Planar Diffusion Joining Structure for Void-Free Semiconductor Bonds
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Solution Overview
Problem
Existing diffusion soldering methods for electronic power semiconductor devices face issues such as oxidation of metal melts, inadequate joining material thickness, tilting of chips, voids in joints, and reduced reliability due to excess low-melting components, which affect thermal and electrical performance and increase the risk of microcracks.
Innovation Solution
A method involving the application of diffusion materials on both sides of semiconductor components, alignment in a reducing atmosphere, and application of compressive pressure for isothermal solidification below the melting temperature of the joined material, forming intermetallic phases and ensuring uniform coating and reduced void rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional diffusion soldering methods are used with excess low-melting joining components, then the joining process can be completed, but the reliability and heat resistance of the diffusion joints are compromised
Solution Approach 1:
The invention changes the compositional parameters of the joining material by using exactly stoichiometric amounts of low-melting and high-melting components without excess, and performs diffusion joining at controlled temperatures below the melting point of the low-melting component to prevent unwanted phase formation and maintain joint integrity
Solution Approach 2:
The invention utilizes controlled phase transitions by heating to a temperature range that enables diffusion and intermetallic phase formation while remaining below the melting point of the low-melting component, thus achieving reliable joints without compromising heat resistance
2Strength
If diffusion joining is performed at high temperature to ensure proper bonding, then the joining strength is improved, but the intermetallic phases extend too far reducing ductility and increasing brittleness
Solution Approach 1:
The invention optimizes the temperature parameter by conducting diffusion joining at temperatures specifically controlled to be below the melting point of the low-melting component, achieving sufficient intermetallic phase formation for strength while limiting excessive phase growth that would cause brittleness
Solution Approach 2:
The invention applies partial action by using exactly the stoichiometric amount of low-melting component needed for diffusion joining without excess, preventing over-diffusion and excessive intermetallic phase formation that would compromise ductility
3Ease of manufacture
If the joining material is applied as a melt to ensure proper wetting, then the joining process can proceed, but oxidation of the metal melt occurs leading to wetting problems
Solution Approach 1:
The invention applies an inert or reducing atmosphere during the diffusion joining process to prevent oxidation of the joining material, enabling proper wetting and bonding without the harmful effects of metal melt oxidation
4Productivity
If conventional joining methods are used, then the joining process can be completed, but voids form in the joining joint reducing thermal conductivity
Solution Approach 1:
The invention optimizes temperature and pressure parameters during diffusion joining to ensure complete bonding without void formation, achieving both process efficiency and high thermal conductivity by controlling the diffusion process to occur below the melting point of the low-melting component
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 method enhances the mechanical, electrical, and thermal capabilities of the diffusion joints, reduces thermal resistance, and minimizes the risk of microcracks by forming stable intermetallic phases and precise control over joint thickness, leading to more reliable and durable connections.
Implementation Method 1
heating up the components to be joined in the reducing atmosphere to a diffusion joining temperature, isothermal solidification takes place
Implementation Method 2
alloy formation between the joining material melt and the material of the copper heat sink and also between the joining material melt and the metallization on the rear side of the chip
Implementation Method 3
introduced into a reducing atmosphere
Data Source
AI summary
A method for the planar joining of components of semiconductor devices involves coating the components with diffusion materials on their upper sides and rear sides, respectively. Subsequently, the components to be joined one on the other are introduced into a reducing atmosphere. The components are aligned and a compressive pressure is exerted on the aligned components. While heating up the components to be joined in the reducing atmosphere to a diffusion joining temperature, isothermal solidification takes place, the diffusion joining temperature lying below the melting temperature of the forming diffusion joint of the joined material.