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July 1997

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Fri, 25 Jul 97 17:23:14 MST
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     Jonathan,
     
     Rivets are used as an alternative method to pin-lam. Tooling holes and 
     rivet holes can be pre-punched in the raw laminate and used to 
     register at I/L print or punched after D/E/S. The innerlayers are 
     stacked on a fixture with pins and rivets inserted, by machine, to 
     secure the alignment of layers to each other. The panel is then 
     removed from the fixture, the remaining outside plies of b-stage and 
     foil added and built up in a lamination book using separators and caul 
     plates without holes/pins.
     After lamination, the panels must be tooled, using either x-ray or 
     optical (after exposing internal targets) alignment.
     
     I can't quantify the difference between pin-lam and riveting in terms 
     of dimensional consistency (shrinkage) or layer-to-layer. But, in 
     earlier testing we saw no overall difference in registration on a 
     particular 10 layer part when employing both methods side by side.
     
     Some of the benefits of riveting are :
     
     *  No epoxy resin on panels and plates.
     *  No expensive tooled caul and separator plates.
     *  Thinner plates - more panels / press opening.
     *  Less expensive material can be used for separators, i.e., aluminum, with 
         a CTE closer to Cu than s.steel.
     *  Tooling can compensate for misalignments.
     
     Some of the drawbacks :
     
     * Additional process step, floor space.
     * Additional equipment required for post-lam tooling.
     * Possibly more operator dependent in terms of layer-to-layer alignment.
     * Maintaining panel to panel alignment within a book.
     
     
     As far as the type of that rivets can be used for... we have been quite 
     successful with fine line , thin core, tight tolerance up to 28 layers.

______________________________ Reply Separator _________________________________
Subject: Fab: Rivets in the lamination press
Author:  [log in to unmask] at INTERNET
Date:    07/25/97 9:54 


    I've seen occasional submissions asking about rivets for holding
multilayer boards together in the lamination press.  Would someone fill
me in on what's involved there?

   What is the purpose of the rivets?  To constrain movement in the press?
Can anyone quantify the benefit?  What kind of tolerances are achieved?
Are they aimed at improving layer to layer alignment within a panel, or
affecting whole panel movement?  Sideways shifting (translation/rotation)
or inch per inch movement (shrinkage)?

   Are they used in addition to pins?  Are they ever removed?  What forms
the composite locating system (for drilling, etc.) if not molded slots?
How and when are the holes for the rivets put in the cores?

   Are rivets only useful in a certain pressure range?  My impression was that
cores will do what they want to do in the press and just deform against
anything you try to put in their way to restrain them.  Do you need to keep
the pressure low to prevent this?

   What kind of products are rivets used on?  Fine line, thin core, tight
tolerance stuff or coarse, thick core, easy stuff?

   Thanks,

 Jonathan Whitcomb

 IBM Microelectronics

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