Looking for Al joining ideas

From: 	Chip Atkinson[SMTP:chip-at-XiG-dot-com]
Reply To: 	Chip Atkinson
Sent: 	Tuesday, December 09, 1997 3:33 AM
To: 	tesla-at-pupman-dot-com
Subject: 	Looking for Al joining ideas


I've been trying to figure out the best way to make a conductive path
between the plates of a rolled capacitor and the terminals.  I figure
straps of aluminum flashing will work well because they are thin, have
good surface area, and should conduct fairly well. 

I was also thinking of providing multiple connections so that the
capacitor would more closely emulate an edge connection like they have on
commercial capacitors.  

I have been pondering the best way to connect the strips to the plates,
and have the following ideas, but they all have various drawbacks.  

Here is what I have tried:

1) Aluminum solder 
   Pros: Joins fairly well.
         Relatively flat
   Cons: Anneals the aluminum
         Melts at a temp. close to that of Al.
         My technique isn't that great, and bumps are left that are 
            difficult to file down.

2) Nuts and bolts, 4-40 
   Pros: Doesn't anneal the aluminum
         Neat (tidy)
   Cons: Bolt heads and Nuts form pointy protrusions that can scratch 
             and damage dielectric.

I have some other ideas too, but I'm wondering if anyone has any other
solutions/ideas, as well as comments on the above and below.

Other ideas:
--  Just slip the strips in and let the bundling of the capacitor hold
      them in place.
--  Hand made small rivets may be flatter
--  Sew the strips in place with strong carpet thread (wouldn't damage 
      dielectric, bumps would be non-conductive, not as intimate a contact
-- Some sort of spot soldering using flattened pieces of Al
      solder between the plate and strap, and either resistance or flame heating from
      the outside while maintaining pressure.

I plan on experimenting a bit, but I am open to suggestions.


Chip Atkinson; Xi Graphics 1801 Broadway, Denver CO 80202
(303)298-7478voice (303)298-1406fax (800)946-7433sales