# Heat Sink for SOT223

I am designing PCB a in which I am placing a BSP296 N-channel MOSFET, for switching solenoids:

• MOSFET supply voltage is 24V
• MOSFET max power dissipation is 1.8W
• Max operating temperature is 150°C.

I have done calculations as follows:

• My operating temperature = 100°C (not taking maximum, I need info about heat sinking)

• $R_{th} = \dfrac{(100°C -25°C)}{1.8W}$
• $R_{th} = \dfrac{75°C}{1.8W}$
• $R_{th} =41.6 °C/W$

I would like to know how to calculate how many ounces of copper I need, what area of copper and if I need a heat sink for this.