to help improve the thermal stabilty of OpenWrt/Lede loaded routers, I have been modding some of the hotspot chips with Ceramic heatsinks.
Ceramic heatsinks function the same as regular metal heatsinks except they are made from ceramic compounds, like Aluminium Oxide.
Ceramic heatsinks have three major advantages; their thermal performance exceeds that of aluminium and copper, they are not electrically conductive and are almost invisible to microwave wavelengths.
Metallic heatsinks deployed inside a wireless router can suffer the dreaded Antenna Effect, a combination of parasitic reflections and oscillations that degrade or even destroy wireless performance. Ceramic heatsinks can be stuck inside a wifi router in close proximity to PCB aerial tracks, and even direcly onto a wifi SoC.
The only downside of ceramic heatsinks is their relative high price when compared to aluminium, but this is ofset by their high thermal performance and physical robustness; they fail at 1200C - by which time your over-clocked Zyxel is a pile of white ash
Below shows a ceramic heatsink deployed inside a TPLINK-710N-V2 on top of the Qualcomm Atheros AR9331 SoC. Wifi performance is unaffected.
Below a ceramic heatsink deployed inside a BT Homehub 5A (HH5A). This one is calming the Lantiq XWAY VRX208 DSL chip. A notorious hotspot often 40C over ambient; even at idle with the DSL_CONTROL disabled. Mounted sideways, the fins add a significant surface area for convection.
Both these heatsinks are 12mm square and 10mm high, and are manufactured by Spreadfast. These devices have fins, but ceramic heatsinks using microporous technology can be flat and just 3mm high.
Anyone else had experiences using ceramic heatsinks on their OpenWrt/Lede projects?
High geek factor. I once wanted to remove an existing heatsink but the glue was too strong and I ripped the whole chip. I should have used some heat but perhaps dependable on the used glue. Now I am too old for that type of stuff :- )
You really don't need a heatsink on an AR9331. It's one of the coolest running chips out there. The whole WR710 router runs on about 1 watt from the DC input, a considerable amount of that being dissipated in the voltage regulator and the RAM chip. The power adapters they send with them are vastly oversized.
@gwlim My white coloured heatsinks are manufactured by Spreadfast and were supplied through RS Components UK - Another readily available heatsink range is manufactured by Amec-Thermasol. Check out Farnell, DigiKey and eBay.
Note: most heatsinks do not come with any form of adhesive. You can use a thermal epoxy, but I use the thin heatsink adhesive tape from 3M - the stuff that sticks third party heatsinks to GPUs. Once you have this tape on the heatsink, attaching the heatsink to the chip is straightforward; The adhesive is veryvery sticky, and will hold a heatsink in place upside down. Line up the two parts, you'll get only one clear shot.
@mk24 I agree the AR9331 is a cool operator. Remarkably so considering what it does. The mission of this project is to improve reliability and device lifespan, especially in ambiently hot environments. Consider all of those vanilla domestic routers; people never notice random reboots on a summer day, but there is nothing domestic about what we expect from our OpenWrt/Lede routers.
@savostyanov On my sample board, my not-so scientific measurement using an infrared thermometer suggested the DSL chip was 62C with ambient at 22C. It was certainly too hot to touch!! After fitting the heatsink, this was down to a typical 45C.
I wonder if the temperature spike is similar on Fritzboxes using this Lantiq chipset? btw inside the recent BT Homehub 6 is one very large heatsink covering all the Broadcom chips. So the designers must have had a heat issue
@Blue Sky - That depends on how many you buy and from whome. On eBay there's sellers wanting € / $ 4 for a similar heatsink, but most of this price is the postage. For small quantities (5 to 10 unit), a realistic price would be nearer to € / $ 2 each.
FYI The one stuck to the AR9331 is a 12x12x10mm Spreadfast device SF-CHS-121210P >> RS Components code 123-5616
I Put a 1inch by 1 inch aluminum heatsink with 7fins on my Ethernet hub's SoC it's a D link DGS-1005D and since it is a Ethernet connection and not a WiFi hub, the aluminum heatsink would not cause the "Antenna Effect"
