I'm working on a new heat transfer idea for my future amp and I was wondering if anyone can help me with this.
In short, I want to get rid of everything I can, that sits between the heat source and the "heatsinkable" surfaces, on ALL sides of LM3875 except the one with leads. It doesn't matter if there will be voltages present on any of the exposed surfaces.
Can anyone suggest me how much can I lap off the chip before I risk damaging the internals? I would like to also remove the integrated heatsink too, if possible, and replace it with my "thing"
Please don't ask me why I want to do this, just help me if you can I promise to share my crazy solution on the forum if it works out
In short, I want to get rid of everything I can, that sits between the heat source and the "heatsinkable" surfaces, on ALL sides of LM3875 except the one with leads. It doesn't matter if there will be voltages present on any of the exposed surfaces.
Can anyone suggest me how much can I lap off the chip before I risk damaging the internals? I would like to also remove the integrated heatsink too, if possible, and replace it with my "thing"
Please don't ask me why I want to do this, just help me if you can
I promise to share my crazy solution on the forum if it works out Great idea, except:
mercury is toxic
mercury has an appreciable vapor pressure, especially when heated, so the container needs to be sealed
mercury dissolves some metals, like gold silver, and copper.
I would NOT try that!
-Charlie
phase transitions carry away heat more effectively - immerse in a FluorInert liquid that boils at the temp you want to hold the device to
I wouldn't cut any metal - there is some effort put into the design of chip bonding/transistion layers to prevent thermal cycling from fatigue cracking the bonding
I wouldn't cut any metal - there is some effort put into the design of chip bonding/transistion layers to prevent thermal cycling from fatigue cracking the bonding
This is a very good approach, except you will need to transfer the heat coming from the chip amp away from the fluid or it will all just boil away and there will be no more phase transition to take up heat. In that case, you are essentially describing something like a refrigeration cycle, although if you use a fluid that has a phase transition above room temp, you could do it passively.
-Charlie
Sorry but I don't see the point...
The manufacturers assemble the "die" onto the "cooling" surface contained in the package and this is where the majority of the heat is transfered to. You won't be able to remove it from this without destroying it. If you expose the die without damaging it, you won't be able to transfer any heat from it using conduction as you will damage the bonding wires which will likely corrode and fail.
Are you considering exceeding the rated dissipation of the package?
Frank
Thanks guys, you are giving me lots of new ideas
FluorInert is an interesting one - although it does have a number of really awkward disadvantages, which aren't advertised very widely:
- it dissolves many soft plastics and rubbers, including silicone
- due to its high dielectric strength, it accumulates static like mad - and as we all know, static anywhere near your hifi is a BAD thing
- it will be destroying ozone layer for tens, if not hundreds of years if it gets out, so must be used in a completely sealed system (which is kinda dificult to achieve with silicone and rubber seals eaten away lol)
- it's rather expensive...
After reading posts from jcx and frank1 I'm having second thoughts about the whole lapping thing actually. It seems like it would be a lot more difficult thing than taking the integrated heat-spreader off a Intel CPU (which I have done).
I have lapped about 0.5mm from the bottom and the top of the chip so far and I haven't even cut through the black plastic yet. I will probably lap a bit more anyway, just to see what's really inside my amplifier (maybe a little imp ).
FluorInert is an interesting one - although it does have a number of really awkward disadvantages, which aren't advertised very widely:
- it dissolves many soft plastics and rubbers, including silicone
- due to its high dielectric strength, it accumulates static like mad - and as we all know, static anywhere near your hifi is a BAD thing
- it will be destroying ozone layer for tens, if not hundreds of years if it gets out, so must be used in a completely sealed system (which is kinda dificult to achieve with silicone and rubber seals eaten away lol)
- it's rather expensive...
After reading posts from jcx and frank1 I'm having second thoughts about the whole lapping thing actually. It seems like it would be a lot more difficult thing than taking the integrated heat-spreader off a Intel CPU (which I have done).
I have lapped about 0.5mm from the bottom and the top of the chip so far and I haven't even cut through the black plastic yet. I will probably lap a bit more anyway, just to see what's really inside my amplifier (maybe a little imp
).Likewise, I also struggle to see the point.
My assumption is that you're trying to operate the device at a higher output power than it's rated to (thermally limited by).
But many other limits come into play usually well prior to thermal problems that invariably cause large distortion increases.
The answer usually would be just to parallel multiple devices and reap all the rewards associated with that (e.g. higher damping factor, higher current limits, etc.) And what's more, as well as being able to handle more heat dissipation, because the chips a physically separate objects, you can place them apart on a heatsink and get better heat spreading through the sink.
