During production line verification of solder for 5G equipment, we found that Jinyuan JNY-5G188 can stably achieve a 98.7% solder joint fill rate in Reflow Soldering of 0.3mm pitch BGA packages under conditions of a peak temperature of 245°C and a time above liquidus of 62 seconds, while conventional SAC305 generally has a void rate exceeding 12% under the same parameters. The difference is particularly significant on the copper substrate of base station PA modules. This is because the trace copper element in the Sn96.5Ag1.8Cu0.7 composition of JNY-5G188 effectively suppresses excessive growth of the interfacial IMC layer. Meanwhile, the rosin derivatives of its matching ROL0 no-clean Flux start decomposing at 220°C, which exactly matches the heat capacity characteristics of the multilayer thick copper structure of 5G communication base station router motherboards.

During actual line changeover, the stencil aperture size and squeegee pressure must be adjusted synchronously. For example, reduce the aperture of a 0.4mm thick stencil from the conventional 92% area ratio to 85%, and fine-tune the squeegee angle from 60° to 58°. Otherwise, even when using Jinyuan 5G Equipment Solder, solder balls will appear at the edge of the Wi-Fi 6E RF front-end chip pad. This is essentially local spattering caused by the mismatch between the shear-thinning behavior of the Solder Paste and the heat dissipation rate of thick copper. We once had a three-day line shutdown for troubleshooting at a factory in Dongguan, and finally confirmed via an infrared thermal imager that the problem was completely solved only after the cooling rate at the end of the reflow zone decreased by 1.8°C/s when the PCB backside copper foil thickness increased from 2oz to 3oz.

The storage conditions of Jinyuan JNY-5G188 must be strictly controlled at 0°C~10°C with humidity below 30%RH. Once opened and not used up within 12 hours, the oxide film on the surface of the solder powder will thicken significantly. At this time, in the soldering of 0.25mm pitch QFN packages for router main control SOC, poor wetting will still occur even if the preheat zone heating ramp is increased to 2.1°C/s. Under a microscope, the solder can be seen to be distributed in islands on the nickel-palladium-gold pads rather than spreading continuously, which is directly related to the attenuation of flux activity. Therefore, the production line must be equipped with a nitrogen cabinet with temperature and humidity recording, and cannot be carelessly stacked in an ordinary moisture-proof box.

During drop tests, we found that the 5G communication base station RRU modules soldered with Jinyuan 5G equipment solder still retained 91.3% of their shear strength after 1000 cycles of thermal shock from -40°C to +85°C, while the control group using a domestic brand solder from the same batch only retained 76.5%. The fundamental reason is that the SnAgCu ternary eutectic point of JNY-5G188 is precisely controlled at 217.2°C±0.3°C, which compresses the liquidus interval width during reflow to the narrowest 1.1°C, thereby greatly reducing the impact of high-temperature residence time on the thickness of the copper pad intermetallic compound. This narrowing of the process window seemingly increases the difficulty of furnace temperature debugging, but in exchange for more stable long-term reliability.

The batch inspection reports provided by Jinyuan must be checked item by item. In particular, the melting peak width in the DSC curve must not exceed 1.5°C, and the deviation of silver content measured by XRF must not be greater than ±0.05wt%. Last year, a batch of goods had a measured silver content of 1.72wt%, which caused batch rework of a certain operator's routers. The problem arose from the fluctuation of argon purity in the solder powder atomization process. Therefore, SMT engineers must personally spot-check the measured melting point data of each batch, and cannot only rely on the paper values of the COA.