On Wed, 9 Jun 2004 15:28:17 +0100, "Dave Marsh"
wrote:

Hi,

I need to space off a PCB by 0.25" behind a small (4" x 1" x 0.06" thick)
anodized aluminum front panel for an electronics project. The PCB contains
the push buttons that protrude through holes in the front panel.

The PCB has M3 holes drilled for fastening purposes but I can't put holes in
the front panel for appearance sake. I need to fasten the PCB strongly
enough so there is no danger of it coming loose when the user presses one of
the buttons.

My idea so far is to glue 4 metal hex spacers to the back of the aluminum
panel. I can then bolt the PCB to that. Alternaitevely the same kind of idea
but glue the flat heads of 4 countersunk M3 screws to the panel instead (I'm
thinking the contact are of a screwhead will be greater than that of a hex
spacer with its central thread hole).

The hex spacers are made of nickel-plated brass. The screws could be zinc
plated or stainless steel.

So far I've tried an epoxy ("plastic steel" by Draper) with the hex spacers.
Initially it seemed ok, but with a small amount of leverage the spacers came
away.

Could someone please suggest whether I would get better adhesion on the
anodized aluminum with the zinc screws, stainless steel screws or the
nickel-plated hex spacers? What epoxies would you recommend? I've also been
advised that curing the epoxy will improve the adhesion - does this make a
big difference?

Many thanks,

Dave


Dave,
If you can, cut a plate the same size as the pcb. Drill and c'sink for
the screws you want to use. Use short screws and thread a spacer onto
them. Then, wet both surfaces to be bonded with epoxy and use a wire
brush to rough up the surfaces through the epoxy. Or, use loctite 330
adhesive. You can get this as a kit for about $20.00. And it sticks
very well. Even on oily surfaces. I have personal experience with both
methods.
Eric