Hi, Ken, I believe ENIG (or any other plating) can be applied either before or after soldermask, but normally it's applied before to save on plating solution costs among other things. Yes, the immersion gold process is aggressive, so be sure your fab house is using an ENIG-compatible mask. This often involves using an alternative hardener in the mask mix, and it's better if your pads are not solder mask defined, as the plating tends to get underneath the edges. Masking from one side only, the holes can be cleaned, but it depends to a large extent on the diameter of the holes and the capability of your fab house. 10 mils and above, I believe, are OK, but smaller than that, the cleaning process may have trouble penetrating properly and cleaning out the bottom of the holes. I suggest you leave the holes open at both ends unless you absolutely have to mask one end. Peter Ken Patel <[log in to unmask] To: [log in to unmask] OM> cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Sent by: Aero/ST Group) TechNet Subject: [TN] Fab Process question related to <[log in to unmask] ENIG ORG> 03/08/02 01:40 AM Please respond to "TechNet E-Mail Forum."; Please respond to Ken Patel At what stage the electroless nickel and immersion gold process is applied, is it after the solder mask application or before? I believe normally it is after the solder mask application but I want to verify it. I have heard that chemistry involved is very nasty if left on the board. If I plug or mask via holes from one side, I want to make sure that there is no residue left of that nasty chemistry. Can it be cleaned if mask from one end? Any comments? re, Ken Patel --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 --------------------------------------------------------------------------------- [This e-mail is confidential and may also be privileged. If you are not the intended recipient, please delete it and notify us immediately; you should not copy or use it for any purpose, nor disclose its contents to any other person. Thank you.] --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d 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 delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------