2 layers265.9 × 75.4 mm Twintail40, the printed circuit board in 3D

Twintail40

40% Keyboard | Neko Layout

Size: 265.9 × 75.4 mm
Copper layers: 2
Thickness: 1.6 mm
Parts: 121
Nets: 93
Pads: 468
Tracks, vias: 733, 172
Pours: 3
Routed: Yes
KiCad: KiCad 9.0 (file 20241229)
Created: 26 Feb 2026
Updated: 28 Feb 2026

Overview

Twintail40 is an open-source printed circuit board by TwintailDreamer, from the TwintailDreamer/Twintail40 repository on GitHub, published under the MIT licence. It is a 2-layer board of 265.9 × 75.4 mm with 121 parts on 93 nets, routed with 733 tracks and 172 vias.

Its parts include 51 diodes, 10 capacitors, 5 switches, 2 ICs and 1 resistor. It belongs with the keyboards and input boards and the STM32 boards of this library.

README

README.md

Twintail40

40% Keyboard for DIYer and Keyboard Designer.

About

Features a Singa neko layout with cutouts for O-rings.
Test production of the PCB and sample case production have been completed and tested.
Provided under the MIT License.

Layout

Identical to Singa neko (solder version).

Removed the screwless cutout and added an O-ring cutout.

layout

Spec

MCU : STM32F072
QMK and VIAL Support

About o'ring

For the sample case build, I used #259.
→ Since it was a bit cramped, using #260 or #261 should also be fine.

Photo

Proto Photo(Production by JLCCNC)

PCB1

PCB2

Future Plan

Special Thanks

Elaine: The original Singa neko designer. I received permission to release this project as open source. Thank you so much!!

I would also like to express my gratitude to everyone at Keyboard Atelier who shared their knowledge about keyboard PCB design.

