CaptnDanLKW
Senior Member
TL;DR
Re-did the thermals on my two RT-AC86U with new Thermal Pads AND switch to Copper Pads for the CPU.
Temps dropped from 90-95c to 75-76c.
This is not a message to rehash the problems, perceived design defect or other opinions about the RT-AC86U.
I just wanted a guide like this so I didn't have to guess with parts and thicknesses.
Full details below.
I've had two RT-AC86Us for years & temps have slowly crept up. I Re-did the thermal pads (not well) a couple months ago, improved one slightly, made the other one worse. (Temps 100>, CPUs being shut down by kernel). So this was a FAIL.
I decided to re-do and do it right with properly cut and sized pads, switch to copper for the CPU, add some pads where I thought it made sense. I didn't know the exact thickness I would need for the copper pads, so I purchased a pack with 1.2mm, 0.8mm, 0.5mm, 0.3mm and 0.1mm.
Copper Pad dimensions - 15mm x 15mm. Thickness ended up being (1.5mm or 1.7mm)*
Thermal Pad thickness - 1.0mm, 1.5mm, 2.0mm
*Note - For the first device (the remote node), I went with a 1.2mm and a 0.5mm stacked combo. For the second one (Main router) I went with 1.2mm and 0.3mm, so a slightly thinner stacked combo.
I'm not sure which one performs better; I can't be sure since the remote node sits in a hot building that is regularly 75+ degrees and can peak in the 90s and I didn't test side by side in the same environment.
Also, not sure if the thicker combination is putting too much pressure on the die, or if the thinner combination is not putting enough.
The realization that a 1.2mm would slip down behind the RF shield, and the need to build up a perimeter added an unexpected beneficial side effect of being a potential buffer, spreading the load if in fact, it is too thick.
I've annotated Picture with letter for clarification.
Front Side
A) CPU - perimeter - Thermal Pad - NARROW SLICED 1.5mm
(This prevents the 1.2mm shim from sliding down into shield.)
(A single 1.5mm or 1.7mm would be thick enough not to slide behind it.)
(I think it also helps balance the pressure against the CPU die, so even a single copper slab this is a good idea.)
B) Radio #1 IC Front (Inside RF Shield) - Thermal Pad - 2.0mm
C) Radio #2 IC Front (Inside RF Shield) - Thermal Pad - 2.0mm
REF #1 - Arctic Silver 5 on CPU
REF #2 - Two copper pads with a blob or arctic silver 5 before they were pressed together.
Side Note:
D) CPU - Copper Pad - 1.2mm + 0.5mm CPU - Copper Pad Placement
Back Side
E) Flash IC - No Pads, For reference only. It's close to, and above, the CPU. Occasional flash errors could be a result of the excessive heat in this area.
F) Antenna Amp #3 - Thermal Pad - 1.5mm
G) Antenna Amp #2 - Thermal Pad - 1.5mm
H) Antenna Amp #1 - Thermal Pad - 1.5mm
I) CPU - Backside (On RF Shield) - Thermal Pad - 1.0mm
(This is my idea, not ASUS) - Extra thermal transfer to the back plate makes sense to me.
J) Radio #1 IC Back - Thermal Pad - 1.5mm
K) Radio #2 IC Back - Thermal Pad - 1.5mm
L) 2R2 Inductor - Thermal Pad - 1.0mm (Or was it 1.5mm? - Sorry, can't remember and don't have a pic. I think it was 1.0 because I remember switching to a thinner one after inspecting the contact pressure on Antenna Amp #1 "H" and noting it was not making contact.)
I think that should do it. I can only attach 5 files so no temp chart here.
Hope this helps someone out.
Re-did the thermals on my two RT-AC86U with new Thermal Pads AND switch to Copper Pads for the CPU.
Temps dropped from 90-95c to 75-76c.
This is not a message to rehash the problems, perceived design defect or other opinions about the RT-AC86U.
I just wanted a guide like this so I didn't have to guess with parts and thicknesses.
Full details below.
I've had two RT-AC86Us for years & temps have slowly crept up. I Re-did the thermal pads (not well) a couple months ago, improved one slightly, made the other one worse. (Temps 100>, CPUs being shut down by kernel). So this was a FAIL.
I decided to re-do and do it right with properly cut and sized pads, switch to copper for the CPU, add some pads where I thought it made sense. I didn't know the exact thickness I would need for the copper pads, so I purchased a pack with 1.2mm, 0.8mm, 0.5mm, 0.3mm and 0.1mm.
Copper Pad dimensions - 15mm x 15mm. Thickness ended up being (1.5mm or 1.7mm)*
Thermal Pad thickness - 1.0mm, 1.5mm, 2.0mm
*Note - For the first device (the remote node), I went with a 1.2mm and a 0.5mm stacked combo. For the second one (Main router) I went with 1.2mm and 0.3mm, so a slightly thinner stacked combo.
I'm not sure which one performs better; I can't be sure since the remote node sits in a hot building that is regularly 75+ degrees and can peak in the 90s and I didn't test side by side in the same environment.
Also, not sure if the thicker combination is putting too much pressure on the die, or if the thinner combination is not putting enough.
The realization that a 1.2mm would slip down behind the RF shield, and the need to build up a perimeter added an unexpected beneficial side effect of being a potential buffer, spreading the load if in fact, it is too thick.
I've annotated Picture with letter for clarification.
Front Side
A) CPU - perimeter - Thermal Pad - NARROW SLICED 1.5mm
(This prevents the 1.2mm shim from sliding down into shield.)
(A single 1.5mm or 1.7mm would be thick enough not to slide behind it.)
(I think it also helps balance the pressure against the CPU die, so even a single copper slab this is a good idea.)
B) Radio #1 IC Front (Inside RF Shield) - Thermal Pad - 2.0mm
C) Radio #2 IC Front (Inside RF Shield) - Thermal Pad - 2.0mm
REF #1 - Arctic Silver 5 on CPU
REF #2 - Two copper pads with a blob or arctic silver 5 before they were pressed together.
Side Note:
D) CPU - Copper Pad - 1.2mm + 0.5mm CPU - Copper Pad Placement
Back Side
E) Flash IC - No Pads, For reference only. It's close to, and above, the CPU. Occasional flash errors could be a result of the excessive heat in this area.
F) Antenna Amp #3 - Thermal Pad - 1.5mm
G) Antenna Amp #2 - Thermal Pad - 1.5mm
H) Antenna Amp #1 - Thermal Pad - 1.5mm
I) CPU - Backside (On RF Shield) - Thermal Pad - 1.0mm
(This is my idea, not ASUS) - Extra thermal transfer to the back plate makes sense to me.
J) Radio #1 IC Back - Thermal Pad - 1.5mm
K) Radio #2 IC Back - Thermal Pad - 1.5mm
L) 2R2 Inductor - Thermal Pad - 1.0mm (Or was it 1.5mm? - Sorry, can't remember and don't have a pic. I think it was 1.0 because I remember switching to a thinner one after inspecting the contact pressure on Antenna Amp #1 "H" and noting it was not making contact.)
I think that should do it. I can only attach 5 files so no temp chart here.
Hope this helps someone out.