As we all know, the printing process is the source process of PCBA processing, and the quality of printing will directly affect the welding quality of the product. So what factors will affect PCBA printing quality?
PCB design
1. Scraper angle: The scraper angle affects the vertical force of the scraper on the solder paste. The smaller the angle, the greater the vertical separation Fy. If the angle is greater than 80°, the vertical component force is almost 0, and the solder paste will not be pressed into the stencil window. The best setting is 45°-60° so that the solder paste will have good rolling properties.
2. Squeegee pressure: that is, printing pressure. Insufficient pressure will cause insufficient solder on the PCB board, which will affect the subsequent production of defective products. Excessive pressure will deform the front part of the scraper and affect the scraper angle, which plays an important role in the pressing force.
3. Printing gap: It is usually best to keep the PCB blank board parallel to the track of the automatic printing machine. If the printing gap is too large, the amount of tin on the PCB pad will be too much, and the printing gap will be too small and higher than the track of the automatic printing machine, which will cause the stencil Being jacked up, causing damage to the steel mesh.
4. Cleaning frequency: During the printing process, the bottom of the stencil must be cleaned to remove solder paste and other attachments to prevent contamination of the PCB. For integrated ICs, if cleaning steps are not set up, tin will stick to the IC pads on the PCB board, resulting in defective products.
To sum up, controlling these parameters can greatly ensure the printing quality of solder paste, reduce the number of repair parts caused by printing problems, and improve the product qualification rate.