It is very common to encounter severe oxidation of pads beneath BGA chips during rework soldering. In particular, for PCBs stored for more than 18 months, a dense CuO film has formed on the pad surface after removal. If conventional RMA-type Flux is still used at this point, reliable wetting cannot be achieved even when the soldering iron temperature is raised to 380°C, and the risk of pad peeling is instead exacerbated. In contrast, JJY JY-808 flux contains a composite activation system of zinc chloride and organic amines. Within the 320–350°C range, it can rapidly penetrate the oxide layer and undergo an in-situ reduction reaction with CuO, simultaneously releasing active hydrogen atoms, reducing the contact angle of the liquid solder from 78° to within 12°.

In actual operation, the shape and pressure of the soldering tip must be strictly controlled. We typically use a 0.5mm conical iron-plated tip and apply a constant pressure of approximately 80g. Insufficient pressure prevents the flux from fully penetrating the pad micro-holes, while excessive pressure easily causes local carbonization of the FR4 substrate. Meanwhile, the nitrogen flow rate must be stable at 15L/min. Below 12L/min, the rebound in oxygen content weakens the reduction efficiency of JY-808, while above 18L/min, it causes molten solder splashing. This window value was confirmed after continuously tracking the rework results of 37 oxidized boards from different batches.

Pad pre-treatment cannot rely on sandpaper polishing, as mechanical scratching introduces new lattice defects on the Cu surface and accelerates secondary oxidation. The correct procedure is to first gently wipe off floating dust with an anhydrous ethanol cotton swab, then apply one drop of JY-808 and let it stand for 8 seconds to complete interfacial wetting. At this point, the oxidized area can be seen to change from dark brown to metallic luster. Immediately transfer it to a PCB carrier preheated to 120°C to avoid moisture condensation in the air causing premature flux failure. The entire process from dropping the flux to soldering must be controlled within 22 seconds. If exceeded, the active components begin to volatilize, and the wetting force attenuates by more than 60%.

For rework soldering of multi-pin QFP devices, we adopt a dual-zone synchronous heating scheme. The main soldering tip is responsible for pin-end wetting, while an auxiliary hot air gun preheats the back of the pad at 280°C for 3 seconds. This allows JY-808 to form a gradient activation layer inside the copper foil, avoiding pad lifting caused by localized overheating. Actual measurements show that this method increases the first-pass soldering success rate from 61% to 89%, and X-ray inspection shows that the void rate is stable within the IPC-A-610E Class II standard, with no flux residue corrosion observed.

Although JJY JY-808 has strong activity, it must not be mixed with silver-containing Solder Paste, as free chloride ions in it will react with silver ions to form AgCl precipitates that clog the mesh. There was once a production line that mistakenly used JY-808 for 0201 package LED rework, resulting in blackened solder joints and a 35% decrease in thrust after reflow. Later, switching to the dedicated matching solder paste JY-Sn63Pb37 for JY-808 restored normal operation. This shows that the chemical compatibility between flux and solder must be verified through actual testing and cannot be based solely on theoretical speculation.