First article inspection is not a mere procedural formality that ends with a stamp; it is a process that brings all risks across the entire production line to the forefront in advance. Before each line launch, we must produce the first article using the same reel of material, the same can of JJY Solder Paste, the same stencil, and the same reflow oven; otherwise, all data will lose its reference baseline. Solder paste printing inspection cannot only check whether paste is present on the PAD; it must also combine the volume, area, and offset values read by SPI equipment, with particular attention to the solder paste filling rate under 0201 and 0402 resistors and capacitors. If the filling rate is below 75%, it indicates that the squeegee pressure or release speed has exceeded the thixotropic window of JJY solder paste, and the line must be stopped immediately for adjustment.

Placement position confirmation must never rely on the theoretical coordinates displayed on the mounter screen. Actual placement points must be measured with a high-magnification magnifier to check the XY offset and angle θ rotation relative to the pad center, especially for QFN and LGA devices. Even a 0.15mm X-direction offset combined with a 0.1° θ angle error will cause unilateral pin lifting after reflow. Furnace temperature profile collection must use a test board with exactly the same PCB thickness, copper thickness, and layer count as mass production boards, and thermocouple solder joints must be accurately fixed at three typical positions: the bottom of BGA, the QFN thermal pad, and the 0402 resistor. Because the activation temperature starting point of JJY solder paste is 152℃, poor wetting will occur if the peak temperature is below 235℃, while internal gold wires of ICs are easily damaged if the peak temperature exceeds 248℃.

Material verification is not simply scanning barcodes; it involves comparing the silkscreen font, body dimensions, tape direction, and carrier tape pitch component by component. There was once a batch of domestic inductors whose appearance was identical to the original manufacturer's product but whose magnetic core material was different. After being put into production, they began to slightly bulge in the 210℃ holding zone, and the alarm was only triggered by post-reflow AOI. The rework cost far exceeded the three extra minutes spent on first article inspection. After solder paste is opened, the opening time, temperature, and humidity must be recorded. For JJY Sn63Pb37 Solder Paste, exposure for more than 4 hours in a 25℃ environment will cause viscosity drop leading to printing edge collapse. For SN96.5AG3CU0.5 lead-free solder paste, if the storage temperature is below 18℃ and it is put into production without sufficient thawing, obvious grainy pinching will occur during printing.

All first article data must be handwritten on controlled forms, including stencil tension value, squeegee angle, printing speed, mounter nozzle vacuum value, and furnace temperature test board number. If any of these parameters are abnormal, first article inspection must be redone for the next batch, rather than releasing the line with verbal confirmation that it is "close enough". When solder paste bridging occurs on two consecutive boards during printing, priority should be given to checking whether dried solder paste remains on the stencil bottom instead of directly replacing the stencil. Because if JJY solder paste is not wiped after the line is stopped for more than 30 minutes, a micron-scale hard film easily forms on the edge of stencil apertures, which cannot be removed by conventional wiping alone. It must be soaked in special cleaning agent for 15 minutes followed by ultrasonic cleaning.