There may be five reasons for SMT tin connection:
The steel mesh is too thick and there is too much solder paste.
The distance between the steel mesh and PCB is too large.
The pressure on the printing scraper is too low.
Multiple prints.
Solder paste collapse (low viscosity)
To address the SMT tin connection issue, the following improvement measures can be taken:
If there is tin connection phenomenon, it can be improved by adjusting the parameters of the solder paste printing machine, such as adjusting the printing pressure, increasing the scraper delay, etc.
If the distance between the steel mesh and the PCB is too large, causing tin connection, the distance can be reduced by adjusting the bottom gasket of the steel mesh.
If there are multiple printing or solder paste collapses resulting in tin bonding, the solder paste can be replaced or its viscosity reduced.
If the component absorbs heat from the tin liquid at the peak, causing tin dragging, the preheating time can be increased in the preheating zone and the preheating temperature can be adjusted to 100-110 ℃.
If the welding speed is too fast and causes tin connection, the welding speed can be reduced.
If the angle of the wave soldering track is less than 7 degrees, resulting in tin connection, the track angle can be adjusted to above 7 degrees.
If there is deformation of the PCB board causing tin connection, the preheating temperature and time curve can be controlled, or the PCB board can be properly stored during transportation.
If the excessive protrusion of pins leads to tin connection, the length of the pins can be controlled or the peak height of the solder liquid can be adjusted.
If there is no or missing solder mask/bridge causing tin connection, solder mask/bridge can be added according to the situation.