Wiring Substrate Warping Control via Layered Thermal Expansion
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Solution Overview
Problem
Conventional wiring substrates with insulating layers having different thermal expansion coefficients face challenges in reducing warping, especially when the layers without glass cloth have adjusted coefficients that are not adequately balanced.
Innovation Solution
A wiring substrate design featuring alternating layers with different thermal expansion coefficients, where the number of insulating layers with a first material having a higher coefficient matches the number with a second material having a lower coefficient, and incorporating glass cloth in specific layers to balance thermal expansion, thereby reducing warping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If insulating layers are made with the same insulating resin and adjusted to have substantially the same thermal expansion coefficient, then manufacturing complexity is reduced, but warping of the wiring substrate cannot be effectively prevented
Solution Approach 1:
The patent applies local quality by differentiating the thermal expansion coefficients of specific insulating layers. The first insulating layer (with glass cloth) has a thermal expansion coefficient of 40-60 ppm/°C, while the second insulating layer has a thermal expansion coefficient of 70-90 ppm/°C. This localized differentiation in material properties allows each layer to contribute differently to warping control, resolving the contradiction between manufacturing simplicity and warping prevention.
Solution Approach 2:
The patent changes the thermal expansion coefficient parameter of the insulating layers by selecting different materials with specific coefficient ranges. The first insulating layer uses glass cloth-based material (40-60 ppm/°C) and the second uses glass-free material (70-90 ppm/°C). This parameter change enables precise control over thermal expansion behavior, allowing the substrate to maintain stability during temperature variations without requiring complex manufacturing processes.
2Ease of manufacture
If glass cloth is included only in the insulating layer with external connection terminal bonding surface, then ease of manufacture is improved, but thermal expansion balance across the substrate is insufficient
Solution Approach 1:
The patent applies local quality by strategically placing glass cloth only in the first insulating layer (external connection terminal bonding surface), while the second insulating layer remains glass-free. This localized material distribution creates different thermal expansion coefficients (40-60 ppm/°C for first layer, 70-90 ppm/°C for second layer) that balance the overall substrate thermal expansion, maintaining both manufacturing ease and thermal reliability.
3Device complexity
If insulating layers are adjusted to have substantially the same thermal expansion coefficient, then device complexity is reduced, but warping control is insufficient
Solution Approach 1:
The patent changes the thermal expansion coefficient parameter from uniform (same for all layers) to differentiated (40-60 ppm/°C for first layer, 70-90 ppm/°C for second layer). This parameter differentiation enables precise warping control during manufacturing and operation, while the simple two-layer structure with clear material specifications keeps device complexity manageable.
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
This design effectively balances thermal expansion coefficients across the substrate, significantly reducing warping and enhancing manufacturing precision and reliability.
Implementation Method 1
the plurality of first insulating layers has a thermal expansion coefficient that is greater than a thermal expansion coefficient of the plurality of second insulating layers
Data Source
AI summary
A wiring substrate includes an insulating layer including a reinforcement member and having a first surface and a second surface positioned on an opposite side of the first surface, an electrode pad exposed from the first surface, a layered body including first insulating layers and being formed on the second surface, the first insulating layers having a first insulating material as a main component, another layered body including second insulating layers and being formed on the layered body, the second insulating layers having a second insulating material as a main component, and another electrode pad exposed from a surface of the another layered body that is opposite to the layered body. The number of the first insulating layers is equal to that of the second insulating layers. The first insulating layers have a thermal expansion coefficient that is greater than that of the second insulating layers.