IPC Says What?
I recently wrote about spacing, IPC standards and such. James M. commented on the post with a question:
"I run into this issue all the time. Assembly houses love to say that they can make anything that meets "IPC Standards for Placement" but when pressed no one can provide the exact number that gives this information. I know of IPC7351A, in fact I own a copy. And the keepout is clear there. But that doesn't influence things like component placement grids, how close things can get to the edge of a board, etc.... Are there other specific IPC standards that do?"
After reading James' comment and re-reading my post, I kind of realized that there isn't a lot of actual content in that blog post. Certainly not much actionable data. And, upon further thought, I think perhaps, all of us assembly folks kind of use that phrase "can make anything that meets IPC Standards for Placement" as a bit of a cop out. Not totally - we do have to set some limits on what we can build, but yikes! I've been trying to navigate the morass of different standard numbers (Maybe I should say "plethora" instead of "morass") and I don't know how anyone that doesn't specifically live the standards for a living could easily find those kind of answers. But us manufacturers really do owe it to our customers to come as close as we can to giving definitive limits that don't take a week of reading to interpret. I think I have to do this in stages.
First, we have three things: IPC-7351A for land patterns and IPC-A-600, covering the PC board workmanship. Then, we have IPC-A-610, covering our workmanship when we build and inspect the board assemblies. Those are the key standards that we live by.
There are a few other questions, such as edge clearances and things like that. I'll dig some more into that one later, but one thing to note is that for the Screaming Circuits prototype service, we don't require any edge clearance, nor do we require panels, rails or fiducials on our full-proto service. I hope this helps.