Popular Assembly Markings - Page 1
Forum section: electronics / beginners

author: LoveLaika
author_rank: Frequent Contributor
timestamp: February 11, 2022, 03:41:00 pm
content: I might be reading too much into this, but for footprints, what kind of fab markings do you like to include in your footprints, or what do you think are some go-to markings for components that are absolutely necessary, that anyone can read it and understand how certain components go? I'm looking through my footprints, and I'm thinking of symbols/markings to add that would assist in fabrication assembly. Now, I know that every fab house has different requirements, but for now, I'm just thinking of just rather generic markings that would instantly make sense to anyone that has to assemble a PCB. There's some that I can understand (like a + for polarity, or a silkscreen diode triangle/wall to indicate diode polarity, or a dot/circle to indicate pin one of an IC/specialized connector), but I was wondering what else would be good to add?

author: Watth
author_rank: Frequent Contributor
timestamp: February 11, 2022, 06:38:40 pm
content: Footprints typically include polarity marks when necessary. ICs too have an indication on which pin is the number 1.

author: LoveLaika
author_rank: Frequent Contributor
timestamp: February 11, 2022, 06:54:14 pm
content: That seems pretty standard. I'm making sure all of my IC footprints have a dot on the silkscreen close to pin 1. Polarized caps have a + sign, diodes have the diode symbol, etc. Anything else you might recommend? Maybe a better way to think about it: if you were to give a layout diagram to someone who knows the bare basics, what info would they need to orient components on the board?

author: Benta
author_rank: Super Contributor
timestamp: February 11, 2022, 07:24:32 pm
content: You're overthinking this.The only thing that an assembly house needs is reference # and orientation. This paired with a parts list of course.In effect, pairing the parts list with the Gerber files is enough for automatic processing.

author: tooki
author_rank: Super Contributor
timestamp: February 11, 2022, 07:27:21 pm
content: For automated assembly, the focus should be on optimization for automation. For boards that are to be manually assembled, I always provide redundant orientation indicators: something on the silkscreen (more if possible) and a different pad shape for pin 1.

author: LoveLaika
author_rank: Frequent Contributor
timestamp: February 11, 2022, 08:38:41 pm
content: If I may, that brings up a follow-up example. Take a standard 2-pad diode. Going from the anode to cathode, the "order" of the pads/pins depends on the symbol. Pad 1 could be linked to the anode or cathode, depending on the software or symbol used. So, a drawing on silkscreen showing the proper orientation of the part is necessary. In such cases like that, what would you do? Furthermore, what if the assembly house interprets the component pins differently based on something like the datasheet (example: software has the left pad as the anode, but datasheet says the left pad is the cathode)?On that note, how do you accommodate for components that don't fit a particular shape?

author: free_electron
author_rank: Super Contributor
timestamp: February 11, 2022, 09:13:27 pm
content: a line or dot adjacent to pin 1 or cathode.width of the line is 6mils (0.15mm) which is screen printable by even the most rudimentary processes.length is the length of the pad it is adjacent to.position it in such a way it remains visible post placement. nothing should cover it.

author: tooki
author_rank: Super Contributor
timestamp: February 12, 2022, 10:37:52 am
content: Quote from: LoveLaika on February 11, 2022, 08:38:41 pmCertainly you need to have your components defined properly in the software to match the datasheet. “Left” and “right” aren’t how things are defined in software or on datasheets.

author: Terry Bites
author_rank: Super Contributor
timestamp: February 12, 2022, 01:25:30 pm
content: good silk screen marking is essential for efficient debug.