The sound on these videos is fairly loud, as any manufacturing environment would be.
Printing paste - First, each board has solder paste applied so that parts placed by the machines will stick. The solder paste is like butter, and it just smeared on to all of the board's pads through a stencil cut specifically for that board.
Entering the machine and fiducials - The board enters the machine on a conveyor belt, and the machine uses a camera mounted on the head to look for fiducials (usually small gold dots) on the board to accurately identify the position of the board.
CP40 placing - The CP40, a six-head machine, placing parts. The red flash you see after the six parts are picked from the reels is when six individual cameras mounted on the head take a picture of the ends of the nozzles to see if parts were really picked up and to adjust rotation if the part got picked up a little crooked.
CP20 placing - The same thing but with the three-head CP20 machine.
CP40 BGA placement - BGA parts are balled on the bottom and have no legs. The fixed red light that you see flash is a fixed camera that takes a picture of the solder balls on the part to correct for rotation, and to make sure that no balls or missing (or bent or missing legs of ICs).
CP20 BGA placement - The same thing with the CP20 machine.
CP40 BGA inspection - The CP40 machine's camera's view as a BGA part is inspected.
BGA on X-ray - Since a soldered BGA part can't be inspected visually (as the solder joints are all covered by the part itself), it must be X-rayed to check for solder bridges or other nonconformities. This is the X-ray machine's view (it is a live, moving picture so it's great to put all kinds of things in the machine).
BGA to rework - If a BGA was placed wrong, such as this one, then it must be reworked.
BGA rework machine - Here is the board ready to be reworked, by using this machine which heats the board from below and also blows hot air around the specific part such as to not melt any surrounding solder.
LEDs going to feeders - Some parts are too big for the surface-mount machines, so we have a new through-hole placement machine. Here are LEDs that will be placed.
Feeders - A closer view of the parts going onto the chain.
LED placement - The chain runs around to the placement head, and in this machine the board moves under the fixed head. It is much louder than the other machines.
Wave machine - The LEDs and other parts with leads are soldered into place on a wave solder.
Wave soldering, soldering part 2 - A display board passing through the wave of solder.
