Copper Feature Design for Substrate Warpage Control
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Solution Overview
Problem
Laminate substrates experience warpage due to mismatched bending resistance and thermal expansion coefficients between conductive and dielectric layers, leading to issues during fabrication and assembly.
Innovation Solution
Incorporating material void patterns in the bottom conductive layers based on the layout of the top conductive layers to balance bending resistances and thermal expansion coefficients, thereby reducing warpage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional laminate substrate design with uniform conductive layers is used, then electrical functionality is achieved, but warpage occurs due to mismatched bending resistance and thermal expansion between top and bottom layers
Solution Approach 1:
The patent applies local quality by creating non-uniform copper distribution in the bottom conductive layer. Specifically, copper is selectively removed from regions corresponding to top-layer signal traces, while maintaining copper in power/ground regions. This localized modification balances the bending resistance and thermal expansion characteristics between top and bottom layers, eliminating warpage while preserving electrical functionality.
Solution Approach 2:
The patent introduces asymmetry by designing the bottom conductive layer with a non-uniform copper pattern that mirrors the top layer's signal trace layout. This asymmetric copper removal creates complementary bending resistance profiles between top and bottom layers, allowing the substrate to maintain flatness during thermal cycling and fabrication processes.
2Shape
If copper is removed from bottom conductive layer to reduce warpage, then substrate flatness improves, but electrical connectivity and power distribution must be maintained
Solution Approach 1:
The patent selectively removes copper from specific regions of the bottom conductive layer while preserving copper in critical power and ground regions. The copper removal pattern is designed to mirror only the signal trace regions of the top layer, ensuring that electrical connectivity for power distribution remains intact while achieving warpage reduction.
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 approach significantly reduces both absolute and thermal warpage of the laminate substrate, improving its stability and functionality by matching the bending resistances and thermal expansion characteristics of the top and bottom conductive layers.
Implementation Method 1
A bottom conductive layer is provided with a material void pattern that is based upon a corresponding top conductive layer and that balances bending resistances of the top and bottom conductive layers
Implementation Method 2
A coefficient of thermal expansion (CTE) mismatch between the dielectric layers and the copper remaining on the conductive layers and dielectric cure shrinkage during fabrication are driving forces for bending as the temperature changes
Data Source
AI summary
An approach is provided in which a laminate substrate includes top layers, bottom layers, and a core layer. The top layers are positioned between the core layer and a top surface metallurgy (TSM) layer and include at least one top conductive layer. The bottom layers are positioned between the core layer and a bottom surface metallurgy (BSM) layer and include at least one bottom conductive layer includes a material void pattern that is based upon the top conductive layer and reduces warpage of the laminate substrate.