Power Module Pressing Plate Maintains Silicone Gel Compressive Stress
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Solution Overview
Problem
Traditional power modules experience insulation performance deterioration due to bubble generation and detachment between silicone gel and the insulating substrate, especially at higher temperatures or working voltages, as the internal stress of silicone gel becomes either tensile or compressive, leading to insulation failure.
Innovation Solution
A power module design that includes a pressing plate in close contact with the sealing resin and a lid fixed to the case, preventing the pressing plate from ascending, thereby maintaining compressive stress within the silicone gel to suppress bubble generation and detachment, even under thermal expansion and contraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the press lid is made movable to allow thermal expansion of silicone gel, then the ease of operation is improved, but the insulation performance deteriorates due to loss of compressive stress
Solution Approach 1:
The press lid is designed to be movable in the vertical direction, allowing it to dynamically adjust its position in response to thermal expansion of the silicone gel while maintaining continuous compressive contact. This dynamic structure enables the lid to follow the gel's expansion without losing the necessary compressive stress for insulation performance.
Solution Approach 2:
Protrusions on the press lid engage with corresponding structures on the case to provide guided movement and maintain proper positioning. These protrusions act as intermediaries that allow vertical movement for thermal expansion while preventing lateral displacement and ensuring the lid remains in the correct position to maintain compressive stress.
2Reliability
If the pressing plate is prevented from ascending, then the insulation performance is maintained through compressive stress, but the device complexity increases
Solution Approach 1:
The lid structure is segmented with protrusions that engage with corresponding features on the case. This segmentation allows the lid to be prevented from ascending in a controlled manner while maintaining simplicity - the protrusions provide the necessary constraint without requiring complex mechanical systems.
Solution Approach 2:
The pressing plate is designed to be movable within controlled limits rather than completely fixed. The ability to move downward for thermal expansion while being prevented from ascending creates a dynamic system that maintains insulation performance without excessive complexity. The asymmetry in movement freedom (downward allowed, upward prevented) achieves the desired stress maintenance.
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 design enhances the reliability of the power module by mitigating thermal stress and maintaining insulation performance across varying temperatures and voltages, preventing insulation deterioration.
Implementation Method 1
the thermally-expanded sealing resin can easily push up the press lid when the power semiconductor elements are operated at a high temperature
Data Source
AI summary
A power module will be provided which can suppress insulation performance deterioration caused by heat cycle to ensure insulation performance, by suppressing generation of bubbles and occurrence of detachments between silicone gel and an insulating substrate at a high or low temperature or at a high working voltage. The power module includes: an insulating substrate 2 on a first face of which a semiconductor element 3 is provided; a base plate 1 joined to a second face of the insulating substrate 2; a case member 6 surrounding the insulating substrate 2 and being in contact with a face of the base plate 1, that is joined to the insulating place 2; sealing resin 8 filling a region surrounded by the base plate 1 and the case member 6 to seal the insulating substrate 2; a pressing plate 9 disposed in close contact with a surface of the sealing resin 8 in a side of the first face of the insulating substrate 2; and a lid member 7 facing an opposite face of the pressing plate 9 with respect to a face thereof in close contact with the sealing resin 8, and being fixed to the case member 6 at a position to prevent the pressing plate 9 from ascending.