First article inspection is not a perfunctory signing process, but a meticulous verification process: using a magnifying glass to check whether the BOM version number is completely consistent with the actual material part number, using a caliper to measure whether the deviation between the stencil aperture size and the Gerber file exceeds ±0.02mm, and using a temperature controller to retest whether the peak temperature of the reflow profile falls within the 235℃±5℃ range. Once it is found that the placement machine coordinate offset is 0.15mm or the Solder Paste printing thickness is lower than 120μm, the line must be stopped immediately for adjustment and the first article must be redone; it must never be released with the mindset of "it's only a tiny bit off".

We once encountered a typical material mix-up incident on the Jiajinuan Dongguan production line. The customer ordered 10kΩ resistors in 0402 package, but the warehouse mixed in substitute materials of the same specification with a resistance of 100kΩ when issuing materials. Since the two materials have identical appearance and the BOM did not mark key parameters, if the step of actually measuring the resistance with an LCR meter during first article inspection had been skipped, all 2000 PCBA boards would have suffered functional failure later. However, during the actual first article inspection, the engineer found abnormal test values at the third component, immediately traced back to the batch number on the material requisition form and locked the source of the problem.

Process parameter errors are more hidden than material mix-ups. For example, after a line change, an operator mistakenly adjusted the Reflow Soldering chain speed from 120cm/min to 100cm/min, causing the peak temperature to rise to 246℃. Although the first article AOI did not report solder ball defects, X-ray sampling inspection found that the void rate at the bottom of the QFN had reached 38%, far exceeding Jiajinuan's internal warning line of 25%. If X-ray re-inspection had not been mandated as a required item for first article inspection, this batch of goods would have experienced periodic thermal failure at the customer's end after delivery.

First article inspection must be tied to actual materials, actual equipment status and actual environmental conditions; the qualified records of the previous batch cannot be used to replace the verification of the current batch. For example, when the humidity exceeds 60%RH, the activity of the solder paste decreases significantly. Even if the first article of the previous shift was OK, the solder paste still needs to be re-stirred and a printing tension test performed before starting up in the current shift; otherwise, the stencil release defect rate will rise to over 17% within half an hour.

All Jiajinuan production lines have broken down first article inspection into 14 mandatory checkpoints, covering the consistency between the feeder list and the actual loading position of the Feeder, SPI solder paste volume CV value ≤12%, post-placement offset XY axis both <30μm, and the slope fluctuation of each segment of the reflow profile not exceeding ±10% of the set value. Any item that fails to meet the standard triggers a red light line stop mechanism, rather than letting the production line judge on its own that "it's close enough".