Laser cutting is currently the main PCB manufacturing method for SMT solder paste printing stencils, and usually requires further processing after cutting, such as electropolishing or physical polishing, nano coating, etc. The morphology of the hole wall before and after electropolishing is shown in Figure 1:
The template processed by laser cutting process has the following features:
(1) The surface of the hole wall is rough, and the transfer rate of the solder paste is 70% ~ 100%, which is suitable for applications with an opening size of not less than 0.15mm.
(2) Suitable for applications where the area ratio of the template opening to the side wall is greater than or equal to 0.66
The processing accuracy of the laser cutting template is as follows:
(1) Opening size accuracy: 0 ~ 0.010mm.
(2) Opening position accuracy: ± 0.040 ~ 0.075mm
(3) Material thickness: 0.050 ~ 0.600mm.
(4) Side wall roughness: 0.005 ~ 0.006mm.
The main materials used are:
(1) SUS304 steel sheet, the life of the general template is over 150,000 times.
(2) FG steel sheet.
(3) FG template + nano coating. The roughness of the laser cut aperture surface is related to the material. The finer the grain of the material, the smaller the roughness, that is, the smoother. This is because metal melting starts from the grain boundary firstly. At present, in the production of fine component printing templates, many pcbs manufacturer use fine grains stainless steel material , which is called FG template in the industry. The biggest advantage of the FG template is that the good consistency of the tin permeation.