During on-site troubleshooting of rework causes, it was found that over 80% of cold solder joints were concentrated at the bottom of fine-pitch devices such as QFN and DFN packages. The root cause lies in the insufficient wetting force of traditional Solder Paste during the reflow stage, which prevents the solder from fully climbing up the sidewalls. In contrast, the Domestic Solder Paste LFP-JJY5RQ-0307 uses 0307 alloy powder (Sn99Ag0.3Cu0.7) paired with a T4 particle size distribution, demonstrating excellent dynamic wetting capability within the 240–255℃ reflow window. The measured solder climb height on QFN32 packages exceeds 0.18mm, approaching the theoretical limit. Meanwhile, its ROL0-level halogen content (<500ppm) significantly reduces the risk of ionic residue, preventing subsequent ICT test misjudgments or long-term electrochemical migration failures.

Compared with commonly used 305-series solder pastes, although the 0307 alloy has the same melting range of 221–227℃, it offers superior eutectic properties. During reflow, it exhibits lower viscosity in the molten state and reduced surface tension. Combined with the gradient release design of the activator in the rosin-based carrier system, it ensures both printing release integrity and suppression of solder ball spattering. After a lighting module manufacturer switched to this rework-reducing solder paste, the SPI first-pass yield increased from 92.3% to 97.6%, the AOI false alarm rate dropped by 41%, and the translucent residue eliminated the need for an additional cleaning process, saving depreciation costs for water washing equipment and DI water consumption.

This Domestic Solder paste is compatible with mainstream stencil aperture designs and has high tolerance for squeegee pressure fluctuations. When printing parameters are set to a stencil thickness of 0.12mm, a squeegee angle of 55°, and a speed of 45mm/s, no solder bridging or insufficient solder was observed across 2000 consecutive boards. Especially on 0.4mm pitch QFN devices, it maintains a 98.2% solder joint bridging suppression rate, while similar imported SMT Solder Pastes exhibit a 3.7% bridging rate under the same conditions. This indicates that its rheological properties are better aligned with the cycle times of domestic equipment, representing not just simple parameter benchmarking but deep adaptation to the entire process chain.

To meet the low void requirements proposed by automotive electronics customers, the zero-halogen version LFP-JJY5RR-0307 from the same series is available. Its measured halogen content is 0ppm, and it is fully REACH compliant. When paired with nitrogen-protected reflow, the X-ray void area ratio of BGA solder joints is stably controlled at ≤3.2%, far superior to the industry standard of 6–8%. This is attributed to the targeted decomposition pathway of the special organic acid compound system in its Flux during the high-temperature stage, which neither prolongs solvent evaporation time nor leaves carbide residue, truly achieving the dual goals of high reliability and low rework.

For production lines already using water-wash processes, the water-wash type domestic solder paste LFP-JJY5RW1-0307 is recommended. While retaining the advantages of the 0307 alloy, it precisely controls the water-soluble resin content at 18.7%. Residues can be completely removed with pure water rinsing for 30 seconds, without white crystal precipitation, avoiding PCB surface corrosion or connector contact issues commonly caused by traditional water-wash solder pastes. Validation by an LED driver board manufacturer showed that after switching to this product, the cleaning defect rate dropped from 1.9% to 0.3%, directly reducing rework labor hours by 127 hours per month.