Glue for SMDs ??

[wmcbride]

Based on his/her experience, can someone advise the best way to attach SMD's to loco shells?

I'm installing some for behind-the-pilot-mounted ditchlights and also some for individual lights in a dual-headlight Intermountain F7A.

In my web search, I've seen people used hot glue (ouch), Aileen's tacky glue, white clue, and superglue.

Thanks...

[carlso]

I have used " Formula 560 " canopy glue with good results.

Carl

[peteski]

Epoxy or CA glue (or a combination). I often tack the LED to the shell using some CA, then I encapsulate it in epoxy. After that I can paint the epoxy with paint which will block the light from shining though the back.  Also, don't forget  to paint the inside of the shell around the LED area with some light-blocking paint, as often the light from the LED is strong enough to shine through the plastic (it depends on the color and opacity of the plastic).

[Wutter]

I usually use CA glue if the LED can be glued on the backside to something but Canopy glue or Kristal Klear if its glued on the front to a lens. The weaker glues also help prevent damage if the LED is attached to the shell piece and you accidentally pull on it when opening the shell up.

[wmcbride]

Thank you, all, for your advice. I had forgotten about canopy glue and must have some somewhere.

Given the brightness of some of these LEDs I appreciate the reminder to paint a LOT of the adjacent interior shell to prevent bleed through...

[peteski]

Thinking about what I wrote earlier, my reason not to use a canopy or white glue is because ... it takes to long to dry!  I'm not about going to wait 6 hours for the glue to dry - specially if I have to hold the LED in place (because the springiness of the wire leads would cause the LED to lift off its desired location.  Tacking with CA and accelerator literally takes 10 seconds, Now (to encapsulate the LED)  I can apply some 5 minute epoxy which will harden fairly quickly.  I guess I'm a Rapido modeler. 

[wmcbride]

I agree. I tacked one in place last night with super glue.

Now I am thinking of illuminating the number boards in the F7A but I fear it might be too bright and not diffused enough. I really don't want to add a resistor (lazy) to reduce the brightness. As to alck of diffusion, the number boards are flush with the outer shell and their is a hole, shell-deep, behind the number boards. Maybe I can fill it with epoxy, paint it black all around the number board area and then attach the SMD to the back of the epoxy...

[peteski]

Unfortunately Bill, to prevent the toy-like appearance, you will have to learn not to be lazy and add resistors.    Besides, you really need a resistor if the LED is powered from 12V or it will instantly burn up.  I used SMD resistors because they are easier to hide.

To further improve the look you can use white Evergreen styrene (I use 0.005 through 0.020", depending on the situation) as a diffuser for white LEDs.  This works even better if the LED can be placed some distance from the diffuser. That not only diffuses the light, it reduces the brightness quite a bit.

[wmcbride]

Ha! I'm using a TCS decoder so the resistors are built into the board for LEDs.

The white styrene is a good idea. Thanks!

[robert3985]

Epoxy or CA glue (or a combination). I often tack the LED to the shell using some CA, then I encapsulate it in epoxy. After that I can paint the epoxy with paint which will block the light from shining though the back.  Also, don't forget  to paint the inside of the shell around the LED area with some light-blocking paint, as often the light from the LED is strong enough to shine through the plastic (it depends on the color and opacity of the plastic).

Good advice from Peteski.  Just to be a little more precise, you'd think that black paint would be the most opaque, but I've found that silver paint is much more opaque. Maybe it's because there are actually metallic particles in the sliver paint which more effectively block the light.

[wmcbride]

Thanks, Bob!