The first thing that comes to mind is why don't you let your laminate supplier do this
for you?  I will assume you have a good reason for doing this your self.  How many high
are you pressing this package, when I worked at a lamination facility we did that kind
of thing 18 panels high in a 48" x 72" format with a large quality of wedge shape wood
blocks against the bolsters.

Another little trick is to replace some of your 7628 with unclad laminate in the
middle.  That way you only need two plies of the prepreg on each side of the unclad
against the copper foil.  This will reduce the slippage considerably.

Good Luck

Chuck Brummer

Wang, William (Suzhou Laminate) wrote:

>    Chuck:
>    I'm sorry that I didn't provide enough information. The slippage
> happens to 1.5 mm or 1.6 mm double sided laminate during the lamination
> process (copper foil, 8 ply 7628 prepreg, copper foil, not PCB
> multilayer lamination). It happens from time to time, sometimes zero
> percent though we change nothing in our process. We reduce the resin
> content of 7628 prepreg, the slippage percentage decrease but lead to
> under-thickness problem.
>
>    Thanks and best regards
>     William Wang
>  ----------
> From: Chuck Brummer
> To: [log in to unmask]
> Subject: Re: [TN] Copper Clad Laminate Slippage
> Date: Wednesday, September 01, 1999 10:52PM
>
> Let us count the ways, sorry just a little joke.  In my last bit of
> advice I suggested
> that the problem could be fixed by increasing the resin to glass ratio.
> But too much
> resin not enough glass can make your package slip.  When was the last
> time you checked
> your press for parallelism?  You might be pushing the package to one
> side or corner.
> If your gel time is off the prepreg can get very slippery.  How many
> layers?  Are your
> making a multilayer that has little "C" stage core and very much
> prepreg.  Do you need
> to block the load.  When we last used vacuum assisted lamination I made
> some aluminum
> frames to assure the load was centered and resisted slippage because we
> use some
> conformals that can cause slippage when the stack was higher.  When we
> do not use the
> vacuum assist we reduce the stack height.
>
> Dan Brandler, where are you?  You should probably have some insight for
> this guy.
>
> Chuck Brummer
> [log in to unmask]
>
> Wang, William (Suzhou Laminate) wrote:
>
> >     I'm a greenhand of copper clad laminate, can anyone tell me why
> > copper clad laminate could slip during press and how to prevent from
> > slippage? (We use vacuum assisted hydraulic press)
> >
> > Thanks and best regards
> > William Wang
> >
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