1. Use red glue technology on one side and solder paste technology on the other side
This method is suitable for PCB boards with denser components and pcb prototype manufacturer different component heights on one side. Especially the large components have high gravity, and then the reflow soldering will fall off. At this time, the red glue will be more firm when heated.

The process flow is: incoming inspection --> PCB A side silk screen solder paste --> SMD --> AOI or QC inspection --> A side reflow soldering --> flip board --> PCB side B silk screen Red glue or red glue (note that whether it is red glue or silk-screen red glue, red glue is applied to the middle part of the component. Do not let the red glue contaminate the pad and cause the component feet to fail to solder) --> SMD -->Drying-->Cleaning-->Testing-->Rework.

It should be noted here that the solder paste surface must be soldered first, and then the red rubber surface must be dried. Because the drying temperature of red glue is relatively low, it can be cured at about 180 degrees. If the red glue surface is dried first, and then the solder paste surface is operated, it is easy to cause the components to drop. After all, the adhesion of the red glue is not good, and the temperature will be as high as 200 when the solder paste board is passed. It is easy to cause the cured red glue to fail and become brittle, causing a large number of components to fall off.

2. The solder paste process is used on both sides
This method is suitable for a large number of components on both sides, and both sides have large-scale close-footed IC or BGA PCB boards. Because if red glue is applied, it is easy to make the IC pin and the pad not aligned.

The process flow is: incoming inspection-->PCB's A-side silkscreen solder paste-->SMD-->QC or AOI inspection-->A-side reflow soldering-->turnover-->PCB's B-side silkscreen Solder paste-->SMD-->QC or AOI inspection-->Reflow soldering-->Cleaning-->Inspection-->Rework. Note here: In order to avoid the falling off of large components when passing the B side, when setting the reflow soldering temperature, the temperature of the lower temperature zone of the reflow soldering should be set higher than that of the upper temperature zone of the reflow soldering. The temperature is slightly lower by 5 degrees. In this way, the tin underneath will not melt again and SMT PCB cause the components to fall off.