Boron nitride is an exciting thermally conductive, electrically insulative material. It is fibrous and highly anisotropic w.r.t. thermal conductivity. Thermal conductivity along the axis of the fibers is 400 W/m*K (gold = 315W/m*K). Perpendicular to the fibers, it is at least 2 orders of magnitude less. There are lots of research papers from China and South Korea related to using it as a filler for epoxy to improve its thermal conductivity, particularly for IC encapsulation. As an epoxy filler, it works well. As adjunct to aluminium oxide (Al2O3), it seems to work even better. The spherical particles of Al2O3 help align the BN particles to facilitate thermal conduction.

Does anyone here have experience with Arctic Silver BN-filled Al2O3 epoxy thermal epoxy?
(https://www.amazon.com/gp/product/B0009IQ1BU/ref=ox_sc_act_title_1?smid=AKFWYWVZ484P5&psc=1 )

The TDS claims a thermal conductivity of 4 W/m*K. That is quite high. I am interested in improving the thermal performance of an MSOP-10 package for charging a 1S Li-ion battery.
https://www.ledsupply.com/accessories/arctic-alumina-premium-thermal-adhesive

Edit: Corrected package name

 

We use Boron Nitride as a electrical insulator in plasma chambers. The high thermal conductivity extends the life of dielectric separators on the ends of arc chambers but this is under extreme conditions. No idea how well it will work as a thermal layer on a chip sized package.

https://www.nature.com/articles/s42005-019-0145-5