Laminated High Melting Point Soldering Layer for SiC Devices
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Solution Overview
Problem
Conventional low melting point solders, such as Sn-Ag alloys, are inadequate for high-temperature applications of SiC devices, leading to issues like short circuits and delamination due to their low melting temperatures, which restrict the operational temperature range of SiC devices.
Innovation Solution
A laminated high melting point soldering layer is developed using TLP bonding with two kinds of metallic materials, specifically a combination of low melting point metal thin film layers and high melting point metal thin film layers, where the low melting point metal is dissolved and diffused into the high melting point metal, achieving a higher melting temperature and allowing for lower processing temperatures and shorter processing times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional low melting point solder (Sn-Ag alloy) is used for bonding SiC devices, then the bonding process can be performed at lower temperatures, but the bonding parts fuse and short circuits occur when driven at high temperatures (above 150°C)
Solution Approach 1:
The invention changes the material parameter (melting point) by transitioning from conventional Sn-Ag low melting point solder to a high melting point solder system (such as Ag-Sn or Cu-Sn). This parameter change enables the bonding to withstand high temperature operation (up to 400°C) without fusion, resolving the contradiction between operational temperature range and bonding reliability.
Solution Approach 2:
The invention uses composite solder material composition, specifically a high melting point solder system containing Ag and Sn in controlled ratios. This composite material approach provides both high melting point characteristics for reliability and appropriate bonding properties, simultaneously achieving high temperature operational capability and bonding reliability.
2Temperature
If TLP bonding with three or four kinds of conductive metals is used to achieve high temperature melting point bonding, then the melting point is increased, but the components become complicated and manufacturing complexity increases
Solution Approach 1:
The invention extracts and eliminates unnecessary metal components from the TLP bonding system. Instead of using three or four kinds of conductive metals, the patent simplifies the composition to primarily Ag-Sn or Cu-Sn binary systems. This extraction of excess materials reduces manufacturing complexity while maintaining the high melting point characteristic needed for SiC device operation.
Solution Approach 2:
The invention applies local quality by optimizing the solder composition specifically for the bonding interface requirements. The high melting point is achieved through targeted material selection (Ag-Sn or Cu-Sn) at the bonding location, rather than using complex multi-metal systems throughout. This localized optimization reduces overall material complexity while achieving the required thermal performance.
3Temperature
If high melting point solder is used to enable SiC devices to operate at high temperatures, then the operational temperature range is extended, but the processing time and temperature control become more critical and complex
Solution Approach 1:
The invention changes the material parameters of the solder system to achieve a balance between melting point and processing characteristics. By selecting specific Ag-Sn or Cu-Sn compositions, the patent obtains a solder with sufficiently high melting point for 400°C operation while maintaining reasonable bonding processability. This parameter optimization reduces process control difficulty compared to extreme high melting point materials.
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 laminated high melting point soldering layer enhances mass production efficiency by enabling lower processing temperatures and reduced processing times, thereby improving the reliability and operational capabilities of SiC devices at higher temperatures.
Implementation Method 1
the low melting point metal thin film layer and the high melting point metal thin film layers disposed on the surface and the back side surface of the low melting point metal thin film layer are mutually alloyed by the transient liquid phase bonding
Implementation Method 2
the low melting point metal is dissolved and diffused into the high melting point metal
Data Source
Figure 1A~1B
Figure 2
Figure 3~4
AI summary
The laminated high melting point soldering layer includes: a laminated structure which laminated a plurality of three-layered structures, the respective three-layered structures including a low melting point metal thin film layer and a high melting point metal thin film layers disposed on a surface and a back side surface of the low melting point metal thin film layer; a first high melting point metal layer disposed on the surface of the laminated structure; and a second high melting point metal layer disposed on the back side surface of the laminated structure. The low melting point metal thin film layer and the high melting point metal thin film layer are mutually alloyed by TLP, and the laminated structure, and the first high melting point metal layer and the second high melting point metal layer are mutually alloyed by the TLP bonding.