Screen printing technology refer to using ready-made stencil, directly connect to the printer in a certain way,
make the solder paste evenly flow on the stencil and then leak into the mesh through the holes. When getting
the stencil away, solder paste had been covered to the printed circuit board solder graphics, then finish the
solder paste printing on the PCB.
The stencil printing function is achieved through a single material namely solder paste which consists of solder
metal and flux. Paste also acts as an adhesive during component placement and solder reflow. The tackiness of
the paste enables the components to stay in place. A good solder joint is one where the solder paste has melted
well and flowed and wetted the lead or termination on the component and the pad on the board.
In order to achieve this kind of a solder joint, the component needs to be in the right place, the right volume of
solder paste needs to be applied, the paste needs to wet well on the board and component, and there needs to be a residue that is either safe to leave on the board or one that can easily be cleaned.
The solder volume is a function of the stencil, the printing process and equipment, solder powder, and rheology or
the physical properties of the paste. Good solder wetting is a function of the flux.