Over-molded Wide Band-gap Transistor Package for High Power RF
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Solution Overview
Problem
Conventional packaging technologies for wide band-gap semiconductor devices are expensive and unsuitable for high-power, high-frequency applications due to material limitations, leading to increased costs and reduced performance in RF power amplifiers.
Innovation Solution
An over-mold packaged wide band-gap power transistor design featuring a lead frame with a wide band-gap transistor surrounded by an over-mold, utilizing materials with specific thermal and mechanical properties to manage heat and expansion, and a die attach material with high thermal conductivity to maintain efficiency and reduce manufacturing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ceramic body and metal substrate packaging is used for wide band-gap semiconductor devices, then heat dissipation and device protection are achieved, but manufacturing cost increases significantly
Solution Approach 1:
The patent replaces expensive ceramic bodies and metal substrates with a disposable-like plastic overmold package that provides sufficient protection and heat dissipation for the wide band-gap semiconductor device. The overmold package, while less durable than ceramic, achieves the necessary reliability at a fraction of the cost, making the overall device economically viable for mass production
Solution Approach 2:
The patent changes the material parameters of the packaging from high-cost ceramic and metal to cost-effective plastic materials that still meet the thermal and mechanical requirements. By selecting plastics with appropriate glass transition temperatures, thermal expansion coefficients, and moisture absorption rates, the package maintains reliability while dramatically reducing manufacturing cost
2Power
If wide band-gap semiconductor devices are used in RF power amplifiers, then bandwidth and output power are improved, but device cost increases due to packaging expenses
Solution Approach 1:
The patent applies the disposable principle by using a cost-effective overmold package that provides sufficient protection for the high-performance wide band-gap device. This allows the expensive semiconductor device to be packaged affordably, making the overall RF power amplifier economically competitive while maintaining high output power and bandwidth performance
Solution Approach 2:
The patent changes the packaging material parameters from expensive ceramic/metal to affordable plastics with tailored thermal and mechanical properties. This parameter change enables wide band-gap devices to be manufactured at lower costs while preserving their superior power and bandwidth characteristics
3Ease of manufacture
If plastic overmold packaging is used for high-power transistors, then manufacturing cost is reduced, but heat dissipation capability may be compromised
Solution Approach 1:
The patent uses composite material strategies by combining plastic overmold with thermal management features such as thermally conductive fillers, thermal vias, and heat sinks. This composite approach allows the package to maintain the low cost and molding flexibility of plastics while achieving the heat dissipation capability necessary for high-power transistor operation
Solution Approach 2:
The patent changes the thermal parameters of the plastic material by selecting polymers with higher glass transition temperatures and lower moisture absorption rates, and by incorporating thermal management features. These parameter changes enable the plastic package to dissipate heat effectively while maintaining cost advantages over ceramic packaging
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 achieves high gain and bandwidth while keeping manufacturing costs low, enabling wide band-gap transistors to operate at peak output powers greater than 150 W up to 3.8 GHz with improved efficiency and reliability, meeting stringent wireless communication standards.
Implementation Method 1
a die attach material with high thermal conductivity to maintain efficiency
Implementation Method 2
The air cavity 18 and the metal substrate 20 dissipate the heat generated by the wide band-gap semiconductor device 12
Implementation Method 3
The air cavity 18 and the metal substrate 20 dissipate the heat generated by the wide band-gap semiconductor device 12
Implementation Method 4
utilizing materials with specific thermal and mechanical properties to manage heat and expansion
Data Source
AI summary
A transistor package includes a lead frame, a wide band-gap transistor attached to the lead frame, and an over-mold surrounding the lead frame and the wide band-gap transistor. The wide band-gap transistor has a peak output power greater than 150 W when operated at a frequency up to 3.8 GHz. Using an over-mold along with a wide band-gap transistor in the transistor package allows the transistor package to achieve an exceptionally high efficiency, gain, and bandwidth, while keeping the manufacturing cost of the transistor package low.