TLP Bond Layer Composition for High-Temperature Power Electronics
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Solution Overview
Problem
Traditional soldering techniques fail to provide suitable bonding of semiconductor devices to metal substrates at elevated operating temperatures, leading to delamination due to thermally-induced stresses caused by coefficient of thermal expansion mismatch.
Innovation Solution
A transient liquid phase (TLP) composition comprising high melting temperature (HMT) particles with core-shell structures and low melting temperature (LMT) particles, which forms a TLP bond layer with graded stiffness and ductility to compensate for thermally-induced stresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If traditional soldering techniques are used to bond semiconductor devices to metal substrates, then bonding is achieved at lower temperatures, but the bonding fails at elevated operating temperatures (approaching 200°C) due to thermally-induced stresses from CTE mismatch
Solution Approach 1:
The patent changes the bonding temperature parameter from traditional soldering temperatures (<183°C) to elevated TLP bonding temperatures (280-350°C). This parameter change enables the formation of a TLP bond layer with intermetallic compounds that have higher thermal stability and matched CTE properties, allowing reliable operation at temperatures approaching 200°C without delamination
Solution Approach 2:
The patent employs a composite bonding layer consisting of multiple materials including tin (Sn), nickel (Ni), copper (Cu), and their intermetallic compounds (IMCs) such as Cu6Sn5, Ni3Sn4, and NiSn. This composite structure provides both the low melting point needed for bonding and the high temperature stability required for elevated operating conditions, resolving the contradiction between bonding feasibility and operational reliability
2Reliability
If TLP bonding is used to achieve reliable high-temperature bonding, then bonding reliability at elevated temperatures is improved, but large thermally-induced stresses during cooling from TLP sintering temperature may cause delamination
Solution Approach 1:
The patent creates local quality variations within the bonding layer by controlling the distribution and concentration of different materials (Sn, Ni, Cu) and their intermetallic compounds at specific locations and depths within the bond layer. This local compositional control allows different regions to accommodate thermal stresses differently, with softer regions absorbing stress and harder regions providing structural integrity, preventing delamination during cooling
Solution Approach 2:
The patent controls the bonding temperature parameter (280-350°C) and holds it isothermally during the TLP process. This temperature parameter control ensures complete melting of the low-melting-point material and proper formation of intermetallic compounds, creating a bond layer with optimized mechanical properties that can withstand thermally-induced stresses during subsequent cooling
3Strength
If a bonding layer is used to bond semiconductor devices to metal substrates, then bonding is achieved, but the bonding layer may lack sufficient stiffness to secure devices reliably at high operating temperatures
Solution Approach 1:
The patent employs a composite bonding layer containing multiple materials (Sn, Ni, Cu) and their intermetallic compounds in specific proportions. The intermetallic compounds (Cu6Sn5, Ni3Sn4, NiSn) provide high stiffness and strength, while the remaining eutectic mixture maintains ductility. This composite structure achieves sufficient bonding strength and device security at high temperatures without requiring overly complex multi-layer structures
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 TLP bond layer effectively mitigates thermally-induced stresses, ensuring reliable bonding and preventing delamination at high operating temperatures, while maintaining sufficient stiffness to secure semiconductor devices to metal substrates.
Implementation Method 1
The bonding layer at least partially melts and isothermally solidifies to form a TLP bond between the semiconductor device and metal substrate at TLP bonding temperatures
Implementation Method 2
The bonding layer at least partially melts and isothermally solidifies to form a TLP bond
Data Source
AI summary
A transient liquid phase (TLP) composition includes a plurality of first high melting temperature (HMT) particles, a plurality of second HMT particles, and a plurality of low melting temperature (LMT) particles. Each of the plurality of first HMT particles have a core-shell structure with a core formed from a first high HMT material and a shell formed from a second HMT material that is different than the first HMT material. The plurality of second HMT particles are formed from a third HMT material that is different than the second HMT material and the plurality of LMT particles are formed from a LMT material. The LMT particles have a melting temperature less than a TLP sintering temperature of the TLP composition and the first, second, and third HMT materials have a melting point greater than the TLP sintering temperature.