Whose gonna pull the trigger on beryllium oxide mounting packages first?
Its the holy grail of having thermal conductivity somewhere between aluminum and copper, while being as electrically insulating as ceramic. You can put the silicon die directly on it.
Problem is that the dust from it is terrifyingly toxic, but in it's finished form it's "safe to handle".
> Whose gonna pull the trigger on beryllium oxide mounting packages first?
Nobody, presumably :)
Why mess with BeO when there is AlN, with higher thermal conductivity, no supply limitations and no toxicity?
Edit: I've just checked, practically available AlN substrates still seem to lag behind BeO in terms of thermal conductivity.
https://en.wikipedia.org/wiki/Aluminium_nitride For anyone else who wasn't familiar with the compound.
""" Aluminium nitride (AlN) is a solid nitride of aluminium. It has a high thermal conductivity of up to 321 W/(m·K)[5] and is an electrical insulator. Its wurtzite phase (w-AlN) has a band gap of ~6 eV at room temperature and has a potential application in optoelectronics operating at deep ultraviolet frequencies.
...
Manufacture
AlN is synthesized by the carbothermal reduction of aluminium oxide in the presence of gaseous nitrogen or ammonia or by direct nitridation of aluminium.[22] The use of sintering aids, such as Y2O3 or CaO, and hot pressing is required to produce a dense technical-grade material.[citation needed] Applications
Epitaxially grown thin film crystalline aluminium nitride is used for surface acoustic wave sensors (SAWs) deposited on silicon wafers because of AlN's piezoelectric properties. Recent advancements in material science have permitted the deposition of piezoelectric AlN films on polymeric substrates, thus enabling the development of flexible SAW devices.[23] One application is an RF filter, widely used in mobile phones,[24] which is called a thin-film bulk acoustic resonator (FBAR). This is a MEMS device that uses aluminium nitride sandwiched between two metal layers.[25] """
Speculation: it's present use suggests that at commercially viable quantities it might be challenging to use as a thermal interface compound. I've also never previously considered the capacitive properties of packaging components and realize of course that's required. Use of Al O as a heat conductor is so far outside of my expertise...
Could a materials expert elaborate how viable / expensive this compound is for the rest of us?
I'm not much of an expert, but maybe this can be useful: AlN is a somewhat widely used insulating substrate that is chosen where sapphire is insufficient (~40 W/mK), but BeO (~300 W/mK) is too expensive or toxic. The intrinsic conductivity of single-crystal AlN is very high (~320 W/mK), but the material is extremely difficult to grow into large single crystals, so sintered substrates are used instead. This reduces thermal conductivity to 170-230 W/mK depending on grade. Can't comment on pricing though.
I think diamond is even more thermally conductive than either. A quick google finds a number of companies working on silicon-on-diamond.
Most packages with beryllium oxide have been abandoned long ago, beryllia being replaced with aluminum nitride.
Because aluminum nitride is not as good as beryllia, packages with beryllia have survived for some special applications, like military, aerospace or transistors for high-power radio transmitters.
Those packages are not dangerous, unless someone attempts to grind them, but their high price (caused by the difficult manufacturing techniques required to avoid health risks, and also by the rarity of beryllium) discourages their use in any other domains.
> Problem is that the dust from it is terrifyingly toxic, but in it's finished form it's "safe to handle".
Doesn't that mean it would be problematic for electronics recycling?
I don't think toxicity levels on compounds used in electronics has even been a stopper for furthering humanity
I know it is an hyperbole. First thing I thought was: Cadmium, Mercury, Lead and CFC. I was slightly annoyed about Cd and Hg
Or getting berylliosis from putting a drill through your electronic device before throwing it out
Won't you have conductivity issues if the oxide layer is damaged?