Power Semiconductor Joining Layer Densification by Ultrasonic Sintering
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Solution Overview
Problem
Existing power semiconductor devices face insufficient heat dissipation performance due to inadequate densification of the joining layer, particularly when using wide-bandgap semiconductors like SiC and GaN, which leads to thermal strain and potential damage during high-temperature operations.
Innovation Solution
A manufacturing method involving a stacked configuration with an intermediate structure containing a metal paste layer and penetrating members, where vibrators attached to these members apply vibrations to enhance sintering and fusion of metal particles, thereby densifying the joining layer and improving heat conduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If ultrasonic waves are applied through a heat spreader to remove air voids in a solder layer, then air void removal is attempted, but the joining layer is not sufficiently densified and heat conductivity remains insufficient
Solution Approach 1:
A dedicated ultrasonic vibrator is introduced as an intermediary device that directly contacts the joining layer through the heat spreader. This vibrator serves as a mediator to transmit ultrasonic energy effectively into the solder layer, enabling proper densification and achieving the required heat conductivity that previous methods failed to attain.
Solution Approach 2:
Ultrasonic vibration is applied directly to the joining layer through the heat spreader during the heating process. This mechanical vibration disrupts air voids and promotes densification of the solder material, transforming the joining layer from a porous, low-conductivity structure to a dense, high-conductivity structure that effectively dissipates heat from the SiC semiconductor chip.
2Manufacturing precision
If higher pressure is applied to densify a joining material containing Ag particles, then densification is improved, but the semiconductor element may be damaged
Solution Approach 1:
The patent replaces the traditional mechanical pressure application method with ultrasonic vibration. Instead of applying high mechanical pressure that could damage the semiconductor chip, ultrasonic waves are used to generate acoustic pressure and cavitation effects that densify the joining material through a non-contact, gentler mechanism that does not risk chip damage.
Solution Approach 2:
The patent changes the physical parameters of the joining process by introducing ultrasonic frequency vibration (typically 20-100 kHz) during heating. This parameter change allows densification to occur through vibrational energy rather than mechanical compression, enabling effective joining without subjecting the brittle SiC chip to damaging high pressures.
3Ease of manufacture
If solder is used as joining material, then ease of manufacture is improved, but thermal strain causes deterioration during high temperature operation
Solution Approach 1:
The patent employs a composite joining material system consisting of silver (Ag) particles dispersed in an organic solvent vehicle. This composite structure allows the Ag particles to provide high thermal conductivity and thermal strain resistance, while the organic binder facilitates screen printing application and subsequent sintering. The resulting sintered Ag layer maintains both manufacturability and high-temperature reliability.
Solution Approach 2:
The patent changes the material state from conventional solder (melting point 96-106°C) to sintered silver (sintering temperature 600-800°C). This parameter change in joining material temperature and phase transformation enables the joining layer to withstand the high operating temperatures of SiC devices while maintaining structural integrity and thermal performance.
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 method enhances the quality and strength of the joining layer, reducing thermal resistance and internal stress, leading to improved heat dissipation performance and reduced risk of cracking in power semiconductor devices.
Implementation Method 1
at least one first vibrator attached to the at least one first penetrating member penetrating the first metal paste layer is vibrated
Implementation Method 2
The first metal paste layer is heated so that the plurality of first metal particles are sintered or fused
Implementation Method 3
The first metal paste layer is heated so that the plurality of first metal particles are sintered or fused
Implementation Method 4
The first metal paste layer is heated so that the plurality of first metal particles are sintered or fused
Implementation Method 5
heat conductivity of a joining layer may be insufficient... heat dissipation performance of a power semiconductor device may be insufficient
Data Source
AI summary
A power semiconductor element and a support member are stacked with an intermediate structure being interposed between the power semiconductor element and the support member. The intermediate structure includes a first metal paste layer and at least one first penetrating member. The first metal paste layer contains a plurality of first metal particles. The at least one first penetrating member penetrates the first metal paste layer. At least one first vibrator attached to the at least one first penetrating member penetrating the first metal paste layer is vibrated. The first metal paste layer is heated so that the plurality of first metal particles are sintered or fused.