Semiconductor Bonding Stack With Reducing Tacking Layers
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Solution Overview
Problem
The challenge in power semiconductor module arrangements is the need to form a permanent connection between semiconductor elements and a substrate while ensuring the removal of tacking agent residues and activating the substrate surface during transport and assembly, without damaging the components.
Innovation Solution
A method involving tacking layers with a first and second material that either evenly distribute a reducing agent or chemically react to form one under heat, forming a permanent mechanical connection by evaporating the first material and activating the surfaces, thereby eliminating residues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional tacking agents are used for temporary attachment, then the semiconductor elements can be temporarily attached to the substrate for transport, but residual tacking agent layers remain after permanent bonding which contaminate the connection surfaces
Solution Approach 1:
The harmful residual tacking agent is completely removed through a multi-step process: first dissolved in a solvent during a first cleaning step, then any remaining traces are eliminated through oxidation in a second cleaning step, ensuring completely clean connection surfaces for permanent bonding
Solution Approach 2:
The connection surfaces are pre-activated by oxidizing them before permanent bonding occurs. This preliminary oxidation creates a fresh, clean metal surface that enhances the quality of the permanent solder connection, and removes any potential contaminants that would interfere with bonding
2Reliability
If the substrate surface is not activated, then the temporary attachment process is simpler, but metal oxide surfaces cannot be reduced to pure metal which is necessary for reliable permanent bonding
Solution Approach 1:
The chemical state of the connection surfaces is changed by controlling oxidation during cleaning. The substrate surface is selectively oxidized to activate it for bonding, creating a fresh metal surface that reduces to pure metal during the bonding process, thereby enhancing bond reliability
Solution Approach 2:
A solvent is introduced as an intermediary substance to dissolve and remove tacking agent residues from the connection surfaces. The solvent acts as a mediator between the contaminated surface and the final clean state, enabling effective cleaning without damaging the underlying metal
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
Enables a residue-free, void-free, and activated connection between semiconductor elements and substrates, facilitating efficient assembly and ensuring electrical conductivity.
Implementation Method 1
the materials comprised in the mixture chemically react with each other under the influence of heat, thereby forming a reducing agent
Implementation Method 2
a metal oxide that might have formed on the surface of the substrate needs to be reduced to pure metal
Implementation Method 3
heating the first tacking layer, the second tacking layer, and the first layer
Data Source
AI summary
A method includes forming a first tacking layer on a first connection partner, arranging a first layer on the first tacking layer, forming a second tacking layer on the first layer, arranging a second connection partner on the second tacking layer, heating the tacking layers and first layer, and pressing the first connection partner towards the second connection partner, with the first layer arranged between the connection partners, such that a permanent mechanical connection is formed between the connection partners. Either the tacking layers each include a second material evenly distributed within a first material, the second material being configured to act as or to release a reducing agent, or the tacking layers each include a mixture of at least a third material and a fourth material, the materials in the mixture chemically reacting with each other under the influence of heat such that a reducing agent is formed.