Can someone explain why a 3 layer board would warp? It seems that the structure would be balanced around the middle if it was 1) ground 2) signal 3) ground. I don't fully understand why an odd number of layers warps. Thanks, Matt Matthew Sanders PWB Procurement Engineer, Trimble Navigation Limited [log in to unmask] Phone: (408) 481-7817 Fax: (408) 481-8590 > -----Original Message----- > From: Charles Barker [SMTP:[log in to unmask]] > Sent: Saturday, July 04, 1998 9:04 AM > To: [log in to unmask] > Subject: Re: [TN] Warpage > > Dear L. Ramesh, > Warpage can be caused by many different things. One frequent cause that I > have run into is poor board design. It is important to keep the amount of > copper on each layer balanced about the middle of the board when viewed > from the edge. As an example, a four layer board with plane layer(s) > should > be: > > Layer one, signal > Layer two, plane layer (Power of Ground) > ========================================= Middle of Board > Layer three, plane layer (Ground or Power) > Layer four, signal > > If the circuitry NEEDS only ONE plane layer (three layer board), duplicate > that layer to provide the necessary balance (make it four layers). > There should always be an even number of layers in a multi-layer board. > > There can also be other issues such as the grain direction, size and > structure of the pre-preg material. One of the board fabricators on > TechNet > will have to explain those issues to you. Other causes could be how the > board is cooled after lamination. > > I hope this helps. > > Charlie B. > > > > Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please > respond > to "L. RAMESH" <[log in to unmask]> > > To: [log in to unmask] > cc: (bcc: Charles Barker/US/I-O INC) > Subject: [TN] Warpage > > > > > Dear Technetters, > I would like to know the possible causes for warpage and its control. All > suggestions is gratefully acknowledged. > Regards, > > L. RAMESH, Tel: +91-8221-26618, 26619, > Indal Electronics Ltd., 26375, 26584 Extn: 345 > No.12 A, Industrial Area, Fax: +91-8221-26641 > Nanjanagud 571 301, email: [log in to unmask] > District Mysore, INDIA. web site:www.indalpcb.com > > ################################################################ > 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's web site (http://www.ipc.org) "On-Line Services" > section for additional information. > For technical support contact Hugo Scaramuzza at [log in to unmask] or > 847-509-9700 ext.312 > ################################################################ ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################