So...sorry, but I doubt this is one you're going to gain much from.
My assumption is that you're trying to operate the device at a higher output power than it's rated to (thermally limited by).
But many other limits come into play usually well prior to thermal problems that invariably cause large distortion increases.
The answer usually would be just to parallel multiple devices and reap all the rewards associated with that (e.g. higher damping factor, higher current limits, etc.) And what's more, as well as being able to handle more heat dissipation, because the chips a physically separate objects, you can place them apart on a heatsink and get better heat spreading through the sink.
So...sorry, but I doubt this is one you're going to gain much from.
Look at heat pipes, and get the heat away from the device efficiently.
ie Thermacore
Amec Thermasol :: Heat Management and Thermal Control Solutions
CRS Engineering - Heat Pipes & Heat Sinks Manufacturers
ie Thermacore
Amec Thermasol :: Heat Management and Thermal Control Solutions
CRS Engineering - Heat Pipes & Heat Sinks Manufacturers
A water cooler for CPU like "Cooler Master" etc will work very well, an advantage in using water cooled setup is your placement can be very flexi. You have only a coolant pipe coming out from behind the IC bend it any way you want. The radiator fan assembly can be placed anywhere.
Heat pipes though a good solution are often fixed geometry and have to be custom made or at least tubes have to be bent according to your placement requirements.
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A potential problem I see is that if you have multiple IC's then you'll need multiple water cooler as they are often designed only to cool the cpu and in some topend models the northbridge and the cpu .
I am noob in electronics but can a thermoelectric device (Temp. difference between two points of two different metals produces voltage) be applied to heatsinks ? Can the Voltage generated be utilized to light a bulb or power a preamp or charge a battery etc. ?
Regards.
If you want to try something with heat pipes, You can buy a "zalman hard drive cooler" which has a whole bunch of heat pipes which can easilly be bent how you want with a "bending spring" which is a spring just bigger than the diameter of the pipe, that stops the pipe from flattening when you bend it.
I used them for an external heatsink CPU case/cooler, and the load temperature on a 60w CPU was great with only 3 heat pipes.
I used them for an external heatsink CPU case/cooler, and the load temperature on a 60w CPU was great with only 3 heat pipes.
I never said it was my intention to dissipate as much power as possible, but to dissipate it as EFFICIENTLY as possible - which is a different story altogether
The objective I'm aiming for is a way of dissipating heat that:
- will not use any highly (electrically) conductive materials, to avoid unnecessary Eddy currents
- will not use any high dielectrics, because they accumulate static charge
- will have good vibrational properties, i.e. will shield the chip from outside vibrations, while allowing it to release its own vibrations freely (see 47 Laboratory philosophy)
- will be capable of maintaining constant low temperature of the chip (obviously)
This may seem like an impossible combination, but I believe it can be achieved. And I'll get a lot closer to that objective if I eliminate as much heat resistance as possible
That is actually a very interesting idea! I'll have to look into that further.
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I do PCB's for very (very) high reliability products, the variety of heat pipes etc (state change from liquid to vapour) are the most efficient way to remove heat from a device to an external heatsink. Especially where space is limited.
The other factors you metion such as eddy currents wont be a problem. Vibration control depends on the level of vibration encounted and the mounting methods of the device. For use in a static home envoironment this will be very little, and so some sort of compliant interface (Berquest thermal pads) would suffice. If its gonna encounter high vibration, plane, car etc then you have to engineer the solution depending on factors such as component positions, can it be bolted to the case etc etc.
The other factors you metion such as eddy currents wont be a problem. Vibration control depends on the level of vibration encounted and the mounting methods of the device. For use in a static home envoironment this will be very little, and so some sort of compliant interface (Berquest thermal pads) would suffice. If its gonna encounter high vibration, plane, car etc then you have to engineer the solution depending on factors such as component positions, can it be bolted to the case etc etc.
Of course you could investigate peltier devices as mentioned, how cost effective they are I dont know. They are less efficient than heat pipes, but do not rely on gravity as much. Unshure about how much electrical noise they generate.
Thermoelectric cooling - Wikipedia, the free encyclopedia
Thermoelectric cooling - Wikipedia, the free encyclopedia
If you want to cool all the sides you could try something like dipping the IC (or the whole PCB) inside mineral oil. I heard of people using it to cool overclocked PCs. Its non-conductive an much cheaper than Fluorinert. But it does have lower thermal conductivity. Here is a video of it being used to cool a PC.
YouTube - Building a Mineral Oil Cooled PC
YouTube - Building a Mineral Oil Cooled PC
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