Modular ITX/DTX/mATX/ATX/SSI-EEB/SSI-CEB/EATX/XL-ATX mainboard frame/tray

Introduction

This is a simple PC mainboard frame/tray system intended for open-air or custom enclosure PC builds. The intent is to support a broad variety of mainboards from iTX to so-called EATX with modules that fasten together with M4 nuts and bolts.

Version log

• v3.1 (2026-01-17)

  • M4 fastener holes increased from 4mm to 4.25mm diameter to ease fitment

  • add "I/O shield" text to indicate orientation of mainboard

  • added back single piece matx for larger printers like Core 1, P1S, U1, etc.

  • added 1.85mm "trimmed" versions of "EATX" parts to correct standoff locations for some boards

  • added fastening holes for upcoming I/O shield and PCIe card holder parts

• v3

  • matx1 piece adds a protrusion for an optional standoff location

  • itx and atx parts add optional standoff locations for SSI mainboards

  • re-uploaded files with “medium” detail level to reduce file size

• v2

  • added missing standoff hole on atx2

  • all standoff and frame holes same size

  • add 0.25mm filets to all edges

• v1.3

  • matx updated to be 4 pieces instead of 1 to print on smaller printers

• v1.2

  • added SSI mounting holes

  • recessed landing pads for frame mounting screws

  • added legible part name inscriptions

• v1.1

  • initial design concept

Required parts

mini-ITX/mini-DTX/ITX

• 1 part (itx.stl)

• 4 mainboard standoffs

• optional: 4 screws to secure frame to other components

DTX

• 2 parts (itx.stl & dtx.stl)

• 2 nuts/bolts + 4 washers to fasten parts together

• 4-6 mainboard standoffs

• optional: 4-6 screws to secure frame to other components

micro-ATX (mATX)

• 4 parts (itx.stl, dtx.stl, matx1.stl, matx2.stl)

• 4 nuts/bolts + 8 washers to fasten parts together

• 5-8 mainboard standoffs

• optional: 4-6 screws to secure frame to other components

micro-ATX (mATX)  alternate for larger printers

• 1 part (matx-full.stl)

• 5-8 mainboard standoffs

• optional: 4-6 screws to secure frame to other components

ATX

• 4 parts (itx.stl, dtx.stl, atx1.stl, atx2.stl)

• 5 nuts/bolts + 10 washers to fasten parts together

• 6-10 mainboard standoffs

• optional: 6-8 screws to secure frame to other components

EATX (SSI-CEB/SSI-EEB/XL-ATX)

• 6 parts (itx.stl, dtx.stl, atx1.stl, atx2.stl, eatx1.stl, eatx2.stl)

• 7 nuts/bolts + 14 washers to fasten parts together

• 8-15 mainboard standoffs

• optional: 8-12 screws to secure frame to other components

Fasteners

• M4 nuts, bolts, and washers to secure frame pieces together

• M3x6x6 mainboard standoffs and m3 screws to secure mainboard to frame

• When fastening the frame to a table or other components use washers to spread the load!

Exterior measurements of the parts

• itx: 170.330mm x 171.600mm

• dtx: 170.330 x 72.240

• matx1: 171.6 x 45.720

• matx2: 72.240 x 45.720

• matx-full: 216.050 x 243.840 (243.840 x 243.840 extended version)

• atx1: 134.470 x 171.600

• atx2: 134.470 x 45.720

• eatx1: 134.470 x 86.360 (134.470 x 84.5 trimmed version)

• eatx2: 170.330 x 86.360 (170.330 x 84.5 trimmed version)

Notes

• Accepts 6-32 and M3 motherboard standoffs. Holes are 3.25mm in diameter gradually tapering to ~2.3mm to grip the standoffs. This may be adjusted in future revisions.

• Extra holes are added to accommodate SSI-style boards in addition to ATX style boards

• 10mm z-height - combined with ~6mm high mainboard standoffs provides ample clearance for PCIe card tabs

• Can use a variety of fasteners to attach the frame parts together and/or secure the frame to a surface or custom chassis. Fasteners can be up to ~4mm in diameter. Washers should be used to spread the load against the plastic to avoid cracking

• PETG recommended for durability/flexibility, but PLA is OK. For environments where air temperature exceeds 60°C, ABS/ASA is probably a better long-term material.

• Most 3D-printed materials are non-conductive and can build-up static charge. I doubt its necessary, but to mitigate static, ~28awg wires terminated with spade connectors can be run between a few motherboard standoffs and then grounded to the power supply.

References for mainboard sizes and standoff locations

• https://web.archive.org/web/20160817033942/http://www.formfactors.org/developer/specs/atx2_1.pdf

• https://www.snia.org/sites/default/files/SSIF/2018-05-31/SSI%20EEB%202011%201.0.1.pdf

• https://digitallibrary.intel.com/content/dam/ccl/public/600565-btx-specification-update-rev1p1.pdf

• https://linustechtips.com/main/topic/812415-ee-atx-standoff-locations/ 

• https://www.gamersnexus.net/guides/3566-e-atx-is-a-lie-vs-xl-atx-eeb-ceb

• https://en.wikipedia.org/wiki/ATX#Variants

• https://hardwarecanucks.com/forum/threads/lets-go-team.12383/page-432#post-527475

• https://www.silverstonetek.com/it/tech-talk/wh11_008 

To-do

• Design add-on parts to hold a clip-on I/O shield and PCIe cards