The key parameters of an effective solder paste printing process of squeegee
Written by HC AUTOMATOIN / Read 68 times
1) Squeegee Speed
The speed of travel of the squeegee determines how much time is available for the solder paste to “roll” into the apertures of the stencil and onto the pads of the PCB. Typically a setting of 25mm per second is used but this is variable depending on the size of the apertures within the stencil and the solder paste used.
2) Squeegee Pressure
During the print cycle it is important to apply sufficient pressure across the entire length of the squeegee blade to ensure a clean wipe of the stencil. Too little pressure can cause “smearing” of the paste on the stencil, poor deposition, and the incomplete transfer to the PCB. Too much pressure can cause “scooping” of the paste from larger apertures, excess wear on the stencil and squeegees, and may cause “bleeding” of the paste between the stencil and PCB. A typical setting for the squeegee pressure is 500 grams of pressure per 25mm of squeegee blade.
3) Squeegee Angle
The angle of the squeegees is typically set to 60° by the holders they are fixed to. If the angle is increased it can cause ‘scooping’ of the holder paste from the stencil apertures and so less solder paste to be deposited. If the angle is reduced it can cause a residue of solder paste to be left on the stencil after the squeegee has completed a print.