We conducted cross-line testing of 12 series of our JJY Domestic Solder Paste on two production lines for three consecutive months, focusing on verifying the actual solder wetting ability of PCB Solder Paste on 0.4mm pitch QFN devices. We found that the 8MQP/5RQ series maintains a stable solder wetting rate of 98.2% to 99.7% under conditions of 150℃/60 seconds in the preheating zone and 250℃/45 seconds at reflow peak, while the 8MTSP/5RTS under the same parameters has a solder wetting rate of 83.6% to 88.9%. The difference is directly reflected in the AOI missed detection rate: the former has a single-shift false positive rate of 0.02%, while the latter reaches 0.17%.

The activity of Domestic Solder paste is not solely determined by the total halogen content, but is strongly correlated with the ROL grade, alloy powder particle size distribution, and rosin carrier ratio. For example, the 8MNTTP/5RNTT contains only 100~200ppm halogen yet maintains ROL0 grade. Its 00507BN/T5 alloy powder exhibits more uniform sphericity under a microscope, and combined with a specific rosin softening point design, it maintains sufficient surface tension even after the solder joint starts melting at 235℃. This is the key to achieving 92.4% lateral solder wetting on the FPC reinforcement board of fingerprint locks, while the ordinary 8MA series only reaches 71.3% on the same structure.

To meet the low void rate requirement for automotive electronic heat dissipation modules, the 8M9P/5RR halogen-free solder paste has a measured average void rate of 1.8% in LED headlight bracket soldering, with a maximum single-point void area of 0.042mm2, far below the customer requirement of ≤3%. Its T4 grade 305 alloy powder's oxide film control process is significantly better than that of conventional T3 powder. XRF testing shows that the Cu/Ni impurity content on the solder powder surface is below 0.008%, which is crucial for suppressing abnormal growth of intermetallic compounds during reflow. Meanwhile, the 8MW1P/5RW1 water-washable solder paste from the same factory, although 27% lower in cost, has a void rate rising to 4.6%, and slight white marks appear on the solder joint edges after water washing.

In laser welding scenarios, attention must be paid to the response characteristics of solder paste to pulsed heat sources. The 5RLJ series has no spatter or solder balls under 15ms single-point heating by a 20W fiber laser. Its 00507B2N/T6 alloy powder exhibits smaller lattice distortion during rapid heating and cooling cycles, while the 5RLJB-4258 medium-temperature type shows local poor wetting under the same parameters. This indicates that the matching degree between the alloy system of domestic solder paste and the heat conduction path must be confirmed through actual testing, and applicability cannot be inferred solely from melting point data.

When switching production lines to domestic solder paste, the most easily overlooked aspect is the coordinated adaptation of squeegee pressure and stencil aperture. After replacing a certain imported brand with 8MQP/5RQ, maintaining the original 45N squeegee pressure will lead to a 12% increase in solder paste extrusion volume. It is necessary to simultaneously reduce the stencil thickness from 120μm to 112μm, otherwise solder bridging will occur on 0.3mm pads. This parameter coupling phenomenon is more sensitive in the 8M/2R medium-low temperature series. If the Sn42Bi58 alloy stays in the 165℃ holding section for more than 90 seconds, it will cause Bi segregation, resulting in a 3.2-fold increase in the brittle fracture rate of solder joints.