Ceramic-Copper Bonding Layer Control for Low-Cu3P Power Modules
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Solution Overview
Problem
Power module substrates using Cu—P-based brazing materials face issues with partial discharge due to the formation of brittle Cu3P phases when subjected to high thermal cycles, leading to reduced bonding reliability and increased risk of cracking in ceramic substrates.
Innovation Solution
Limiting the area ratio of the Cu3P phase in the bonding layer to 15% or less by controlling the atomic ratio of Ti to P between 0.1 and 0.8 and adjusting the heating rate during the heat treatment process, preventing excessive formation of Cu3P and ensuring a stable bond between ceramic and Cu members.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Cu—P-based brazing material is used to bond ceramic substrate and Cu foil, then bonding strength is improved, but brittle Cu3P phases form causing partial discharge and reduced reliability under thermal cycles
Solution Approach 1:
The patent applies parameter changes by controlling the atomic ratio of Ti to P within 0.05 to 0.5 (optimally 0.1 to 0.3) and adjusting the heating rate during heat treatment (5 to 30°C/min). These parameter modifications prevent excessive Cu3P phase formation while maintaining strong bonding, resolving the contradiction between bonding strength and thermal cycle reliability
Solution Approach 2:
The patent introduces Ti as an intermediary element that reacts with P to form TiP or Ti2P compounds instead of allowing excessive Cu3P phase formation. This intermediary substance (Ti) mediates the reaction between Cu—P brazing material and ceramic substrate, preventing the harmful Cu3P phases while maintaining bonding integrity
2Productivity
If heating rate is increased to improve productivity, then manufacturing efficiency is improved, but excessive Cu3P phases form reducing bonding quality
Solution Approach 1:
The patent establishes an optimal heating rate range of 5 to 30°C/min that balances productivity and bonding quality. This parameter optimization allows sufficiently fast processing while preventing excessive Cu3P phase formation, resolving the contradiction between manufacturing efficiency and bonding quality
3Reliability
If Ti content is increased to prevent Cu3P formation, then reliability is improved, but bonding rate decreases and manufacturing complexity increases
Solution Approach 1:
The patent optimizes the Ti to P atomic ratio within 0.05 to 0.5 (optimally 0.1 to 0.3), preventing excessive Cu3P formation without requiring excessive Ti content. This balanced parameter setting maintains both reliability and bonding rate, avoiding manufacturing complexity
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
Inhibits partial discharge and enhances bonding reliability, even under high thermal cycles, by reducing the occurrence of brittle Cu3P phases and maintaining a stable interface between ceramic and Cu members, thus improving the power module's operational reliability.
Implementation Method 1
an intermetallic compound containing Cu, Mg, or Ti is formed in the vicinity of the ceramic substrate
Implementation Method 2
a Cu foil (Cu member) is bonded to one surface of a ceramic substrate (ceramic member) through a Cu—P-based brazing material
Implementation Method 3
a heat treatment is performed to bond the Cu foil
Implementation Method 4
a bonding layer formed between the ceramic member and the Cu member
Data Source
AI summary
A bonded body of the present invention includes a ceramic member formed of ceramics and a Cu member formed of Cu or a Cu alloy. In a bonding layer formed between the ceramic member and the Cu member, an area ratio of a Cu3P phase in a region extending by up to 50 μm toward the Cu member side from a bonding surface of the ceramic member is equal to or lower than 15%.