IPC-7351B Electronic Component Zero Orientation [pdf] (2010)

> If the assembly fab had access to the schematic (I know a lot of people wouldn't want to share the schematic, but if we suppose that's not a problem), would that clarify most situations?

Haha, no, not at all; that's a disaster!

No, really, the schematic usually makes it worse. CMs don't speak schematic, as a general rule. EEs don't usually draft good schematics either. And, honestly, a good schematic usually won't have this information at all. The needed information might be found in the BOM, in theory. In practice, it's probably actually also in the PLM. If your company uses a PLM system. It might not be there either.

The actual barrier here is that there's really only one guy who has all the necessary information, and that's the guy who's loading the reel into the pick-and-place machine. He's going to have to check the work no matter what. So he often ends up having to do the work instead of just check it.

This is because what orientation is required depends on what part was purchased. Not the component type; not the manufacturer; not even the specific part number. The actual dead-ass specific part purchased, and how they decided to reel it that week at the packaging subcontractor facility. This is stable over time for the major chip vendors (unless they just issued a PCN this week! hope it wasn't retroactive!); for the Shenzhen specials, don't bother. But it is not consistent among second sources for the same part, and guess what -- your purchasing department will buy the cheapest thing you allow them to buy. And those two orderable PNs that are completely identical according to the datasheet, so you listed them as fully qualified alternates, and one is way cheaper this week for some reason? Yeah, that's a reeling code difference: same part, different orientation in the tape. And it's cheap this week because some big company (probably medical...) bought the wrong one and is unloading it instead of dealing with it.

So things end up different week to week.

And only the guy loading the reels knows which reel he's grabbing. So he's got to do the work.

> Is 100% automation possible at all?

No. No one genuinely cares. This is a throughput-optimized industry: the first board takes a while to get set up to build. Then there's thousands and thousands of them.

At the end of the day, the manufacturing data packages have (should have) centroid, orientation, and pin 1 data. That's enough to get the job built. Any more information is very likely to overconstrain things, leading to conflicting information, leading to build stops (conflicting information should always stop the build, always), leading to the engineer who did the overconstraining getting called in to fix it. Probably by not realizing what they did and saying "uh, just, uh, you know what to do, so just do that I guess".

The good professionals learn to make the manufacturing data files say that from the beginning.

I’m extremely grateful for your informative answer, thanks a lot! I may have been wrong about everything I thought I knew, but at least I was not wrong about the interesting conversation that would come out of posting this pdf :)

If I could ask one more thing, and be even more direct about it - I’ve been curious whether it would make sense to start doing board assembly in NY. I don’t have a plan, and I don’t have the necessary knowledge - but in some sense it seemed like a “more” automated assembly line, … better software (?)…, and fast/guaranteed turnaround could interest some part of the market - especially those doing small runs and hating to wait 2-3 weeks per revision. That, and tariffs.

Is this crazy and silly, or worse? Is there any juice in trying to run any pick and place operation? In or near Brooklyn?