"... the screw from the mosfet will not fit into the heat sink." In other words how is the alignment of the mounting holes in the device tab and in the heatsink specified and controlled during assembly? Two more questions should be how have you identified and specified: 1. any insulating thermal pads and; 2. insulating mounting bushes; if the device tab is to electrically isolated from the heatsink.

Hello Please check the datasheet for both the heat-sink and the Mosfet, then take the necessary measures in your design to keep them aligned in a way to get the screw from the Mosfet aligned with the screw hole of the heatsink, most likely about to make the right measures and the our Assembly will follow your settings. you can verify your deign using the 3D view as well.

@JLCPCBsupport, The X and Y positioning of both the heatsink and the device are easy to define. It is also easy to define Z axis position of the heatsink mounting hole because it is specified in the datasheet for the heatsink and it is mounted directly onto the board. It is the Z axis position of the hole in the device tab that is harder to control. How can the user specify the Z axis position of the hole in the device tab when there is no Z axis reference point on the device other than the hole itself? The Z axis position of the hole in the tab depends on how far into the board the pins on the device are pushed. The user has no control over this because it depends on the operator who hand assembles the device onto the board. So how is the Z axis position of the hole in the tab controlled with respect to the Z axis position of the hole in the heatsink during assembly?

@JLCPCBsupport, Also: How is the position of the mica washer or thermal pad to insulate the tab from the heatsink specified and controlled during assembly? How is the placement of the insulating bush to insulate the mounting both from the tab specified and controlled during assembly? How are the mounting bolt, washer and nut and tightening torque be applied specified? EasyEDA has no mechanism to specify the assembly details of these parts so how is all this information passed from the user to the operator who does the hand assembly of these parts?