Hi Steve, I agree with your assessment that the 'K' or Cathode side of the diode is typically the indicator for the polarization of the part. There are no references that I have seen in my 30+ years of PCB design that indicated that it should be otherwise. I did find the industry change on radial electrolytic CAPs to be a bit disturbing back in the 1980's they started marking the NEG side of the capacitor with a stripe that indicated the minus symbol. Before that, we always indicated the Positive terminal of the Cap on our silk screen legends. The connection between pin one and the polarization of the part is traditional, and has been an industry wide practice since the 1960's.. so I am told. I was in grade school back then so I guess I will have to take their word for it. We often indicated the polarity or pin one by using a square or rectangular pad shape in that component lead instead of a cut pad or oval pad. Our indications for polarity came from observing the manufacturer's standard practice. Transistors typically indicated the lead that was connected to the emitter junction as opposed to indicated the base or collector leads. We followed their choice for indication on the legend. IC's are also customarily oriented by the location of pin one with a DOT or an indentation on the correct end of the molded plastic package... In Darryl Lindsey's book "The Design and Drafting of Printed Circuits" published by Bishop Graphics back in 1979, Chapter 3 refers to discrete component polarization and he says that Diodes MUST be identified by the cathode end. I started laying out boards in 1970 and it has always been the 'standard' practice to identify the cathode, not the anode, of discrete diodes. All Diode manufacturers indicate the cathode on the actual physical part with some sort of band or marking close to the lead or surface mount termination. They do not indicate the anode side of the diode. Therefore I would suggest that perhaps your customer is trying to set a new precedent in the component marking standards, hoping that the rest of the world will follow their lead.... (don't count on it) or, they just made a mistake in creating the symbol and should correct their database. I hope that helps a little. Bill Brooks, CID -----Original Message----- From: Steve Vargas [mailto:[log in to unmask]] Sent: Friday, June 20, 2003 7:18 AM To: [log in to unmask] Subject: [TN] Diode Pin Assignment All: As a SMT subcontractor, we see CAD files from many different sources. An item of frustration for us is how some customers assign a Pin 1 designator to diodes. Primarily, we see Pin 1 being assigned to Cathode and Pin 2 to Anode. For those customers who use Pin 1 to anode, we manually rotate the part within our CAM system to stay consistent with what our operators typically see on their visual aids. This is both cumbersome and inefficient. I don't believe (or should I?) that there is an industry standard that addresses this, but is there some type of defacto standard that exists which I can use as evidence to some of our customers that they should consider using the 'Pin 1 to cathode concept'? Thanks. --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ----------------------------------------------------- --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------