Liquid Metal Power Module Packaging for Thermal Stress Relief
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Solution Overview
Problem
Conventional power module packaging structures face thermo-mechanical stress issues due to mismatched coefficients of thermal expansion and high Young's modulus, leading to reliability and lifetime reductions, especially in high-power and high-temperature environments, and rigid connections exacerbate these problems.
Innovation Solution
A power module packaging structure utilizing liquid metal for electrical connections, incorporating a groove filled with gallium indium silver alloy to decouple thermal strain between components, with an insulating sealing ring to prevent short circuits and a flexible connection mode to reduce shear stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid soldering materials are used to connect chip and substrate, then electrical connection is achieved, but thermo-mechanical stress increases due to CTE mismatch
Solution Approach 1:
The patent changes the physical state of the connection material from solid (rigid solder) to liquid, allowing the material to flow and adapt to thermal expansion differences. The liquid metal maintains electrical conductivity while accommodating CTE mismatch through its fluid nature, reducing thermo-mechanical stress at interfaces.
Solution Approach 2:
The liquid metal acts as an intermediary between the chip and substrate, providing both electrical connection and stress relief. It mediates the mechanical incompatibility between components with different CTE values while maintaining functional electrical connectivity.
2Stress or pressure
If soft buffer materials are used to reduce thermo-mechanical stress, then stress is reduced, but thermal resistance increases
Solution Approach 1:
The patent uses a composite approach by combining liquid metal properties - achieving both mechanical compliance (like soft materials) and high thermal conductivity (unmatched by conventional soft buffers). The liquid metal phase provides unique dual benefits of stress absorption and superior heat dissipation.
3Reliability
If rigid connection is used to ensure electrical connection, then electrical connectivity is achieved, but mechanical damage risk increases under thermal cycling
Solution Approach 1:
The patent transitions from a static rigid connection to a dynamic liquid connection that can adapt its shape and flow in response to mechanical stresses. The liquid metal remains connected but changes configuration under stress, preventing brittle failure while maintaining electrical continuity.
4Ease of manufacture
If conventional packaging materials are used, then manufacturing is simplified, but CTE mismatch with SiC chip causes stress concentration
Solution Approach 1:
The patent changes the physical state parameter of the connection material from solid to liquid, fundamentally altering how stress is transmitted and distributed. This phase change enables the material to flow into stress concentration areas and eliminate them while maintaining manufacturing feasibility.
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 liquid metal-based packaging significantly reduces thermo-mechanical stress, maintains electrical and thermal performance, improves module reliability, simplifies manufacturing, and facilitates cost-effective maintenance and recycling.
Implementation Method 1
the liquid metal absorbs the lower cermet substrate and the upper printed circuit board together through surface tension
Implementation Method 2
liquid metal is filled in the groove, and the power semiconductor chip is embedded into the liquid metal in the groove so as to realize electrical connection
Data Source
AI summary
A power module packaging structure based on liquid metal, including an upper printed circuit board or an upper cermet substrate, a power semiconductor chip and a lower cermet substrate, wherein a lower surface copper layer of the circuit board is connected with the chip through a soldering layer, a groove is formed in an upper copper layer of the lower cermet substrate through etching, the surface of the upper copper layer of the lower cermet substrate is subjected to silver plating, liquid metal is filled in the groove, and the chip is embedded into the liquid metal to realize electrical connection between the upper surface of the lower cermet substrate and the lower surface of the chip; an insulating sealing ring is arranged on the circuit board around the chip; and the liquid metal absorbs the lower cermet substrate and the upper printed circuit board together through surface tension.