Osram SMD LED polarity inconsistency

[dadler]

So, I bought Osram 0805 SMD LEDs in red, green, and orange.

I am populating a board with them now, but thought I would test the polarity of them first.

I discovered that for some reason, the Hyper red LEDs are marked with the dot on the anode, but the rest are marked with the dot on the cathode.

If I wouldn't have tested, all of the red LEDs would have been populated backwards.

http://www.mouser.com/Optoelectronics/LED-Emitters/Standard-LEDs-SMD/_/N-ec21j?P=1yzvlvb&Keyword=OSRAM&FS=True

In the Osram 0805 LEDs above on mouser, only the Hyper Red is backwards from the rest.

Is there some manufacturing/logistical reason to mark LED polarity in an inverse fashion?

Yes, this information is in the datasheet:

[mikeselectricstuff]

Probably to do with the bonding - you sometimes find TH LEDs with the "big" internal part as anode instead of the normal cathode.

Regardless of marking, the cathode should always be towards the index holes on the tape.

[nukie]

It's more reliable to determine the anode of a TH LEd by the leads. If in doubt always check with dmm in diode mode.

[Skashkash]

I remember this coming up in a screaming circuits blog post a while ago. .

http://blog.screamingcircuits.com/2013/01/how-not-to-mark-a-diode.html

You just really need to check the data sheets and not make any assumptions.