Classification and function of SMT scraper
In the SMT printing process, the quality of the squeegee has an important influence on the quality of the printing, and the squeegee has different classifications according to the shape of the material.
1. Classification of scrapers:
Common scrapers can be divided into rubber scrapers and metal scrapers according to their materials. Now most of them use stainless steel metal scrapers; according to their shapes, they can be divided into diamond scrapers and trailing scrapers. Trailing scrapers are mostly used in production.
1. The diamond squeegee is composed of a square with a cross section of about 10*10mm, clamped by a splint to form an angle of 45° on both sides. This squeegee can work in two directions, and the solder paste strip will be skipped at the end of each stroke, so only one squeegee is needed. However, it is easy to get dirty, because the solder paste will run up, and its insufficient flexibility means that the distorted PCB cannot be attached, which may cause a missing area. Therefore, the diamond squeegee is rarely used now.
2. The trailing squeegee is made of rubber or metal with a rectangular cross-section, supported by a splint, and requires two squeegees, one squeegee for each printing stroke direction, no need to skip the solder paste strip, because the solder paste is between the two squeegees. The angle of each stroke can be determined individually. About 40mm squeegee is exposed, and the solder paste only moves upwards 15-20mm, so this form is cleaner.
In fact, there are many types of scrapers. Later generations have done a lot of research on scrapers and made various improved scrapers, such as anti-overflow scrapers and energy-saving scrapers.
2. The role of the scraper:
During printing, the squeegee pushes the solder paste to roll in front to make it flow into the template hole, and then scrapes off the excess solder paste, leaving solder paste as thick as the template on the PCB pad.