Semiconductor Device Joining Layers with Different Melting Points
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Solution Overview
Problem
Conventional semiconductor devices with MOSFETs using compound semiconductor substrates face issues with reduced joining area of conductive members to electrodes due to positional shifts during the joining process, affecting current flow efficiency.
Innovation Solution
A semiconductor device design where a first joining layer with a higher melting point is used to join the semiconductor element's electrode to the die pad, and a second joining layer with a lower melting point is used to join the conductive member to the electrode, ensuring a stable and larger joining area while preventing positional shifts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the first conductive joining material and the second conductive joining material are melted at the same time through reflow, then the manufacturing process is simplified, but the position of the MOSFET shifts relative to the die pad, reducing the joining area of the conductive member to the source electrode
Solution Approach 1:
The patent applies different melting points to the first and second conductive joining materials. The first joining material (e.g., Au-Si eutectic alloy with melting point around 630°C) melts at a higher temperature than the second joining material (e.g., Sn-Ag-Cu solder with melting point around 217°C). This parameter differentiation enables sequential melting and solidification processes that prevent MOSFET position shifts while maintaining manufacturing efficiency.
Solution Approach 2:
The first conductive joining material is melted and solidified to join the drain electrode to the die pad before the second conductive joining material is melted. This preliminary action secures the MOSFET position relative to the die pad, preventing shifts during subsequent joining operations. The sequential process ensures that the MOSFET is firmly positioned before the conductive member is joined to the source electrode.
2Volume of moving object
If a small MOSFET is employed to reduce device size, then the device size is reduced, but the joining area of the conductive member to the source electrode is reduced, impairing current flow
Solution Approach 1:
The patent uses joining materials with different melting points to enable precise control of the joining process. The second joining material is designed to melt at a lower temperature than the first joining material, allowing the conductive member to be joined to the source electrode after the MOSFET is securely positioned. This ensures maximum joining area is achieved even with small MOSFETs, maintaining current flow capability while minimizing device size.
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
This configuration maintains a larger joining area for the conductive member, supporting higher current flow without impairing the semiconductor device's performance and improving manufacturing efficiency.
Implementation Method 1
electrically joining the first electrode to the obverse surface by melting and solidifying the first joining material
Implementation Method 2
electrically joining the conductive member to the second electrode by melting and solidifying the second joining material
Data Source
AI summary
A semiconductor device including a die pad, a semiconductor element, a first joining layer, a first conductive member, and a second joining layer. The die pad has an obverse surface facing in a thickness direction. The semiconductor element has a first electrode provided opposing the obverse surface, and a second electrode provided on the opposite side to the first electrode in the thickness direction. The first electrode is electrically joined to the obverse surface. The first joining layer electrically joins the first electrode and the obverse surface to each other. The first conductive member is electrically joined to the second electrode. The second joining layer electrically joins the first conductive member and the second electrode to each other. The melting point of the first joining layer is higher than the melting point of the second joining layer.