# How to calculate MOSFET temperature increase in PCB

I want to calculate MOSFET(DATASHEET) temperature increase for PCB.

MOSFET - FDD86250_F085-D

Totally 13 MOSFET's will be mounted in PCB. At the same time, maximum 8 MOSFET's will be used in PCB

1, Actual power dissipation for total MOSFET's?

2, Temperature increase in complete MOSFET(max. 8) in PCB?

3, Position of MOSFET's in PCB?

4, Will it require Heatsink?

PCB size is 90(L)*62(W) mm

From MOSFET Datasheet,

Maximum Power Dissipation 160W

Operating Junction Temperature Tj - 55 to 175 °C

Thermal Resistance, Junction to Case Rthj c 0.94°C/W

Thermal Resistance, Junction to Ambient Rthj a 40°C/W

• "heat dissipation" isn't the correct term, use: "Power dissipation" and "temperature increase". From the information you provide, nothing meaningful can be calculated. You need to mention the actual power dissipation (total or per MOSFET), not the maximum power dissipation. If all MOSFETs would continuously dissipate 160 W you'd need a really large heatsink (and possibly a fan) to keep the MOSFETs cool. – Bimpelrekkie Aug 12 '19 at 13:39
• What is your specific application? Is this pulsed power? Continuous? Are the devices paralleled? A schematic would be of great help here. – Peter Smith Aug 12 '19 at 14:32
• @PeterSmith I have added block diagram. Kindly help me to calculate power dissipation. – Kanaga Senthil Raja Aug 13 '19 at 1:59
• @Bimpelrekkie yes correct. I have updated. And I want to calculate total MOSFET temperature increase. – Kanaga Senthil Raja Aug 13 '19 at 2:00
• standard thickness PCB foil (1 ounce/foot^2) has thermal resistance of 70 degree Centigrade per watt, flowing from edge to edge of the square, for any size square. – analogsystemsrf Aug 13 '19 at 3:18