Resin Multilayer Substrate Thermal Stress Mitigation
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Solution Overview
Problem
Conventional resin multilayer substrates face damage due to stress caused by thermal expansion, particularly at the joint portions where different resin layers with varying linear expansion coefficients are subjected to heat, leading to potential delamination and mechanical failure.
Innovation Solution
The resin multilayer substrate design incorporates a via conductor in a first resin layer with a higher linear expansion coefficient and a joint portion on the second resin layer, which has a smaller expansion coefficient than the first resin layer, reducing stress on the joint portion during heating. This configuration involves attaching a second resin layer with a smaller linear expansion coefficient to the first resin layer, forming via conductors, and creating joint portions on the second resin layer to mitigate thermal expansion-induced damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a low melting point material is used for the joint portion to adhere resin layers at low temperature, then the resin layers can be joined effectively, but the joint portion becomes more brittle and susceptible to damage from thermal expansion stress
Solution Approach 1:
The patent changes the material parameters of the joint portion by using a low melting point material that becomes brittle at operating temperatures. This parameter change allows low-temperature joining while accepting the brittleness as a trade-off, which is then compensated by the intermediate resin layer design
Solution Approach 2:
The patent introduces an intermediate resin layer (second resin layer) between the joint portion and the first resin layer. This intermediate layer acts as a mediator that absorbs thermal expansion stress, protecting the brittle joint portion from direct stress while allowing the low melting point material to function effectively
2Device complexity
If the joint portion is in contact with the first resin layer having a large linear expansion coefficient, then joining is simplified, but stress on the joint portion increases during heating causing damage
Solution Approach 1:
The patent applies local quality by creating different resin layers with different linear expansion coefficients at different locations. The second resin layer has a smaller linear expansion coefficient than the first resin layer, providing localized stress relief at the critical joint portion interface while maintaining overall structural integrity
Solution Approach 2:
The second resin layer serves as an intermediary between the joint portion and the first resin layer. This intermediate layer buffers the thermal expansion stress from the high-expansion first resin layer, reducing the stress transmitted to the brittle joint portion while maintaining structural connectivity
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 reduces damage to the joint portions by distributing thermal stress more evenly, enhancing the mechanical integrity and reliability of the resin multilayer substrate during heating processes such as reflow or bending, while also allowing for easier manufacturing and reduced conductor loss in high-frequency applications.
Implementation Method 1
when the linear expansion coefficient of the second resin layer in contact with the joint portion is large, there is a risk of damaging the joint portion with stress applied to the joint portion, due to expansion of the second resin layer as a result of heating of the multilayer substrate
Data Source
AI summary
A resin multilayer substrate includes a laminate including resin layers including a first resin layer and a second resin layer that are laminated, a via conductor in the first resin layer, and a joint portion that includes at least a portion in the second resin layer and is joined to the via conductor. The joint portion is more brittle than the via conductor. A linear expansion coefficient of the second resin layer is larger than a linear expansion coefficient of the via conductor and a linear expansion coefficient of the joint portion, and is smaller than a linear expansion coefficient of the first resin layer.