Wiring Substrate High Elongation Outer Insulating Layer
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Solution Overview
Problem
Existing multilayer wiring substrates face stress and potential cracking issues due to differences in thermal expansion coefficients between insulating layers and conductor pads, leading to defects when external components are connected.
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 elongation rate than inner layers, and a covering insulating layer exposing the entire surface of the conductor pads to alleviate stress and prevent cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the insulating layers have uniform elongation rates, then the manufacturing process is simple, but thermal stress causes cracking at the conductor pad connections
Solution Approach 1:
The patent applies local quality by making the outermost insulating layer (first insulating layer) have a different elongation rate than the inner insulating layers. Specifically, the first insulating layer has a higher elongation rate to accommodate thermal expansion differences at the conductor pad interface, while inner layers maintain standard properties. This localized differentiation resolves the contradiction by improving connection reliability at the critical interface without unnecessarily complicating the entire layer structure.
Solution Approach 2:
The patent changes the physical parameter of elongation rate for the insulating layers to solve the thermal stress problem. By setting the elongation rate of the first insulating layer higher than that of other insulating layers, the patent creates a gradient structure that progressively absorbs thermal stress, preventing crack formation at the conductor pad connections while maintaining manufacturing feasibility.
2Object-affected harmful factors
If the covering insulating layer completely covers the conductor pads, then protection is improved, but stress concentration increases causing cracks
Solution Approach 1:
The patent applies the taking out principle by creating openings in the covering insulating layer (second insulating layer) that expose the conductor pads. Instead of completely covering the conductor pads with the second insulating layer, the patent extracts the insulating material from specific regions to form openings, allowing the conductor pads to be partially exposed. This reduces stress concentration at the pad-insulating layer interface while maintaining protection in other areas, resolving the contradiction between protection and stress concentration.
3Ease of manufacture
If all insulating layers have the same material properties, then manufacturing is easier, but thermal expansion differences cause cracking
Solution Approach 1:
The patent applies local quality by differentiating the material properties of insulating layers based on their functional requirements. The first insulating layer (outermost) uses material with higher elongation rate to handle thermal expansion at the conductor pad interface, while inner insulating layers use standard materials. This localized material differentiation improves manufacturing precision for crack-free connections without significantly complicating the overall manufacturing process.
Solution Approach 2:
The patent employs composite materials by using different insulating layer materials with different elongation rates in the same wiring substrate structure. This composite approach allows each layer to be optimized for its specific function: the outermost layer handles thermal stress, while inner layers provide structural support and electrical insulation, achieving crack-free connections while maintaining manufacturing feasibility.
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 increased elongation rate of the outermost insulating layer effectively relaxes thermal and external stresses, suppressing the occurrence of cracks and ensuring reliable connections and signal transmission quality.
Implementation Method 1
differences in thermal expansion coefficients between insulating layers and conductor pads
Implementation Method 2
elongation rate of the first insulating layer is greater than an elongation rate of each of the insulating layers other than the first insulating layer
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 an elongation rate of the first insulating layer is greater than an elongation rate of each insulating layer other than the first insulating layer in the build-up part, and the covering layer is formed such that the covering layer has an opening entirely exposing an upper surface and a side surface of the first conductor pad.