Power Module Silicone Gel Compressive Stress Sealing
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Solution Overview
Problem
The existing power module sealing structures using silicone gel face issues with bubble formation and detachment at higher temperatures, leading to degraded insulation performance due to reduced gas solubility and increased internal stress, which also complicates the sealing process and increases module size.
Innovation Solution
A power module design that maintains compressive stress in the silicone gel filling, using a sealed region with a cover and case structure, where the silicone gel is cured under pressurization to prevent bubble formation and detachment, ensuring reliable insulation performance across varying temperatures and pressures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone gel is used for sealing in high-temperature environments, then insulation sealing is achieved, but bubbles form and detachment occurs due to reduced gas solubility
Solution Approach 1:
The patent applies preliminary anti-action by pre-compressing the silicone gel during the sealing process to establish compressive stress before the module operates. This pre-applied compression counteracts the tendency of bubbles to form and detach when gas solubility decreases at high temperatures, preventing the harmful effect before it can occur during operation.
Solution Approach 2:
The patent changes the stress state parameter of the silicone gel from neutral or tensile to compressive by applying external pressure during sealing. This parameter change ensures that the gel maintains compressive stress under operating conditions, which suppresses bubble formation and detachment caused by temperature-induced gas solubility changes.
2Reliability
If internal stress of silicone gel is made tensile to suppress detachment, then bonding is improved, but bubbles are promoted and insulation performance degrades
Solution Approach 1:
The patent inverts the conventional approach by applying compressive stress instead of tensile stress to the silicone gel. Rather than pulling the gel tight to prevent detachment, the patent compresses the gel, which simultaneously achieves both bonding and bubble suppression, reversing the traditional understanding of how to secure adhesive materials.
3Reliability
If a pressurized gas sealing structure is used to maintain compressive stress in silicone gel, then bubble formation is suppressed, but module size increases and productivity decreases
Solution Approach 1:
The patent extracts the pressurizing function from the operational phase and relocates it to the manufacturing phase. By applying compression during sealing and maintaining the sealed structure without requiring continuous pressurization, the patent eliminates the need for complex pressurizing mechanisms while preserving the beneficial compressive stress state.
Solution Approach 2:
The patent performs the pressurization action preliminarily during the sealing process rather than maintaining it continuously during operation. The compressive stress is established in advance during manufacturing, and the sealed structure is designed to maintain this stress state without requiring active pressurization systems during the module's operational life.
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 solution effectively suppresses bubble formation and detachment between the silicone gel and insulating substrate, maintaining reliable insulation performance and reducing the module's size while improving productivity.
Implementation Method 1
the internal stress of the silicone gel should be compressive stress. This is because when the internal stress is tensile stress, the tensile stress acts to increase and promote the bubbles and the detachment.
Implementation Method 2
Generally, the amount of gas that can be dissolved in silicone gel decreases as the temperature increases. Therefore, as the operating temperature range of a power module increases and silicone gel is used at a higher temperature, an excess of gas, which cannot be dissolved in the silicone gel, forms bubbles.
Data Source
AI summary
A power module that can realize insulation performance by suppressing the occurrence of bubbles in silicone gel and the detachment between the silicone gel and an insulating substrate during high temperature, during low temperature and during low atmospheric pressure, to thereby suppress degradation of insulation performance. The power module includes: an insulating substrate having a front surface on which a power semiconductor element is mounted; a base plate joined to a back surface of the insulating substrate; a case fixed to the base plate and surrounding the insulating substrate; a cover fixed to the case and forming a sealed region; and a silicone gel serving as a filling member filling the entire sealed region and having internal stress maintained at compressive stress.