George, I did resolve my polishing artifact issue. It was all in the water /IPA rinse. Do you know of a chemical etchant for LF solder? Thanks for you input. Victor, -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Wenger, George M. Sent: Monday, April 25, 2005 4:04 PM To: [log in to unmask] Subject: Re: [TN] Lead Free, Ball Grid Array, solder bump cross section Victor, We use MasterPrep all the time and don't see the problem you are referring to. As Wade indicated if there is separation between your sample and mounting material, or for that matter if you have lots of voids in the solder joints you will trap water and polishing compound in the separation or voids that well come out slowing and mess you nicely polished surface up. Regards, George George M. Wenger Reliability / FMA Engineer Base Station and Subsystems Group Andrew Corporation, 40 Technology Drive, Warren, NJ 07059 (908) 546-4531 [log in to unmask] -----Original Message----- From: TechNet [mailto:[log in to unmask]]On Behalf Of McFaddin, Wade Sent: Monday, April 25, 2005 4:51 PM To: [log in to unmask] Subject: Re: [TN] Lead Free, Ball Grid Array, solder bump cross section Hi Victor, We use a colloidal silica solution (0.05 micron) for our final polish. We polish for about one and a half minutes, with the final half minute running water on the cloth (Buehler's micro-cloth) and cross-section. This cleans the cloth and the cross-section mount of the colloidal solution. We then rinse just the cross-section mount again with water and then quickly rinse with alcohol (IPA) and blow dry with nitrogen and wipe lightly with a cotton ball. This usually gives us a clean, stain free surface. However, if you have pull-away (separation) of your mounting epoxy to the sample surface, it can be very difficult to get all the water and polishing solution out of the separation area. Hope this helps. Wade McFaddin Nextek Inc. -----Original Message----- From: Victor G. Hernandez [mailto:[log in to unmask]] Sent: Monday, April 25, 2005 1:48 PM To: [log in to unmask] Subject: [TN] Lead Free, Ball Grid Array, solder bump cross section Fellow TechNetters: I have conducted many of LF solder bump cross section and final polish is conducted with a Buehler Masterprep Polishing Suspension Alumina 0.05 microns. Micro craves, epoxy shrinkage/voids, on the sample surface retain the polishing compound which contaminate the surface appearance. This step can cause staining and/or water marks on the bulb solder prior to mid range magnification examination with inverted stage microscope. Can some one recommend a LF chemical etchant that I can replace the alumina step in my process? 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