This is a process of polishing of the micro-irregularities in the apertures that leads to a better paste release and improved printing quality.
In more than 90% of the applications a laser-cut stencil with just a mechanical polishing for deburring of the apertures is more than enough. But as the components get smaller and smaller at some point the apertures become so small that the paste won’t transfer through the stencil anymore. The paste just gets “stuck” in the aperture. In that case you either lower the stencil thickness to improve the printing (if applicable) or make the apertures smoother so that it’s easier for the paste to release, i.e. the stencil undergoes a process of Electrochemical polishing.
The improvement of the quality of the printing is achieved by reducing the capillary forces that the apertures exert on the paste. These capillary forces are the main reason why on the same stencil some apertures print well and others don’t.
The need for electrochemical polishing is determined individually depending on the thickness of the stencil, design and the size of the apertures.
As a guideline, we recommend it for stencils with apertures for 01005 components, round apertures with dimensions below 0.25 mm or stencils with a thickness of more than 130 microns that will be used for fine-pitch components.
This is a special water- and flux-repellent coating that adheres to the surface of the stencil and to the aperture’ walls, forming a micro-film. This micro-film assists the release of the paste from the aperture itself, which, on one hand, reduces the need for frequent cleaning of the stencil, and on the other – makes the print cleaner and prevents soldering defects.
Benefits of Nanocoating:
- improves print quality;
- improves the paste transfer from apertures with a size below 0.5mm;
- reduces print deviations;
- lowers the risk of getting shorts, respectively, the need to repair the circuit board;
- lowers the expenses on cleaning consumables and lengthens the cleaning interval of the stencil.
To ensure the best longevity of the coating (100,000+ print cycles) we recommend:
- to use a solvent cleaning process instead of dry cleaning;
- clean with non-abrasive tissue/paper;
- use cleaning agents with a neutral pH (not greater than 10);
- reduce the frequency of cleaning.