Low FC PDB stack for tight mini quad builds

by Oscar

Konrad shares his experience on how to save space in a mini quad tight build by lowering the FC/PDB stack as much as possible.

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Screw it!

For the tightest builds – you should forget your standard nylon spacers. They are too bulky and take up too much space. What you really need are 4 long nylon screws, some nylon washers and nuts:

low stack save space fc pdb tight biuld mini quad nylon screws

Separate PDB from carbon with a single washer and use nylon nuts and more washers to add space between FC and PDB. After assembly, cut the screw to length if needed.

I used that method on my Airblade Assault 130mm micro quad build:

That’s a 12mm screw, bottom plate is 2.5mm, entire stack height is only 9.5 mm! Here I used a simple, low profile PDB – that gave me over 10mm of free space for other components above the stack.

You can see the entire build log here.

Need more space?

In case when You need to use metal screws in FC holes – for example when You have an X frame that uses them as structural support or just have a tall PDB, use the smallest spacer You have. If Your PDB has flat bottom, You can mount it upside down – that saves some height as PDB components are then located between spacers.

If Your FC of choice also has a no components on the bottom, then a washer between it and the PDB is enough. Use two if You need more airflow.


My first low profile build – Naze32 rev5 + Demon Core PDB combo under 25mm frame spacers:

low stack save space fc pdb tight biuld mini quad airblade assault example

Bottom FC spacers are 8mm. Stack is about 16mm tall.

Another build with Naze32 rev6 + Demon Core combo under 30mm frame spacers:

low stack save space fc pdb tight biuld mini quad low profile example

Bottom FC spacers are 8mm. Stack is also about 15mm tall. So much free space in that frame :)

I have checked other PDBs as well – there are a lot PDB’s with flat bottom to choose from. In both methods, always check for shorts – if FC solder blobs don’t touch the PDB or PDB blobs are not shorting on the frame.

Cable management made easy

Method that saves you most space is direct soldering wires to Your FC – pin headers simply take up too much space. For a clean look, you can solder the wires on the bottom of the FC like this:

low stack save space fc pdb tight biuld mini quad open

The finished result looks like this:

low stack save space fc pdb tight biuld mini quad top

Another good idea is to make sure you don’t cut he wires too short, leave some room in case you need to take the FC out. I found by routing all the wires from one side of the board would prevent this.

low stack save space fc pdb tight biuld mini quad wires routing

If you want to achieve the absolute minimum wiring, I normally would desolder all the ESC wires (both power and signal) and solder them on to the PDB and FC first. Then you can close the stack, shorten power and signal wires as needed, and solder them back to the ESC’s. Some really good soldering skills might be required.

Hope that saves some trouble fitting components on your next, tight build. Cheers!

Author : Konrad If you like this article please subscribe to his youtube channel.

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Mark Haslinghuis 10th October 2019 - 9:35 pm

I am also concerned about electric noise. Imho for a cleaner build you should use a AIO Flight Controller which includes the PDB on the FC it self. You solder all individual ESC wires (power, signal, ground) directly to the FC.

Lion 19th March 2018 - 5:10 am

What about electric noise from FC perspective ? isn’t it important to keep fc a little bit far from PDB?

Faris 6th July 2016 - 12:58 pm

Hi, great post. I like the Matek Power Hub V2.1 PDB. You have put the ESC power wires across the PDB, all soldering pads are in the right position. Much cleaner build, love it.

Rook 22nd June 2016 - 11:39 pm

Some good ideas and points. Thanks. I started stacking a de pinned X4R, PDB on top then fc on top of everything. I can gain some more space using your ideas and can probably fit the vtx on top of the sandwich.

Andrey Skl 22nd June 2016 - 10:09 pm

That’s my low-profile build. Everything is inisde 1cm spacer between two plates. Only Camera and VTX is outside : )