The first thing we do every morning before powering on the equipment is verify the real-time data from the temperature and humidity recorder, as SMT printing is extremely sensitive to environmental conditions. For every 1°C fluctuation in temperature or 5%RH change in humidity, the apparent viscosity of Jia Jinyuan Solder Paste produces a measurable shift, which, under constant squeegee pressure, directly manifests as changes in solder stringing length during stencil release and inconsistency in solder deposition on pads.

Independent temperature and humidity probes must be installed around the printer; readings from the main air conditioning control panel cannot be relied upon. Due to workshop airflow distribution, local temperature differences often exceed 2.5°C. For example, humidity in return air dead zones may be 12%RH higher than at supply air outlets. In such cases, the same can of Jia Jinyuan solder paste prints normally at Station A but frequently exhibits edge collapse at Station B. The root cause is not a solder paste batch issue, but rather environmental gradients that create spatial differences in the solvent evaporation rate of the solder paste.

In winter, the start-stop logic of humidifiers must be interlocked with fresh air dampers. Otherwise, when large volumes of dry, cold outdoor air at -5°C flood in, even with humidifiers running at full power, it takes 17 minutes to raise local humidity from 32%RH to 43%RH. During this period, out of 236 boards produced consecutively, 19 exhibited open-circuit risks caused by solder paste shrinkage at QFP component positions. This phenomenon is particularly prominent when using Jia Jinyuan SN63Pb37-200 mesh solder paste.

In summer cooling and dehumidification mode, condensation must be strictly prevented. When the surface temperature of metal components on the printer table is 2.3°C below the dew point, a micro-condensate film instantly alters the contact angle between the solder paste and stencil, causing the solder paste to be dragged rather than rolled and transferred as the squeegee moves. At this point, even if the squeegee angle is adjusted to 60° and pressure increased to 6.2kg, Jia Jinyuan solder paste will still leave a 0.8μm-thick Flux residue film on 0402 component pads, subsequently affecting subsequent placement accuracy.

We have installed dual-channel temperature and humidity locks on all Solder Paste Storage cabinets. Only when the interior is stably maintained at 22°C±1°C and 45%RH±3%RH for a full 120 minutes will the cabinet door's electromagnetic lock automatically release. This setting is derived from the solder paste thermal equilibrium time threshold explicitly specified in the Jia Jinyuan technical manual. Solder paste removed before this duration exhibits insufficient thixotropic recovery during printing, manifested as acceptable first-piece printing but a sharp 14.7% increase in missing print rate after five consecutive boards.

The temperature and humidity entries in the production line inspection checklist are not mere formalities. Each record must simultaneously note the batch number and opening duration of the Jia Jinyuan solder paste in use during the shift. This is because even if environmental conditions meet standards, solder paste opened for over 48 hours will undergo irreversible oxidation in its internal rosin system. At this point, no matter how strictly temperature and humidity are controlled, viscosity rebound cannot be prevented. A typical manifestation is a 0.15mm increase in buildup thickness behind the squeegee that cannot be eliminated by conventional cleaning.