Direct-Bonded Metal Substrates with Phase Change Materials
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Solution Overview
Problem
Electronic assemblies in high-power applications face thermally induced mechanical stress due to differing coefficients of thermal expansion among components, which can lead to mechanical failure, especially at operating temperatures approaching 200-250°C, where heat conduction rates are limited.
Innovation Solution
A direct-bonded metal substrate with a ceramic substrate and a conductive layer that includes a phase change material core encapsulated by a layer with a higher melting temperature, allowing the phase change material to absorb heat and reduce mechanical stress through increased heat capacity and flexible encapsulating layer that flexes without melting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metal substrates are used without phase change materials, then the structure is simple and manufacturing is easier, but thermally induced mechanical stress causes mechanical failure at high operating temperatures
Solution Approach 1:
The patent applies composite materials by creating a multi-layer conductive structure consisting of a core material layer, phase change material layer, and encapsulating layer. This composite structure combines materials with different properties to simultaneously achieve thermal management, stress absorption, and mechanical strength, resolving the contradiction between reliability improvement and structural complexity
Solution Approach 2:
The patent utilizes phase transitions of the phase change material (PCM) to absorb and release thermal energy during temperature cycling. The PCM transitions between solid and liquid phases to mitigate thermally induced mechanical stress, thereby improving mechanical robustness without requiring a fundamentally different substrate architecture
2Power
If operating temperature is increased to 200-250°C for high-power applications, then power handling capability is improved, but heat conduction rate becomes limited causing greater temperature increases
Solution Approach 1:
The phase change material layer undergoes phase transitions at temperatures relevant to high-power operation (200-250°C), absorbing excess thermal energy through latent heat of fusion. This mechanism enables the substrate to handle higher power loads by providing an additional heat sinks capability, preventing runaway temperature increases
Solution Approach 2:
The encapsulating layer acts as an intermediary between the core material layer and the external environment, providing thermal management functionality. This layer facilitates heat dissipation while protecting the underlying structures, enabling sustained high-power operation without direct thermal damage to sensitive components
3Adaptability or versatility
If different materials with different coefficients of thermal expansion are used in the electronic assembly, then functional requirements are met, but thermally induced mechanical stress increases during temperature cycling
Solution Approach 1:
The patent explicitly addresses thermal expansion by designing a multi-layer conductive structure where each layer can accommodate differential thermal expansion. The encapsulating layer and phase change material layer act as compliance layers that absorb expansion stresses, allowing the assembly to maintain functional integrity while reducing mechanical stress during temperature cycling
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 configuration minimizes thermally induced mechanical stress during temperature cycling and high operating temperatures by enhancing heat removal and accommodating thermal expansion mismatches, maintaining thermal and electrical conductivity while improving mechanical robustness.
Implementation Method 1
The first core includes a phase change material having a first melting temperature
Implementation Method 2
heat flux generated by the semiconductor device during temperature cycling, for example, may cause mechanical stress due to the metal layers, the ceramic substrate, and other additional components of the electronic assembly having different coefficients of thermal expansion
Implementation Method 3
the first encapsulating layer includes an encapsulating material having a second melting temperature, and the second temperature is greater than the first melting temperature
Implementation Method 4
The heat generated through operation of the electronic assembly is thermally conducted away from the electronic devices to prevent damage to the electronic assembly
Data Source
AI summary
Direct-bonded metal substrates of electronic assemblies are disclosed. For example, the direct-bonded metal substrate includes a ceramic substrate and a first conductive layer. The first conductive layer is bonded to a first surface of the ceramic substrate, and the first conductive layer includes a first core and a first encapsulating layer that encapsulates the first core. The first core includes a phase change material having a first melting temperature, the first encapsulating layer includes an encapsulating material having a second melting temperature, and the second temperature is greater than the first melting temperature.