Greg, typically the laser does not scribe directly into the plastic of the package body because it does not create enough contrast. The surface of the package is usually coated with a thin film and it is this material that is scribed by the laser. Unfortunately, I do not know the chemical composition of these coating materials, but I suspect that this is what you are having trouble adhering to. Regards, Marshall On Jun 06, 1996 13:22:40, '"Greg Bartlett" <[log in to unmask]>' wrote: >RE>ASSY: Laser Ash? 6/6/96 > >Funny that you should mention this, Norm. I believe that we're seeing a = >related problem. While we're not seeing a white residue, we are seeing a = >problem with laser etched devices. We use thermally-screened devices on = >certain products. Our screening house uses a yellow epoxy dot on the = corner >of the device to signify successful screening, but these dots have = been >falling off of the laser etched parts. We suspect that the laser is = >modifying the surface of the devices somehow (redeposition of carbon, perha= >ps?) to cause this. > >Any thoughts on how to either clean the device surface or come up with an = >alternative, inexpensive way to mark these devices? > >Greg Bartlett >Mercury Computer Systems >Chelmsford, MA >[log in to unmask] > >-------------------------------------- >From: Dill, Norm J > >After cleaning (soap & water) soldered assemblies, has anyone had a white >residue problem that was traced back to the laser etched characters = on >plastic DIP's? >We currently have a white residue problem under investigation where = the >initial evidence indicates the source to be a certain brand of DIP IC. = The >top of the DIP has laser etched character markings that appear to leach a >chemical component(s) that combines with the rinse (tap) water to form a white >residue after drying. The residue is easily removed with a cotton swab and >alcohol. >At this point the complaint is only visual and easily corrected by hand >cleaning but the concerns are what is actually being deposited on the = > >board surface and is it being completely removed. >Any inputs on this will be greatly appreciated. > >Norm Dill >Harris RF Communications >[log in to unmask] >