The causes and solutions of incomplete melting of SMT solder paste are as follows: (1) Low temperature—low peak temperature of reflow soldering or short reflow time, resulting in incomplete melting of solder paste. Solutions: Adjust the temperature curve, the peak temperature is generally set at about 30 ~ 40 degrees higher than the melting point of solder paste, and the reflow time is 30 ~ 60s. SMT processing template
(2) reflow oven—uneven transverse temperature. Generally, it occurs when the furnace body is narrow and the insulation is poor. The equipment solution measures are: appropriately increasing the peak temperature or prolonging the reflow time. Try to place the PCB in the middle of the furnace for soldering.
(3)PCB design—When the solder paste is not completely melted in the big solder joints, big components, and around big components, or there are big devices on the back of the printed board. Solutions: A. Try to place the big components on the same side of the PCB, but they can't be arranged. Staggered arrangement should be made. B. Increasing the peak temperature or prolonging the reflow time appropriately.
(4) Infrared furnace-deep color heat absorption. Multi-solutions: In order to make the solder joints around the deep color and large-volume components reach the welding temperature, the welding temperature must be increased.
(5) Quality problems of solder paste-high oxygen content of metal powder and poor soldering performance; Or improper use of solder paste: do not use inferior solder paste to formulate a management system for the use of solder paste.