TECHNET Archives

September 1997

TechNet@IPC.ORG

Options: Use Monospaced Font
Show Text Part by Default
Show All Mail Headers

Message: [<< First] [< Prev] [Next >] [Last >>]
Topic: [<< First] [< Prev] [Next >] [Last >>]
Author: [<< First] [< Prev] [Next >] [Last >>]

Print Reply
Subject:
From:
Reply To:
TechNet Mail Forum.
Date:
Wed, 24 Sep 1997 09:27:00 -0700
Content-Type:
text/plain
Parts/Attachments:
text/plain (44 lines)
     Technetters:

     I have been having a "heated" debate with a co-worker on PCB warpage
     and I need some practical "real-world" feedback:

     The hypothetical scenario is as follows:

     A multilayer PCB is constructed with prepreg layers of DIFFERENT
     curing time/temperature characteristics.  The resultant stack is
     laminated in accordance with the requirements for the lesser material,
     thus leaving one or more prepreg layers partially cured.

     Questions:

     1) Will this board warp during reflow and/or wave soldering?  (Assume
     no components are mounted, so component weight is not a factor in the
     equation)

     2) If so, will it continue to warp with multiple thermal cycles (e.g.
     additional reflow cycles)?  What forces are at work to cause the
     warpage in the first place?

     3) If the answer for #2 is YES, is the additional warpage with
     successive thermal cycles predictable as a percentage of the original
     warpage?

     Thank you in advance for your assistance in "cooling" the argument.

     Bill Fabry
     Plantronics, Inc.
     [log in to unmask]

##############################################################
TechNet Mail List 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://www.ipc.org/html/forum.htm) for additional information.
For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311
##############################################################


ATOM RSS1 RSS2