For SMT assembly plants, Solder Paste is not about choosing the most expensive option; instead, it is crucial to precisely match the coupling points of the reflow window, stencil aperture, squeegee pressure, and component pad structure. For example, using ordinary SMT Solder Paste on the bottom thermal pad of a QFN easily leads to cold solder joints. However, the 8MQP/5RQ series, thanks to its high activity and optimized 0307T4 alloy powder particle size distribution, has a measured solder wetting climb rate close to 100%. The prerequisite is that placement and reflow must be completed within 30 minutes after printing; otherwise, Flux volatilization will cause poor wetting. The 8MNTTP/5RNTT series is specifically designed for smartphone fingerprint locks and Bluetooth modules, with halogen content of only 100–200ppm and transparent residue. During rework of 0.3mm pitch BGA, there is almost no ionic residue under a microscope, avoiding long-term electromigration failure.

Automotive lighting SMT plants are sensitive to void rate. The 8M9P/5RR zero-halogen solder paste stably controls the void rate within 3% at a peak temperature of 245℃. This is attributed to its ROL0 level halogen control and the sphericity consistency of the 305 alloy powder. The 8MTSP/5RTS series, which also uses 305 powder, has halogen <500ppm and a solder wetting climb rate of 70–90%, making it suitable for mixed process scenarios where QFN and 0201 components coexist on tablet motherboards. However, note that its soak zone time needs to be 15–20 seconds longer than that of the 8MQP/5RQ series to fully release the solvent. If ordinary SMT Solder paste is used on laser welding production lines, nozzle clogging is highly likely. The 5RLJ series is compatible with pneumatic valves and jet valves. The T6/T7 grade ultra-fine powder combined with 00507BN alloy reduces solder ball occurrence to zero. Measured under a dispensing frequency of 120Hz, it runs continuously for 8 hours without clogging.

For water-washable solder paste, one cannot only focus on low cost. The 8MW1P/5RW1 can wash off rosin residue with water on LED lighting boards, but if mixed with nickel-plated heat sinks, it must be replaced with the 8MW5/5RW5. Because it contains Sn42Bi58 and SC07 composite powder, it forms uniform wetting on aluminum surfaces without leaving grayish-white marks. In low-temperature scenarios, although the 64351 alloy has a melting point of 151–172℃, the 8M/2R series is prone to slump if paired with T2.5 powder. It is necessary to use powder grades above T3 and compress the reflow time to within 45 seconds; otherwise, crystal oscillator pins will develop internal stress cracks due to prolonged thermal soaking. The ultra-low-temperature 5RG series uses In52Sn48 alloy with a melting point of only 118℃, but the T5/T6 powder has a narrow particle size distribution. If the stencil thickness in an SMT plant exceeds 0.1mm, solder bridging is inevitable, and a 0.08mm laser-etched stencil must be used simultaneously.

The real-world adoption of Domestic Solder Paste depends on batch stability. Our JJY LFP-JJY5RQ-0307T4 has a metal content deviation of <±0.3% per batch, which is 0.8 percentage points lower than a certain imported brand of the same specification. This means that the same weight of solder paste contains more actual solder, and SMT plants need to adjust stencil tension two fewer times during first-article confirmation. The LFP-JJY5RR-305 has no detectable cadmium, lead, or mercury in full REACH testing, so automotive electronics customers directly accept the report during audits without retesting, saving a 2-day waiting period per batch. All series are rosin-based, but the 8MW1A-4258 water-washable low-temperature model has a high Bi element ratio, so the cleaning water temperature must be controlled at 42±2℃. Below 40℃, rosin saponification is incomplete; above 45℃, it easily causes blistering of the PCB solder mask.