Solder paste is a special thixotropic fluid. The change of environment temperature will cause the viscosity of solder paste to change, the temperature rise, and the viscosity will decrease. After pcb manufacturing printing will cause the solder paste to collapse which will eventually lead to bridging after soldering. If the environment humidity is too high, the solder paste will absorb the moisture in the air, causing Pcb manufacturing soldering defects such as solder balls after soldering. Therefore, it’s high requirement for solder paste printing environment of the PCB prototype board.
Although solder paste coating working environment belongs to the overall environment of Pcb manufacturers,but volatility and instability of solder paste, patch adhesive, flux and other technics consumables are considered. The environmental factors which affect components solder paste coating mainly include temperature, humidity, air cleanliness, ventilation and wind speed.
The temperature of the solder paste on the board is based on the usage conditions (about 23 °C). Unsuitable temperature conditions may cause the solder paste to be thick or too dry. The humidity requirement is about 50%. If it is less than 50%, the solder paste will dry out and the volatile materials will evaporate. If it is more than 50%, the solder paste will absorb moisture, and the solder paste will be invalid or the solder balls will be produced. Maintaining minimum ventilation in the printing area is also a guarantee of the best Pcb manufacturing printing quality.
Ensure that the pcb manufacturing printing environment has sufficient cleanliness. Specific requirements are as follows:
(1) Power supply requirements: the power supply voltage and power should meet the requirements of the equipment, and the voltage is stable. It requires single-phase AC220 (220±10%, 50/60Hz) and three-phase Ac380V (220±10%, 50/60Hz).
(2) Indoor temperature: the environment temperature is best at 23±2°C, generally 17°C~28°C is the best, and the extremity temperature is 15°C~35°C.
(3) Humidity: The relative humidity is 45%~70% RH.
(4) Working environment: the workshop is hygienic, free from dust and free-of corrosive gases. Air cleanliness is 100000. (BGJ73-84); In the air-conditioning environment, there must be a certain amount of fresh air, try to keep the carbon dioxide content below 1233Mg/m3 to ensure human health.
(5) Anti-static: The production equipment must be well grounded. It should be grounded by three-phase five-wire grounding method. The floor, work table mats, and chairs of the production site shall comply with the anti-static requirements.
(6) Exhaust air: pcb manufacturing reflow soldering and wave soldering equipment both have exhaust requirements.
The above is the industry information provided by FASTPCBA, I hope to help you!