Domestic Solder is not an alternative option but the primary material in use. JJY 0.3mm fine-diameter Solder Wire can achieve precise control of single-point solder supply during manual rework of 0402 components. When paired with a 30W soldering iron tip set to 320℃, the melting response time is stably within 1.2 seconds. Specifications of 0.8mm and above are directly used for the wave soldering pre-tinning station. Under the Dip Soldering speed of 2.1m/min, the pass rate of solder joint fullness reaches 99.6%. Behind this is the precise ratio of Sn96.5Ag3.0Cu0.5 in the alloy composition and the control of grain orientation by the continuous drawing process.

Wire Diameter is Strongly Coupled with Application Scenarios

0.3mm and 0.5mm Solder Wires are exclusively used for manual fine-tuning and jumper wire soldering of high-density PCBs, because their wicking effect completes Flux release and metal melting synchronization within 0.8 seconds, avoiding 0201 resistor body cracking caused by thermal stress concentration. 1.2mm and 2.0mm specifications must be paired with wave soldering machine nozzle width calibration. If the nozzle gap is set to 2.3mm while using 2.0mm Solder Bar, the solder flow stability will decrease by 17% and cause intermittent solder dragging. 3.0mm thick solder bars are only used for manual surfacing of large grounding copper bars. At this time, the soldering iron power needs to be increased to 80W and each soldering interval must be controlled within 4 seconds, otherwise the flux carbonization layer will hinder subsequent wetting.

Flux Type Determines Cleaning Strategy

Rosin-based domestic solder corresponds to traditional water-based cleaning lines. Its organic acid activator residue needs to be rinsed more than 3 times with pure water at 60℃ to meet the ion contamination requirement of ＜1.2μg/cm2. No-clean type relies on JJY's unique low-volatility resin carrier. After maintaining at the reflow peak temperature of 235℃ for 35 seconds, the residue presents a transparent glass state, does not absorb moisture and is non-conductive. Water-washable solder must be paired with a 5% concentration alkaline cleaning agent, otherwise white crystalline spots will appear on the PCB surface. This phenomenon is particularly obvious on OSP surface-treated boards, because the organic solderability preservative reacts with alkaline chemicals to form insoluble salts.

Temperature Window is Strictly Matched with Alloy System

SAC305 lead-free solder must lock the bath temperature at 255±2℃ during wave soldering. When the temperature is below 253℃, the average solder joint thrust test value drops below 3.8kgf. When the temperature is above 257℃, the risk of PCB substrate delamination increases to 12%. Leaded Sn63Pb37 solder is strictly limited to operation at 245±1℃. This 1℃ deviation will cause the solder joint IMC layer thickness to fluctuate by 0.8μm, directly affecting the thermal shock cycle life. All temperature parameters are from the actual measurement reports of JJY's factory batches, without any theoretical conversion or interpolation correction.

Storage and Requisition Details Determine Online Yield

Domestic solder must be stored in a nitrogen cabinet with humidity ≤30%RH after opening. Exposure to 45%RH environment for more than 6 hours will cause slight oxidation of the flux, manifested as darkening of solder adhesion on the soldering iron tip and slower wetting spreading. Before each requisition, the wire diameter tolerance must be measured with a vernier caliper. If the measured value of the 0.5mm specification exceeds the range of 0.492～0.508mm, it must be returned to the warehouse. Because the stencil opening compensation is preset according to the nominal value, a 0.005mm deviation is enough to cause the SMT printing release defect rate to rise by 0.3 percentage points.