Nitride Ceramic Substrate Brazing for Stronger Power Module Joining
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Solution Overview
Problem
Ceramic substrates, particularly aluminum nitride, face challenges with low mechanical strength and thermal conductivity, leading to cracking under assembly and thermal cycles, which is exacerbated in high-load and thermal conditions, necessitating improved mechanical reliability and bonding strength for power modules.
Innovation Solution
A method involving the use of active metal brazing with a mixed raw material containing Y2O3 and rare-earth elements, followed by tape casting, sintering, gradual cooling, and surface sandblasting to enhance joining strength and thermal conductivity, using Ag—Cu active metal paste for conductive wiring patterns on both aluminum nitride and silicon nitride substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If aluminum nitride substrate is used for high thermal conductivity, then thermal conductivity is improved, but mechanical strength and toughness deteriorate, causing cracks under tightening and thermal cycles
Solution Approach 1:
The patent uses aluminum nitride ceramic substrate as a composite material that combines high thermal conductivity with sufficient mechanical strength. The ceramic substrate integrates both thermal management functionality and structural integrity, resolving the contradiction between thermal performance and mechanical reliability in power module applications
2Strength
If active metal bonding method is used to bond metal plate on ceramic substrate, then bonding strength is improved, but manufacturing complexity increases due to additional process steps
Solution Approach 1:
The patent applies preliminary surface treatment to the ceramic substrate before bonding, including roughening the surface and applying a primer layer. These preliminary actions prepare the surface to enhance subsequent bonding strength while systematically organizing the manufacturing process to manage complexity
Solution Approach 2:
The patent introduces a primer layer as an intermediary substance between the ceramic substrate and the metal plate. This primer layer acts as a mediator that chemically bonds to both surfaces, significantly enhancing bonding strength while providing a standardized interface that simplifies the overall bonding process
3Strength
If silicon nitride substrate is used for excellent mechanical strength, then mechanical strength is improved, but thermal conductivity deteriorates compared to aluminum nitride
Solution Approach 1:
The patent selects aluminum nitride as the ceramic material, changing the material parameter from silicon nitride to achieve optimal balance between thermal conductivity and mechanical strength. This parameter change in material selection resolves the contradiction by choosing a ceramic composition that simultaneously provides high thermal conductivity (≈200-250 W/mK) and adequate mechanical strength for power module applications
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 method achieves high joining strength, thermal conductivity, and heat dissipation, improving the mechanical reliability and thermal performance of nitride ceramic substrates, with joining strengths ranging from 10 to 20 KN/m and enhanced thermal conductivity.
Implementation Method 1
a step of performing sintering at a temperature of 1,800 to 1,900° C. for two to ten hours under 1 to 10 atm of nitrogen and hydrogen gas
Implementation Method 2
a step of forming an aluminum nitride sintered substrate by performing gradual cooling at a speed of 50 to 100° C. per hour
Implementation Method 3
a step of forming unevenness at surfaces of aluminum nitride and silicon nitride through sandblasting
Implementation Method 4
a step of bonding a copper plate to the aluminum nitride sintered substrate with active metal brazed copper (AMC)
Data Source
AI summary
A method for manufacturing active metal-brazed a nitride ceramics substrate having excellent joining strength, includes: a step of preparing a mixed raw material; a step of forming a green sheet of the mixed raw material by a tape casting method; a step of removing a binder by performing degreasing; a step of performing sintering; a step of forming an aluminum nitride sintered substrate by performing gradual cooling; and a step of printing a conductive wiring pattern with active metal paste on the aluminum nitride sintered substrate.