TECHNET Archives

August 1999

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:
Eric Christison <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Thu, 26 Aug 1999 10:27:37 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (47 lines)
> Hello
> My first post and first question to the experts.
> I am new to the electronic game most of my experience has been in mechanical
> inspection and test.
> My question: is there a rule of thumb on material shrinkage on board
> material or a spec. Our boards are coming in with all the dimensions at
> nominal but after wave they have shrunk down to the low limit and sometimes
> below low limit. Most of our tolerances are +/- .003.
> This is giving us headaches with interference problems when we put other
> components on the boards.
> Is it normal for the boards to shrink. Our arrays are approx. 4" x 12" with
> 25 separate boards on each array.
> Thx's in advance
> Tom Oliver
> Eagle Comtronics
> [log in to unmask]


Tom,

Wait a few days and measure them again. The reflow process will dry the boards
out making them shrink. Once back in the real world they'll re absorb moisture
 from the atmosphere and expand.

If you want a quick test, measure a board, process it, measure it, put it in a
bucket of water overnight and measure it again.

Regards,



Eric Christison

##############################################################
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.
If you need assistance - contact Gayatri Sardeshpande at [log in to unmask] or
847-509-9700 ext.5365
##############################################################

ATOM RSS1 RSS2