"Upside down" construction?

[hukka]

Would it be possible to have a Rock 5 variant built partially “upside down” on top of a heat sink?

Inspiration
Recently I bought a new router as part of upgrading my home network. The unit chosen is a Mikrotik RB5009 (the one without PoE out). The interesting part isn’t the performance or the size of the unit but rather how the router is constructed. The PCB is mounted to a large aluminium heat sink that also is the bottom of the case. The SoC and network chip are mounted on the underside of the PCB connected with thermal pads to the heat sink. A plastic top then covers the rest. The unit is so small that it is possible to have four of them in a 1U rack space, and still needs no fans at all.

Idea
My main computer since about a year back is a Rock 5B and it has served me well. Recently, I bought a second one because the household simply needed a backup computer. …so I know what the 5-series can do by now. In time I hope to add a third unit that will take on the server duties (storage, web, etc.).That third unit would be located by the router for obvious reasons. It will also need to be quiet.

The first thought was to contact Mikrotik to suggest they make a mini server in the RB5009 form factor, which I did, but then I thought of presenting the idea here too.

The idea is to have Rock 5-series hardware built with the SoC and memory on the underside of the PCB, attached with thermal pads to a heat sink that also is the bottom of the case. The GPIO and m.2 would be on top, accessible by removing the top cover. All sockets (HDMI, USB, µSD, etc.) would have to be on one edge of the unit.

Size
A suggestion is to have the unit sized for usage with something like the RB5009 series 1U brackets.That would allow the unit to be rack-mounted among routers and switches. Even without mixing with Mikrotik units there would be room for four servers in one 1U space. The size would allow for some extra volume to tinker with, like adding internal add-on boards. …or maybe front-loaded SSDs? The unit could be built so thin that the top of the Ethernet ports are cut out from the rest of the plastic cover.

Dream
As the idea is a combination of stuff from two companies, the logical dream scenario is a collaboration between the two – Radxa × Mikrotik.

Thank You for taking time.

[hukka]

Further Thoughts

• Ethernet
  Implementing PoE on the device could remove one DC power cable from the “rack spaghetti”. The 5-series hardare uses a 2.5Gbps connection which is fast enough for small workgroups and web servers. The device would only need one Ethernet port. Powering the unit with PoE would also make the use of the USB-c port easier. One such use case could be to add a second ethernet port via dock or adapter cable.

• Wifi and more
  The current Rock 5B+ has built-in 802.11ax (wifi6) hardware that could be used in this unit as well. An alternative would be to have an internal m.2 socket (like the Rock 5B), making it possible to use the unit with or without wifi and bluetooth. By having a m.2 socket, other forms of wireless communications could be supported (such as home automation or LoRa). Internal antennas could be used as the top cover would be plastic.

• Video out …and in
  Being placed in a rack probably means that the unit rarely would be used with dual displays. Removing one of the full-size HDMI out ports and instead having an easily accessible and full-sized port for HDMI-in might be attractive to users that do streaming or video editing. For those who require it, a second display could be connected to the USB-c port, directly or via a dock.

[hukka]

Photo shows a unit complete with a grey plastic top cover.
Note the cut-out for the ethernet ports.

Final thoughts

The latest SBCs seem to share the problem of sufficient cooling, especially if aiming for a passively cooled (fanless or silent) unit. Having a heat sink is the bare minimum nowadays. The router that inspires this thread adds the necessary heat sink and makes it larger than anticipated. The aluminium profile is cut big enough to become the sturdy bottom of the enclosure.

Even without adapting to a rack-mounted format, the idea is simple and quite logical. A zero-series form factor would be possible. If the design of the PCB is intended to put the hot components on the underside then both factory-supplied and aftermarket heat sinks would be feasible options. With some clever planning, one extruded aluminium profile could be used for products of different widths. The plastic covers could be availalble in different heights for additional HATs. …and they would be easy to 3D-print too, if needed.

Having a passively cooled solution that stretches the envelope a bit more, simply by being larger, makes SBCs with higher performance (while still being silent) a reality. Silent units are nothing less than a bliss for music and movie lovers, and Radxa’s produts are now powerful enough to satisfy most of the audiovisual needs that a modern household has. A larger heatsink would allow an even snappier experience without any extra noise.