Hello,
Just wanted to know an estimated maximum dimensions of an FC that can fit inside something like a 5" - 7" frame.
I know the mounting holes are 30.5 x 30.5 mm with 36 x 36 mm - 38 x 38 mm board dimension on the bigger modern FCs but I wanted to know how much the full board outline can fit in.
For context, I’m designing a FC that I may probably have to hand assemble.
Unless you have special needs that can’t be addressed with existing hardware I wouldn’t bother with designing a.custom FC. COTS board will always be cheaper if it is an option.
Exact space available will heavily depend on your hardware choices.
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If you will do a design for hand assembly, plan for about 80 x 80 mm board…
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Designing for fun and better aligned with my usage are the purposes.
As for cost, since it is a 4 layer board, it seems it will cost only as much or probably lesser than a COTS board as far as I’ve estimated. I’m giving a lot of effort on choosing parts with pretty much the lowest costs while also achieving the specs.
Okay, I have access to an smd rework station (hot air and possibly hot bed). So just wanted to know what size fits in popular frames
You will be paying a lot more for sensors and MCU than a regular manufacturer, with 4 layers you will struggle to use medium small pin count MCUs (IIRC exposing all pins on H7 169 BGA requires 6 layers with via in pad).
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@LupusTheCanine
Oh, the STM32H743 is also available as LQFP, but than the size is little bigger. The 176 pin version has 24*24mm footprint. 
That would barely fit between screws on 30.5x30.5 mm mount 
unless you do 45° MCU thingy.
Yes, but total will hopefully still come equal or under COTS from my location.
I am using the 64 pin version. Might as well make a 100-pin variant.
Currently in the routing stage and seems like I’ll be able to fit stuff on a 42x42 board which I guess fits in the frames designed for the 30x30 mounts.
Can someone confirm the max size that can fit? Also want to point out that the post is not about the cost.
Also, it is an H5 MCU, so when H5 support comes, I don’t have to either wait for H5 MCUs or pay a premium. But the main thing is designing for fun, education and practice.
I don’t know if this will help you but here is generic 7" bottom plate. You can see where the standoffs mount, it would need to be inside those.
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It is not that bad
However… I would not consider going 6 tayers as a bad thing nor a significant cost when compared to gyros. I designed 6layer PCB and with 200pcs it is less than a 1$ per piece, where ICM-42688-P is like 17$ alone next to 10$ MCU.
Also 6 layers gives You way more flexibility in components placement and improves PDN a lot.
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Thanks. This will help I guess. Yes the mounts are still 30x30. Just wanted to know the board outline limit. Some frames have a covering on the side I guess
Okay this is the 100 pin version, which is commonly used on common FCs. There are 144, 176 and I think H7 even comes in a 204 LQFP which measures 28x28. LOL.
A little aside: I discovered yesterday that JLCPCB cost for a 4-layer board measuring absolutely under 53x53 (50x50 to be safe) only costs 2 dollars (considering the base options are still selected)
Here is a link to a 7" Frame Stp assy model.
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