Can it go back to normal after second re-flow? I sectioned the boards at the same location and the bundles look similar. Vladimir SENTEC Testing Laboratory Inc. 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca -----Original Message----- From: "Stadem, Richard D." <[log in to unmask]> Date: Thu, 29 Sep 2011 14:44:51 To: TechNet E-Mail Forum<[log in to unmask]>; Vladimir Igoshev. PhD<[log in to unmask]> Subject: RE: [TN] Board question It could be the ORIENTATION of the PWB with respect to the direction of the glass bundles. If the boards were cut from the blank with the long dimension oriented with the strand orientation at one vendor and the short dimension with the other, the warpage can occur at one and not at the other. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Vladimir Igoshev. PhD Sent: Thursday, September 29, 2011 11:50 AM To: [log in to unmask] Subject: [TN] Board question Hi TechNetters, I have a question for board gurus, as I'm almost lost. Here is a story. A panel of four simple 4 layers FR4 twists after going through the first side re-flow and flatten out after the second side is re-flowed. It does the same thing with and without the components placed. The panels are from new vendor and the old ones had never exhibited the problem. What confused me is that both boards (from both of the vendors) were built identically: dielectric layers and Cu layers are look identical thickness- wise. There are no signs of resin recession or delamination in cross-sections which could have pointed out at incomplete curing. Glass bundles look also identical. What else it could be? Any suggestions are deeply appreciated. -- Best regards, Vladimir Igoshev. PhD mailto:[log in to unmask] SENTEC Testing Laboratory Inc. 11 Canadian Road, Unit 7. Scarborough, ON M1R 5G1 Tel: (416) 899-1882 Fax: (905) 882-8812 www.sentec.ca ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- ______________________________________________________________________ This email has been scanned by the MessageLabs Email Security System. For more information please contact helpdesk at x2960 or [log in to unmask] ______________________________________________________________________ --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 16.0 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 For additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 -----------------------------------------------------