William,

        Chuck's advice is still pertinent for laminate manufacturing.  You
probably remember there are three factors that affect the epoxy flow:  Resin
Content, Resin Flow, and Gel Time.  (All TM-650 test methods)  Now, I thought
Allied Signal was the one that developed the viscosity type control system
which would replace the flow and time tests.  But, it's been over three years
since I was involved in any of that, so my memory may not be so good.  Other
factors deal with the press operation as Chuck pointed out.

        The other thing you can do, if you don't want to mess the with the
epoxy properties too much, is to use 7629 instead of 7628.  The 7629 is a
little thicker, but for all purposes meets the spec for the 7628 cloth.  I
think there are some other cloths out there that would also work, somewhere in
the 1500 series.  The vendors for this will know for sure.

        Anyway, good luck.  The intermittent problems are the hardest to
solve.

Glenn

"Wang, William (Suzhou Laminate)" <[log in to unmask]> 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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