Silver-Indium TLP Bonding Joint for Low-Resistance Heat Spreading
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Solution Overview
Problem
The challenge in manufacturing high power semiconductor devices is to develop a reliable bonding method between semiconductor devices and diamond-based heat-spreading mounts that minimizes thermal resistance, is mechanically robust, chemically stable, and resistant to thermal fatigue, while avoiding the high cost and CTE mismatch issues associated with gold-rich eutectic bonding methods.
Innovation Solution
A silver-indium transient liquid phase (TLP) bonding method is developed, which forms a sandwich bonding structure with a first Ag—In solid solution layer in contact with the semiconductor device, a second Ag—In solid solution layer in contact with the heat-spreading mount, and an Ag2In intermetallic compound layer sandwiched between, achieving a bonding joint thickness of ≤3 μm through a low-temperature, low-pressure process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gold-rich eutectic bonding is used, then bonding reliability is improved, but cost increases and CTE mismatch issues occur
Solution Approach 1:
The patent changes the material parameters by using Ag-In eutectic bonding instead of Au-Sn bonding, achieving a lower melting point (119°C vs 280°C) and better CTE matching with diamond. This parameter change resolves the contradiction by providing reliable bonding without the harmful CTE mismatch stress and reduced cost
Solution Approach 2:
The patent replaces expensive gold-rich eutectic materials with cheaper Ag-In eutectic materials. The Ag-In bonding joint achieves comparable or superior reliability at lower cost, effectively substituting expensive materials with more economical alternatives that maintain performance
2Strength
If bonding pressure is increased, then bonding strength is improved, but semiconductor devices are easily cracked
Solution Approach 1:
The patent utilizes the phase transition of Ag-In from solid to liquid at its eutectic melting point (119°C). The liquid phase enables low-pressure bonding by flowing into interface gaps and wetting surfaces, achieving strong bonding without applying high mechanical pressure that would crack the semiconductor devices
Solution Approach 2:
The patent replaces mechanical pressure-based bonding with thermal-energy-based bonding. By heating to the eutectic temperature, the Ag-In material transitions to liquid phase and bonds through capillary action and surface tension, substituting mechanical force with thermal and surface energy mechanisms that avoid device damage
3Object-generated harmful factors
If bonding temperature is reduced, then CTE mismatch stress is reduced, but bonding reliability may be compromised
Solution Approach 1:
The patent changes the thermal parameter by using a lower eutectic temperature (119°C for Ag-In vs 280°C for Au-Sn). This temperature reduction decreases CTE mismatch stress during cooling while the eutectic reaction ensures complete bonding. The low temperature maintains reliability through liquid-phase bonding mechanics rather than compromising it
4Loss of energy
If bonding joint thickness is reduced, then thermal resistance is reduced, but mechanical robustness may be compromised
Solution Approach 1:
The patent uses the liquid-phase eutectic reaction to create an ultra-thin bonding joint. The liquid Ag-In flows under low pressure to form a uniform thin layer that solidifies into a robust joint. The phase transition mechanism enables achieving both thin thickness (low thermal resistance) and mechanical strength simultaneously
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 Ag—In TLP bonding method provides a reliable, ultra-thin bonding joint with high thermal conductivity, mechanical strength, and chemical stability, reducing thermal resistance and avoiding CTE mismatch-induced stress, while being more cost-effective than gold-rich eutectic methods, thus enhancing the performance and reliability of high power semiconductor devices.
Implementation Method 1
silver-indium transient liquid phase (TLP) bonding method is developed, which forms a sandwich bonding structure
Implementation Method 2
a first Ag—In solid solution layer in contact with the semiconductor device, a second Ag—In solid solution layer in contact with the heat-spreading mount
Data Source
AI summary
A semiconductor structure having a silver-indium transient liquid phase bonding joint is provided. With the ultra-thin silver-indium transient liquid phase bonding joint formed between the semiconductor device and the heat-spreading mount, its thermal resistance can be minimized to achieve a high thermal conductivity. Therefore, the heat spreading capability of the heat-spreading mount can be fully realized, leading to an optimal performance of the high power electronics and photonics devices.