I am designing a PCB board, and it has lots of components on it. It has like 8 MOSFETs, diodes, fuses, current sensors, a STM32 and other components, and with an exception to a few (like mosfets and diodes) the datasheets don't include thermal resistance. To get to the point - I am getting concerned about if my PCB will get too hot, despite having more than appropriate trace specs (3oz copper rated for <20 C rise ). Is there a way to have a general heat sink that just sits on the board? Or am I better off selecting one components and attaching a heat sink to it? or sitting a heat sink on like a copper pad not connected to a component? And if I select a component, how do I decide which one?