The source of your sulphur may be the elastomer (rubber) products in contact with or in close proximity to your exposed copper. Sulphur can be used in the elastomer cure process and can out-gass, especially if the cure is not complete. Some options to consider may include further curing the elastomer or switching to a non-sulphur based elastomer. ---------- From: John Loveluck <jol Subject: Copper Sulphide corrosion Date: Wednesday, May 21, 1997 6:06AM Hi We have seen failures on a bought-in assembly due to growth of copper sulphide on the copper traces of a flexible PCB. The failure occurs at the base of SnPb solder joints, where the copper traces are not covered by photoresist. The whole area of exposed copper and solder joints is covered by a silicone based potting material. Unfortunately our supplier is not being very helpful, so I am looking for clues as to what is happening and how to stop it myself. The source of sulphur is not known, but there are various rubber components within the immediate area. Does anyone have any experience of this type of corrosion system? If so, I would appreciate a discussion about the factors involved - in particular, the role of the potting compound and whether an alternative passivating material would do a better job. Thank you John Loveluck Group Quality Manager Tadpole Technology plc Cambridge Science Park Cambridge CB4 4RB Tel: (+44)1223.428200 Fax: (+44)1223.428201 email: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** Received: from kani.wwa.com (kani.wwa.com [198.49.174.58]) by aidsrv.advanced-input.com (8.6.9/8.6.9) with SMTP id GAA00134; Wed, 21 May 1997 06:06:53 -0700 Resent-Date: Wed, 21 May 1997 06:06:53 -0700 Received: from ipc.org/ipc.ipc.org [209.42.29.23] by kani.wwa.com with smtp (Smail3.2.WWA) id m0wUB6X-003rPnC; Wed, 21 May 1997 08:07:24 -0500 (CDT) Received: by ipc.org (Smail3.1.28.1 #2) id m0wUAwz-000BjYC; Wed, 21 May 97 07:57 CDT Resent-Sender: TechNet-request Old-Return-Path: <[log in to unmask]> Message-Id: <[log in to unmask]> X-Sender: [log in to unmask] X-Mailer: Windows Eudora Pro Version 2.2 (16) Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Date: Wed, 21 May 1997 14:07:16 -0700 To: [log in to unmask] From: John Loveluck <[log in to unmask]> Subject: Copper Sulphide corrosion Resent-Message-ID: <"F8_Fd1.0.nX6.I4lWp"@ipc> Resent-From: [log in to unmask] X-Mailing-List: <[log in to unmask]> archive/latest/12858 X-Loop: [log in to unmask] Precedence: list Resent-Sender: [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To subscribe/unsubscribe send a message <to: [log in to unmask]> * * with <subject: subscribe/unsubscribe> and no text in the body. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************