Power Semiconductor Module Solder Flow Control
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Solution Overview
Problem
Power semiconductor modules face challenges in suppressing corona discharge due to voids formed between the insulating substrate and solder, which can lead to insulation reliability issues, especially when the mounting position accuracy of the insulating substrate is not precise, causing solder flow and resin filling gaps.
Innovation Solution
A power semiconductor module design that includes a solder flow resistance portion, such as a solder resist, metal oxide film, non-plated portion, or metal base recessed portion, to regulate solder flow and position, ensuring that any voids formed between the insulating substrate and solder are sandwiched between components of the same ground potential, preventing voltage application and thus suppressing corona discharge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the insulating substrate is mounted with high density, then the productivity is improved, but the manufacturing precision deteriorates due to difficulty in securing insulation properties
Solution Approach 1:
The patent divides the metal base surface into different functional regions: a soldering region for mounting the insulating substrate and a solder flow resistance region that prevents excessive solder flow. This segmentation allows high-density mounting while maintaining insulation properties by containing solder within controlled boundaries.
Solution Approach 2:
The patent applies different surface properties to different regions of the metal base. The solder flow resistance region has modified surface characteristics (through oxidation, plating, or recesses) that locally prevent solder from spreading beyond desired boundaries, while the soldering region maintains good solder wettability for reliable bonding.
2Manufacturing precision
If a metal oxide film is formed to suppress solder flow, then the manufacturing precision is improved, but the reliability deteriorates due to void formation and corona discharge
Solution Approach 1:
The patent ensures that both the insulating substrate and the solder flow resistance portion are at ground potential (GND). This equipotential configuration eliminates voltage differences across voids, preventing corona discharge even when voids form between the insulating substrate and solder.
Solution Approach 2:
The solder flow resistance portion acts as an intermediary structure that serves dual functions: it controls solder flow to achieve precise positioning while simultaneously providing a ground potential barrier that prevents corona discharge in voids.
3Reliability
If the space distance and creeping distance are increased, then the reliability is improved, but the device complexity increases due to difficulty in securing insulation properties
Solution Approach 1:
Instead of increasing horizontal space distances, the patent introduces a vertical dimension solution by creating recessed portions in the metal base. This allows the solder flow resistance function to be achieved in the vertical dimension, maintaining compact horizontal dimensions while ensuring insulation reliability.
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 design effectively suppresses corona discharge and enhances insulation reliability by ensuring that voids are electrically neutralized, even when they occur, thereby improving the module's operational safety and performance.
Implementation Method 1
the upper surface of a metal base is irradiated with a laser, to form a metal oxide film, thereby suppressing solder flow
Implementation Method 2
a solder flow resistance portion formed on a surface on which the back surface solder of the metal base is disposed
Implementation Method 3
an insulating resin filled in the insulating case... suppresses corona discharge to improve insulation reliability
Data Source
AI summary
When a distance between an end portion of a brazing material and a downward extended line of a side surface of an insulating substrate is taken as “a”, and a distance between an end portion of a solder resist on the side of a solder and the downward extended line of the side surface of the insulating substrate is taken as “b”, the positional relationship a<b is satisfied. The position of the end portion of the solder is regulated by the solder resist, and the position of the end portion of the brazing material on the side of the side surface of the insulating substrate is closer to the side of the side surface of the insulating substrate than to the position of the end portion of the solder on the side of the side surface of the insulating substrate.