How to control the tips of solder paste printing in PCBA processing?

How to control the tips of solder paste printing in PCBA processing?

Solder paste printing is very important for PCBA, which directly affects the overall welding effect of PCBA. In the process of PCBA processing, how to do well in solder paste printing has become a problem that production managers must consider. The effect of solder paste printing consists of steel screen, solder paste, printing process and detection method.

1、 Steel mesh

The steel mesh must be properly enlarged or reduced according to the layout of electronic components on the PCBA board to determine the amount of tin on the bonding pad, so as to achieve the best soldering effect and avoid the occurrence of tin bonding, less tin, etc., which requires strict evaluation by the process engineer. In addition, the material of the steel mesh is also critical, which affects the tension of the steel mesh and the service life of the steel mesh.

In addition, the cleaning and storage environment before feeding the steel mesh is particularly critical. Strictly clean the vias before going online each time, and check whether the vias are blocked or have tin slag. Some PCBA manufacturers suggest to purchase steel mesh tensiometer, and conduct tension test of steel mesh before each feeding.

2、 Solder paste

Solder pastes should be of medium and high grade brands, such as Qianzhu, Vitel, etc. It is better to use solder pastes containing active ingredients such as gold or silver. Solder paste must be strictly stored in a refrigerator with a temperature of 2 to 10 degrees. Relevant statistics must be made for each warehousing and outbound. The recovery of solder paste must be strictly controlled within the scope of IPC standards, and the solder paste mixing procedure must be strictly implemented before going online.

3、 Solder paste printing

At present, manufacturers are using full-automatic solder paste printers, whose equipment can well control parameters such as printing strength and speed, and has certain automatic cleaning functions. The operator only needs to set the parameters in strict accordance with the regulations.

In the process of mass production, it is particularly important to detect such phenomena as plugging and offset of the steel mesh. Especially when some defects detected by SPI after printing show an upward trend, the machine must be stopped to check the operation of the steel mesh itself.

4、 SPI printing effect detection

After the solder paste printing machine, it is particularly important to configure SPI solder paste detector, which can effectively detect a lot of defects in the solder paste printing process, such as little tin, continuous tin, notch, wire drawing, offset, etc. To maximize the overall welding PPM value.

It is not a secret to manage the printing effect of solder paste. It requires managers to carefully implement each management method in the PCBA processing process. And design a closed-loop mechanism that can find and detect defects.