Paste printing is very important to do a good job in PCBA, it directly determines the overall welding effect of PCBA, in the process of PCBA processing, how to do a good job in solder paste printing has become a problem that production managers must consider. The effect of solder paste printing consists of four parts: steel mesh, solder paste, printing process and detection method.
The opening of the steel mesh must be properly enlarged or reduced according to the layout of the electronic components on the PCBA board, so as to determine the amount of tin on the solder pad, so as to achieve the best soldering effect and avoid the phenomenon of connecting and less tin, which requires strict evaluation by the process engineer. In addition, the material of the steel mesh is also more critical, which affects the tension of the steel mesh and the life of repeated use.
In addition, the steel mesh before feeding cleaning and storage environment is particularly critical. Each time before on-line must carry out strict cleaning, and check whether the hole is blocked, the existence of tin slag and other situations. Some PCBA manufacturers suggest purchasing steel mesh tensiometer and testing the tension of steel mesh before feeding each time.
Solder paste needs to choose high-grade or above brands, containing gold or silver and other active ingredients is better. The solder paste must be strictly stored in the refrigerator of 2 to 10 degrees, and the relevant statistics must be made for each incoming and outbound storage, and the recycling of solder paste must be strictly controlled within the range of IPC standards, and the solder paste mixing procedure must be strictly implemented before the on-line.
At present, manufacturers are using automatic solder paste printing machine, its equipment can well control the printing force and speed of parameters, and has a certain automatic cleaning function. The operator only needs to set the parameters strictly according to the regulations.
In the process of mass production, it is particularly important to detect such phenomena as hole blocking and deviation of the steel mesh, especially when some defects detected by SPI show an upward trend after printing, it is necessary to stop the machine to check the running condition of the steel mesh itself.
After the solder paste printing machine, it is particularly important to configure the SPI solder paste detector, which can effectively detect many defects in the solder paste printing process, such as less tin, tin, notch, wire drawing, deviation, and so on. To maximize the overall welding PPM value.
The management of the solder paste printing effect itself is not a secret, it requires managers to carefully implement each management means in the PCBA processing process. And design a set of closed-loop mechanisms to find and detect defects.
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