-- [ From: Doug Jeffery * EMC.Ver #2.5.1 ] --


Well, Nss?  There are a lot of things to address.. But First a couple of
questions?

1.  Are you using Vacuum Lamination?

2.  Are the "Measles" surface or internal to the laminate?

3.  Why did you drop the heat rise so Low?

4. Do you have the problem in all layups or is it specific to a
particular construction?

5. Is it present on all panels or only on a percentage? What Percentage?
Top of a book or middle of a book?

6. Where do the measles occur?  On the edges of the panel?  In the
center or all over?

7. How long is the "squeeze" outside the panel?

I would think that to over come a measling problem I would first
normalize the heat rise, too fast or too slow can cause problems. 
Assure that the air is properly evacuated at lamination, if you are not
using vacuum assist then assure that prepreg is at room temperature in a
dry environment prior to lamination.  Check the platens for flatness to
assure even pressure,  Pressure lows and highs can trap air or prevent
good flow and cause some problems.  Lastly (most costly) up the resin
content in the package, more resin with good flow should move you away
from measles....However doing this may or maynot solve the problem.
Without knowing what the problem is we could guess a lot so lets try to
find out what it is.   




..
-------- REPLY, Original message follows --------

> Date: Sunday, 22-Sep-96 07:45 AM
> 
> From: Nss                      \ Internet:    ([log in to unmask]
in)
> To:   IPC Technet              \ Internet:    ([log in to unmask])
> 
> Subject: Measling/ Frosty Edge Problem
> 
> What are the probable causes and remedies for "measling" in ML PCB's ?
> 
> We have adopted pinless method of laminating PCB's. Under this method
the heat
> rise  is 6-8 deg F (The supplier recommends max heat rise of 12 deg F)
. The
> reduced heat rise, no doubt, reduced the problem of frosty edges but
measling
> is on the rise.
> 
> Cud some one out there help us over come the problem of measling &
frost edge?
> 
>
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-------- REPLY, End of original message --------


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