When I place an SMD diode in my pcb art top layer, (SOD123) and it's rotated 90 degrees -- is the anode on the right or left? (and obviously the opposite for 270).
I'm asking because I still don't get the silkscreen layer symbol for the part but maybe there is a standard based on rotation and the screen symbol doesn't matter? Like even if I had a generic 1206 or something there, they would know the anode/cathode based on rotation?
Depends on how it started, and your definition of rotation.
Show us a picture of the silk symbol.
It depends on what the manufacturer's data says. Given a random example of a SOD123 part I'd do this:
John Larkin <jlarkin@highland_atwork_technology.com> wrote in news: snipped-for-privacy@4ax.com:
Real simple. There are a numbre of 'standards' and they all generally depend on what the design engineer prefers or what he wants a technician to see on the finished product.
This is a simple google images search for "Diode silk screen"
mkr5000 snipped-for-privacy@gmail.com wrote in news: snipped-for-privacy@googlegroups.com:
Here is one site's take on making sure there is no confusion...
There is a standard, but it is only marginally respected. For two pin devices they are oriented horizontally with pin 1 on the left or in the case of a diode the cathode on the left. Rotation is positive. So 90 degrees would have the cathode at 12 oclock.
That's funny. In about half the cases, the diode covers its own polarity indication!
snipped-for-privacy@highlandsniptechnology.com wrote in news: snipped-for-privacy@4ax.com:
Yeah, I saw that. It is like they don't know what a silk screen is for.
Look at my follow up to the OP.
That guy did it right.
It may be useful to see the markings when trying to verify the orientation, but not to the machine operator. They get a bare board and just need to see the markings long enough to get the machine programmed for the placement. I'm surprised they can do this as quickly as they do. They don't typically charge much for the initial setup. I think a board with over a hundred parts cost me $200 for set up and that is probably more for the machine time as it is for the operator's time. I imagine places like JLCPCB can work so cheaply because they either throw out designs they have too many questions about or they just make it without being sure. I saw a PCB they made where the interchange suffered from lack of understanding. The via pads ended up as hexagons because of minimum spacing. I'm not sure it met the design rules for minimum annular ring anymore, but they got the drill hole pretty much dead center anyway.
Does it have to be in P and P comments (note polarity) or will they look?
they will usually look and ask if in doubt, but I wouldn't rely on it
just look at the preview when you upload and reup load a file with corrected rotations until you get the desired result
The convention is to tag the cathode of diodes, with a dot or bar or + or something. That's a legacy of selenium rectifiers.
An arrow is OK, but if the part covers it it impedes inspection.
Here's one:
JLC use the rotation standard that LCSC uses for EasyEDA; all parts are unrotated when they are "as the come off the reel". Look at the part on LCSC, and click the "EasyEDA Model" link. Make sure that your footprint matches the orientation shown, because that's what they use for assembly.
JLC also provide a placement viewer that you can use to detect rotated parts. In one case, I found that the viewer showed the wrong rotation, which turned out to be because the JLC viewer got it wrong - but the EasyEDA drawing and my own rotation matched up.
CH
What does "P and P" mean???
What's wrong with giving them the proper orientation? Two pin devices are aligned east/west with pin 1 to the west. Pin 1 is also the positive terminal of caps and inductors or the cathode of diodes. Pin 1 is always the pin to be marked. So that would seem to preclude marking the anode of diodes.
I think they will look. especially of the refdes is D-something.
PCBway asked me about polarity of some bidirectional TVS diodes because it wasn't marked in the silk.
Twice.
In the third batch I called out the part numbers in the fabrication notes something like: "D1,D2,D3,D4,D5,D6: these parts are not polarised, either direction is acceptable" I think that worked.
In the next revision I switced to duals in a SOT323 package for other reasons.
What software are you using to design your pcb?
Hul
mkr5000 snipped-for-privacy@gmail.com wrote:
Instead of hijacking this thread, perhaps as the question in a new thread J
Before they do the assembly they will send you an email, so you can confirm the polarity of misc components
Thanks Klaus. I've been trying to submit an order for a week. (my first that needs assembly).
The latest?............. "Attention! The PCB specs you chose are not available for SMT assembly. To have your PCB assembled, please reset the PCB specs. "Panel By JLCPCB" option is not supported"
My single size board is 45 x 43 mm. I put 5pcs for panel quantity. (I thought they wanted panelized boards on assembly? !). I listed columns 5 and rows 5. And get the error above.
So then, I made it single boards, made the qty 30pcs and the error went away. THEN, I made it 50 pcs because THAT is what I want, and the error came back.
"Attention! The PCB specs you chose are not available for SMT assembly. To have your PCB assembled, please reset the PCB specs."
So I looked at it and see I want .8mm boards on this and it only ALLOWS 30pcs max ! WTF ? (and it only allows 50pcs on thicker boards).
I don't get their ordering process AT ALL. I may go to PCBWAY which I've always used before but seems I can save a bit using JLC? Not?
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