Hi, Moonman and All, especially Ian, Brad and Jeff, I'm trying to correlate the information each of you has shared with me, and I want to ask one or two more questions (first one aimed mostly at Ian, I think): Given the ductility information given by Earl and IPC 2221/6012, and Ian's gen on copper cracking under temp cycling, do you know if the T/C failure info was obtained using IPC 2221/6012 boards and the Cu plating thickness of 1 mil? If not, do you know what boards were used? BTW, our hole copper thickness is between 0.7 mils and 1 mil as a rule. Do you have an opinion one way or the other about retaining 'non-functional' pads on inner layers when considering copper ductility in holes? Do they help or hinder? I contributed to the recent TechNet thread on this issue and strongly favour retaining them, but my Technical Director is now seriously considering taking them out to use the space for trace routing, etc (functional stuff). He know my opinion and reasons, but other design considerations may make him over-rule my humble manufacturing experience. My profound thanks to you all again for coming to the rescue. Earl, what's a comumn? Peter Earl Moon <[log in to unmask] To: [log in to unmask], DUNCAN M.COM> Peter/Asst Prin Engr/ST Aero/ST Group@ST Domain cc: 03/06/02 Subject: Re: Pads, holes, traces and Class 3 08:29 PM field reliability Peter, It just doesn't seem too hard to me. 5:1 aspect ratio holes, especially the diameter vs board thickness you describe is completely acceptable. Actually, it is in the preferred comumn. You know we've talked about this before realizing cu plating thickness and ductility requirements must be met as .001" thickness, and all the rest entailed in 6012, and ductility well exceeding 10%. Nothing will make the hole walls come apart using this criteria to the extent all else meets 6012's figure 3.5 and associated requirements in that section. Of course, laminate integrity is important as well and voiding requirements in the laminate evaluation area cannot exceed that which is specified. Don't want any voids propagating into cracks extending into the thermal evaluation zones/holes and causing cracks. Copper foil, for very high reliability boards, such as some Class III types, also should be very ductile. This means using rolled annealed copper instead of ED type. We need the plated hole interface to internal layers to be capable of withstanding thermal stress and shock as well. Also, as indicated in section 3, clear requirements must be met for hole plating to surface conductors. Actually, instead of more discussion on my part, IPC 2221, etc., and 6012 cover all the ground, and much more, you are concerned about. There's little else to say. Very best wishes on your endeavor and its success, Earl [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 ---------------------------------------------------------------------------------