Parts

121

Qty	Value	Footprint	References
51	D_Small	Diode_SMD:D_SOD-123	D1, D2, D10, D11, D12, D13, D14, D15, D16, D17, D18, D19, D20, D21, D22, D23 +35
5	100n	Capacitor_SMD:C_0402_1005Metric	C1, C5, C6, C7, C8
3	1u	Capacitor_SMD:C_0402_1005Metric	C2, C3, C10
1	10k	Resistor_SMD:R_0603_1608Metric	R1
1	10n	Capacitor_SMD:C_0402_1005Metric	C9
1	4.7u	Capacitor_SMD:C_0402_1005Metric	C4
1	7u_SPACE	PCM_marbastlib-mx:SW_MX_1u	MX46
1	7u_SPACE_STAB	PCM_marbastlib-mx:STAB_MX_P_7u	S2
1	A	PCM_marbastlib-mx:SW_MX_1u	MX16
1	B	PCM_marbastlib-mx:SW_MX_1u	MX33
1	BOOT	Button_Switch_SMD:SW_SPST_TL3342	SW2
1	C	PCM_marbastlib-mx:SW_MX_1u	MX31
1	CONMA	PCM_marbastlib-mx:SW_MX_1u	MX36
1	CORON	PCM_marbastlib-mx:SW_MX_1u	MX25
1	CTRL	PCM_marbastlib-mx:SW_MX_1.25u	MX15
1	Conn_01x04	PCM_marbastlib-various:Molex_Pico-EZmate_78171-0004_1x04-1MP_P1.20mm_Vertical	J1
1	D	PCM_marbastlib-mx:SW_MX_1u	MX18
1	DEL	PCM_marbastlib-mx:SW_MX_1u	MX14
1	DOT	PCM_marbastlib-mx:SW_MX_1u	MX37
1	E	PCM_marbastlib-mx:SW_MX_1u	MX4
1	ENT	PCM_marbastlib-mx:SW_MX_1.75u	MX27
1	ESC	PCM_marbastlib-mx:SW_MX_1u	MX1
1	F	PCM_marbastlib-mx:SW_MX_1u	MX19
1	FN	PCM_marbastlib-mx:SW_MX_1u	MX40
1	G	PCM_marbastlib-mx:SW_MX_1u	MX20
1	H	PCM_marbastlib-mx:SW_MX_1u	MX21
1	I	PCM_marbastlib-mx:SW_MX_1u	MX9
1	J	PCM_marbastlib-mx:SW_MX_1u	MX22
1	K	PCM_marbastlib-mx:SW_MX_1u	MX23
1	L	PCM_marbastlib-mx:SW_MX_1u	MX24
1	L_ALT	PCM_marbastlib-mx:SW_MX_1.25u	MX43
1	L_BRACKET	PCM_marbastlib-mx:SW_MX_1u	MX12
1	L_CTRL	PCM_marbastlib-mx:SW_MX_1.25u	MX41
1	L_LAYER	PCM_marbastlib-mx:SW_MX_1u	MX44
1	L_SHIFT	PCM_marbastlib-mx:SW_MX_1.75u	MX28
1	L_SPACE	PCM_marbastlib-mx:SW_MX_1u	MX45
1	L_SPACE_STAB	PCM_marbastlib-mx:STAB_MX_P_2.25u	S1
1	L_WIN	PCM_marbastlib-mx:SW_MX_1u	MX42
1	M	PCM_marbastlib-mx:SW_MX_1u	MX35
1	N	PCM_marbastlib-mx:SW_MX_1u	MX34
1	O	PCM_marbastlib-mx:SW_MX_1u	MX10
1	P	PCM_marbastlib-mx:SW_MX_1u	MX11
1	Q	PCM_marbastlib-mx:SW_MX_1u	MX2
1	QUOTE	PCM_marbastlib-mx:SW_MX_1u	MX26
1	R	PCM_marbastlib-mx:SW_MX_1u	MX5
1	RST	Button_Switch_SMD:SW_SPST_TL3342	SW1
1	R_ALT	PCM_marbastlib-mx:SW_MX_1.25u	MX49
1	R_BRACKET	PCM_marbastlib-mx:SW_MX_1u	MX13
1	R_CTRL	PCM_marbastlib-mx:SW_MX_1.25u	MX51
1	R_LAYER	PCM_marbastlib-mx:SW_MX_1u	MX48
1	R_SHIFT	PCM_marbastlib-mx:SW_MX_1.25u	MX39
1	R_SPACE	PCM_marbastlib-mx:SW_MX_1u	MX47
1	R_SPACE_STAB	PCM_marbastlib-mx:STAB_MX_P_2.75u	S3
1	R_WIN	PCM_marbastlib-mx:SW_MX_1u	MX50
1	S	PCM_marbastlib-mx:SW_MX_1u	MX17
1	SLASH	PCM_marbastlib-mx:SW_MX_1u	MX38
1	STM32F072CBTx	Package_QFP:LQFP-48_7x7mm_P0.5mm	U2
1	T	PCM_marbastlib-mx:SW_MX_1u	MX6
1	U	PCM_marbastlib-mx:SW_MX_1u	MX8
1	V	PCM_marbastlib-mx:SW_MX_1u	MX32
1	W	PCM_marbastlib-mx:SW_MX_1u	MX3
1	X	PCM_marbastlib-mx:SW_MX_1u	MX30
1	XC6206PxxxMR	Package_TO_SOT_SMD:SOT-23-3	U1
1	Y	PCM_marbastlib-mx:SW_MX_1u	MX7
1	Z	PCM_marbastlib-mx:SW_MX_1u	MX29

Questions

How big is the Twintail40 PCB?

It measures 265.9 × 75.4 mm and has 2 copper layers, 1.6 mm thick.

What parts does the Twintail40 use?

121 parts. The full list of its parts is on this page, with links to each part's symbol and footprint where PCBKit's library has them.

Where can I download the Twintail40 KiCad files?

From the TwintailDreamer/Twintail40 repository on GitHub, at the commit this page was made from: the board is pcb/Twintail40/Twintail40.kicad_pcb and its schematic pcb/Twintail40/Twintail40.kicad_sch. PCBKit opens the board in the browser, with nothing to install.

Can I use the Twintail40 design in my own project?

Its repository publishes it under the MIT licence: you may reuse it on that licence's terms (keep the author's notice, and for a copyleft licence share your changes alike).

Category and platform

Keyboards and input STM32

Project files

Show this board on your page

A live frame, for any web page

<iframe src="https://pcbkit.io/embed/boards/twintaildreamer-twintail40" title="Twintail40 in PCBKit" width="100%" height="480" style="border:0;border-radius:12px" allow="fullscreen" loading="lazy"></iframe>

A picture

<img src="https://pcbkit.io/embed/boards/twintaildreamer-twintail40.jpg" alt="Twintail40" width="1200" height="900">

A picture that opens the board, for a README

[![Twintail40](https://pcbkit.io/embed/boards/twintaildreamer-twintail40.jpg?size=s)](https://pcbkit.io/boards/twintaildreamer-twintail40)

Source

Repository: TwintailDreamer/Twintail40
Board file: pcb/Twintail40/Twintail40.kicad_pcb
Commit: 343c096
Licence: MIT

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