
Boron arsenide crystals can dissipate the heat generated in electronic devices - rbanffy
https://cacm.acm.org/news/229534-crystals-could-cool-down-your-future-electronic-devices/fulltext
======
strainer
"In the future, further studies which will enhance the growth of the crystal,
as well as explore potential large-scale applications"

Hinting at awesome GPU cooling and such, with not one mention of the materials
exceptional hazard.

Boron Arsenide

GHS Hazard Statements

H301 + H331 - Toxic if swallowed or if inhaled

H410 - Very toxic to aquatic life with long lasting effects. Safety
Precautions

P261 - Avoid breathing dust

P273 - Avoid release to the environment

P301 + P310 - If swallowed: Immediately call a Poison Center or
doctor/physician

P311 - Call a Poison Center or doctor/ physician

P501 - Dispose of contents/ container to an approved waste disposal plant.

[https://www.azom.com/article.aspx?ArticleID=8425](https://www.azom.com/article.aspx?ArticleID=8425)

~~~
mchannon
This material is hardly exceptionally dangerous. Its close cousin Gallium
Arsenide has been nearly the exclusive source of Yellow, Red, and Infrared
LED's since the 70's. The screen you're looking at now would not exist without
arsenide compounds, both for lights and for other circuit components.

While you could probably make yourself sick by taking old chips of this
nature, grinding them up, and inhaling or eating them, or engaging in an
accident with their raw materials during their manufacture, they rank pretty
low on the list in terms of practical toxicity. Arsenic is a common trace
element, and even (in small quantities) has been used to ward off disease in
chicken and cattle.

It's not good for you, but this is a positive development, not a poisonous
watershed.

~~~
strainer
If not limited to trace amounts for microscopic components, in the heat
spreading role there could be demand for it in much greater quantity than
elementally similar LED pigments.

Most manufacturing materials do not require such careful treatment and
disposable -thankfully. The concern is not just about unusual behavior such as
'grinding up and eating'. This is a particularly hazardous material - as
documented.

~~~
civilitty
You're exaggerating how dangerous BAs would be in this situation. As far as I
know, useful single crystal boron arsenide is very expensive to make in
industrial quantities and it's too brittle to be used as a large heatsink - at
best you can grow a several micron thick layer of it on a semi-flexible
substrate like for solar panels. Instead, I'm guessing their design uses small
quantities of single crystal BAs to interface between the wafer and the rest
of the chip package so it would better transfer heat from the internal silicon
to a regular heatsink. Thermal conductivity at that interface is a hard limit
to how fast the heatsink can draw heat from the chip package and since its
contained, toxicity is largely a concern for recycling.

~~~
strainer
Its a concern for manufacturing, containment and disposal. In few places
public disposal and recycling facilities guarantee complete compliance. The
materials hazard specs are not exaggerated, they are intended to be taken
seriously as they are stated.

"Instead, I'm guessing their design..." There were no designs indicated here,
only research on the crystals thermal properties with the vague mention of
"electronic cooling" and "potential large-scale applications"

~~~
mng2
Absolutely, arsenic-containing materials have the potential to be extremely
dangerous. Unscrupulous GaAs manufacturers have put their employees at risk in
the past.

[0]: [https://www.eastbayexpress.com/oakland/the-axt-
way/Content?o...](https://www.eastbayexpress.com/oakland/the-axt-
way/Content?oid=1073304)

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Scene_Cast2
The original article and the "full" article don't actually list any numbers.
Looks like the performance is 1000 ± 90 W/m/K [0]

For comparison, a traditional high-end thermal paste may have 10 W/m/K, a
liquid-metal thermal paste is up to 73 W/m/k [1]. Copper is 385, Aluminum is
200, Diamond is 1000.

[0]
[http://science.sciencemag.org/content/early/2018/07/03/scien...](http://science.sciencemag.org/content/early/2018/07/03/science.aat8982)
[1] [http://forum.notebookreview.com/threads/liquid-metal-
showdow...](http://forum.notebookreview.com/threads/liquid-metal-showdown-
thermal-grizzly-conductonaut-vs-cool-laboratory-liquid-ultra-pro.791489/) [2]
[http://hyperphysics.phy-
astr.gsu.edu/hbase/Tables/thrcn.html](http://hyperphysics.phy-
astr.gsu.edu/hbase/Tables/thrcn.html)

~~~
the8472
> Diamond is 1000.

The paper itself gives diamond as 2200 and isotopically pure diamond has even
higher conductivity.

The question is whether it's any easier to manufacture than a diamond layer.
Edit: The paper claims as much.

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dskhatri
There are interesting non-metallic materials already in large-scale production
which serve as excellent heat sinks and pipes. As an example, pyrolytic
graphite has a thermal conductivity several times greater than that of Cu:
[https://www.mouser.com/m_new/panasonic/panasonicthermalgraph...](https://www.mouser.com/m_new/panasonic/panasonicthermalgraphite/)

~~~
the8472
Heat sinks and pipes don't matter all that much since you can simply increase
the area to achieve higher conduction. The bottleneck is getting it from small
chip hotspots to the heat spreader on top of the chip. So this would sit as a
layer directly on top of the chip beneath the more conventional heat spreader.

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magicalhippo
So how would such crystals be used? Fairly large crystals as shims between the
tiny silicon chip and a larger heat spreader? Or lots of microscopic crystals
as part of a TIM paste?

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amelius
Does this mean we can now have fully 3-dimensional ICs? (I imagine with
stacked layers of silicon crystal).

