In one of answers to the question What are the long term effects of Space Weathering on man-made materials? there is a link to Wikipedia article about Kapton. In this article mentioned that
NASA's New Horizons spacecraft used Kapton in an innovative "Thermos bottle" insulation design to keep the craft operating between 10–30 °C... The main body is covered in lightweight, gold-colored, multilayered thermal insulation which holds in heat from operating electronics to keep the spacecraft warm.
Also in article about New Horizons itself said that
To conserve heat and mass, spacecraft and instrument electronics are housed together in IEMs (integrated electronics modules).
So my question is:
Are these IEMs sealed, filled with some neutral gas (like nitrogen) and pressurized, with thermal exchange by means of this gas, or are all electronics inside IEMs in vacuum and, as mentioned above, thermal insulation reflects the heat towards IEMs?
I had read that one of the problems with some old Russian (Soviet) satellites was that their electronics were housed in such sealed and pressurized compartments, filled with nitrogen, with fans inside. If fans became inoperative, or nitrogen leaked out after several years due to non-100% sealing, a satellite would become inoperative too.