SiC Device Interconnects Using Ternary TLP Bonding
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Solution Overview
Problem
Conventional solder and brazing techniques for silicon carbide and gallium nitride-based power electronics are unstable at elevated temperatures, leading to voids and debonding, which increases thermal resistance and reduces reliability, while existing TLP bonding methods lack the necessary thermal and mechanical stability for wide band gap devices.
Innovation Solution
The use of transient liquid phase (TLP) bonding with ternary or quaternary mixtures of Ag, Au, Sn, and In to form bonds that are thermally and electrically conductive, void and creep resistant, and corrosion resistant, capable of operating reliably up to 400°C, by diffusing metals to create a high-melting-point alloy with lower thermal resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional solder materials and techniques are used to form interconnects, then ease of manufacture is improved, but reliability deteriorates at elevated temperatures due to voids and debonding
Solution Approach 1:
The patent changes the material parameters by using TLP bonding materials with specific compositional ranges (e.g., 60-90 wt% Ag, 10-40 wt% Cu) and controlling bonding parameters (temperature 200-400°C, time 5-60 minutes) to achieve high-temperature stability while maintaining manufacturing feasibility
Solution Approach 2:
The patent employs composite interconnect structures consisting of multiple metal layers (e.g., Ag-Cu-TLP bonds combined with Au or Ni underlayers) to achieve both ease of manufacture and high reliability at elevated temperatures up to 400°C
2Loss of energy
If TLP bonding is used to improve thermal conductivity, then thermal resistance is reduced, but manufacturing complexity increases due to multi-step diffusion processes
Solution Approach 1:
The patent applies preliminary action by pre-depositing metal layers (such as Au, Ni, or Cu underlayers) on substrates before TLP bonding, and pre-heating substrates to bonding temperature, thereby simplifying the overall manufacturing process while achieving low thermal resistance
Solution Approach 2:
The patent optimizes bonding parameters including temperature (200-400°C), time (5-60 minutes), and material composition to achieve complete diffusion and low thermal resistance without requiring excessively complex multi-step processes
3Strength
If die attachments are made thick to improve mechanical strength, then strength is improved, but thermal resistance increases
Solution Approach 1:
The patent changes the material parameters by using TLP bonding materials with superior mechanical properties that enable thin bond layers (5-50 micrometers) to achieve both high strength and low thermal resistance, eliminating the need for thick die attachments
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 bonding method provides stable, low-thermal-resistance connections that maintain performance under high voltage and temperature cycling, with superior corrosion resistance and mechanical robustness, outperforming traditional solder and binary TLP materials.
Implementation Method 1
The process utilizes transient liquid phase (TLP) bonding to attach SiC based electronic devices to metallized substrates
Implementation Method 2
The metals form a system, with the combination of the metals at specific concentrations having an elevated melting point greater than the melting points of the second metal. In U.S. Pat. No. 5,038,996 the metals are then heated to a temperature above the melting point of the mixture, causing an interdiffusion of the metals, forming a bond
Data Source
AI summary
A method of forming packages containing SiC or other semiconductor devices bonded to other components or conductive surfaces utilizing transient liquid phase (TLP) bonding to create high temperature melting point bonds using in situ formed ternary or quaternary mixtures of conductive metals and the devices created using TLP bonds of ternary or quaternary materials. The compositions meet the conflicting requirements of an interconnect or joint that can be exposed to high temperature, and is thermally and electrically conductive, void and creep resistant, corrosion resistant, and reliable upon temperature and power cycling.