I am not sure what you mean by Post T/C? -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez Sent: Tuesday, July 14, 2009 9:31 AM To: [log in to unmask] Subject: [TN] Maximum Allowable Bow & Twist for Post T/C Reliability Richard, I did not receive any comments on my Post T/C Reliability inquiry so I will post again. What about Bow & Twist on Post reliability testing, T/C? Does the 1.5% still applied for SMT/PTH assemblies? The assembly is a rectangle, 10.5 x 8 inch, form factor. Victor, -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Stadem, Richard D. Sent: Monday, July 13, 2009 10:07 AM To: [log in to unmask] Subject: Re: [TN] Maximum Allowable Bow & Twist for PWB-PCB Bev, I totally agree with you, but the point they are getting at in IPC 2221 is that no section of the PWB should have more than .75% per inch as a rate of warpage, extending in both the X and Y directions, after reflow. This is because if you have more warpage than that you are putting a stress on the resultant solder joints that leads to a reduction in reliability, especially with a lead-free joint and also especially if you need to straighten the CCA when mounting it into a chassis or frame. I think this specification, like so many others that were based on leaded solder, should be revisited for unleaded solders. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian Sent: Friday, July 10, 2009 3:24 PM To: [log in to unmask] Subject: Re: [TN] Maximum Allowable Bow & Twist for PWB-PCB I contend this is old school and if you aren't measuring warpage at reflow temperatures how do you know you aren't suffering from head on pillow? I suggest the term head in pillow be dropped because you don't actually put your head IN a pillow. Bev RIM PS Waiting for my Dewism. -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Genny Gibbard Sent: Friday, July 10, 2009 4:20 PM To: [log in to unmask] Subject: Re: [TN] Maximum Allowable Bow & Twist for PWB-PCB IPC-2221 5.2.4 ... Unless otherwise specified by master drawing, max bow and twist shall be 0.75% for boards that use surface mount components and 1.5% for all other board technologies. ... Values are measured as per IPC-TM-650 Method 2.4.22 Genny Gibbard, P. Eng Manufacturing Engineer, Vecima PTS dept. x.4229 -----Original Message----- From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez Sent: July 10, 2009 2:15 PM To: [log in to unmask] Subject: [TN] Maximum Allowable Bow & Twist for PWB-PCB What is the maximum allowable Bow & Twist value? Not able to locate in IPC-2221, 2222, & 6012A Victor, --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a service by IPC using LISTSERV 15.0 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 Please visit IPC web site http://www.ipc.org/contentpage.asp?Pageid=4.3.16 for additional information, or contact Keach Sasamori at [log in to unmask] or 847-615-7100 ext.2815 ----------------------------------------------------- --------------------------------------------------------------------- This transmission (including any attachments) may contain confidential information, privileged material (including material protected by the solicitor-client or other applicable privileges), or constitute non-public information. 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