LM3481 FET heat dissipation

Hello,

I like to learn  a bit more on the heat dissipation of the FET using the LM3481 in Sepic mode. Although the setup seams to work ok, It seems my FET is getting too hot. In some cases it desolders itself from the board.

I have used different types of fets; some with higher, some with lower RDS-on. the one in at the moment has 0.005 RDS-on. 

Have used webench for the design. 8-35 Volts in. 24 Volts out at 1 Amp.

Is there any one I can discuss some pics from my scope with? 

kind regards,

Rob van vreden