Compliant Pin Deformation Prevention in PCB Interconnects
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Solution Overview
Problem
The challenge is to prevent damage to compliant pins during the assembly of printed circuit boards (PCBs) due to excessive force, which can lead to permanent deformation and connection failure, especially when one PCB is a ceramic direct bonded copper (DBC) style board, as a result of thermal expansion mismatches.
Innovation Solution
A compliant terminal assembly is introduced, featuring a stop member and U-shaped compliant pins with a stop portion that limits compression, allowing the pins to deform during assembly and accommodate thermal expansion differences, while a stop comb or housing frame secures the pins to prevent excessive force from being applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stiff or sturdy pin is used to connect two PCBs, then the connection strength is improved, but the pin cannot accommodate thermal expansion mismatches between PCBs with different CTE
Solution Approach 1:
The pin is designed with a compliant portion that can dynamically change its mechanical properties. During assembly, the pin is stiff to provide strong connection, but during thermal cycling, the compliant portion flexes to accommodate expansion mismatches. This dynamic adaptation resolves the contradiction between needing strength and needing adaptability.
Solution Approach 2:
The pin's effective stiffness parameter changes based on operating conditions. The compliant portion's geometry (U-shaped, S-shaped, or coiled) allows it to exhibit different mechanical responses under different loads and temperatures, enabling the pin to be stiff when needed and flexible when needed to accommodate thermal expansion.
2Reliability
If excessive force is used when seating the upper PCB to ensure proper connection, then the connection reliability is improved, but the compliant pins can be damaged or permanently deformed
Solution Approach 1:
A stop member is pre-positioned within the compliant portion's path to limit the maximum compression distance before the PCB is fully seated. This preliminary constraint prevents excessive force from being applied during assembly, protecting the pin from damage while still allowing sufficient compression for reliable electrical connection.
Solution Approach 2:
The stop member acts as a protective mechanism that cushions against excessive assembly forces. By being in place before the PCB is seated, it prevents the kind of force that would damage the pin, thereby protecting the pin's integrity while still allowing normal assembly forces to achieve proper connection.
3Strength
If a stop is built directly into the pin design to prevent damage during assembly, then the pin protection is improved, but the stop can still translate damaging force directly to the lower PCB
Solution Approach 1:
The stop member is designed as a separate intermediary component rather than being integrated into the pin itself. This separate stop member absorbs and dissipates excessive assembly forces, preventing them from being transmitted directly to the lower PCB while still protecting the compliant portion from damage.
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 effectively prevents pin damage during assembly and ensures reliable electrical connections by allowing compliant pins to absorb mechanical and thermal stresses, maintaining connectivity over time.
Implementation Method 1
a compliant terminal. The terminal includes a first terminal end for electrical connection to a first circuit board, a second terminal end for electrical connection to a second circuit board and a compliant portion
Data Source
AI summary
An assembly for preventing deformation of compliant pins when interconnecting two printed circuit boards with the pins includes a mechanism for limiting an amount of movement of a flexible portion of the pins. In one approach, a bar is placed within the flexible portion of the pins to block damaging movement. In another approach, wing portions of the pins are locked into a surface thus preventing movement of the pin that could cause damage to the flexible portion of the pin.