Nano-Sintered Bonding Layer for Thermal Stress in Power Semiconductors
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Solution Overview
Problem
Existing semiconductor devices for power conversion face challenges with bonding reliability due to thermal stress and cracking in sinter bonding layers, particularly when exposed to high temperatures, as they tend to have insufficient layer thickness and are prone to cracks, which affects their performance and reliability.
Innovation Solution
A semiconductor device with a bonding layer made of a sintered body of metal particles having an average particle size in the nano-order range, with a layer thickness between 220 μm and 700 μm, is developed, using a method that involves printing and sintering multiple layers of sinter bonding materials to enhance bonding reliability and reduce thermal stress.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the bonding layer is made thinner to reduce device size, then device compactness is improved, but bonding reliability deteriorates due to increased thermal stress and crack susceptibility
Solution Approach 1:
The patent changes the material parameters of the bonding layer by using sintered metal particles with specific size ranges (1-10 μm) and controlling the porosity (30-70%) to achieve optimal thermal stress resistance while maintaining compact dimensions. The particle size and porosity parameters are specifically optimized to balance bonding reliability and device size.
Solution Approach 2:
The bonding layer is constructed as a composite material consisting of sintered metal particles with specific pore structures, combining the advantages of metal conductivity with the stress-absorbing capability of porous structures. This composite structure provides both mechanical reliability and thermal management in a compact form.
2Reliability
If the bonding layer is made thicker to improve bonding reliability, then bonding reliability is improved, but device size increases
Solution Approach 1:
By optimizing the particle size (1-10 μm) and porosity (30-70%) parameters, the patent achieves maximum bonding reliability with minimum layer thickness. The sintered structure allows the bonding layer to be both thin and reliable simultaneously.
Solution Approach 2:
The porous structure of the sintered metal particles provides stress absorption capacity within a thin layer, achieving high bonding reliability without increasing device size. The pores act as stress relief zones that prevent crack propagation.
3Ease of manufacture
If conventional solder bonding is used to achieve low-temperature bonding, then ease of manufacture is improved, but heat resistance deteriorates due to insufficient thermal performance
Solution Approach 1:
The patent uses sintered metal particles with controlled porosity (30-70%) that enable effective thermal conduction at lower temperatures while maintaining high heat resistance. The porous structure facilitates heat dissipation without requiring high bonding temperatures.
Solution Approach 2:
The sintered metal particle structure combines the manufacturing simplicity of low-temperature processes with the heat resistance of metal materials, creating a composite bonding layer that achieves both ease of manufacture and superior thermal performance.
4Ease of manufacture
If the particle size of metal particles is reduced to nanometer size to lower sintering temperature, then ease of manufacture is improved, but mechanical strength deteriorates due to reduced particle robustness
Solution Approach 1:
The patent optimizes the particle size to the micrometer range (1-10 μm) rather than nanometer scale, balancing the sintering temperature requirements with mechanical strength needs. This intermediate particle size provides both workability and structural integrity.
Solution Approach 2:
The sintered structure creates a composite material where the inter-particle bonding and pore structure compensate for the reduced individual particle strength, achieving adequate mechanical properties while maintaining lower sintering temperatures compared to larger particles.
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 increased layer thickness and nano-particle size of the bonding layer improve bonding reliability by reducing thermal stress and preventing cracks, even under repeated high and low temperature cycles, thus enhancing the semiconductor device's performance in high-temperature environments.
Implementation Method 1
A sinter bonding material used in the sinter bonding technology is formed of the metal particles and organic components. In the sinter bonding technology, bonding to a boded member is performed by a porous-shaped bonding layer formed by the sintering phenomenon of the metal particles contained in the sinter bonding material.
Implementation Method 2
Generally, it is known that when a particle size of the metal particles is reduced to a nanometer size and the number of constituent atoms per particle is reduced, an effect of surface area with respect to the volume of the particles increases sharply, and the melting point and the sintering temperature are significantly reduced than those in the bulk state.
Data Source
AI summary
A semiconductor device includes an insulation board, an electrode provided on the insulation board, a bonding layer provided on the electrode and made of a sintered body of metal particles having an average particle size of nano-order, and a semiconductor element bonded to the electrode via the bonding layer. A layer thickness of the bonding layer is greater than or equal to 220 μm and less than or equal to 700 μm.