For communication motherboard SMT, the most feared defects are cold solder joints and voids, especially incomplete solder climb between the bottom pads of QFN packages and the thermal pads on the PCB. Once the solder climb rate after reflow falls below 85%, IMC fractures are likely to occur during subsequent high-temperature aging. In actual tests, our JJY 8MNTTP/5RNTT series Solder Paste for communication boards achieves a solder climb rate of over 92% for 0.4mm-pitch QFN packages. This is attributed to the synergistic effect of its ROL0-level low-halogen formulation (100~200ppm) and 00507BN/T5 alloy powder, which ensures wetting tension while suppressing excessive growth of intermetallic compounds.

After production lines switched to LFP-JJY5RNTT-0307 to replace a certain imported high-temperature solder paste, the printing yield increased from 94.7% to 98.3%. This is mainly because the rosin carrier of this Domestic Solder Paste has better ductility at the edges of stencil apertures. The concentration of T4 powder particle size distribution is 12% higher than that of T3, resulting in a 0.015mm reduction in solder paste edge collapse after the squeegee passes. This is particularly critical for communication boards with 0.3mm-thick stencils and 0.25mm apertures; otherwise, microvoid clusters are likely to form at BGA corners after reflow.

Solder paste for communication boards must balance high-reliability solder paste characteristics with REACH compliance. The measured data for the 8M9P/5RR series—zero halogen (0ppm) and void rate below 1.8%—comes from cross-sectional analysis by an optical module customer after 500 cycles of thermal shock between -40℃ and 125℃. The IMC layer formed by its 305/T4 alloy at a peak temperature of 245℃ has a stable thickness of 3.2±0.4μm, which is 0.6μm thinner than that of the 8MQP/5RQ under the same conditions but with better continuity, indicating that low halogen does not compromise interfacial bonding strength.

Domestic Solder paste is not just a pile of parameters. For example, although the 8MTSP/5RTS has halogen <500ppm>, solder beads are a critical defect when laser welding communication boards. The 5RLJ series laser lead-free high-temperature solder paste, in jet valve dispensing mode, uses 00507B2N/T6 powder to reduce the viscosity in the molten state by 18% compared to conventional 305/T4, combined with <500ppm>