When you are creating a footprint in your favorite CAD program, or reusing someone else’s footprint, double check the zero orientation. This post discusses the IPC-7351 specified zero rotation orientation.
This picture on the left shows a library component with the improper zero rotation orientation. Your centroid file will never be correct if you start from the wrong point.
IPC-7351 states that the LED should be oriented horizontally and the cathode (pin 1) should be to the left. Obviously, vertical and cathode up is not the same thing as horizontal and cathode left. If it’s obvious, why do I feel the need to state it? I don’t know. I just do.
Duane Benson
Red is gray and Yellow white
But IPC decides which is right
It takes virtually no time to get it right the first time, then it’s right – period.
If only the LED manufacturers would be consistent in how the parts are oriented and marked we could really be productive. I can’t say how many times boards have come back with wrongly oriented LEDs because a last minute BOM change didn’t take that into account.
I follow the IPC-7351 guidelines, as to assembly, the component origin as presented to the machine can vary even between batches of the smae component, thiese problems can be solved on mosr semi intelligent pick and place machines and the assembly process software. The best way I found is to have simple to follow pictues of how the component should look in the tape when inserted in the machine, and if then else pictures if the orientation is different to indicate the cvorrect theta rotation to enter. A few secons QA every time a reel of comps is inserted can save a lot of time later on.