How do they solder these teeny tiny parts on the PCB?

Question

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)...

tabbypurr · Accepted Answer

the search term is 'surface mount' NT

Klaus Kragelund · Answer

Even the smallest machines can handle 0201: (0.25mm x 0.125mm)  Cheers Klaus

Rheilly Phoull · Answer

have you been stuck in a time warp or something ?? Hidden in the amazon for 30 years ?? Time traveller ??

tabbypurr · Answer

Even 30 years ago sm parts were being used. I can't remember if they were still using MELFs or had moved on to rectangular then. NT

John Larkin · Answer

This does it:  Solder paste stencil, dual-head reel-fed pick and place, reflow oven, clean things. This places about a part per second. The gatling-gun things are 6 or so per head. --  John Larkin         Highland Technology, Inc lunatic fringe electronics

John Larkin · Answer

This is pretty good:  There are lots of youtubes about SMT. --  John Larkin         Highland Technology, Inc lunatic fringe electronics

krw · Answer

Placing them by hand isn't too hard. I wouldn't want to do hundreds but replacing individual parts isn't hard. ...at least down to 0402, size.

Make them in sheets (wafers). Saw into individual dice.

Lasse Langwadt Christensen · Answer

Den tirsdag den 28. november 2017 kl. 17.37.14 UTC+1 skrev John Larkin:  must have taken a bit of work to get the control right to   move the pcb around that fast and accurate

John Larkin · Answer

Yes, but nothing like a wafer stepper/scanner, that manages multi-G accelerations with nm overlay accuracy. --  John Larkin         Highland Technology, Inc picosecond timing   precision measurement  jlarkin att highlandtechnology dott com

Tom Del Rosso · Answer

And it runs Windows 2000, the best (or least bad) OS Microsoft ever  made.

bill.sloman · Answer

On Wednesday, November 29, 2017 at 12:50:39 AM UTC+11,  wr ote: and IDE age ad 0 . 0 d ly en ve s. ll ? r ) E d y en  still using MELFs or had moved on to rectangular then. Thirty years ago is 1987. In 1988 I got stuck with introducing surface moun t parts at Cambridge Instruments in the UK. They were a low volume manufact urer - of the order of a hundred electron microscopes a year, and a bit slo w off the mark. I got stuck with the job because I had to use Gigabit Logic GaAs parts to g et the speed I needed, and they only came in surface-mount packages. The ne xt generation of electron microscopes (eventually sold as the S.420 and the  S.440 machines) used surface mount parts to cut manufacturing cost and boa rd area, but they didn't fix on surface mount early enough that I could pig gy-back on them. --  Bill Sloman, Sydney

How do they solder these teeny tiny parts on the PCB?

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