When we actually welded industrial control motherboards equipped with Xilinx Zynq-7000 series FPGAs on 8-layer thick copper PCB production lines, we found that ordinary Solder Paste easily forms a void rate greater than 15% at the bottom of BGA, while after using JJY JY-928A industrial control motherboard solder, the void rate is stably controlled within 6.2%. This is due to its optimized Sn96.5/Ag3.0/Cu0.5 alloy ratio and low-temperature activated rosin system, which can still maintain a continuous wetting front under the reflow window with a peak temperature of 235℃ and a time above liquidus of 68 seconds, and will not cause carbonization failure of the Flux due to long-time high-temperature residence.

In the printing process, the stencil opening size must be reduced by 8% according to the pad area and matched with a 12μm nickel-coated scraper, otherwise the thixotropic index 3.8 of JJY industrial control motherboard solder will lead to poor demolding, especially solder bridging at 0.4mm pitch QFN packages. We once reworked the entire batch of AM335x core boards for this reason, and later uniformly switched to 30° scraper angle and 0.8MPa constant pressure printing parameters to completely solve the problem.

The chain speed setting of the reflow oven must be dynamically matched with the PCB thickness. For example, the running speed of a 1.6mm thick double-sided mounted industrial control motherboard is set to 1.1m/min. If the speed is increased to 1.3m/min, the IMC layer of the second-side BGA solder joint will be too thin. X-ray inspection shows that the thickness of Cu6Sn5 drops sharply from 2.1μm to 1.4μm, which directly weakens the drop resistance of the solder joint. However, JJY industrial control motherboard solder can still maintain an average value of 1.7μm under this condition, indicating that its tin powder oxide film control accuracy is better than the conventional industry level.

When wave soldering repair is performed on ARM Cortex-A9 main control modules with large-area grounding pads, the preheating temperature must be increased from 120℃ to 135℃ and extended to 90 seconds, otherwise JJY industrial control motherboard solder will produce micro-splash the moment it contacts the solder wave. This is because its internal moisture residue is lower than 300ppm but the latent heat of volatilization is higher. Insufficient preheating will prevent the gradient activation of flux components, eventually leading to incomplete wetting on the OSP surface.

The storage environment must be strictly controlled at a temperature of 25±3℃ and a humidity of 40±5%RH. If the unused JJY industrial control motherboard solder after opening is placed at room temperature in the workshop for more than 4 hours, the viscosity of the solder paste will increase by 18%, and the printing demolding drawing length will increase from 0.3mm to 1.1mm. We have installed nitrogen sealed tanks on the third-line SMT line body to realize nitrogen filling immediately after opening the lid, ensuring that the viscosity fluctuation during the use cycle of each tank is ≤5%.