I disagree with the statements regarding reproduction of scratches or debris on reflectors of collimated exposure units. It may be true that in some applications small scratches will not reproduce; but I have seen it happen in our fine line work (<5/5). I could certainly reproduce something as large a quarter with no problem. Different equipment/applications have different requirements. We use an Optibeam 7120, maintained at 10 % or less uniformity across the printing area. Using a high resolution resist, I have seen a crack (O.K., it was a big crack) in the collector cause a fuzzy area on the panel. Perhaps it would be safer to say that in some cases, scratches or debris can be reproduced. I agree with the cleaning methods described. Again, we try not to clean mirrors or reflectors unless absolutely necessary. On collimated units in particular, the risk of damage is significant when cleaning. On a well maintained unit, collectors should not require cleaning except at bulb changes; mirrors every week or two. Each shop needs to evaluate the requirements and risks for their particular application. Mark Dowding Multek, Inc. Irvine, CA ______________________________ Reply Separator _________________________________ Subject: Re: FAB: CLEANING EXPOSURE UNIT REFLECTORS Author: [log in to unmask] at INTERNET_GATEWAY Date: 4/27/96 5:27 AM Paul's right about not reproducing. I have tied a quarter to a string and lowered it to lay flat on the the center of the lower collimating mirror in an Optibeam 7550. Then I printed a 5/5 board as usual. After develop there was no evidence of the shadow from the coin. Spots on the mirror do not reproduce. Dirty mirrors just reduce the overall intensity. I have found that in collimated systems the closer to the lamp a reflector is the more critical is it's cleanliness. Just a slight haze on your collector will cut the output as much as 20%. It also tends to cause the lamp output to degrade faster. My theory on that is the contaminant does not allow heat to be feflected away from the lamp as well and causes higher lamp temps. --------------------------------------------- While cruising the Internet, be sure to visit our home page at http://www.automata.com --------------------------------------------- On 27 Apr 1996, Paul Waldner wrote: > The optics of non-collimated exposure machines are much less sensitive than the > optics of collimated machines, though it is not true that scratches on the > optics of collimated machines will reproduce on the panel. Damage on reflectors > in general (on both collimated and non-collimated systems) normally result in > loss of energy at the exposure plane. Our technicians are taught to clean > optics in a three-stage method. First try blowing the optics clean with > nitrogen gas under some pressure. If the contamination remains, then try a > rinse comprised of 50% isopropyl alcohol and 50% de-ionized water. If the > reflector requires still more cleaning then soak a lint free, soft cloth with > the above mixture and wipe the optics with a very gentle pressure, making sure > that the cloth/reflector contact is well "lubricated" with the liquid mixture. > Any further attempts to clean will probably damage the coating on the optics and > defeat the purpose of the cleaning. > > Paul Waldner > Multiline International Europa > [log in to unmask] > >