When debugging a certain base station RF front-end board, we found that the 40GHz power amplifier chip soldered with conventional Solder Paste frequently exceeded the S22 parameter limit during complete machine testing. Re-testing via X-ray revealed that the average void rate of BGA solder joints reached 16.3%. After switching to JJY JH-5G low-void solder paste paired with a nitrogen atmosphere reflow process, the void rate was reduced to 7.2%, and the yield of this batch jumped from 81.5% to 99.2%.

The metal powder sphericity of JJY JH-5G solder paste reaches 92.6%, with a particle size distribution D50 of 22.4μm. Combined with its specially formulated rosin-based Flux system, it exhibits more uniform release behavior during the stencil printing stage. Even when the squeegee pressure is maintained at 5.8kgf, the aperture filling rate remains above 94%, which directly reduces the risk of gas entrapment during reflow caused by post-Printing Solder Paste edge collapse.

We have tested the impact of different reflow profiles on voids. When the peak temperature is set to 248℃ and the time above liquidus is controlled at 62 seconds, the decomposition gas from the flux of JJY JH-5G solder paste can be directionally released before the solder fully melts. If the soak zone is extended to 110 seconds, some active components will be prematurely depleted, resulting in incomplete oxide film removal, and the void rate will rebound to 11.7%.

The stencil aperture design must match the thixotropic index 2.8 of JJY JH-5G solder paste. We once used the 1:1 aperture ratio of the old 0.12mm thick stencil, which led to insufficient solder volume on the pads of 0.3mm pitch QFN devices and caused clustered micro-voids after reflow. After switching to trapezoidal apertures with a 1:0.92 ratio, the solder paste volume accuracy was stabilized within ±4.3%.

Fluctuations in ambient temperature and humidity will significantly alter the viscosity decay curve of JJY JH-5G solder paste. When the workshop RH exceeds 65% and the temperature reaches 28℃, the window period from stencil printing to placement completion is shortened to 38 minutes. Solder joints that exceed this time limit will have an average void rate increase of 3.1 percentage points. Therefore, the solder paste constant temperature cabinet must be set to 25±1℃, and the workshop dew point temperature must be monitored in real time.

When the mounter nozzle vacuum is lower than -82kPa, 0201-sized coupling capacitors are prone to micro-shift. Combined with the surface tension contraction of the solder paste in the early stage of reflow, closed cavities will form at the bottom of the solder joints. The lower initial wetting angle (28°) of JJY JH-5G solder paste allows it to rapidly spread and squeeze out residual gas in the early stage of melting.

We compared the impact of three cleaning processes on voids. When the ultrasonic cleaning frequency was set to 40kHz, void residue was instead aggravated. After switching to megasonic cleaning (frequency 1.2MHz) paired with JJY's special water-based cleaning agent, the removal rate of oxides at the solder joint interface was increased to 99.1%, and the void rate was further reduced by 0.9 percentage points.

After multiple temperature recoveries, the viscosity recovery rate of JJY JH-5G solder paste is only 12.4%, which is far better than the 35.7% of ordinary solder paste. This means that the same can of solder paste can still maintain printing accuracy after 48 hours of continuous use on the production line. However, it must be ensured that the temperature difference for each temperature recovery does not exceed ±3℃, otherwise local flux precipitation will occur, leading to increased dispersion of void distribution.