The selection of high-temperature Solder Paste cannot rely solely on the nominal melting point; it must be dynamically matched by combining the actual peak temperature of the Reflow Soldering solder paste profile, PCB heat capacity distribution, and component temperature resistance limits. For example, although both the 0307 alloy (Sn99Ag0.3Cu0.7) and 305 alloy (Sn96.5Ag3Cu0.5) fall within the 221–227℃ melting range, the former exhibits slower wetting and lower voiding rates within the 240–260℃ reflow soldering solder paste window, making it particularly suitable for addressing local cold joint issues caused by rapid heat dissipation from QFN bottom pads.

Among Domestic Solder Pastes, our JJY 8MQP/5RQ series uses T4-grade 0307 alloy powder, with single halogen content <900ppm and dual halogen content <1500ppm. Tested on 0.4mm pitch QFNs, the solder climb rate exceeds 95%. Its rosin-based carrier leaves minimal, transparent residue at a 250℃ peak temperature. The same factory's 8MNTTP/5RNTT series further reduces halogen content to 100–200ppm and incorporates 00507BN/00507B2N micro-alloy powder, with no solder joint microcracks observed in high-frequency vibration scenarios of fingerprint lock motherboards.

When zero-halogen requirements are stringent, the 8M9P/5RR series can be directly selected. With 0ppm halogen and an ROL0-grade rosin system, it stably controls voiding rates below 3% during reflow soldering solder paste operations on automotive LED circuit boards. The prerequisite is that stencil apertures must be enlarged by 5% compared to conventional ones; otherwise, solder balls may easily form due to excessively fast Flux volatilization. The water-washable high-temperature solder paste 8MW1P/5RW1 uses a mixed SC07/0307 powder; although its residue is water-washable, an excessively high proportion of T3 powder reduces printing release rate by 12%, so it is recommended to use with a stencil below 38μm.

Laser welding scenarios must avoid the viscosity mutation risk of traditional high-temperature solder pastes. The 5RLJ series is optimized for jet valves; T6/T7-grade ultra-fine powder ensures no spattering or solder balls under 10ms-level laser pulses. However, its 0307+00507BN dual-alloy formulation causes local incomplete fusion if the reflow soldering solder paste peak temperature falls below 245℃, which must be verified via X-ray sampling before mass production. Low-temperature solder pastes such as the 5RG series use In52Sn48 to achieve a 118℃ melting point, but their solder joint shear strength decays by 37% after thermal cycling, making them only suitable for sensor modules requiring one-time assembly and no mechanical stress.

When purchasing Domestic Solder pastes, do not be misled by the literal term "halogen-free"; ROL0 and ROL1 correspond to completely different cleaning verification standards. For example, although the 8MA series is labeled with <900ppm halogen, it belongs to the ROL1 grade. It is acceptable for lighting LEDs, but if mixed into communication motherboards, it may cause ionic contamination leakage. The <500ppm ROL0 grade of 8MTSP/5RTS is the reflow soldering solder paste that truly meets IPC-J-STD-004B Class L0 requirements. Additionally, all low-temperature alloys containing Bi elements, such as 4258 or 64351, once mixed into high-temperature Solder Paste Production lines, will form eutectic phases in the 250℃ reflow soldering solder paste zone, leading to batch cold solder joints. Storage and feeding pipelines must be physically isolated.