Curved Contact Pin Tip for Constant IC Test Pressure
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Solution Overview
Problem
Existing test pins for integrated circuit devices apply uneven contact force, leading to excessive wear and potential damage, and the use of matte tin on device under test (DUT) components can disrupt testing due to debris formation.
Innovation Solution
The design of test pins with curved and tapered contact surfaces that maintain constant pressure by widening or narrowing as they engage and wear, along with features like tapered necks and sidewalls, to ensure consistent contact force over the life of the pin and compensate for wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a test pin with a flat contact surface is used, then the manufacturing is simple, but the contact pressure becomes uneven and increases excessively during engagement, leading to wear and damage
Solution Approach 1:
The contact surface of the pin tip is formed with a curved profile instead of a flat surface. This curvature allows the contact area to progress along the curved surface during engagement, distributing the contact pressure more uniformly and preventing excessive stress concentration at any single point.
Solution Approach 2:
The pin design incorporates a tapered neck portion with varying cross-sectional area along its length. This creates local variations in structural properties, with the narrower sections providing flexibility and the broader base providing support, allowing the pin to deflect and maintain uniform contact pressure during engagement.
2Stress or pressure
If the pin contact surface is made wider to distribute pressure, then the contact pressure is more uniform, but the pin becomes less flexible and cannot compensate for wear over time
Solution Approach 1:
The pin is designed with a tapered neck that provides gradual flexibility along its length. This dynamic structure allows the pin to deflect and adapt during engagement while maintaining uniform contact pressure. The tapered geometry enables the pin to compensate for wear over time through controlled deflection, extending its operational life.
Solution Approach 2:
The curved contact surface works in conjunction with the tapered neck to create a dynamic engagement process. As the pin engages, the contact area progresses along the curved surface, allowing the flexible tapered structure to maintain uniform pressure distribution even as the pin wears and deflects during repeated use.
3Reliability
If excessive wiping action is applied to ensure good contact, then the transmission path quality improves, but the component parts at engagement points are damaged, decreasing tester life
Solution Approach 1:
The curved contact surface eliminates the need for excessive wiping action by providing a progressive engagement mechanism. As the pin engages the DUT, the contact area naturally progresses along the curved surface, ensuring good electrical transmission quality without requiring aggressive lateral motion that would cause abrasion and damage to the load board and other components.
4Ease of manufacture
If matte tin is applied to DUT leads and pads to facilitate soldering, then the solderability improves, but the soft material sheds as debris that disrupts testing
Solution Approach 1:
The pin design incorporates features that minimize the interaction between the contact surface and matte tin debris. The curved contact surface and controlled engagement geometry reduce the likelihood of picking up and transferring soft tin debris to the load board, thereby eliminating the harmful effect of debris disruption while maintaining the solderability benefits of matte tin on the DUT.
Data Source
AI summary
A structure and method of constructing a tip for a contact pin used in IC test housing for testing integrated circuits. As the pin is deflected when the device under test (DUT) pad engaged the tip of the pin, the tip pressure normally increases as the elastomers biasing the pin are engaged. This causes the elastomer supporting the tip to increase pressure. By widening the tip as it rolls, the pressure is maintained more constant. Also, as the top wears, the pressure on the DUT will be reduced. By making the contact area of the tip to DUT smaller as it wears, the pressure can be made more constant.