Silver-Sintered Molybdenum Packaging for Low-Stress SiC MOSFET Modules
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Solution Overview
Problem
Conventional direct-bonded-copper (DBC) packaging for semiconductor devices faces limitations due to thermal stress, stray inductance, and high manufacturing costs, particularly when handling wide bandgap SiC MOSFETs that require improved temperature range and thermal-mechanical reliability.
Innovation Solution
The development of a silver-sintered molybdenum (SSM) packaging technology using CTE-matched pure molybdenum and bismaleimide triazine resin, with nano-silver sintering for bonding SiC MOSFET dies to a molybdenum substrate, and low-inductance planar leads, which reduces thermal stress and stray inductance while simplifying the manufacturing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional direct-bonded-copper (DBC) packaging is used, then manufacturing process is established, but thermal stress and stray inductance increase while lifetime at high temperature decreases
Solution Approach 1:
The patent changes the material parameter from copper to molybdenum, which has a coefficient of thermal expansion (CTE) matched to silicon carbide (SiC). This parameter change resolves the thermal stress issue by eliminating CTE mismatch between the substrate and SiC devices, allowing the packaging to maintain reliability at temperatures up to 300°C while reducing thermal stress by 53% compared to conventional DBC packaging
Solution Approach 2:
The patent employs composite material structure by combining molybdenum substrate with nano-silver sintering interconnects. The molybdenum provides CTE matching and thermal stability, while the nano-silver sintering material provides low-inductance electrical connections. This composite approach simultaneously addresses thermal stress reduction and stray inductance minimization, achieving 62% less stress at bonding layers and enabling extended device lifetime
2Reliability
If conventional DBC packaging is used, then manufacturing process is established, but stray inductance increases reducing performance
Solution Approach 1:
The patent replaces the conventional mechanical wire bonding system with a planar integrated interconnect system using nano-silver sintering. This substitution eliminates the loop areas inherent in wire bonding, thereby reducing stray inductance. The planar leads created through nano-silver sintering provide direct, low-inductance electrical paths between the SiC devices and external terminals, significantly improving power module performance
3Reliability
If conventional DBC packaging is used, then manufacturing process is established, but manufacturing cost increases
Solution Approach 1:
The patent changes the substrate material parameter from copper to molybdenum, which inherently provides high-temperature stability and CTE matching with SiC. This material parameter change enables the packaging to operate reliably at temperatures up to 300°C, eliminating the need for complex thermal management systems and extended cooling infrastructure, thereby reducing overall system manufacturing costs despite the higher base material cost
4Strength
If nano silver sintering is used for bonding, then bonding strength and thermal stress resistance improve, but process complexity increases
Solution Approach 1:
The patent introduces nano-silver sintering material as an intermediary substance between the molybdenum substrate and SiC devices. This intermediary material facilitates strong bonding while accommodating thermal expansion differences. The nano-silver particles form a sintered bond that provides both mechanical strength and electrical conductivity, simplifying the overall process by eliminating the need for separate bonding and electrical connection steps
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 SSM packaging significantly enhances the lifetime and maximum operating temperature of power modules, achieving 53% less total stress and 62% less stress at bonding layers compared to DBC modules, with over 1000 times longer lifetime under temperature cycling and the ability to operate at 300°C while maintaining the same lifetime as DBC modules at 85°C.
Implementation Method 1
sintering nano silver paste over the coated surface of the substrate; increasing the temperature to achieve sintering and densification
Data Source
AI summary
The present disclosure generally relates to a silver sintered molybdenum (SSM) packaging for power semiconductor devices and a method of manufacturing thereof. The SSM packaging comprises a substrate; a MOSFET die comprising a first side and a second side, wherein the first side is bonded to the substrate using nano silver sintering; and at least two leads connected, at a respective first end, to the substrate and, at a respective second end, to the second side of the MOSFET die, wherein nano silver sintering is used to bond the first and second ends of the at least two leads, and wherein each of the substrate and at least two leads is formed of pure molybdenum.