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#1417
Author: Charles A. Bishop, C.A. Bishop Consulting Ltd.
Email:
Subject: There are a couple types of de-metallization.
There are a couple different types of de-metallization. One is total de-metallization where all the aluminum is removed to recover the film for reuse. Here the aluminum is dissolved off using immersion into a bath of sodium hydroxide or potassium hydroxide followed by a water wash and dry.
Another type of de-metallization is where a patterned coating is required. Here there are many options and the processing can be at any of three stages. A pattern can be printed on before metallization using a water-soluble polymer that can be dissolved off in water post deposition. Alternatively post metallization, an inert polymer can be printed on top of the metallization that protects the metal in the areas where it is to be retained. The unprotected metal is dissolved off using one of the hydroxides.
The third method, which is starting to be used more widely, is to use a printing roll within the vacuum chamber to print a very thin oil onto the areas where no coating is required just before the deposition zone. The way this works is that the oil changes the surface energy so the aluminum will not stick to the surface. If the oil thickness is optimized, the aluminum and the radiant heat removes it by the end of the deposition zone yielding a dry polymer web. Originally used for simple straight lines needed for capacitor film, the process now can produce much more complex patterns with very fine lines. Valmet General and Aerre both have machines with this technology installed and can supply samples demonstrating the fine line widths and edge quality. This type of technology can be retrofit on many metallizers at a relatively modest cost, and this process is often more cost effective than having corrosive chemicals and the problems of safety and disposal to consider.
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