0
\$\begingroup\$

I have 8 no. DO-41 sized diodes in a row like so (representative image):-

diode row

I'm hoping to place them adjacent to each other on a 2.54mm pitched proto board. They're glass cased and I need to totally screen them from all light. They can't be screened via the overall circuit's enclosure as it's translucent.

It's a sign of good quality in that they actually manage to butt up against each other on a 2.54mm pitch, despite the data sheet suggesting they might not. However this means that they cannot be heat shrink covered, due to lack of space. So are there any alternatives to screening them from all light? Remember that a proto board will have holes beneath the diodes. The proto board is an Arduino shield of 80mm x 60mm size so I'm hoping to keep it tight.

For interest, this is the spec. for a DO-41 package:-

DO-41 spec.

\$\endgroup\$
18
  • 2
    \$\begingroup\$ hot glue. foil. more hot glue. \$\endgroup\$ – dandavis Apr 26 '17 at 23:22
  • 5
    \$\begingroup\$ Any reason you're not using diodes with opaque packages? \$\endgroup\$ – Abe Karplus Apr 26 '17 at 23:26
  • 3
    \$\begingroup\$ How is it a sign of good quality that they butt up to each other? All that says is the tolerance stack gods were kind to you this time. \$\endgroup\$ – Matt Young Apr 26 '17 at 23:48
  • 4
    \$\begingroup\$ Put heatshrink on the diodes, then install diodes 1, 3, 5, 7 flat against the board, followed by diodes 2,4, 6, 8 held off the board by the first four. \$\endgroup\$ – Peter Bennett Apr 26 '17 at 23:59
  • 2
    \$\begingroup\$ @PaulUszak Um. Hasn't 3M taken over the world, yet?? ;) Doesn't Digikey sell to the UK? What's wrong with the UK?? \$\endgroup\$ – jonk Apr 27 '17 at 2:01
3
\$\begingroup\$

A black, quick setting and thick/not runny epoxy could be poured over them.

\$\endgroup\$
4
  • \$\begingroup\$ Some inspiration: google.com/search?q=circuit+board+opaque+epoxy \$\endgroup\$ – Jason C Apr 27 '17 at 4:20
  • \$\begingroup\$ Of course, potting compound is good for mass production, but a one off design or prototype can use standard epoxy from any hardware or auto store @jason \$\endgroup\$ – Passerby Apr 27 '17 at 4:24
  • \$\begingroup\$ The only potting I've seen is of the whole circuit board. Is that what you're suggesting? \$\endgroup\$ – Paul Uszak Apr 27 '17 at 11:28
  • 1
    \$\begingroup\$ @Paul no, you can pot individual components. That's what a Chip on Board is. I'm this case I'm saying just use some to cover the diodes. \$\endgroup\$ – Passerby Apr 27 '17 at 12:11
2
\$\begingroup\$

Paint them. If these are already assembled, a suitable nonconductive paint might be GC Electronics Corona Dope (10-4702), or Insulating Varnish(10-1762). Be aware, though, that it may be important to block infrared as well as visible light, so some testing should confirm light blockage.

\$\endgroup\$
2
\$\begingroup\$

Don't...

No idea why you would want them covered, but if your circuit is that sensitive to light, chose a different diode or package.

The cost difference in the devices will be far less than the costs involved, including labor, of covering them.

\$\endgroup\$
2
\$\begingroup\$

There is nothing that says that they have to be flush-mounted to the board. Heat shrink them and stagger them vertically.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.