Assembly Drawing

FAB and Assembly Drawings for Turnkey PCB Assembly

A successful PCB assembly operation requires a lot of data. In a perfect world, all of that data would be in a nice IPC-2581 intelligent CAD file. Sadly, we don’t live in a perfect world. Who knew?

What that means is that we, the PCB assembly service provider, are often confronted with the dreaded ambiguity. Sometimes this ambiguity can be countered by printing information on the blank PC board. If the instructions are simple, then doing so might be adequate. For anything other than simple instructions, we’d like to see an assembly drawing – like I suggest here. But what about information that is needed at the PCB fab shop rather than at assembly house.

For that type of information, you will want to provide a fab drawing.

One of the challenges is that the “standards” for assembly and fab drawings are so often only loosely adhered to, if you can call them standards at all. If in doubt, label the fab drawing “Fab drawing” and the assembly drawing, “Assembly drawing.” That may seem obvious, but in the wide world of technology, obvious too often is anything but.

(image from XKCD.COM)

On the upside, simple clarity may very well go farther here than would a standard. If you think a fab shop might need a bit of information that isn’t obvious from the GERBER, just Clearly label in the fab drawing. Then make a PDF, and label it “Fab drawing.pdf.” Do the same thing for assembly information and label it “Assembly drawing.pdf.” If information is needed by both the fab shop and us, the assembly house, put it in both drawings.

We recently had a case where a component polarity wasn’t marked on the board or in the assembly drawing but was in the fab drawing. We do our best to catch such things, but it adds a bit of ambiguity to the process. If you’ve been reading this blog before, you’ve likely picked up that I’m not a fan of ambiguity.

Once you’ve got your files, including fab and assembly drawings as needed, jump over to our online assembly quote page and get the process started.

Duane Benson