Be careful and check your lamp holders before filleting the corners of the key ways. The lamp holders usually have fairly sharp corners.
@tartantriumph , check your lamp holders before placing fillets in the corners of the cutouts.
Thank you so much. After Paul suggested I add an internal fillet, I did precisely this and widened them all last night. I’ll make sure the board hole extends slightly beyond the physical.
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Years ago I had a client ask me to make a copy of a small (0.6 x 1.5") 2 sided very crowded PCB. Original company was out of business so replacement parts were NLA.
I stripped the parts off a board and scanned both sides using a hi-res photo scanner, the type used to scan 35mm slides or old photos. Used GIMP to tweak the size and mirror the bottom image. Imported both scans to user layers. By turning these layers on or off I could see exactly where the SMD pads, PIH pads, and traces needed to be.
The extra work up front paid off in the end by clearly showing the errors in my original try at the schematic as well.
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Would it not make sense to place high brightness LEDs directly at the PCB where the lamp holders were? Or they have to stick out mechanically?
It might make sense and maybe a good modification down the road, but with the current instrument housing, they need to stick out more than that.
Here’s the PCB design in OnShape:
Imported into KiCAD PCB designer, it looks like this:
It’s too large for the selected page size. Does this matter?
You can change the page settings in PCB Editor / File / Page Settings. It does not matter much, as Gerber output does not have the page border at all, but having the page graphics across your own artwork may be a bit confusing.
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I simplified the schematic, created the footsteps, designed the board in OnShape, and routed the wires.
Here’s the schematic:
To ensure it physically fits, I printed out the board shape (Edge.Cuts) and footprints (F.Cu) on a transparency, cut out the bulb holes, and attached it to the back of the instrument housing.
I need maybe one more pass to tweak some bulb locations, but it’s pretty good.
There are zero errors in DRC.
As @iabarry pointed out, I’ll add large copper areas to the empty space to assist mechanical strength, as Triumph originally had it.
Is there anything else you would do before sending this for fabrication?
What about using through hole LEDs then? You have these THT LED spacers if you want them more rigid. Sorry for posting PDF. https://www.we-online.com/components/products/datasheet/705820065.pdf There might be some central dimming system to your light bulbs which are not directly compatible with LEDs and I completely understand why to hold off using LEDs.
The factory bulb holders mechanically hold the flex PCB to the housing. I have LEDs in the factory bulb holders. If I mount the LEDs on the board directly, I need another mechanism to attach the board to the housing while keeping the LEDs flush.
I understand why you need these bulb substitutes.
Be careful that unlike the bulbs, LEDs are fussy about power polarity
Yes, that’s right. Gotta twist them in the right way around!
The LEDs were installed a few years ago, long before I started tinkering with the board. The only thing I didn’t replace is the ignition light, which you want to fade out as the voltage from the alternator increases until both terminals have no voltage drop.
Looks quite good. One of the things you should check before ordering the PCB is if the solder mask layer is correct. Scratching off solder mask to be able to make a connection is no fun.
That is a good start, but it’s no guarantee. How have you set clearances for example? Are they adequate for your design (and for your PCB manufacturer? I don’t have experience with Flex.)
You should also think about the surface finish when ordering your flex (and be sure to order a flex 
). Some prefer a gold plating (ENIG) for contacts. Others prefer to make it the same material as for the mating connector. (Is that chrome, or tin plating on the LED’s?)
I am also curious in how you experience the difference in working with or without the schematic? How much work was it to do the schematic? Do you thing it was good to do it, or a waste of time / effort?
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Great! What do I need to go from there to “good,” or even, “great”?
Using the schematic took me a lot longer - like three days versus one. Part of this is the learning curve, of course.
Using OnShape for the physical layout is much more time-consuming than using polygons in KiCad. Yes, the results are better, but there are often errors in DRC, and I need to go back and tweak them. Initially, I completed everything before running DRC, and there were over 50 errors. So, I started again from scratch, running DRC after each step; that worked out better for me.
KiCad DRC particularly doesn’t like the OnShape 3-point curve. I had to replace several curves with fillets.
In some ways, doing it “properly” seems riskier, as I now have to consider all of the board parameters - and may miss something that was a feature of the original board (such as the large extra tracks). If I had traced the original, I think there would’ve been a good chance it would work, as the original board has worked for 50 years.
That doesn’t sound fun!
It looks right to me, Paul. Your suggestion of using SMB pads to expose the areas where the bulbs contact was spot on.
Having neatened up some of the tracks, here’s the board I’m going to push for production:
I sent it off to JLCPCB just now, and it’s under review. I did try to parse their specs. The main one I suspect I’m not in compliance with is:
5 mm panel borders on all sides. Copper should be present throughout the borders except 1 mm clearance around fiducials and 0.5 mm around tooling holes. SMT fiducials should be 1 mm diameter and tooling holes 2 mm diameter.
There’s a point on the right of the board where one of my hole connectors is right on the edge of the board, so I’m guessing that won’t wash.
We’ll see. Very curious to see what they say!
Does the 5mm panel not simply mean you need to draw a frame around the whole layout? Can’t find a good picture but by using a frame you can locate the board for a pick and place so need location holes and fiducials - but you can put these on the frame which is thrown away when depanalised. I’m not sure how the flex boards are made but can imagine that they need a regular outline frame to make them easy to handle.
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Ah, that does make sense. Or they do.
Either way, they approved the order this morning, so I’ll pay my money and take my chances. I went cheap on shipping, so it’ll be a couple of weeks before we see the results.