The ISO rating blindly assumes half a Volt drop over the switch, it gives 35W dissipation which at 33K/W equals 1155 deg. C above ambient.
It probably is a left-over from the time these smart switches had TO220 tabs, which would give realistic temps with good grease and an infinite heat sink.
The 17A are OK, 17Ax17Ax7.9mR=2.3W, and 2,3Wx33K/W = 75deg. above 85C ambient = 150C. (7.9mR is the Rds,on at 150C)
You could get away with a Copper heat slug below the D2PAK and a heat spreader/sink below that, if cool down time after the 10 second pulse is long enough.
Some board makers incorporate Copper "coins" in boards with holes the size of D2PAK tabs just for this purpose.
It probably is a left-over from the time these smart switches had TO220 tabs, which would give realistic temps with good grease and an infinite heat sink.
The 17A are OK, 17Ax17Ax7.9mR=2.3W, and 2,3Wx33K/W = 75deg. above 85C ambient = 150C. (7.9mR is the Rds,on at 150C)
You could get away with a Copper heat slug below the D2PAK and a heat spreader/sink below that, if cool down time after the 10 second pulse is long enough.
Some board makers incorporate Copper "coins" in boards with holes the size of D2PAK tabs just for this purpose.