system that leverages the strengths of different materials at different locations to resist cracking
2Reliability
If the covering insulating layer completely covers the conductor pads, then protection is maximized, but stress dispersion and crack prevention are reduced
Solution Approach 1:
The covering insulating layer is designed with local quality by creating an opening that entirely exposes the upper surface and side surface of the first conductor pad. This localized exposure allows stress to be dispersed away from the conductor pad interface, preventing crack formation at critical locations while the rest of the covering insulating layer continues to provide protection
Data Source
AI summary
A wiring substrate includes a core substrate, a build-up part formed on a surface of the substrate and including insulating layers and conductor layers, and a covering insulating layer formed on the build-up part such that the covering layer is covering the outermost surface of the build-up part. The build-up part is formed such that the insulating layers include a first insulating layer forming the outermost one of the insulating layers, that the conductor layers include a first conductor layer formed on the first insulating layer and including a first conductor pad, and that a tensile strength of the first insulating layer is higher than a tensile strength of each insulating layer other than the first insulating layer in the first build-up part, and the covering layer is formed such that the covering layer has opening entirely exposing an upper surface and a side surface of the first conductor pad.