A lapping film must have the highest lot-to-lot consistency. When you establish your process there are many factors to control and the film might rank at the top. Others include, but aren’t limited to the quality of your polishing machine, its fixturing and rubber pads, and the connectors you are using. If your supplier switches ferrules or changes springs, your polished results may change.
So when you are developing your processes you need to be sure all these items are controlled, and most importantly, you need lapping film that will act the same every time. Without that inconsistency will rule.
Here is how the lapping film is typically used. After the epoxy is cured and the fiber is scribed it must be denubbed. This step usually requires a rough grit silicon carbide film, something between 16 um and 5 um, depending on the bead size. This allows for a consistent start point for epoxy removal. As a more aggressive material, Silicon Carbide is often recommended over Aluminum Oxide for epoxy and glass removal. We’d like to stop the epoxy removal step at the moment all epoxy is removed from all connectors, but because the epoxy bead differs, the connector protruding from the fixture might vary slightly, the springs might be a bit different, or the polish, more likely than not, will start to cut into the ferrule, the ferrule will need to be reformed. The silicon carbide usually somewhat alters the ferrule. Connector supplies with any quality supply their UPC or pre-angled APC connector ferrules within the Telcordia spec for Radius of Curvature and Apex Offset. Depending on the size of the ferrule and the amount of damage or reforming that needs to been done, this step is usually one or two steps with diamond lapping film. Diamond lapping films cut and polish the hard ceramic ferrules and the softer fibers close to the same rate, easily controlling fiber undercut or protrusion. If the ferrules aren’t pre-radius or pre-angled additional steps might be required. The final step is almost always a specialized final film that both buffers out the minuet defects and allows for the correct fiber height.
So in short, Silicon Carbide is typically used for epoxy removal, Diamond is used to recover or form the Radius of Curvature and Apex Offset, and the final film gives the end-face its shine and affects the fiber height. The lot-to-lot consistency of these films must be spot on to give consistent results.
Abrasive lapping films are coated with precision graded abrasives on a polyester film. The raw materials used to make up the abrasives and the adhesives used to secure them onto the backing need to be controlled. The coating process should be carried out in a cleanroom. Quality assurances must be in place to check the cut rates of each lot. Only then can you hope to have consistent film and thus consistent polishing processes. Make sure your film supplier at least has these safeguards in place before you commit to them.
Abrasive minerals are available in Alumina Oxide, Silicon Carbide, or Diamond. Lapping films are available of plain or PSA (Pressure Sensitive Adhesive) back. Lapping films are available in various sizes, disk, sheets rolls etc.
- Diamond Lapping Film. Available in grades from 0.2um – 30um
- Aluminum Oxide Lapping Film. Available in grades 0.5um -30um.
- Silicon Carbide Lapping Film. Available in grades 0.5um -30um
