I was thinking of creating a few new parts in our schematic library, like BOX and BOX/1Lead and BOX/2Lead maybe. Each will be just a box on the schematic and not have a layout decal. The leads allow the object to be grounded or whatever.
The idea is that I can use them for heat sinks, tie-downs, even the bare PCB itself, things that would not usually be on the schematic but we want to remember to put on the BOM.
fredag den 23. juni 2023 kl. 20.51.19 UTC+2 skrev John Larkin:
maybe a question of terminology, but in my mind BOX is just a schematic symbol
the "part", say a tie-down would be the partnumber, description, etc. that get in the BOM and that is uses the schematic symbol box all in the parts database
would you just plop down a BOX and manually fill out the properties without creating the part in your parts database?
Yes, it would be a visible dummy schematic symbol, but would have the attributes that cause a part on the schematic to appear in the BOM.
One attribute of any part is its MAX number, namely the stock number in our material control system. When we buy a part, we create a bin and assign a 7-digit stock number and declare the manufacturer(s) and their part numbers that are acceptable buys. Every part on a schematic has a MAX number attribute, and the schematic generates the BOM. But we have been manually adding the non-electronic parts, like the PCB itself!, to the BOM and that's a nuisance, especially for board revs. I thought it would be cool to put the non-electronic parts on the schematic too.
We already have schematic symbols for a few sizes of screw holes, like for mounting screws and scope grounds, but they don't include the screws themselves.
What do other people do about adding non-schematic parts to the BOM of a PC board?
Have a separate mechanical diagram for the PCB assembly, et al. In some cases, the core drawing number is the same, and different three-letter prefixes differentiate PCB schematic from PCB mechanical design. And there is a document tree (itself a drawing) that defines how it all fits together.
Part of the reason for this is that schematics use one set of electronic design tools, and mechanical assemblies a different tool, and so on.
Joe Gwinn
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