Silver-Sintered DBC Substrates for Defect-Free Ceramic-Copper Bonding
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Solution Overview
Problem
Traditional high-temperature bonding processes for direct bonded copper (DBC) substrates often result in internal defects such as ceramic-copper interfacial voids and cracks, which are unacceptable for high-power devices like IGBTs and FRDs, affecting the integrity and reliability of power modules.
Innovation Solution
A method involving sinter bonding of leadframes to a ceramic tile using a sinter material layer at low temperatures (less than 500°C) and pressures (less than 100 MPa), avoiding the defects associated with high-temperature copper cladding, and utilizing a metallized or unmetallized ceramic tile with a sinter precursor material layer to promote bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high-temperature copper cladding process is used to bond copper to ceramic tile, then strong bonding is achieved, but internal defects such as ceramic-copper interfacial voids and cracks are formed
Solution Approach 1:
The patent changes the bonding parameters from high-temperature copper cladding to low-temperature sintering process. By using sintering temperatures below 500°C with silver-based precursor materials, the process achieves strong bonding without forming interfacial voids and cracks that occur in traditional high-temperature processes.
Solution Approach 2:
The patent introduces a silver-based sintering precursor material layer as an intermediary between the copper leadframe and ceramic tile. This intermediate layer enables bonding at lower temperatures, preventing the formation of harmful interfacial defects while maintaining bond strength.
2Ease of manufacture
If traditional high-temperature bonding process is used, then copper is bonded to ceramic tile, but internal defects are formed affecting reliability
Solution Approach 1:
The patent fundamentally changes the bonding process parameters by replacing high-temperature copper cladding with low-temperature sintering. This process change maintains ease of manufacture while eliminating internal defects that compromise power module reliability.
Solution Approach 2:
The patent uses a silver-based sintering precursor material that is applied as a thin layer and consumed during the sintering process. This approach replaces the need for complex high-temperature cladding equipment and procedures with a simpler, more reliable low-temperature process.
3Reliability
If low-temperature sintering is used to avoid internal defects, then reliability is improved, but bonding strength may be compromised
Solution Approach 1:
The silver-based sintering precursor material acts as an effective intermediary that enables strong bonding at low temperatures. The silver particles sinter together and bond to both the copper leadframe and ceramic tile, achieving both high reliability and strong bonding strength simultaneously.
Solution Approach 2:
The patent employs a composite bonding approach using silver-based precursor materials that combine metallic bonding capabilities with sintering behavior. This composite material system enables strong, defect-free bonding at low temperatures by combining the advantages of both bonding mechanisms.
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 approach enables the fabrication of DBC substrates with improved reliability and minimal defects, suitable for high-power devices, by ensuring strong and defect-free interfacial bonds between ceramic and copper components, enhancing the thermal conductivity and performance of power modules.
Implementation Method 1
sinter bonding the first leadframe and the second leadframe to the ceramic tile to form a sinter bonded DBC substrate
Implementation Method 2
metallizing the first surface of the ceramic tile and applying a sintering precursor material layer to the metallized first surface of the ceramic tile
Data Source
AI summary
A method includes applying a sintering precursor material layer to each of a first surface and a second surface of a ceramic tile, and assembling a precursor assembly of a direct bonded copper (DBC) substrate by coupling a first leadframe on the sinter precursor material layer on the first surface of the ceramic tile and a second leadframe on the second surface of the sinter precursor material layer on a second surface of the ceramic tile such that the ceramic tile is disposed between the first leadframe and the second leadframe. The method further includes sinter bonding the first leadframe and the second leadframe to the ceramic tile to form a sinter bonded DBC substrate.