That is the rub here, isn�t it? For those posting, it�s easier [but much slower] to start a new thread than to search the archives. [And posters could view their issue so unique and novel that it could never have been discussed several years earlier, as implied when contemplating 'search'.] And on the other hand, it�s easier for responders to send someone to search the archives than to respond to a posting.
In keeping with that precept, I�m tempered to suggest that you �searching the fine SMTnet Archives�. Unfortunately, I can�t recall a thread that responds to your question, should I send you there.
Several points on polarity marks are: * Any polarity mark is a good polarity mark. We prefer silk screen over cut corners of pads, because silk screen remains easily observable after mass soldering. * Generally, polarity marks on the bare board should directly correlate with polarity marks on the component. * Recently, we see less silk screen on boards than in the past. * Basically, 2221 - Generic Standard On Printed Board Design says that if you change the pad shape to indicate pin 1, you should be careful not to mess-up.
Our typical mark varies with the component * Diodes and caps: �+� mark, line under the part closer to one end than the other, �U� with chamfered corners * IC with leads on two sides: Dot or triangle in the center of the part at the top/bottom closest to pin 1. * IC with leads on four sides: Chamfer or dot on one corner if pin 1 is at that corner. Dot or triangle in the center / above the row of leads, if pin 1 in the center of a row. * Connector with multiple row of leads: �U� with chamfered at the corner for pin 1.
reply »