Pressure Contact Lead Assembly Without Cold Solder Failure
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Solution Overview
Problem
Power electronics substrates face reliability issues due to cold solder phenomena, particularly in harsh environments, leading to unreliable connections between power leads and substrates.
Innovation Solution
A pressure contact assembly is introduced, featuring a power substrate with etched cavities and modified leads that utilize spring-like actions and solderless connections, such as resistance welding, to secure the lead to the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If soldering is used to connect power leads to substrates, then electrical connection is achieved, but connection reliability deteriorates due to cold solder phenomenon in harsh environments
Solution Approach 1:
The patent removes the solder material from the connection system entirely, replacing the soldered joint with a direct mechanical press-fit connection between the power lead and substrate cavity. This extraction eliminates the cold solder phenomenon while maintaining electrical connectivity through the metal-to-metal contact.
Solution Approach 2:
The patent replaces the thermal-mechanical soldering process with a purely mechanical press-fit system. The power lead is inserted into a cavity in the substrate and secured through mechanical interference fit, eliminating the need for solder melting and cooling while achieving reliable electrical and mechanical connection.
2Reliability
If solderless pressure contact connection is implemented, then connection integrity is improved in harsh environments, but manufacturing complexity increases due to cavity etching and lead modification
Solution Approach 1:
The cavity is pre-formed in the substrate and the lead is pre-modified with a fitting geometry before assembly. This preliminary preparation allows the components to self-align and self-secure during the press-fit process, reducing the complexity of the actual assembly operation while ensuring reliable connection integrity.
3Ease of manufacture
If traditional soldering process is used, then manufacturing process is simple, but connection reliability deteriorates under thermo-mechanical stress
Solution Approach 1:
The patent extracts the solder material and heating process from the manufacturing system, replacing them with a cold press-fit operation. While this adds cavity etching and lead modification steps, it eliminates the thermal cycle and material degradation associated with soldering, resulting in superior resistance to thermo-mechanical stress.
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 provides a reliable, solderless connection that withstands thermo-mechanical stress, maintaining electrical isolation and connection integrity in harsh conditions.
Implementation Method 1
The second portion is perpendicular to the first portion and has a modification to its smooth surface... The first surface has a cavity inside which the modification is press-fit
Data Source
AI summary
A pressure contact assembly includes a power substrate, a chip, and a lead. The power substrate has a surface connected to a ceramic tile and a cavity. The chip is soldered to the surface. The lead is to be inserted into the cavity and has a top portion to connect to an external device and a bottom portion to fit into the cavity.