..quoted from the Klondike thread:
-collecting numbers in this post here-
1) Junction to chippackage 0.001K/W
2) Solder layer between chippackage and board 0.01K/w
3) Board with 25 vias 3.8K/W
4) Thermal paste between board and aluminum 2.5K/W
Watercooling:
5a) X mm aluminum
6a) Aluminum to water
--> I'll simplify this to "T_alu = T_water"
7a) Radiator with/without fan to air 0.25K/W
Aircooling:
5b) Heatsink with/without fan to air 0.5K/W
2w per chip
5x5mm for 2) and 3)
somewhat larger area for 5a) 6a) and 5b)
This tutorial was posted earlier, it has almost all answers already:
http://www.electronics-cooling.com/2004/08/thermal-vias-a-packaging-engineers-best-friend/
1) Silicon to chippackage: 0.001K/W
2) As shown on the thermal imaging here:
https://bitcointalk.org/index.php?topic=190731.msg2043405;topicseen#msg2043405
I calculate with a delta of 7K between chip and board (62°C and 55°C respectively).
This assumes the soldering and boardsetup is comparable between Avalon and Klondike.
--> Nah, 3.5K/W is waay too high. The tutorial says 0.008K/W, 0.01K/W seems more realistic here. We don't use the length of the board for heat transportation, but the thickness!
3) 5x5mm area with 5x5 grid of vias, each 0.3mm diameter.
Bottom layer is 1 oz. copper
electronics-cooling says 3.8K/W with a 5x5 grid of vias (at 2mm spacing though, ignored)
4) https://en.wikipedia.org/wiki/Thermal_grease says 0.5K/W @ 12.6cm², which calculates to 2.5K/W for our 5x5mm area.
5b) I randomly found a value of 0.3K/W for a CPU-cooler with a fan. Let's calculate with 0.5K/W for our non-sophisticated DIY solution.
7a) Found 0.21..0.35K/W for a 12cm radiator. The larger the radiator, the wore heat gettin' rid of. I'll use 0.25K/W here, although this value is pretty random - can be reduced at will with more/larger radiator.
..I'll calculate a bit with those values later.
Ente
1) Junction to chippackage 0.001K/W
2) Solder layer between chippackage and board 0.01K/w
3) Board with 25 vias 3.8K/W
4) Thermal paste between board and aluminum 2.5K/W
Watercooling:
5a) X mm aluminum
6a) Aluminum to water
--> I'll simplify this to "T_alu = T_water"
7a) Radiator with/without fan to air 0.25K/W
Aircooling:
5b) Heatsink with/without fan to air 0.5K/W
2w per chip
5x5mm for 2) and 3)
somewhat larger area for 5a) 6a) and 5b)
This tutorial was posted earlier, it has almost all answers already:
http://www.electronics-cooling.com/2004/08/thermal-vias-a-packaging-engineers-best-friend/
1) Silicon to chippackage: 0.001K/W
2) As shown on the thermal imaging here:
https://bitcointalk.org/index.php?topic=190731.msg2043405;topicseen#msg2043405
I calculate with a delta of 7K between chip and board (62°C and 55°C respectively).
This assumes the soldering and boardsetup is comparable between Avalon and Klondike.
--> Nah, 3.5K/W is waay too high. The tutorial says 0.008K/W, 0.01K/W seems more realistic here. We don't use the length of the board for heat transportation, but the thickness!
3) 5x5mm area with 5x5 grid of vias, each 0.3mm diameter.
Bottom layer is 1 oz. copper
electronics-cooling says 3.8K/W with a 5x5 grid of vias (at 2mm spacing though, ignored)
4) https://en.wikipedia.org/wiki/Thermal_grease says 0.5K/W @ 12.6cm², which calculates to 2.5K/W for our 5x5mm area.
5b) I randomly found a value of 0.3K/W for a CPU-cooler with a fan. Let's calculate with 0.5K/W for our non-sophisticated DIY solution.
7a) Found 0.21..0.35K/W for a 12cm radiator. The larger the radiator, the wore heat gettin' rid of. I'll use 0.25K/W here, although this value is pretty random - can be reduced at will with more/larger radiator.
..I'll calculate a bit with those values later.
Ente
I am an engineer with a background in aerodynamics/fluids and am capable of performing Heat/CFD simulations. Is there any way I can contribute to the heat sink/dissipation design. I can't promise anything but I can try if I had more understanding of what the goals/design are.
Awesome! :-)
Quick question about watercooling:
How about building a simple aluminum "box" from 5mm aluminum, no fins or similar, and screwing the K16s on that? We could use both sides of the cooler and it would be pretty easy to build.
I guess even with a low waterstream it should cool the board enough?
Cooling the water with a big radiator and a fan, outside, 35°C outside-temp worstcase.
With a few dozen watt per 100cm² this should be a piece of cake for the actual cooler?
Your gut-feeling is enough for me now :-)
(Else we might migrate to the K16 DIY thread)
Ente
Edit: OK, I've seen a design similar to what you are talking about. So, these current designs are placing heatsinks/aluminum housing on the underside of the board... how is heat being conducted from the thermal pad on the chip, through the board, and to the heatsink/aluminum? If it is just silicon then there may be a conduction/heat-transfer issue. It seems that this QFN design isn't really made for external heat dissipation.
About silicon-to-heatsink: I collected some numbers here:
https://bitcointalk.org/index.php?topic=190731.msg2295823;topicseen#msg2295823
My conclusion is we'll be in the 10 to 15 degree ballpark, difference between junction and coolingmedium.
Yes, normally we want some turbulence in the water, for quick mixing of the fresh, cold water with the heatsink and warmer water.
In our setup, where we ultimately cool the water with room-temp air, I am sure there will be no thermal gradient over the whole setup at all! I.e. the water going into the heatsink and the water coming out will be the same temperature, in equilibrium. And with such low power over such a high area - I am sure such a minimalistic waterblock is enough. Having a potent enough radiator, with a strong enough fan, is a totally different story though ;-)
So. Who can tell me anything about running a bit of water over flat aluminum, which is heated with <50w per 100cm²?
Ente
So, my goal is to have an even easier build. Ideally from stock material, with "household machinery" needed only.
Any hints?
Ente
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