Exemplars Beat Suspects

This month’s counterfeit investigation from Princeps demonstrates the value of maintaining a library of known-good devices to compare against suspect parts.

 The part in Figure 1 was received from a European broker but suspect conditions were identified during initial x-ray inspection.

Princeps has a long history of supplying this part to a commercial customer, but it was made obsolete by the last year. Princeps’ extensive image library of known-good devices proved invaluable, making it possible to pull images of two previously received known-good devices for comparison.

The parts received carried a 2138 date code (week 38, 2021). The library brought up known-good samples from weeks 7 and 49 for comparison (exemplars bracket the suspect parts). The exemplars showed consistent lead-frame layout and die size (Fig 3 and 4). Die measurements of the known-good parts were approximately 3 by 1.7mm.

When the suspect parts were inspected: the lead-frame shape is different (fig 2); the die is tilted by around 15deg (Fig5); and the die is smaller at approximately 1.5 by 0.95mm.

The parts were therefore rejected as suspect. The image library of known-good comparison parts was essential to determining the differences observed were not simply due to the manufacturer changing materials. The parts were reported to the ERAI and removed from the supply chain.