Ultrasonics clean so well that the colored emulsion used to coat the screen portion of the stencil can be eliminated. The primary purpose of the emulsion is to fill in the tiny holes of the screen’s mesh because if solder paste were to contaminate the screen, it would be very difficult to clean it out if using a spray-type stencil cleaner.
An ultrasonic stencil cleaner can clean the screen mesh just as well as the fine-pitch apertures. Many stencil manufacturers no longer apply the emulsion coating if it is known that the customer will be using a good ultrasonic stencil cleaner. Eliminating the need for screen-emulsion coatings, help reduce the cost of providing an SMT stencil.