I feel you pain. Just went through a similar execise in Jan. Had 16 and 20 soic-8 op-amps and a high power voltage reg. Had to remove the parts remove soldermask and the manually apply paste to the pad and reflow. The op-amps use this as both a ground and heatsink. Really I think you are doing the best you can, unless somebody comes up with a laser for you. I assume the mask is the usual green so you will probably need a neon or ruby laser. Several years ago we used a conformal coat stripper which we found by accident would soften LPI, I just can't remember the name of it. -----Original Message----- From: Stephen Gregory [mailto:[log in to unmask]] Sent: Wednesday, 30 March 2005 11:25 AM To: [log in to unmask] Subject: [TN] Selective LPI soldermask removal... Happy "Hump-day"! I might have asked the list about this over a year ago, I can't remember. But I have this assembly that goes into a Radar system. There's a device on the assembly that has to be sitting over the metal of the top layer plane, with no solder mask on the board beneath the footprint of the device for it to work properly. Unfortunately, the solder mask file in the gerbers didn't reflect this. So at the time (over a year ago), I reworked the boards that we had to correct the problem...and let me tell you, it's a REAL PIA! Go to: http://www.stevzeva.homestead.com and look at "Mask Removal", and "After Tinning" to see what I'm trying to do. I did this over a year ago, and we got an order for these assemblies again...but the gerber never got corrected, and I get to do this again. WHOOPEE! I have to remove the solder mask beneath where the device is going to be installed, and then I solder coat the area to cover the exposed copper. I'm removing the solder mask very, very carefully with a Dremel and a very fine abrasive tip, and I'm using an exacto knife with various blades. This is all being done tediously under a microscope to prevent the copper from being removed from the plane. We have a micro-blaster here to remove conformal coating, but it can't get down to the bare copper. That's why I'm using the Dremel and exacto knife. This time when the board house did their micro-etch or pumice scrub just prior to applying the solder mask, they really did a good job! That mask is on there, and meant to stay put! I'm really having a hell of a time doing this on these latest fabs. Is there any other way to remove this coating in the area that I need to? I'm thinking maybe a laser. Does anybody know where I would go to get this done, and about what it would cost? There's only 5-boards that I need this done to, but it takes me a couple of hours with each board to complete the job. Kind regards, -Steve Gregory- Senior Process Engineer LaBarge Incorporated Tulsa, Oklahoma (918) 459-2285 (918) 459-2350 FAX __________________________________________________________________ This message may contain information that is privileged and confidential to LaBarge, Inc. It is for use only by the individual or entity named above. If you are not the intended recipient, you may not copy, use or deliver this message to anyone. In such event, you should destroy the message and kindly notify the sender by reply e-mail. --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------