Straps, cont’d
I’m 71+ and I’ve always been using the word “strap” to name the piece of bent wire used to connect two pads (well before the plated through holes were commonly used), in all the companies I worked in: medical, house appliances and space industries. This isn’t an invention from myself but a common term. Jumpers being more restrictive as components containing a pin array with one or several caps. Sorry if I’m no more up to date.
@BobZ I’m not entirely sure this addresses your point, but I vaguely remember doing a two-layer, non plated hole, design years ago. Such a board would require your jumpers / straps to connect top to bottom layers at the via holes. As I recall, we did the PCB layout normally, as if it had plated holes, but simply switched to non-plated via the fabrication instructions to the PCB shop. This approach, however, wouldn’t give the jumper wires in the parts list, although I suppose you could make the vias themselves a part (that could get tedious depending on how many there were).
A similar approach could be used with a single-sided board that was relying on wire jumpers / straps to jump over traces (you may see this done on really cheap products, or really simple auxiliary boards like a connector-only PCB). You do the PCB design as a two layer board, keep the top layer very simple and its traces become jumpers in the final design. Again, you instruct the PCB shop it is a single layer board (just don’t send them the top layer artwork). Getting a list of jumpers and their lengths for your parts list in this case would be more challenging, although I suppose doable with post processing of the PCB file or the Gerbers.
These jumpers that I use right now are for home made boards, so I do not need to have them in the BOM. They are for a 2 layer board with PTH. I simply prefer to use jumpers sometimes instead of bottom traces so that I do not chop up the ground plane too much.
Two layer non-pth boards sounds like what you are likely to get with a board mill. But having to stuff and solder wires into the non PTHs is a pain. If you can solder a complete jumper it is easier but just a short top to bottom wire in the via hole tends to fall out when you are soldering it.
These days (or even 20 years ago by my recollection) for anything built in the USA there was not much point in using single sided pcbs. Those can be some SEM1 (??) or some cheaper material instead of FR4. That approach may still be cheaper if building 100K pieces in China or Thailand. For a 100 mm square board from JLCPCB the difference between 2 layer and 4 layer is small enough so that I think I would use 4 layer if I were to do my design over again.
You’d be surprised at the price calculations. Even for 1000s quantities, switching some of your design to single layer FR-1 or FR-2 (paper / phenolic) board can be economical. My first product to be made in these quantities, I remember the factory engineers suggesting we put all the connectors on a separate FR-1 board. I thought it was crazy, it added an extra board, a pair of connectors, and complexity. But the savings was cost warranted in production. I was lucky and was able to route that board entirely on one layer without jumpers (it helped that I could control the pinout of the connector).
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