Power Module Substrate Alloy Gradient for Ceramic Bond Reliability
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Solution Overview
Problem
Existing power module substrates face challenges in achieving high bonding strength and reliability between ceramic and metal components, particularly under thermal cycle loads, due to limitations in surface roughness and the use of brazing filler materials, which can lead to interfacial peeling and excessive stress.
Innovation Solution
A power module substrate with a concentration gradient layer of additional elements like Ag, Zn, and Ge at the bonding interface, where these elements are solid-solubilized in the metal plate, enhancing bonding strength through solid solution strengthening, and a method for producing this substrate without the need for a thin film of brazing filler material, using a fixation layer and diffusion bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If surface roughness of the ceramic substrate is reduced to improve bonding strength, then bonding strength is improved, but interfacial peeling occurs during peeling tests
Solution Approach 1:
The patent applies local quality by creating a concentration gradient layer where additional elements (Ag, Zn, Ge, or Mg) are distributed non-uniformly across the metal plate thickness. The concentration is highest at the bonding interface and decreases toward the opposite surface, with specific concentration ranges defined at different depths (0.01-10% at interface, 0.001-1% at 50μm distance). This localized compositional variation provides enhanced bonding strength at the interface while maintaining overall structural integrity, resolving the contradiction between improving bonding strength and preventing interfacial peeling.
Solution Approach 2:
The patent employs parameter changes by systematically varying the concentration of additional elements within the metal plate to achieve optimal bonding performance. By controlling the concentration gradient of elements like Ag (0.05-10% by mass), Zn (0.01-5% by mass), Ge (0.01-5% by mass), or Mg (0.01-5% by mass) at positions 50μm from the interface, the patent optimizes both bonding strength and peeling resistance simultaneously, transforming a binary choice into a continuous optimization problem.
2Temperature
If a heat sink is bonded on the power module substrate to improve heat dissipation, then heat dissipation is improved, but shearing force acts on the bonding interface under thermal cycle load
Solution Approach 1:
The concentration gradient layer with highest element concentration at the bonding interface provides localized strengthening where the heat sink bonds to the substrate. This localized reinforcement specifically addresses the shearing force generated by thermal cycling at the heat sink interface, while the gradual concentration decrease toward the power element side maintains appropriate thermal and mechanical properties for device operation.
Solution Approach 2:
The patent creates a composite structure by incorporating additional elements (Ag, Zn, Ge, or Mg) into the aluminum or aluminum alloy metal plate, forming a compositionally graded composite material. This composite structure with varying local composition provides enhanced mechanical strength at the heat sink bonding interface to resist thermal cycle-induced shearing forces while maintaining overall thermal conductivity for effective heat dissipation.
3Strength
If brazing filler material is used to bond ceramic and metal components, then bonding strength is improved, but production cost and process complexity increase
Solution Approach 1:
The patent extracts and eliminates the brazing filler material from the bonding process. Instead of using a separate filler material layer, the additional elements (Ag, Zn, Ge, or Mg) are directly incorporated into the metal plate itself, creating a concentration gradient that provides bonding functionality inherently within the metal substrate. This integration removes the need for separate brazing operations and filler material handling, simplifying the manufacturing process while maintaining strong bonding.
Solution Approach 2:
The patent merges the functions of the metal plate and brazing filler material into a single integrated structure. The additional elements distributed in the concentration gradient layer serve both as structural components of the metal plate and as bonding agents at the ceramic interface, eliminating the need for a distinct filler material layer and reducing production complexity.
4Volume of moving object
If power module size is reduced to improve integration, then miniaturization is achieved, but bonding interface reliability becomes more critical
Solution Approach 1:
The concentration gradient layer provides localized enhancement of bonding interface quality without increasing overall module dimensions. By concentrating additional elements (Ag, Zn, Ge, or Mg) at the bonding interface with specific concentration ranges (0.01-10% by mass at interface), the patent achieves superior bonding strength and reliability in a compact form factor, enabling miniaturization without compromising interface reliability.
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 provides a power module substrate with improved thermal cycle reliability, strong bonding between ceramic and metal components, and cost-effective production, reducing the risk of interfacial peeling and excessive stress, while maintaining a thin oxide layer for enhanced bonding yield.
Implementation Method 1
a concentration gradient layer in which a concentration of one or more additional elements selected from Ag, Zn, Ge, and Mg gradually decreases with moving away from the bonding interface between the ceramic substrate and the metal plate in a stacked direction; and a high concentration part of the one or more additional elements selected from Ag, Zn, Ge, and Mg formed in the bonding interface, wherein the one or more additional elements selected from Ag, Zn, Ge, and Mg are solid-solubilized in the metal plate
Implementation Method 2
a method of producing this substrate without the need for a thin film of brazing filler material, using a fixation layer and diffusion bonding
Data Source
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AI summary
Provided is a power module substrate including a ceramic substrate, and a metal plate which contains aluminum or an aluminum alloy, and which is stacked and bonded on a surface of the ceramic substrate, wherein one or more additional elements selected from Ag, Zn, Ge, Mg, Ca, Ga, and Li are solid-solubilized in the metal plate, and the Ag concentration in the metal plate in the vicinity of the interface with the ceramic substrate is greater than or equal to 0.05% by mass and less than or equal to 10% by mass, or the total concentration of Zn, Ge, Mg, Ca, Ga, and Li in the metal plate in the vicinity of the interface with the ceramic substrate is greater than or equal to 0.01% by mass and less than or equal to 5% by mass.