Flexible PCB Solderless Joint Reduces Fretting Corrosion
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Solution Overview
Problem
Solderless electrical connections in PCBs are prone to fretting corrosion due to movement between the conductive element and the plated through-hole, leading to increased contact resistance and reliability issues over time.
Innovation Solution
A solderless joint arrangement featuring a conductive compliant pin with a flexible PCB receptacle that reduces movement between the pin and the plated through-hole, utilizing a flexible portion of the PCB and a two-piece conductive compliant pin with a press-fit interconnection end and a piezo interface end to minimize fretting corrosion, and optionally incorporating a C-shape or ring-shape contact for improved stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a solderless connection is formed by positioning a conductive element in a plated through-hole with deformation, then manufacturing complexity is reduced and heat-cycling is eliminated, but fretting corrosion occurs due to contact point movement leading to increased contact resistance
Solution Approach 1:
The patent applies the dynamics principle by making the PCB flexible portion capable of movement to accommodate thermal expansion and contraction. The flexible PCB portion with drill holes allows the structure to dynamically adjust during heat-cycling, preventing rigid stress concentration at the solderless joint interface and reducing fretting corrosion while maintaining manufacturing simplicity.
Solution Approach 2:
The patent implements this principle by incorporating a flexible PCB portion with drill holes that acts as a flexible structure. This flexible portion absorbs mechanical stress and movement during thermal cycling, protecting the solderless joint from fretting corrosion while maintaining the simplicity of cold-press assembly.
2Reliability
If the conductive element is oversized for the through-hole diameter to ensure good contact, then contact resistance is reduced, but deformation is required which increases manufacturing complexity
Solution Approach 1:
The flexible PCB portion provides dynamic compliance that allows the oversized conductive element to maintain continuous contact pressure without requiring permanent deformation. The flexibility compensates for dimensional variations and ensures reliable electrical contact while avoiding the need for complex deformation processes.
Solution Approach 2:
The patent changes the mechanical parameters of the PCB by introducing flexibility through drill holes, allowing the structure to adapt to the oversized conductive element. This parameter change enables good electrical contact through compliance rather than through deformation, reducing manufacturing complexity.
3Reliability
If fretting corrosion is allowed to occur naturally, then contact resistance increases over time, but preventing it would require eliminating all movement which reduces adaptability to thermal expansion
Solution Approach 1:
The flexible PCB portion with drill holes creates a dynamic system that accommodates thermal expansion and contraction movements. This dynamic flexibility prevents rigid stress concentration at the contact interface, reducing fretting corrosion while maintaining the ability to adapt to thermal cycling, thus achieving both long-term stability and thermal adaptability.
Solution Approach 2:
The flexible PCB structure acts as a compliant element that absorbs thermal expansion stresses. This flexible portion prevents excessive movement at the solderless joint interface, reducing fretting corrosion and improving long-term reliability while still allowing necessary thermal adaptation.
Data Source
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AI summary
A solderless joint arrangement comprising a receptacle (11, 12) of a PCB (10) arranged to receive a conductive compliant pin, the receptacle (11) comprising a conductive portion (12) for contact with the compliant pin wherein the receptacle is positioned on a flexible portion (20) of the PCB.