GaN Over-Mold Packaging for Heat and Thermal Expansion Control
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Solution Overview
Problem
Conventional packaging for wide band-gap semiconductor devices is expensive due to costly materials like ceramic bodies and metal substrates, which are not suitable for high power density and high frequency operations, leading to heat dissipation and thermal expansion issues.
Innovation Solution
An over-mold packaging solution using a plastic or plastic polymer compound with a glass transition temperature greater than 135°C, a flexural modulus less than 20 GPa, and a low moisture absorption rate, combined with a die attach material of high thermal conductivity and low flexural modulus, to handle heat and prevent damage from thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ceramic bodies and metal substrates are used for packaging wide band-gap semiconductor devices, then protection and heat dissipation are achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent changes the material parameters of the packaging bymold from conventional ceramics and metals to a specifically formulated plastic polymer compound. The compound achieves suitable thermal expansion characteristics (coefficient of thermal expansion between 5-15 ppm/°C) and acceptable heat dissipation properties, thereby reducing manufacturing cost while maintaining adequate protection and thermal management for wide band-gap semiconductor devices
Solution Approach 2:
The patent employs a composite plastic polymer compound containing multiple components including polyphenylene sulfide, polyether ether ketone, glass fibers, and various additives. This composite material combines the advantages of different materials to achieve a balance between cost, thermal properties, mechanical strength, and thermal expansion characteristics, replacing expensive ceramic and metal materials
2Power
If high power density operations are implemented, then output power increases, but thermal expansion and structural damage risks increase
Solution Approach 1:
The patent modifies the thermal expansion parameter of the packaging material by selecting a plastic polymer compound with a coefficient of thermal expansion (5-15 ppm/°C) that closely matches the wide band-gap semiconductor device. This parameter matching reduces thermal stress and prevents structural damage during high power density operations, enabling sustained output powers above 150W
Solution Approach 2:
The patent incorporates heat dissipation features into the packaging design before the device operates at high power. The plastic polymer compound and packaging structure are pre-configured to conduct and dissipate heat efficiently, preventing thermal accumulation and reducing the risk of thermal expansion-induced damage before it occurs
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 solution reduces manufacturing costs and allows wide band-gap semiconductor devices to operate at full capacity with improved heat dissipation and thermal management, supporting peak output powers above 150W and frequencies up to 3.8 GHz without structural damage.
Implementation Method 1
the die attach material with a bulk thermal conductivity greater than 40 W/m-K
Implementation Method 2
The over-mold and the die attach material handle the heat produced by the wide band-gap semiconductor device
Implementation Method 3
prevent damage to the wide band-gap semiconductor device due to thermal expansion and/or contraction of the over-mold
Data Source
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AI summary
A transistor package includes a lead frame and a gallium nitride (GaN) transistor attached to the lead frame. The lead frame and the GaN transistor are surrounded by an over-mold with a glass transition temperature greater than about 135° Degrees C and a flexural modulus less than about 20 GPa. Using an over-mold with a glass transition temperature greater than about 135° Degrees C and a flexural modulus less than about 20 GPa allows the over-mold to handle the heat produced by the GaN transistor while preventing damage to the GaN transistor due to thermal expansion and/or contraction of the over-mold.