MOSFET Electrode Joining Layout for Reflow Shift Stability
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Solution Overview
Problem
Semiconductor devices with MOSFETs face challenges in maintaining a stable joining state of conductive members to electrodes, particularly due to the lightweight nature of MOSFETs and the use of solder, which can lead to positional shifts and reduced joining areas, affecting current conversion efficiency and yield.
Innovation Solution
A semiconductor device design featuring a die pad with a semiconductor element having electrodes of different sizes, where a first conductive member with a higher Young's modulus is joined to a larger electrode, and a second conductive member with a lower Young's modulus is joined to a smaller electrode, using specific joining layers and methods to ensure stable electrical connections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a lightweight MOSFET is used to reduce device size, then the device size is reduced, but the MOSFET position shifts relative to the drain lead during solder reflow
Solution Approach 1:
The patent applies preliminary action by forming a support structure (protrusion and groove mechanism) before the solder reflow process. The protrusion from the drain lead fits into a groove on the drain electrode, pre-establishing a mechanical constraint that prevents position shifts during subsequent soldering operations. This preliminary mechanical support compensates for the lightweight nature of the MOSFET without increasing overall device size.
2Reliability
If the MOSFET position shifts relative to the die pad, then the joining area of the metal clip to the gate electrode is reduced, but this degradation of joining state reduces yield
Solution Approach 1:
The support structure (protrusion-groove mechanism) performs preliminary action by establishing precise positional alignment before the metal clip joining process. The mechanical constraint ensures that even if the MOSFET shifts during solder reflow, the gate electrode remains properly positioned relative to the die pad, maintaining adequate joining area for the metal clip and preventing yield reduction.
Solution Approach 2:
The patent applies parameter changes by modifying the mechanical support parameters - specifically, the protrusion dimensions (width W1, length L1) and groove dimensions (width W2, length L2) are optimized to provide sufficient positional stability. By adjusting these geometric parameters, the system maintains reliable joining conditions without requiring larger electrodes or clips that would reduce productivity.
3Power
If a metal clip is used to electrically join multiple electrodes to increase current capacity, then the current handling capability is improved, but the joining area is reduced when position shifts occur
Solution Approach 1:
The protrusion-groove support structure performs preliminary action by establishing and maintaining precise spatial relationships between the drain lead, drain electrode, and gate electrode throughout the manufacturing process. This preliminary mechanical constraint ensures that when the metal clip is applied to join multiple electrodes, the electrodes remain in their correct positions, maximizing the joining area and ensuring reliable high-current connections.
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 improves the joining state of conductive members to each electrode, supporting larger currents while reducing the impact of positional shifts and enhancing manufacturing efficiency, thereby increasing the yield and reliability of semiconductor devices.
Implementation Method 1
electrically joining the first electrode to the obverse surface by melting and solidifying the joining material
Data Source
AI summary
A semiconductor device includes a die pad, a semiconductor element, a joining layer, a first conductive member, and a second conductive member. The semiconductor element has a first electrode opposing an obverse surface of the die pad, and a second electrode and a third electrode that are opposite to the first electrode in a thickness direction. The first electrode is electrically joined to the obverse surface. The 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 conductive member is electrically joined to the third electrode. The area of the third electrode is smaller than the area of the second electrode as viewed along the thickness direction. The Young's modulus of the second conductive member is smaller than the Young's modulus of the first conductive member.