I'm looking at a PCI computer board, made to plug into the mainboard and be used to connect both SATA and IDE hard drives. Along side of that IDE connector, there are 42 teeny tiny parts in a row (surface mounted). These things are about the size of one quarter of the size of an average grain of rice. (about 1/8" x 1/16"). The spacing between them is less than 1/16".
Put it this way, if I held one of these parts in my fingers, it would possibly get lost in the flesh on a knuckle joint.
Using a magnifying glass as well as reading glasses, I was able to read the printing next to them. It appears all but two are resistors (R54, R55, R56....). Two began with a "C" so I would guess they are caps.
But that is just that side of the board. There are probably another 50 or so similar parts on the rest of the board, (more of them are caps). Then there is a large chip, about one inch in size, that has maybe 100 leads coming out of it (too small to count). And they are all soldered to the board and the spacing between them is not much thicker than a human hair.
Every one of those tiny parts are perfectly lined up. None are slightly on an angle or anything like that.
This has to all be done by machine. I cant see how any human could even lay those parts on the board with such precision, or even handle them without losing them all over the floor. What seems more amazing, I have to assume that there are caps and resistors that have different values. So the 1000 ohm and 47K resistors need to go in the right place as well as the .001 and .5 caps.
Then comes the soldering. That I cant even imagine how it's done, especially on that chip. If I attempted to solder that chip by hand, every lead along each side of it would be soldered together.
How the heck do they put these boards together? How are they soldered? How can a machine put the right value resistors in the right place, or for that matter, how does a human know which resistors or caps to put into some bin, when none have any color codes.
I dont think I could replace anything on that board. Maybe (big maybe) the 3 small electrolytic caps. And I suppose I could unsolder that IDE connector if I spent hours with solder wick to unsolder all 40 pins.
It's amazing how even a machine can work with such tiny components and get everything right.....
Then to take this one step further, how do they manufacture those tiny parts? What is there, one grain of carbon in each resistor? I wont even try to imagine how they layer the caps.... (And still get the right resistance and capitacance)...