Although I've not made any type of scientific study on cleaning of reflectors, I've been using Isopropyl Alcohol for years with no obvious problems. This is a case where an ounce of prevention is worth a pound of cure. Try to keep the inside of the printer as clean as possible. Don't introduce any unfiltered air. Obviously, the less you clean reflectors the better. Gently wiping with a soft cloth dampened with alcohol should suffice. With non-collimated exposure units (flood type reflectors) you would have to really scratch or dent the reflector to cause any noticeable problems. A collimated reflector is much more susceptible to damage, and even a small scratch can be reproduced on the panel. You might try vacuuming the reflectors with a cleanroom type vacuum using a soft bristle attachment. Check with your equipment supplier; they may have some specific recommendations Mark Dowding Multek, Inc Irvine CA [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: FAB: CLEANING EXPOSURE UNIT REFLECTORS Author: [log in to unmask] at INTERNET_GATEWAY Date: 4/26/96 9:06 AM Has anyone made a study on how to clean the UV exposure unit's reflectors in particular on non-collimated + soldermask exposure machines ? What to do / not do, frequency of cleaning, pros and cons.. - From what we can see, some people are using alcohol iso to clean, but is it a good solution ? Won't it remove natural protection and enhance oxydation ? - Isn't it more suitable to polish, if so with which product ? We are very concerned because exposure time for Probimer 52 is rather long (over 120 seconds) on two BASF 60/75 (Probimer 330) and PEPR 2400 (ED Resist) on a PC-130 and a BASF 60/75 using Gallium lamps. Thank you in advance Regards, Roland Roland Jaquet Technical Director Henri Jaquet SA PCB manufacturer Geneva Switzerland Prototypes and small qties tel. xx41-22-794-7878 fx. xx41-22-794-3052 [log in to unmask]