2, Short circuit
(1) The stencil is too thick, deformed severely, or the stencil opening is deviated, which does not match the position of the PCB pad.
(2) The stencil was not cleaned in time.
(3) The blade pressure is set improperly or the blade is deformed.
(4) The printing pressure is too high, making the printed graphics blurred.
(5) The reflux time of 183 degrees is too long, (the standard is 40-90S), or the peak temperature is too high.
(6) Poor incoming materials, such as poor IC pin coplanarity.
(7) The solder paste is too thin, including low metal or solid content in the solder paste, low thixotropy, and the solder paste is easy to explode.
(8) The solder paste particles are too large and the surface tension of the flux is too small.
3, Displacement
A. Offset before REFLOW
(1) The placement accuracy is not accurate.
(2) The solder paste has insufficient adhesion.
(3) The PCB vibrates at the furnace inlet.
B. Offset during REFLOW
(1) PROFILE heating curve and warm-up time are appropriate.
(2) Whether the PCB is vibrating in the furnace.
(3) If the preheating time is too long, the activity will be lost.
(4) The activity of the solder paste is not enough, so use a solder paste with strong activity.
(5) The PCB PAD design is unreasonable.