Morning All - We've come across a sticky issue regarding LED marking. One of our facilities got a batch of PCBs in with ALL the LED's installed backwards. The assembly print shows marking/orientation on cathode side (only a line and a dot [which I don't like], not the typical diode notation --|>-- )
After some digging, we're finding the LED makers are ALL marking the orientation differently. See chart below for 3 Company part numbers, with alternate sources;
Company P/N Vendor Vendor P/N Description Marking Notes
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Part Number1 Lite-On LTST-C193KRKT-5A DIODE LED RED HIP RECT 20MA 50MW SMT Cathode 3
Part Number1 Panasonic LNJ237W82RA DIODE LED RED HIP RECT 20MA 50MW SMT Anode
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Part Number2 Lite-On LTST-C190GKT DIODE LED 0603 GREEN SMT Cathode 3
Part Number2 Lumex SML-LX0603GW-TR DIODE LED 0603 GREEN SMT Cathode 2
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Part Number3 Dialight 597-5112-402F DIODE LED RED STD RECT 15mA 40mW SMT Cathode 1
Part Number3 Lumex SML-LX0603SRW-TR DIODE LED RED STD RECT 15mA 40mW SMT Anode 1,2
Part Number3 Avago Tech HSMH-C191 DIODE LED RED STD RECT 15mA 40mW SMT Anode 1
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Note 1: 3 sources, one (1) vendor marking is cathode vs. two (2) vendors on anode
Note 2: same vendor, two (2) different part numbers (colors), two (2) different marking (1 anode vs. 1 cathode)
Note 3: marking is on the bottom of the part and can't be determined from the top side.
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So my questions are;
1) How do you ensure proper orientation during assembly, based upon LED sourced?
2) How do you inspect orientation, based upon what LED source you've used?
3) Do you have to adjust on-sertion programming, based upon what LED source your using?
4) How do you deal with storage if you have stock of vendor A and B?
5) Is this a known, on-going issue that assembly houses have to deal with?
6) How important is it that the marking consistent for the same Company part number?
This affects so many aspects (assembly, inspection, procurement) and looking for as much input as possible before we going making some blanket changes.
Ultimately we're trying to find a solution (driven from the CAD library) that will prevent this type of error. If you have any other questions or need more information, let me know.
SIEMENS
Michael Kuczynski Healthcare Diagnostics Inc.
Product Eng. II CID 511 Benedict Ave.
914-524-3118 (Ph) Tarrytown, NY 10591
914-524-3322 (Fax) Mail Stop P25-1-C
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