TECHNET Archives

January 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:
"Gagnon, Gerry" <[log in to unmask]>
Date:
Fri, 24 Jan 1997 09:51:23 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (105 lines)
Ian

I have an answer and a question.

The processes described by others, which utilize a glass filled epoxy
resin will work. However I'm not sure you may want to do this in-house.

For one design, I remember we sent an 0.080" thick solid piece of copper
(with clearance holes pre-drilled) to a laminator. The laminator filled
the holes with glass filled epoxy and then laminated pre-preg on both
sides. The epoxy used was the same resin system as the prepreg. The
result looked like an etched piece of copperclad produced to our specs.
We easily worked it into the stackup and it worked fine! 

My question is "at what copper (or metal) thickness does the ability of
pre-preg to fill clearance holes end"? Is it 4 ounce copper? In my case,
at .080" the answer was obvious. I'm sure the answer is complex (it
always is) but I'd be interested in what folks have to say anyway.

Regards

Gerry
======================================================
>----------
>From: 	[log in to unmask][SMTP:[log in to unmask]]
>Sent: 	Friday, January 24, 1997 3:29 AM
>To: 	[log in to unmask]
>Subject: 	FAB:
>
>
>We received this via fax at the IPC office and are forwarding to technet 
>for comment.  Can anyone help?
>
>Regards
>Dave Bergman, IPC
>
>Statement of Process Problem
>
>We are fabricating a 10 layer multilayer PWB with a 0.025" thick solid copper
>heatsink (12" x 18") in its center, with 5 layers on each side.  This PWB has
>been previously fabricated using a conventional multilayer layup methodology 
>with all layers assembled and then laminated in one package.  We experienced
>a
>low yield rate.  It was attributed to shorts caused by bubbles that formed 
>within the drilled holes of the heatsink.
>
>We are currently experimenting with changing the production process to 
>laminate the PWB in two stages - first completely fill the holes in the 
>heatsink with prepreg, inspect and Second - layup the layers as usual.  The 
>heatsink undergoes pattern hole drilling, sanding and black oxide surface 
>preparation treatment.  The heatsink is assembled in the following package in
>the Multilayer Lamination Room:  steel (12" x 18") lamination plate, aluminum
>sheet, 1 sheet tedlar release, 1 sheet each of 1080 prepreg, 2 sheets each of
>106 prepreg, heatsink, 2 sheets each of 106 prepreg, 1 sheet each of 1080 
>prepreg, 1 sheet tedlar release, 1 aluminum sheet, steel lamination plate.  
>The package undergoes lamination in a sealed vacuum "turkey" bag attached to 
>a vacuum bag pulling 30" hg, in a Wabash single opening lamination press for 
>30 minutes at 375 deg. F & 4500# total force.  Upon visual inspection, the 
>heatsink/pregreg package exhibited bubbles in every drilled hole.  It this
>the
>result of resin starvation in the holes? 
> 
>
>***************************************************************************
>* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
>***************************************************************************
>* To unsubscribe from this list at any time, send a message to:           *
>* [log in to unmask] with <subject: unsubscribe> and no text.        *
>***************************************************************************
>* If you are having a problem with the IPC TechNet forum please contact   *
>* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
>***************************************************************************
>
>Ian Wylie
>Technical Systems Manager
>Exacta Circuits Ltd
>Printed Circuit Manufacturers
>Selkirk
>Scotland  TD7 5EJ
>00 44 1750 21601 Ext 3219
>
>***************************************************************************
>* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
>***************************************************************************
>* To unsubscribe from this list at any time, send a message to:           *
>* [log in to unmask] with <subject: unsubscribe> and no text.        *
>***************************************************************************
>* If you are having a problem with the IPC TechNet forum please contact   *
>* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
>***************************************************************************
>
>

***************************************************************************
* TechNet mail list is provided as a service by IPC using SmartList v3.05 *
***************************************************************************
* To unsubscribe from this list at any time, send a message to:           *
* [log in to unmask] with <subject: unsubscribe> and no text.        *
***************************************************************************
* If you are having a problem with the IPC TechNet forum please contact   *
* Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask]      *
***************************************************************************



ATOM RSS1 RSS2