Only up to about 35 or 40 requests so far but it is not a problem. So there is your opportunity, if you've been thinking of asking me for the article but did not want to be a bother let those e-mails loose now before I change my mind. :-) Brian >Brian ... thanks for the article !! Reading the number of requests you've >gotten reminds me of the time I offered to share a conformal coating >evaluation study with someone on Technet ... I ended up with about 50 >requests for the report! Sheila > > >At 12:27 PM 2/17/98 -0800, you wrote: >>Mark, >> >>This is exactly what the article I have been referring to discusses. Did you >>need a copy as well? If you did I need your fax number. >> >>Technetters, >> >>I am receiving a lot of requests for the PCB Warpage article so it is taking >>some time to get to all of you. Please help me to ensure that I do not miss >>anyone. If you do not receive the article within 2 days of your request >>please remind me by e-mail. Thank you for your patience. >> >>Sincerely, >> >>Brian Stumm >>ETS >> >> >> >> >>>Another possible cause for this type of defect can be attributed to your PCB >>>suppliers method of curing the Soldermask. If PCB's are cured vertically >>>then it is extremely important that the support during the thermal cure does >>>not allow the boards to sag. As the TG temperature of FR4 laminate (135 >>>degC) in PCB construction is usually below that of the soldermask >>>cure.(Normally 150 deg C) >>> >>>This would then allow the prepreg to assume the shape of the sag and once >>>cooled will retain this bow. We have overcome this issue and if you need >>>further details please contact me. >>> >>>I hope this is of some help. >>> >>>Mark Gillan >>> >>>Process Engineer >>>Prestwick Circuits >>>Scotland >>> >>> >>> ---------- >>>From: ririzarr >>>To: TechNet >>>Subject: Re: [TN] PCB warpage >>>Date: 17 February 1998 10:04 >>> >>>This is due to thermal stresses in the PCB sometimes when they pass the >>>oven they become more "soft" and they warp. Why don't you try some >>>stiffeners to make the PCB strong enough to withstand the higher >>>temperatures? >>>Regards, >>>Rub?n E. Irizarry-Guzm?n >>>Operations Engineer >>> >>> >>> >>> >>>[log in to unmask] on 02/16/98 04:52:39 PM >>> >>>Please respond to [log in to unmask]; Please respond to [log in to unmask] >>> >>>To: [log in to unmask] >>>cc: (bcc: Ruben Irizarry) >>>Subject: [TN] PCB warpage >>> >>> >>> >>> >>>What causes PCBs to warp? How can we prevent this from happening? >>>(Thanks to all responses in advance!) >>> >>>################################################################ >>>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >>>################################################################ >>>To subscribe/unsubscribe, send a message to [log in to unmask] with following >>> text in the body: >>>To subscribe: SUBSCRIBE TechNet <your full name> >>>To unsubscribe: SIGNOFF TechNet >>>################################################################ >>>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional >>>information. For the technical support contact Dmitriy Sklyar at >>>[log in to unmask] or 847-509-9700 ext.311 >>>################################################################ >>> >>>################################################################ >>>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >>>################################################################ >>>To subscribe/unsubscribe, send a message to [log in to unmask] with following >>>text in the body: >>>To subscribe: SUBSCRIBE TechNet <your full name> >>>To unsubscribe: SIGNOFF TechNet >>>################################################################ >>>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional >>>information. >>>For the technical support contact Dmitriy Sklyar at [log in to unmask] or >>>847-509-9700 ext.311 >>>################################################################ >>> >>>################################################################ >>>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >>>################################################################ >>>To subscribe/unsubscribe, send a message to [log in to unmask] with following >>text in the body: >>>To subscribe: SUBSCRIBE TechNet <your full name> >>>To unsubscribe: SIGNOFF TechNet >>>################################################################ >>>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional >>information. >>>For the technical support contact Dmitriy Sklyar at [log in to unmask] or >>847-509-9700 ext.311 >>>################################################################ >>> >>> >>> >> >>################################################################ >>TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c >>################################################################ >>To subscribe/unsubscribe, send a message to [log in to unmask] with following >text in the body: >>To subscribe: SUBSCRIBE TechNet <your full name> >>To unsubscribe: SIGNOFF TechNet >>################################################################ >>Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional >information. >>For the technical support contact Dmitriy Sklyar at [log in to unmask] or >847-509-9700 ext.311 >>################################################################ >> >> > > > ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################