Fujitsu Could Help Smartphone Chips Run Cooler 51
angry tapir writes: If parts of your phone are sometimes too hot to handle, Fujitsu may have the answer: a thin heat pipe that can spread heat around mobile devices, reducing extremes of temperature. Fujitsu Laboratories created a heat pipe in the form of a loop that's less than 1mm thick. The device can transfer about 20W, about five times more heat than current thin heat pipes or thermal materials, the company said.
Re: (Score:3)
Re: (Score:3)
Normally current decreases as resistance increases. Why is chip power management different?
(no snark intended. I really want to know.)
Re:Waste of time (Score:5, Informative)
Because the parent got one word wrong. Typically resistance decreases as temperature increases in semiconductors, not the other way around. Metallic conductors behave in the opposite way.
Re: (Score:3)
Re: (Score:1)
An entirely different principle.
Re: (Score:2)
Rds increases as temperature increases in MOSFET's.
It's BJT's that decrease as temperature increases.
Re: (Score:2)
In undoped semiconductor resistance will usually decrease as temperature is raised because a higher temperature excites more electrons into the conduction band where they can carry current.
But for cases where there is already a lot of charge the opposite usually applies. In something like a MOSFET the electrons are supplied by the source contact or in a doped bulk semiconductor there will be lots of charge from dopants. In these cases increasing the temperature doesn't significantly increase the charge.
Re: (Score:2)
Re:Waste of time (Score:5, Informative)
You're thinking of resistance as a current-limiting mechanism, and you're absolutely correct in that respect. What happens, though, as the resistance of the signal path through a CPU increases, the switching current of the gates of the individual transistors in that data path also increases. This increase in switching current is greater than the current-limiting effect of the added resistance, increasing the over-all current draw of the chip.
That explanation is surely chock full of WTF-level inaccuracies, so don't quote me on that; standing by for correction.
Re: (Score:2)
Some of that is actually pretty okay, but the bit you're missing is that CMOS used in most microprocessors effectively draws no gate current. Sure you need to charge up the gate but that quantity is not appreciably related to the switching resistance beyond the fact that you want to switch a gate as fast as possible to minimise time in the active region.
Re: (Score:1)
The efficiency at UHF depends on other factors. The temperature coefficient of Rds or Vce(sat) isn't the issue.
What matters here is THERMAL resistance, or if you prefer, call it by the inverse, thermal conductivity. It's just about moving the heat around to get it out. Semiconductors fail when junction temperatures are too high.
Re: (Score:2)
Do that for the laptops as well (Score:2)
Re: (Score:2)
laptops and desktops don't have the space restrictions and hence heatpipes and many other cooling solutions are readily available and already in use.
Re: (Score:2)
They DO have space restrictions, just not as severe as those in a smartphone.
Interestingly, heatpipes in a laptop are a way to deal with the space restrictions - they allow a laptop to dissipate MUCH more heat in a smaller space.
With smartphones, they simply had to "dissipate less heat".
Although I question how much of a benefit this will really be. As it is, even without heatpipes, smartphone thermal throttles are usually set WELL below the CPU's junction temperature limit - the reason is that it's to prev
Re: (Score:2)
Re:Do that for the laptops as well (Score:4, Funny)
Nobody uses laptops and desktops! If you do, you're a dinosaur. Please die off already. A young hipster deserves to have your job, which you're so selfishly occupying.
Re: (Score:2)
Re: (Score:3)
"That would reduce the fans work (and their own heat!)"
Years ago, I bought a Shuttle barebones Pentium 4 with a heat pipe, hoping that it would be as quiet as the Mac Minis of the time. It was disappointing. It saved having separate CPU and PSU fans and it was a bit less noisy than the average beige box pc, but still very noticeable.
A problem with heat pipes is that they are not flexible, so the motherboard, case-mounted fan, and heat pipe must match exactly. Not so suitable for do-it-yourself pc building.
Re: (Score:2)
I bought a Shuttle barebones Pentium 4 with a heat pipe, hoping that it would be as quiet as the Mac Minis of the time. It was disappointing.
So I'm inclined to ask, what's the Mac Minis secret to be so silent?
Re: (Score:2)
Not using a Pentium 4, I guess.
My core i5-3350p has passive cooling.
Re: (Score:3)
So I'm inclined to ask, what's the Mac Minis secret to be so silent?
