Multi-Chip Substrate Layout for Thermal Stress Relief
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Solution Overview
Problem
Conductive traces in multi-chip devices experience stress and potential cracking due to thermal expansion and warpage of the substrate, leading to reliability and yield issues.
Innovation Solution
Replacing a portion of the substrate material with a material having a lower coefficient of thermal expansion underlies conductive traces between chips, reducing substrate expansion and warpage, thereby alleviating stress on the traces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the substrate material is used as-is, then the device structure is simple, but the conductive traces experience stress and cracking due to thermal expansion and warpage
Solution Approach 1:
The patent applies local quality by replacing only a specific portion of the substrate material (the first portion) with a different material (second material) that has a lower coefficient of thermal expansion. This localized material substitution targets the area underlying the conductive traces and gaps between chips, providing differential thermal expansion control where needed without modifying the entire substrate, thus resolving the contradiction between reliability improvement and device complexity.
Solution Approach 2:
The patent employs composite materials by creating a substrate structure that combines two different materials (first material and second material) with different coefficients of thermal expansion. The first portion of the substrate retains the original material while the second portion uses a material with lower thermal expansion, creating a composite substrate that reduces overall thermal expansion and warpage, thereby improving conductive trace reliability without requiring complete substrate redesign.
2Reliability
If the substrate material is replaced with lower thermal expansion material, then thermal expansion and warpage are reduced, but manufacturing complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the substrate into distinct portions (first portion and second portion) with different material compositions. The first portion uses the original substrate material while the second portion uses a material with lower thermal expansion coefficient. This segmented approach allows selective material placement in critical areas, reducing thermal expansion and warpage effects on conductive traces while maintaining manufacturing feasibility through targeted rather than universal material replacement.
3Temperature
If the substrate expands under heat, then the substrate responds to thermal energy, but the conductive traces experience stress and potential breakage
Solution Approach 1:
The patent directly addresses thermal expansion by incorporating a second material with a lower coefficient of thermal expansion in the portion of the substrate underlying the conductive traces. This material substitution reduces the differential thermal expansion between the substrate and the conductive traces during temperature changes, minimizing stress accumulation and preventing trace breakage, thus resolving the contradiction between temperature response and structural strength.
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 approach enhances the reliability and yield of multi-chip devices by minimizing the risk of cracks and breakage in conductive traces, improving their performance under heat exposure.
Implementation Method 1
The second material reduces expansion and warpage of the substrate in the presence of a heat source compared to the expansion and warpage of the substrate of the first material in the presence of a heat source
Data Source
AI summary
A multi-chip device includes a first material within a substrate. The first material has a first coefficient of thermal expansion different than a second coefficient of thermal expansion of the substrate. A first chip overlies a first portion of the first material and a first portion of the substrate. A second chip overlies a second portion of the first material and a second portion of the substrate. The first material is between the first portion of the substrate and the second portion of the substrate.