Identifying polarity on SMDs

[jdcolombo]

Another vote for the solder blob method.  I use 750 degrees.

John C.

[peteski]

I've found 600 F (315 C) is adequate. I just finished stripping 40 wires for Ed's Dirty Dog, and it went very smoothly. Starting with the very end of the wire was the only thing I found important, for reasons I don't yet understand--if you just stick the wire in sideways near the end, it won't strip.

Maybe because the molten solder contacts the bare copper end of the wire, which then transfers the heat very fast down the wire, "peeling" the enamel back?  If you stick it in sideways, the enamel acts like heat insulator.  Just hypothesizing here.

There are many different types of enameled wire. Low heat and high heat.  For example, N-gineering's enameled wire is the low-heat variety and they specifically state that in the instructions on stripping their wire.  I have a collection of different enameled wires I accumulated over the years, so I don't know the heat rating of their enamel coating.  But setting my iron to 800 deg. F pretty much strips all those different wires.

[Steveruger45]

So, post coffee -

• These SMDs have different length leads.  SMDH 
• Even if these have differing color lacquers for insulation, I can't tell the difference.
• I have 2025 3V batteries for our car key fobs, and holding one vertically in a small all plastic spring clamp makes a decent test rig.

So far I only have one bad SMD.  But getting good contact is not easy owing to the insulation lacquer. What have we decided is the right removal protocol?

Phil, if you have one of those Digital multi meters that are free with a purchase of something else at Harbor Freight, your can test an smd led with that.  Its the red Cen-Tech one see photo. [ Guests cannot view attachments ]
I do this all the time. On the 0-200 ohm scale it pumps out just enough juice to light up the led when you have the positive and negative test leads on the correct led pads. If it doesnt light up reverse the leads. Now you know which is the leds positive and negative.
I stress the make and type of multimeter here as this works for this multi meter but it will not or may not work or damage an led if using another make Multimeter.

[DKS]

Maybe because the molten solder contacts the bare copper end of the wire, which then transfers the heat very fast down the wire, "peeling" the enamel back?  If you stick it in sideways, the enamel acts like heat insulator.

My bet is on that, FWIW.