It's probably explained in some video with white background and soft piano music: "I saw my friend's PC. It was okay, but it wasn't exactly quiet. I asked myself, how could that be improved. I wanted it to be whisper quiet. I knew it was okay to ask more. And that's where the story of the new cooling system of Mac Mini begins. The iCool."
In practice: some buzzy 40 mm radial fan with the text "O.E.M." silkscreened onto it, accompanied with thick layer of the most crusty thermal compound found in the market.
Re: (Score:2)
"Mac Minis of the time".
Which in the P4 era (mid 2000s), would have been powered by motorola PowerPC chips as used in mac laptops.
Re: (Score:2)
Years ago, I bought a Shuttle barebones Pentium 4 with a heat pipe, hoping that it would be as quiet as the Mac Minis of the time. It was disappointing. It saved having separate CPU and PSU fans and it was a bit less noisy than the average beige box pc, but still very noticeable.
Nah, there are other reasons to use a heat pipe. I've got a $20 cooler master cooler with three heat pipes in it, and a big upright heat sink with a big fan on it. The heat sinks carry the heat up to the big fan where it can be efficiently removed.
I may also try a peltier cooler, I just broke down three peltier refrigerator coolers. THAT would allow me to eliminate a fan, so long as I redesign case airflow to go over the heat sink.
1 mm is a lot (Score:1)
Plenty of phones sub-10mm today. 1mm is not an insignificant piece of the thickness budget.
Wrong reason they'll use it. (Score:2)
This won't make your phone cooler; the manufacturers will just push their chips harder for the same temperature.
Re: (Score:2)
Re: (Score:2)
Yeah. Lots of people rave about spec e-peen, but the truth is, even older chips are MORE than powerful enough to provide a good experience except for the niche things like hardcore gaming.
Interestingly, for hardcore gaming, NVidia gave up on the phone form factor. The SHIELD Portable's form factor allowed it to have active cooling for the Tegra4, and the SHIELD Tablet has a phase change heat spreader (aka heatpipe) over its CPU - a predecessor to this stuff Fujitsu is working on.
For nearly all smartphone u
Re: (Score:2)
This won't make your phone cooler; the manufacturers will just push their chips harder for the same temperature.
"Push the chips harder" = "Empty the battery quicker".
Transfer the heat to.... where? (Score:2)
In a laptop, the use of similar devices makes sense, as the heat can be transferred
somewhere where it can be dissipated into the air. Unfortunately it's more efficient
to transfer it to the table you have it on, so the bottom gets the heatsink which
makes it horrible to actually put your laptop on your lap-top.
In a smartphone, it's being held in your hand (on the back) and up to your face (on
the front) with fingers on the sides. Where to exactly are they going to move the
heat??? Heat exchanging is nothing
Re: (Score:2)
In a laptop, the use of similar devices makes sense, as the heat can be transferred
somewhere where it can be dissipated into the air. Unfortunately it's more efficient
to transfer it to the table you have it on, so the bottom gets the heatsink which
makes it horrible to actually put your laptop on your lap-top.
Can you mention one laptop that uses the bottom as a heatsink by design? Hint: there is none.
In real notebook computers the heat is transferred using heatpipes to one or two heatsinks and then transferred to air using fan(s). The heat leakage to the casing is in most cases an unavoidable misfeature - though Apple did/do(?) use the casing as a heatsink in order to avoid spinning up the fans.
In a smartphone, it's being held in your hand (on the back) and up to your face (on
the front) with fingers on the sides. Where to exactly are they going to move the
heat??? Heat exchanging is nothing new, but the ability to remove heat requires
the device interact with a cooler medium to transfer that heat. Normally that's
your palm, or the air, or both.
So... I ask again... transfer the heat to where?
E
The (metal) casing. The power consumption in a phone is much lower than a notebook computer so it is a valid design.
Rem
Re: (Score:2)
It depends what you mean by "by design" is :)
Air is a great insulator, but poor conductor of heat.
My familiarity is with generatios of Dell laptops that exchange more heat through the bottom of the case they do they through venting to the air. Their support system even ensures you tell them if you're using your laptop "on a solid hard surface".
FYI 100C is higher than most hardware's failure point.
I know you want links. I'm off to bed. Google is that way --> Lazy is that way ---, and links are found
Re: (Score:1)
Re: (Score:2)
Lower Power Chips (Score:1)