Raised Metal Pad Ceramic Substrate Thermal Stress Mitigation
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Solution Overview
Problem
Ceramic substrates used in high-power electronic components face interfacial breaks and thermal stress due to significant differences in thermal expansion coefficients between metal layers and ceramic substrates, leading to deformation and reliability issues.
Innovation Solution
A ceramic substrate component with a raised metal pad featuring a thicker base portion and a thinner top layer, where the top layer has a thermal expansion coefficient greater than the ceramic substrate, is designed to mitigate thermal stress by distributing temperature differences and enhancing extensibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the thickness of metal layer is increased to handle high-power chips, then the heat dissipation capability is improved, but the thermal stress at the interface increases causing interfacial breaks
Solution Approach 1:
The patent applies local quality by creating a non-uniform metal layer structure where the pad region has greater thickness than the surrounding circuit traces. This localized thickening concentrates the thermal expansion accommodation capability at the critical pad-substrate interface, allowing the pad to absorb thermal stress while maintaining thinner metal layers elsewhere to minimize overall thermal stress.
Solution Approach 2:
The patent changes the geometric parameter of the metal layer by creating a raised pad structure with increased thickness (e.g., 50-200 micrometers) compared to standard trace thickness. This parameter change allows the pad to accommodate thermal expansion differences between the metal and ceramic substrate, reducing interfacial stress while maintaining the necessary electrical and thermal functions.
2Reliability
If the metal layer is thickened to reduce thermal stress, then the reliability is improved, but the substrate becomes prone to bending and deformation
Solution Approach 1:
The raised pad structure concentrates the stress-absorbing metal thickness only at the pad locations where thermal expansion differential is most critical, rather than uniformly thickening the entire metal layer. This localized approach provides thermal stress resistance where needed while minimizing the overall metal mass that could cause substrate bending.
3Reliability
If the metal layer thickness is increased to accommodate thermal expansion differences, then the thermal stress is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent incorporates the thickened pad structure during the initial substrate fabrication process, forming the raised pads as integral part of the substrate before component assembly. This preliminary action ensures the thermal stress mitigation structure is already in place, eliminating the need for separate post-processing steps to add thickness to specific areas.
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 solution effectively reduces thermal stress at the interface, preventing interfacial breaks and ensuring reliable installation and heat dissipation for high-power chips, while allowing for customizable thicknesses to suit various applications.
Implementation Method 1
The top layer has a thermal expansion coefficient greater than the ceramic substrate body. As such, damages due to thermal stress occurring at the interface between the base portion and the ceramic substrate body can be mitigated.
Data Source
AI summary
A ceramic substrate component suitable for high-power chips includes a ceramic substrate body and at least one raised metal pad. The ceramic substrate body has an upper surface and a lower surface opposite to the upper surface. The raised metal pad includes a base portion and a top layer. The base portion, which is attached to the upper surface of the ceramic substrate body, has a thickness between 10 and 300 micrometers, and a thermal expansion coefficient greater than the ceramic substrate body. The top layer is formed on the base portion and adapted to install a high-power chip thereon. The top layer extends an area less than the base portion but greater than the high-power chip, and has a thermal expansion coefficient greater than the ceramic substrate body. As such, damages due to thermal stress occurring between the base portion and the ceramic substrate body can be mitigated.