Mounting LEDs flush to PCB, OK over temperature?

Surface mount LEDs make me think 'duh'. They are smaller though.

I've taken apart plenty of equipment with LEDs and transistors supported by nylon spacers, but I've never seen them in catalogs.

Tim

-- Deep Friar: a very philosophical monk. Website:

Bivar

-- Boris

I've seen flush mounting done lots of times with no problems. Make sure they're loose in the holes before soldering; LED plastic tends to soften up during soldering, so that's the worst stress situation.

A short spacer wouldn't help much anyhow.

John

Bivar and others make spacers, but I've had much better results by machining up a jig to hold the LEDs while they are being hand-soldered. You can get them accurate that way. They'll slop all over the place in a spacer. You can even get water-soluble spacers that give the same effect (except for the sloppy LEDs pointing in every cross-eyed direciton).

Best regards, Spehro Pefhany

I agree, a jig wuld be best. I'd like it to be machine soldered if possible. I've come up with a posible solution of using an M4 nylon washer as a spacer, it's only 0.5mm thick but is soft enough to absorb any tension if thermal expansion is really a problem. What i don't want is to make 1000s of the things and find some fail after they've been thermally cycled in the field. I was also wondering whether RTV could be used to hold them in place although I'd have to make sure it doesn't percolate through the holes. Actualy that might work, a couple of blobs either side (they are 8mm LEDs with 0.1" pitch leads) and that might hold them even while machine soldering.

Mark.