Electronic – What does the “MH1 – MH4” pin mean

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I am reading the Intel D1000 Reference Board Schematics. I see the following block:

enter image description here

I located the J8 chip on the physical board. But I only see PIN1~PIN20 marked on it.

So what does the MH1~MH4 mean? It seems MH1/3 and MH2/4 are connected, respectively.

ADD 1

Inspired by @bitsmack 's answer, I replaced my image to include more details.

Best Answer

I've never seen that prefix, but it is representing the mounting tabs (or pins, or clips, etc) for the header. The tabs are soldered to pads (or plated-thru-holes) on the PCB.

Sometimes the mounting features are only there for mechanical strength. In that case, they are soldered to the pcb but they don't need to connect to anything electrical.

Often, however, the tabs are connected to a metal chassis and also serve as EMI shielding. Then the pads (or holes) on the pcb should be connected to ground.

Look at these two pins on a USB connector. They are thicker than the others, and are also part of the metal chassis.

enter image description here

In your schematic, it appears that MH1/3 are connected and so are MH2/4, but this is just the way they were drawn. Each of these is connected to ground (the red triangle), so in reality they are all connected.

"Mounting Hole", perhaps? "Mounting Hardware"? "Header Mount"?

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