In this case we can tell either how this sheet can help replace a burned transistor from a Audio amplifier box ; Whenever it's for guitar, Hi-def car sound or event sub-woofer they all uses 2n3055 a big one, some believing downing the heat out of coupling 2 TIP-122 to it ... True... Getting miniaturized by doing a trustworthy effort of coupling 4 or even 6 general appliance transistor, totally true too . If some had feared heat coming out of this the datasheet talk about thermal junction to case for all npn epitaxial and not the 2n3055, datasheet talk about max operating junction at 150 degree ; while epitaxial talk also about degree by watt for junction to case... Of cource all alone it does not burn it melt the epoxy case, semi-conductor get contact with air and change it ratio and die.
While coupling with 4 or 6 transistor home general appliance for general amplification the ratio is high in amplification and casing 3 set of 2 transistor 2n4401 , the first rank on side will not heat as center one where the contact are and you can be surprise it really decreasing heat... We only have these set of electronic since end of tube and starting from 1968 to 2015 we have only merged for bigger transistor and did not make a range toward expansion and serialization of the electronic we « Supposed have evolved at the speed of light », but it's brother of 2n4401, the on-surface MMBT4401 a SOT-23 can virtually flow at the surface of melted lead, and combination of lead-tin is a bit higher ; And working after you just take the spoon to take it and put it on your surface mount .
The answer toward not smelling the epoxy is around methyl-formaldehyde, a product used to make silicon resistant to heat glove or pan or even muffin-pan, so applying another process to turn a npn epitaxial into air resistant is our technology view-sight we suppose to had see at the speed of light...