Power Module Holding Plate for Insulation Reliability
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Solution Overview
Problem
Conventional power modules experience deteriorated insulation performance due to bubble formation and detachment of silicone gel from the insulating substrate at varying temperatures and high voltages, leading to potential dielectric breakdown.
Innovation Solution
A power module design featuring a holding plate fixed to the inner wall of the case, in contact with the sealing resin, which maintains compressive stress on the silicone gel to prevent bubble formation and detachment, using a releasing treatment layer to manage thermal expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the holding cover is made movable to accommodate thermal expansion of the sealing resin, then the sealing resin can expand freely at high temperatures, but compressive stress cannot be generated to suppress bubble formation
Solution Approach 1:
The holding plate is designed to be movable in the vertical direction to accommodate thermal expansion of the sealing resin at high temperatures, while still maintaining contact to generate compressive stress. This dynamic structure allows the system to adapt to temperature changes without compromising insulation performance.
Solution Approach 2:
The holding plate changes its position parameter (vertical displacement) in response to temperature changes, allowing the sealing resin to expand while maintaining compressive stress. The plate moves downward when the resin expands and upward when it contracts, dynamically adjusting to maintain optimal stress conditions.
2Reliability
If the end portion of the cover is fixed to the case to generate compressive stress, then bubble formation is suppressed, but tensile stress occurs at low temperatures causing bubble growth and detachment
Solution Approach 1:
The holding plate is designed to be movable rather than fixed, allowing it to dynamically adjust its position based on temperature conditions. At low temperatures, the plate moves upward with the contracting resin, preventing tensile stress. At high temperatures, it moves downward to allow expansion while maintaining compressive stress through its weight and positioning.
Solution Approach 2:
The holding plate is divided into a fixed portion (attached to the case) and a movable portion (that contacts the sealing resin). This segmentation allows the fixed portion to provide stable mounting while the movable portion accommodates thermal expansion and contraction, generating appropriate stress conditions.
3Temperature
If the operating temperature range is increased to achieve higher performance, then the power module can operate at higher temperatures, but excess gas forms bubbles in the silicone gel deteriorating insulation
Solution Approach 1:
The holding plate is positioned and weighted to pre-establish compressive stress on the sealing resin before thermal expansion occurs. This preliminary compressive stress counteracts the tendency of gas to form bubbles when the resin expands at high temperatures, preventing insulation deterioration in advance.
Solution Approach 2:
The holding plate's vertical position changes in response to temperature changes. At operating temperatures, the plate moves to maintain optimal compressive stress on the sealing resin, ensuring that even when gas expansion occurs, bubbles do not form or grow, thereby maintaining insulation performance across the extended temperature range.
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 enhances the reliability of the power module by suppressing bubble growth and detachment, thereby maintaining effective insulation across a wide temperature range and high voltage conditions.
Implementation Method 1
when the power semiconductor element is operated at a high temperature, the sealing resin can be thermally expanded to readily push up the holding cover
Implementation Method 2
the silicone gel is pulled to the cover portion at a low temperature while being thermally contracted
Data Source
AI summary
The power module includes: an insulating substrate having an upper surface on which a semiconductor element is mounted; a base plate joined to a lower surface of the insulating substrate; a case member surrounding the insulating substrate and adhered to the base plate; a sealing resin provided in a region surrounded by the base plate and the case member, so as to seal the insulating substrate; and a holding plate projecting from an inner wall of the case member to above an outer peripheral portion of the insulating substrate, the holding plate being fixed to the inner wall, the holding plate being in contact with the sealing resin.