October 20, 2014

50 million cycles!

Background:

PFC made contact with a sensor manufacturer that was having circuit cracking issues in a dynamic flex application. The flex was inside a sensor package, and carried the signal between the cycling arm. The arms moved at a very high rate of speed and the flex circuit needed to attach to the arms of the sensor.

To make matters worse, the sensor company was promoting the number of cycles the sensor could endure to be 1,000,000 cycles but had never stress tested the sensor itself. In reality, they wanted 5,000,000 cycles and the circuit was cracking at 1,000,000 cycles.

Design:

The circuit was a double-sided design with some of the traces being wide to carry power. PFC engineering evaluated the cracked circuits (cross sections), material thicknesses and make-up, the range of motion of the sensor arms, arm travel speed, sensor temperature requirements and sensor assembly.

Proposed Solution:

1) Thinner materials. Thinner materials can withstand flexures, and bends, however, it is difficult to measure the endurance of the design.

2) Separating (delaminating) the circuit layers at the stress point of the circuit cycle. This allows virtually twin single thin layers to stress during cycles versus one larger, thicker layer.

Benefits:

Thinner materials and circuit separation have proven very successful. PFC delivered a redesigned circuit that has proven to withstand far more flexures than originally imagined. At last check the test circuits had endured over 50,000,000 cycles with the goal of getting to 250,000,000 cycles. We’ll check back in a couple of months to see where we stand.

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