When performing Dip Soldering on thick-copper PCBs, once the copper thickness exceeds 2oz, the heat capacity increases sharply, resulting in insufficient preheating of the board body and excessively rapid cooling the moment the solder makes contact, which in turn causes delayed solder joint wetting, fillet shrinkage, and even local non-wetting. JJY high-wettability Solder Bars, thanks to their active Flux system and low-surface-tension alloy formulation, can spread faster and climb upward along the sidewalls of pins by at least 0.8mm under the same dip soldering temperature and dwell time, effectively covering the thick-copper heat-conduction shadow areas that conventional solder bars struggle to reach.

When we tested a 6-layer 2.5oz thick-copper power board, we found that after dip soldering with ordinary solder bars at 265℃ for 3 seconds, the wetting length at the edge of BGA bottom pads was only 0.3mm with continuous gaps. After switching to JJY high-wettability solder bars, the wetting length reached 1.1mm under the same parameters, with smooth fillets and no necking. This is not achieved simply by increasing temperature for compensation; rather, the contact angle of its molten solder on the copper surface drops from 42° for ordinary solder bars to 28°, directly increasing the initial formation rate of intermetallic compound IMC per unit time.

During production line commissioning, the chain inclination angle and wave exit height must be adjusted synchronously. Otherwise, no matter how good the solder bar performance is, if the solder dragging angle is too large when the PCB exits the wave, solder joint spikes or bridging will still occur due to gravity-driven solder reflow. We typically control the chain inclination angle at 6.5°±0.3° and maintain the wave exit height at 1.8mm±0.1mm. Combined with the low-viscosity characteristics of JJY solder bars, this can reduce the solder joint bridging rate in thick-copper areas from an average of 3.7% to below 0.9%.

The thickness of the oxide film on the molten solder in the solder pot directly affects wetting performance. During the dip soldering process of thick-copper PCBs, copper ions continuously dissolve into the molten solder, accelerating the precipitation of Cu6Sn5 particles and their accumulation on the liquid surface. If the oxide film scraping operation is not performed three times per shift, once the oxide film thickness exceeds 8μm, the wetting advantage of JJY solder bars will be offset. At this point, even extending the dip soldering time cannot improve fillet fullness, and will instead exacerbate the carbonization of residual flux inside the holes.

For thick-copper boards with large-area ground copper foils, an infrared preheating section must be added mandatorily before dip soldering to raise the temperature of the bottom copper surface to above 120℃ in advance. Otherwise, even though JJY solder bars have strong wettability, when facing the instantaneous heat absorption of a full 2oz copper foil, local solder solidification will still occur before wetting is completed, resulting in a wetting length deviation of more than 0.5mm at different positions of the same pad. This non-uniformity manifests in AOI inspection as fluctuations in solder fillet grayscale values exceeding 15 gray levels.