How do you document bodges?

Question

After making the PCBs, we decided on some bodges and implemented them on the PCBs. What's the standard way to document that on the schematics?

For now, I hand drew with the mouse, paint style, on the schematics PDF files, to convey the idea that it's a bodge, but is there a better way?

Is this something that is going to continue in production, or merely for a small run of prototypes? — uint128_t, Jun 11 '16 at 15:24
for now I have 10 modified boards at the office, I'm decided yet if i'll re-spin the design or carry on with the bodges (for unrelated reasons). I'm interested in what the pros do. There is a lot of bodging out there, I guess it's a bit industrialized. — nraynaud, Jun 11 '16 at 15:49
@nraynaud the pros run a new spin with the issue fixed, unless cost or time restricts that option. In that case, professionalism has kind of broken down... — Marcus Müller, Jun 11 '16 at 16:09
... and in that case, it's always the professional way to make things as clear as possible to avoid future mistakes. — Marcus Müller, Jun 11 '16 at 16:09
I don't know, there is a lot of quality test equipment teardown on youtube where we see bodges. — nraynaud, Jun 11 '16 at 17:52
@nraynaud I promise that good equipment was probably made by experienced engineers who knew that they needed to document their failures extensively. Failing, and fixing, is not that bad – you can learn from that, but you need to be clean about it. — Marcus Müller, Jun 11 '16 at 19:19
@nraynaud, bodges are usually called rework. What the pros do: As with much in engineering, it is largely a cost/benefit trade-off. Depending on the policies of your company and when it is in the life-cycle of the product, doing a new version of a board can require a partial or complete QA run-through. This could cost large amounts of money. I've seen millions of $ for one pass through the process, or even just for a pre-QA board spin. The trade-off is largely dependent on end product unit cost. I've seen billions of $ of production product with multiple main-board revisions, all with rework. — Makyen, Jun 11 '16 at 21:31
@Makyen we are 4 dudes in a 30 sq.m. office, and I'm creating the rules. The aim of many of my questions is to understand what the industry does, and then decide if I want to do it now, when we're bigger; or never because I find it stupid (generally artefacts of the past). — nraynaud, Jun 12 '16 at 17:50

score 5 · Accepted Answer · answered Jun 11 '16 at 16:02

The modification is a proper part of the design of the product. So, no, don't "hand draw that on the PDF".

Add it to the schematics. You should have proper versioning control for your schematics anyway (Try git. It's thought for source code, but it works with any file type – you just won't get useful differences displayed between revisions, but that's not a problem here). Clearly annotate it in your schematics. If your EDA suite allows that, change color, stroke, whatever of the modification to make clear it's a modification.

If your modification is just a wire bridge: it's not uncommon for schematic design programs to have some kind of special "external connection" component.

Since you're probably want to still be able to generate a valid board from that schematic, make sure the "external connection" component you have has a small single pad that you can place on a wire in your board design. That way, you also get a guarantee you have something to solder too in the end.

Again, I don't know what software you use, but it will still make sense to "formalize" even the crudest hack into some kind of footprint/component: your wire bridge could simply consist of two components with one pad each, which share the same net name. That way, you could actually "place" the fix in your board design, and hence, have it documented.

Also, your board might fail design rule checks. Which would obviously be correct.

score 5 · Answer 2 · answered Jun 11 '16 at 19:11

Create a new minor revision for the intermediate changes and indicate them however you like as long as they can be printed out or copied reliably. They will not be used to create new faulty PCBs hopefully in the future so it is a dead end path.

The next more significant revision should incorporate those changes and any others that may have occurred which will allow new boards to have missing parts placed and traces to be routed correctly. That version does not need to indicate the history of how you got there as it is in the version history already.

Avoid reallocating part designators if you have released any documents outside the design office.

score 4 · Answer 3 · answered Jun 11 '16 at 16:43

The classic way is to designate a (paper) copy of the schematic as a working master. All changes get entered on the schematic in red. When you're ready to fab the next rev of the board, you hand over the master to whoever is doing the schematics.

At the same time, you need to start keeping a notebook. Sketch out your design ideas as you think of them, and record your design experience. When it comes time to start troubleshooting, record all changes you make in your notebook, as well as marking up the schematics. Then, when you're ready to update the design, cross-check the master schematic with the notebook, and make sure that they agree.

How do you document bodges?

3 Answers3