Power Module Resin Molding to Eliminate Voids and Cracks
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Solution Overview
Problem
Existing power modules face issues with voids and cracks due to insufficient heat resistance of silicone gel encapsulants, leading to reduced insulation reliability, and the use of liquid epoxy resin results in incomplete filling and CMR substance concerns.
Innovation Solution
A method involving a thermosetting resin composition is used, with processes including disposition, melting, pressurization-depressurization, and curing, to produce a power module with no voids or cracks, utilizing a thermosetting resin composition that is solid at 25°C, heated to melt and cure within specific temperature and pressure ranges to ensure complete filling and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If silicone gel is used as encapsulant material, then the power module can be manufactured with simple process, but the heat resistance is insufficient causing the gel to harden and crack at high temperatures
Solution Approach 1:
The patent changes the material parameters by selecting a thermosetting resin composition with specific glass transition temperature (Tg ≥ 80°C) and viscosity characteristics, replacing silicone gel to achieve both manufacturability and high-temperature reliability
Solution Approach 2:
The patent uses a composite material system consisting of thermosetting resin composition blended with inorganic filler, combining the advantages of resin (heat resistance) and filler (mechanical properties, thermal expansion matching) to resolve the contradiction between ease of manufacture and heat resistance
2Reliability
If liquid epoxy resin is used as encapsulant material to improve heat resistance, then the reliability improves, but the high viscosity causes voids and incomplete filling
Solution Approach 1:
The patent controls the viscosity parameter of the thermosetting resin composition within a specific range (100-10000 cP at 25°C) to balance heat resistance and filling completeness, avoiding the high viscosity problem of conventional liquid epoxy resin
Solution Approach 2:
The patent performs preliminary heating to melt the solid thermosetting resin composition before molding, reducing its viscosity in advance to ensure complete filling and eliminate voids, while maintaining the required heat resistance properties
3Reliability
If liquid epoxy resin is used to improve heat resistance, then the reliability improves, but CMR substances are present causing environmental concerns
Solution Approach 1:
The patent extracts and eliminates CMR substances from the encapsulant material by selecting alternative thermosetting resin compositions that do not contain carcinogenic, mutagenic, or reprotoxic substances, maintaining heat resistance while removing harmful factors
Solution Approach 2:
The patent replaces conventional epoxy resin with alternative thermosetting resin compositions that may have shorter service lives or different degradation characteristics but eliminate CMR substances, trading material longevity for environmental safety
4Stability of the object's composition
If inorganic filler is added to liquid epoxy resin to match linear expansion coefficient, then the warpage is suppressed, but the viscosity increases causing voids and cracking
Solution Approach 1:
The patent optimizes the particle size distribution and blending ratio of inorganic filler to achieve the desired linear expansion coefficient while controlling viscosity, preventing void formation during molding
Solution Approach 2:
The patent performs preliminary heating to melt the thermosetting resin composition, reducing viscosity in advance to allow complete infiltration of inorganic filler and elimination of voids before curing
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 method results in a power module with no voids or cracks, enhanced reliability, and the absence of CMR substances, effectively addressing the limitations of previous encapsulant materials.
Implementation Method 1
heating the container to melt the thermosetting resin composition
Implementation Method 2
performing one or more depressurizations and one or more pressurizations inside the molding apparatus
Implementation Method 3
performing one or more depressurizations and one or more pressurizations inside the molding apparatus
Implementation Method 4
heating the inside of the molding apparatus to cure the thermosetting resin composition
Data Source
AI summary
The present invention is a method for producing a power module, including processes (1) to (4) in the following order: (1) a disposition process of disposing a thermosetting resin composition that is solid at 25° C. into a container housing an insulator substrate with multiple semiconductor components mounted thereon; (2) a melt process involving disposing the container having the thermosetting resin composition disposed therein into a molding apparatus capable of heating, pressurization, and depressurization, and heating the container to melt the thermosetting resin composition; (3) a pressurization-depressurization process of performing one or more depressurizations and one or more pressurizations inside the molding apparatus; and (4) a cure process of heating the inside of the molding apparatus to cure the thermosetting resin composition. This is to provide a method for producing a power module having few voids at the time of molding and excellent reliability.