Daan, As a supplement to my previous mail, I should say that our boards have an alchromated (alodined) aluminiuim strip between board and chassis on one side and wedgelocks (card retainers) on the other side. Each pair of interfacing surfaces is filled with a thin thermal tape to take up the irregularities between the surfaces, so that the different metals are not actually in contact with each other, but are connected thermally as well as possible. Peter Brian Ellis <[log in to unmask]> 18/03/2003 08:54 PM Sent by: TechNet <[log in to unmask]> Please respond to "TechNet E-Mail Forum."; Please respond to Brian Ellis To: [log in to unmask] cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group) Subject: Re: [TN] Heat transfer from ENIG board to aluminium casing Daan I would have thought exactly the opposite! An uneven HASL surface will have fewer contact points to the aluminium than a flat ENIG surface. That having been said, I would have thought that both would be bad, electrochemically speaking, if subjected to humidity. From very poor memory, the Al-Au couple is somewhere about 4 V, roughly double that of Al-Sn/Pb. Brian d. terstegge wrote: > Hi Technet, > > We are in the process of converting some of our boarddesigns from HASL > to ENIG conductor finishing. Now one of our designers is worried about > the effect that this change may have on heat transfer from the plated > board-edges to the aluminium casing on which the board is mounted. He > feels that the heattransfer from leadtin to aluminium is better that for > nickel/gold to aluminium, possibly resulting in heat problems in the end > product. > > Any ideas on this ? > > Daan Terstegge > Thales Communications > Unclassified mail > Personal Website: http://www.smtinfo.net > > --------------------------------------------------- > Technet Mail List provided as a free 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/html/forum.htm for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > ----------------------------------------------------- > > > --------------------------------------------------- Technet Mail List provided as a free 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/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 1.8e 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/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------