During production line commissioning, we found that simply replacing with high-activity Solder Paste without synchronously adjusting the type of soldering auxiliary material instead caused large-area wetting defects on OSP boards. This is because JJY RMA-type solder paste needs to be matched with a Flux pen of medium rosin content; if a no-clean high-volatility auxiliary material is mistakenly used, the flux will dry out prematurely before reflow and lose its activation ability, which in turn leads to uneven solder joint shrinkage and increased void rate.

Small fluctuations in squeegee pressure and speed after solder paste printing directly affect the solder paste transfer rate, and this effect is further amplified by the surface tension characteristics of the soldering auxiliary material. For example, when using JJY 705 series solder paste, if the proportion of ethanol in the auxiliary material is too high, it will accelerate solvent volatilization at the edge of the solder paste, causing collapse and bridging at the stencil openings. At this point, the dilution ratio of the auxiliary material must be adjusted from 1:3 to 1:5, and the demolding speed of the printing machine must be synchronously reduced to below 15mm/s.

The filling effect of the bottom pads of QFN devices depends not only on the metal content and particle size distribution of the solder paste, but also on the spreading rate of the soldering auxiliary material in the early stage of reflow. When JJY MG-880 solder paste is used with a low-boiling-point auxiliary material, a liquid film will form prematurely in the 150℃ range, hindering the coalescence of solder powder particles and instead reducing the consistency of solder joint height. After switching to a medium-temperature activated auxiliary material containing terpene components, the coplanarity CPK value of solder joints increased from 0.91 to 1.33.

In most cases, the tombstoning problem of 0201 components is not caused by abnormal reflow curves, but by soldering auxiliary material remaining on the sidewalls of the openings during the stencil wiping process, leading to an imbalance in surface tension on both sides of the solder paste. We once verified on a customer's production line that after changing the combination of JJY SG-600 solder paste and conventional halogen-free auxiliary material to its dedicated low-temperature slow-release auxiliary material, the tombstoning rate decreased from 427 per million to 89 per million, and the AOI false positive rate also dropped by 31% synchronously.

The compatibility of the cleaning process is often overlooked, but the organic acid salt system in JJY solder paste and the amine stabilizers in certain Soldering Auxiliary Materials will undergo complexation reactions, generating colloidal precipitates that are difficult to dissolve in water-based cleaning agents. These precipitates attached to the root of BGA solder balls can easily induce interfacial delamination after subsequent high-temperature storage. Therefore, it is necessary to use matching auxiliary materials under the same technical platform and avoid cross-series mixing.

The application method of soldering auxiliary material in Solder Wire operations directly affects the service life of the soldering tip and the glossiness of solder joints. Manual dispensing will cause local flux accumulation, while atomized spraying is prone to splashing and contaminating surrounding devices. We recommend adding a micro-spray module for auxiliary material after the wave soldering preheating section, used in conjunction with JJY HS-90 solder wire, which not only ensures the continuity of tinning on the pins, but also controls the flux residue within the limit of IPC-J-STD-004B Class L standard.