A new power cycling technique for accelerated reliability evaluation of plated through holes and interconnects in PCBs

A simple power on-off cycling technique that can rapidly assess the reliability of plated-through-hole (PTH) copper barrels and interconnects in printed circuit boards (PCBs) is described. A chain of PTH copper barrels and interconnected tracks are resistance heated by passing 5-8 A of DC for a few minutes. Switching the current on-off creates thermal cycling between 25 and 130 degrees C within the PCB, which induces cyclic fatigue strain in barrels and precipitates any latent defects or weaknesses in plated copper and interconnects. The experimental technique, test coupon design, and procedure are outlined and a valid correlation is established with the industry standard MIL-P-55110D thermal shock test. This technique can very effectively and quickly distinguish between good and poor quality of electroplating without introducing new PTH failure mechanisms. The power cycling technique is useful as a process control tool, a quick qualification method, or as an alternative to more cumbersome and time-consuming reliability valuation techniques. About 100 cycles of this technique, achieved in about 16 h, seem to be sufficient to assure the lifetime reliability of PTHs of most classes of PCBs.<
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