How a motherboard is builted...

A motherboard is a “printed circuit board” (PCB) with components soldered onto it. A printed circuit board is a piece of thin fiberglass with thin copper traces etched onto it. In the long-ago past, the components could be soldered onto the board using a soldering iron and manual assembly.
Except for hobbyists building things at home, that process is far too expensive at a factory level today.


The next innovation was wave soldering. The components are mounted on the printed circuit board and then the board is preheated. The board runs over a pool of rippling liquid solder and the components are soldered onto the board by the ripples.
But on a modern circuit board, the chips often have so many pins, and the parts are so small, and the parts often sit on both sides of the board (open up an old cell phone to see what I mean)… so wave soldering can’t be used. Instead, the components are all “surface mounted”. The chips use ball grid arrays (BGAs) and either an oven or hot air is used to melt the balls of solder.


A ball in a ball grid array is just a tiny ball of solder on the bottom of the chip.
If you place that chip on a printed circuit board and heat it, the balls melt and solder the chip to the board.