Hi Mike,

I think you will find misregistration kills this lay-up method for higher
layer count panels.  It comes down to basic physics - material expansion,
prepreg flow, thermal variations in the lam stack that some thing has to
maintain registration during the lamination process.  I've heard of a shop
in Az (Phoenix or Chandler) that uses rivet lay-up for 10 layers or less and
the more reliable 4-pin lay-up for higher layer counts (12+ layers).  (Can't
remember the name off the top of my head.)  What you're describing is a step
up from mass lamination.  What registration are you trying to maintain?  Why
not switch to the standard 4 pin lay-up?  What kind of press cycle/lam book
do you run?

Hans

Integrity First  -  Service Before Self  -  Excellence in All We Do
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Hans M. Hinners
Electronics Engineer
Warner Robins - Air Logistics Center (WR-ALC/LUGE)
226 Cochran Street
Robins AFB GA 31098-1622

mailto:[log in to unmask]

Com: (478) 926 - 5224
Fax:   (478) 926 - 4911
DSN Prefix: 468


-----Original Message-----
From: Mike Holst. [mailto:[log in to unmask]]
Sent: Wednesday, February 27, 2002 3:51 AM
To: [log in to unmask]
Subject: [TN] MLB - spotwelding


We constructed our own machine for spotwelding mlb lay-ups prior
to pressing. It works fine for 6 and 8 layers (standard FR4 thin
laminates and prepreg). However, for higher layer counts especially
12 layers we seem often to loose internal layer / layer registration.

Could anyone kindly suggest a set of operating parameters
(temperature / pressure / time etc) to give more reliable welds for
higher layer counts. Pressed thickness about 1.6mm. Panel sizes
are relatively small - 14" x 11" would be typical, with 3 welds on
each long side about 4" apart.

The welder heads have a round flat point 10mm diameter and
existing settings are as follows:
Air pressure on the 16mm dia. welder cylinders is 5.5 bar, head
temperatures are controlled at 280C and weld timer set at 90 sec.

Any other input on this subject will also be welcome.

Thanks,

Mike Holst


Mike Holst.
TraX Interconnect (Pty) Ltd
Tel:(++27 21)712 5011
Fax:(++27 21)712 5798
Cape Town
South Africa

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