Gen7 Board 1.4
Gen7 Board v1.4 has received an enhancement while keeping the same PCB layout and is now superseded by Gen7 Board 1.4.1. The enhancement is a well researched, bigger MOSFET, making the heatsink obsolete.
Reason for the Bugfix Release
See Gen7 Research#Test_results. The numbers speak on their own, especially the ones in the second diagram (PWM at 76 Hz).
How to upgrade from v1.4 to v1.4.1
If your RepRap works fine and the heated bed MOSFET gets only moderately hot, there is no need to upgrade. If you're not that lucky, an upgrade means replacing the heated bed MOSFET with this part:
|MOSFET IRLB 8743||1||Q2||RS||Mouser|
To ease desoldering the previous one, cutting it at it's pins is a good idea, so you can unsolder each pin seperately. After that, solder the new one in and ... you're already done. There's no need to reconfigure your firmware or doing other fancy things.
MOSFETs are usually vastly oversized, as even big ones still come with a reasonable price tag. So the simple reason for the replacement is it's better reliability and the heatsink going away. Board space for future expansions!