Low-Stress Thermally Conductive Spacer with Steps
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Solution Overview
Problem
Current semiconductor device assemblies face stress issues due to thermal mismatch between substrate materials and conductive spacers, leading to potential damage to semiconductor dies, and existing solutions like copper-molybdenum spacers are costly and ineffective in stress reduction.
Innovation Solution
The implementation of a semiconductor device assembly with thermally conductive spacers featuring a plurality of steps coupled to the substrate and a surface between the steps, which distributes stress to the substrate rather than the semiconductor die, using lower-cost materials like copper or copper alloys, thereby reducing tensile stress by 10% or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional conductive spacers are used, then electrical and thermal connections are provided, but thermal mismatch stress damages semiconductor dies
Solution Approach 1:
The spacer is divided into multiple segments or layers with different material properties. Each layer is designed to handle specific stress types, with the first layer having lower modulus of elasticity to reduce tensile stress on the die, and subsequent layers providing structural support and thermal conductivity. This segmentation allows the spacer to distribute and manage thermal mismatch stress across multiple interfaces rather than concentrating it on the semiconductor die.
Solution Approach 2:
The spacer is constructed as a composite structure with at least two different materials. The first layer uses a material with lower modulus of elasticity (such as copper or copper alloy) to minimize stress transmission to the die, while other layers may use materials with higher strength and thermal conductivity. This composite approach allows optimization of each layer for its specific function: stress reduction, thermal conduction, and mechanical support.
2Reliability
If copper-molybdenum spacers are used, then stress levels are reduced, but product cost increases
Solution Approach 1:
The invention replaces expensive copper-molybdenum alloy spacers with a multi-layer structure using more cost-effective materials. The first layer uses copper or copper alloy which is cheaper than CuMo, while maintaining the stress reduction function. This substitution significantly lowers material costs while achieving comparable or better stress management performance through the composite structure.
Solution Approach 2:
The invention changes the material parameter selection from high-cost single-material spacers to low-cost multi-material spacers. By selecting materials with specific modulus of elasticity values (first layer with lower modulus), thermal conductivity, and cost characteristics, the design optimizes the balance between stress reduction effectiveness and manufacturing cost. The parameter optimization allows using abundant, cheaper materials like copper instead of rare, expensive materials like molybdenum.
3Temperature
If spacers with high thermal conductivity are used, then heat dissipation is improved, but thermal expansion mismatch increases stress
Solution Approach 1:
The spacer is segmented into multiple layers where the first layer has optimized thermal conductivity for heat dissipation while having lower modulus of elasticity for stress reduction. Subsequent layers provide additional thermal conduction pathways and structural support. This segmentation allows each layer to be optimized for its primary function while collectively managing both heat and stress.
Solution Approach 2:
The composite structure uses materials with complementary properties: the first layer uses copper or copper alloy which provides excellent thermal conductivity for heat dissipation while having lower modulus of elasticity to reduce stress. Other layers may use materials with different thermal and mechanical properties to balance heat conduction and stress management across the entire spacer structure.
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 stress on semiconductor dies, preventing damage and allowing for the use of less expensive materials while maintaining thermal conductivity, facilitating dual-sided cooling and efficient heat dissipation.
Implementation Method 1
a thermally conductive spacer having a first side and a second side
Implementation Method 2
The first side of the thermally conductive spacer can include a plurality of steps that are coupled with the substrate... distributes stress to the substrate rather than the semiconductor die
Data Source
AI summary
In a general aspect, a semiconductor device assembly can include a substrate, a semiconductor die disposed on the substrate, a thermally conductive spacer having a first side and a second side, the second side being opposite the first side. The first side of the thermally conductive spacer can include a plurality of steps that are coupled with the substrate. The first side of the thermally conductive spacer can also include a surface that is disposed between the plurality of steps, where the surface can be coupled with the semiconductor die.