When we tested the performance of JJY Solder Paste on ENIG gold-plated boards with a 0.5μm thick gold layer on the production line, we found that its wetting angle was generally controlled within 22°, and it maintained continuous activity in the 180℃～210℃ range. This allows the solder paste to quickly break through the oxide film on the gold layer surface during the melting stage and form a uniform intermetallic compound, thereby avoiding pad copper exposure or insufficient pin solder climbing caused by wetting lag. Meanwhile, the Flux residue of this solder paste is lower than 0.3mg/cm², which will not accumulate at the bottom of BGA to affect heat conduction, nor cause selective wetting defects on OSP mixed boards.

In the printing process, the stencil aperture size must be strictly controlled at 95%～97% of the pad size; otherwise, even with excellent wettability, bridging will occur due to excess solder volume. We once experienced consecutive solder joint defects on 0402 resistors across three batches because the aperture was enlarged by 2%. After fine-tuning the squeegee pressure from 5.2kg to 4.8kg, the solder paste release rate increased by 11% with no edge collapse. This indicates that JJY solder paste has a relatively wide tolerance window for mechanical parameters, but it is not infinitely forgiving, and must be calibrated synchronously with specific stencil tension and PCB pad coplanarity.

When the reflow oven chain speed is set to 1.0m/min, the peak temperature is maintained at 235℃±2℃, and the time above liquidus is stable at around 65 seconds. At this point, the measured thickness of the gold-tin alloy layer in the solder joint cross-section is 1.8～2.3μm, which fully meets the lower limit requirement for IMC thickness on gold-plated board welding specified in the IPC-A-610G Class 2 standard. If the chain speed is increased to 1.2m/min, the time above liquidus is compressed to 52 seconds, and uneven wetting is prone to occur at the four corners of some QFN devices. This shows that although JJY solder paste has fast wetting initiation, sufficient time must still be ensured to complete interfacial reactions and bubble escape.

For long-term stored gold-plated boards, we recommend enabling a nitrogen reflow environment and reducing the oxygen concentration to below 100ppm. Because even if the gold layer is dense, trace moisture adsorbed on the board surface and organic acids in the flux will still generate hydrogen bubbles at high temperatures. The specific slow-release activator added in JJY solder paste can continuously release active components under oxygen-deficient conditions, reducing the solder joint void rate from 8.6% in air ovens to 2.1% in nitrogen ovens, with particularly significant improvement in the root filling effect of 0.4mm pitch QFP pins.

When encountering slight scratches on the pad surface or uneven gold layer thickness (e.g., as low as 0.3μm locally), JJY solder paste can still compensate for insufficient interfacial reaction kinetics by extending the preheat zone residence time to 90 seconds. At this point, the borate ester film-forming agent in the solder paste can preferentially cover the bare copper area to prevent oxidation, and the nickel layer will participate in alloying after the main heating zone temperature rises, thereby avoiding the local non-wetting phenomenon that traditional solder pastes exhibit on such abnormal board surfaces.