Ceramic Circuit Board Brazing with TiN Phase Stress Relaxation
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Solution Overview
Problem
Ceramic-metal circuit boards face issues with thermal cycle resistance and thermal shock resistance due to voids in the brazing material layer, leading to cracking of the ceramic substrate during the etching process for forming circuit patterns.
Innovation Solution
A ceramic circuit board with a brazing material protrudent part comprising a Ti phase and TiN phase by 3% by mass or more, bonded to a copper circuit plate through a brazing material layer of Ag, Cu, and Ti, with minimal voids less than 200 µm², to relax thermal stress and improve bonding defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a brazing material layer is made to protrude outward from the copper circuit plate to relax stress concentration, then thermal cycle resistance is improved, but voids are produced in the protruding brazing material layer during etching process
Solution Approach 1:
The invention changes the chemical composition parameters of the brazing material layer by adding aluminum (5-20 mass%) to the Ag-Cu-Ti system. This compositional modification alters the material's etching resistance properties while maintaining its stress relaxation capability, thereby preventing void formation during the etching process without sacrificing thermal cycle resistance.
Solution Approach 2:
The invention creates a composite brazing material system combining Ag-Cu-Ti with aluminum addition. This composite composition leverages the stress relaxation properties of Ti phases and the etching resistance of aluminum, achieving both improved thermal cycle resistance and reduced void formation during etching.
2Power
If copper plate thickness is increased to improve electrical and thermal conductivity, then electrical conductivity and thermal conduction property are improved, but thermal cycle resistance and thermal shock resistance are decreased due to stress mismatch with ceramic
Solution Approach 1:
The brazing material layer acts as an intermediary between the copper circuit plate and ceramic substrate. By incorporating Ti phases and aluminum, this intermediate layer provides stress relaxation capabilities that compensate for the thermal expansion mismatch between thick copper plates and ceramic, thereby maintaining both high electrical/thermal conductivity and improved thermal cycle resistance.
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 enhances thermal cycle resistance and reduces bonding defects, resulting in a ceramic circuit board with improved reliability and thermal shock resistance.
Implementation Method 1
substrates of silicon nitride or aluminum nitride having a high thermal conduction property and high electrical insulation property are used
Implementation Method 2
A ceramic-metal circuit board including the high-thermal-conduction ceramic substrate bonded to a metal plate with an active brazing metal comprising Ag-Cu
Data Source
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AI summary
According to one embodiment, a ceramic circuit board includes a ceramic substrate (1), a copper circuit plate (5) and a brazing material protrudent part (4a). The copper circuit plate (5) is bonded to at least one surface of the ceramic substrate (1) through a brazing material layer including Ag, Cu, and Ti. The brazing material protrudent part (4a) is formed by the brazing material layer which protrudes outward from a side surface of the copper circuit plate. The brazing material protrudent part (4a) includes a Ti phase and a TiN phase by 3% by mass or more in total, which is different from the total amount of a Ti phase and a TiN phase in the brazing material layer (4b) that is interposed between the ceramic substrate and the copper circuit plate. The number of voids each having an area of 200 µm2 or less in the brazing material protrudent part (4a) is one or less (including zero).