Ladder stencil is made of two or more thicknesses on the same screen. In order to cope with all large and small electronic parts appearing on the same circuit board at the same time, but also to obtain good soldering quality. We usually need to print different solder paste thicknesses on the same stencil so that the amount of tin can be accurately controlled, so there is a step steel stencil (ie STEP-UP partial thickening, STEP-DOWN partial thinning). Was born.

The stepped stencil can be increased in thickness by increasing the thickness of the stencil to increase the amount of solder paste printed, or reduced in thickness by reducing the thickness of the stencil to reduce the amount of solder paste printed. Partially thickened steel mesh can overcome the problem that some parts are not flat enough, while partially thinned steel mesh can effectively control the short circuit of the FINE PICTH part foot.

So is it better to make the stepped stencil on the upper surface or on the small surface? The stepped opening on the upper surface is easy to scrape in the direction of the scraper. Opening on the lower surface easily makes the PCB and the steel mesh not in close contact. If there are no components or denser components around the step position, both UP and DOWN can be used.