George, The most common reason for warp and twist is tempter. If a board cools unevenly then the board might warp and twist. Best way to avoid this is to make sure that your layer stack up must be symmetrical apposed to asymmetrical. (S,S,P,S,S,P,S,S correct/ S,P,P,S,S,S,S wrong). If the edges of the board cool before the center has a chance too then it will warp, after lamination. If this is the problem then you should be able to heat the board up and cool it down slower and relive the problem. It can also be that there is an uneven amount of resin on the board. I hope this answers you question, Ted -----Original Message----- From: Nancy Trumbull [mailto:[log in to unmask]] Sent: Friday, March 16, 2001 5:42 AM To: [log in to unmask] Subject: Re: [TN] twist and wrap issue Sorry George, What it is you what to know. Your question is not clear. Nancy T. >>> [log in to unmask] 03/15/01 09:31PM >>> Hello, Everyone Does anyone kindly help me explain the reason for wrap and twist of rigid PCB? I'm appreciate your generous guidance and your any advice. George Chu Quality Dept. Phone: ++86 512 5651961 ext.6201 Fax: ++86 512 5613446 Email: [log in to unmask] ---------------------------------------------------------------------------- ----- 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------- ----- --------------------------------------------------------------------------------- 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 the following message: SET Technet NOMAIL 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 ---------------------------------------------------------------------------------