The handle and precautions of OSP board in SMT process

a. Before opening the PCB vacuum package, check whether the PCB packaging is damaged and whether the humidity indicator card is discolored. If it is damaged or discolored, it cannot be used, need bake before start SMT. OSP PCB needs to be start production within 8 hours after opening. It is recommended to open packages as less as possible according to SMT quantity, and vacuum packaging should be applied in time for PCBs that have not been used.

b. It is necessary to control the temperature and humidity of the SMT workshop. It is recommended that the workshop set temperature: 25±3℃, humidity: 50±10%. During the SMT production process, it is forbidden to directly touch the surface of the PCB pad with bare hands to prevent sweat pollution, causing oxidation and leading to poor soldering.

c. After printing solder paste, components should be mounted and pass the reflow oven as soon as possible. Try to avoid printing errors or mounting problems leading to PCB washing during SMT process, because washing PCB surface will damage the OSP film, if you do need to wash the board, do not use high volatile solvent to soak PCB for cleaning, it is recommended to wipe off the solder paste with a non-woven cloth dipped in 75% alcohol. The PCB after cleaning must be soldered within 2 hours.

d. After the first side SMT is completed, the placement of the second side SMT components needs to be completed within 24 hours, and the selective soldering or wave soldering of the DIP (plug-in) components must be completed within 36 hours.

e. Since the solder paste on OSP surface PCB has poorer fluidity than other surface treatment PCBs, the solder joints are likely to expose copper. When designing the stencil opening, you can increase it appropriately. It is recommended to open the hole according to the pad with ratio 1:1.05 or 1:1.1, but you need to pay attention to the anti-tin bead treatment of the chip component.

f. The peak temperature and reflow time of the OSP board during reflow soldering are recommended to be as close to the lower limit of the process as possible when the soldering quality is satisfied. when mounting double-sided PCBs, it is recommended The temperature of the first side reflow (the small component side) should be lowered appropriately, and the temperature on both sides should be set separately to reduce the damage of high temperature to the OSP film. If possible, it is recommended to use nitrogen reflow oven, which can effectively improve the problem of oxidation and poor soldering of the second side of the double-sided OSP board.