Question about PCB

hello guys, i need to know please about these very small components of PCB http://www.talkingelectronics.com/projects/Testing%20Electronic%20Components/images/SMresistorsOnPCB.jpg

-i need to know what is the difference between these and the normal size components, is it just the size or there is another technical difference ? -and how are these soldered to the PCB ? -and is it a must to use these components in for commercial production or not ?

It's just the size, these are surface mount, and for large commercial products yes, you can get your size way smaller, the labor is way way cheaper as through hole usually uses a line of workers whereas SMD uses pick and place machines. They are also cheaper than through hole components.

They are usually soldered in a reflow machine using solder paste, look for dave jones's video on youtube that is a tour of a Chinese assembly line. You can solder them by hand if they are big enough and you can reflow for prototyping in a toaster oven.

aha great so it's just less place consuming right ? but i think what is expensive here is the machine that solder these kind of components isn't it ?

firashelou: aha great so it's just less place consuming right ? but i think what is expensive here is the machine that solder these kind of components isn't it ?

Well, yes but when you are making hundreds of a product you just send it off to a factory to do it.

XOIIO:

firashelou: aha great so it's just less place consuming right ? but i think what is expensive here is the machine that solder these kind of components isn't it ?

Well, yes but when you are making hundreds of a product you just send it off to a factory to do it.

yea or you have a factory :D

firashelou:

XOIIO:

firashelou: aha great so it's just less place consuming right ? but i think what is expensive here is the machine that solder these kind of components isn't it ?

Well, yes but when you are making hundreds of a product you just send it off to a factory to do it.

yea or you have a factory :D

Mike from mikeselectric stuff actually owns one though, not a super big one like the factories but still a damn nice unit, no idea on the price but it must have been a lot.

Its perfectly possible to pick-and-place by hand, there are jigs that make it easier (basically a vacuum nozzle on a cantilever with a rotation control. Solder paste is applied through a stencil, components placed, then the board heated to melt the solder.

Smaller components are not just smaller, they have lower power ratings (this often matters for resistors as through-hole resistors are usually 0.25W or 0.3W, but small surface mount are 0.1W or less. Conversely some surface mount components have more power dissipation rating than their through-hole counterparts as the copper on the board can be used as a heatsink (if there is enough area of copper).

Small components also have much less lead-inductance - for high frequency circuits this is a really big deal (chip capacitors were invented for precisely this reason).

For instance modern fast processors require dozens of small surface mount decoupling capacitors within a couple of mm of the package leads - through-hole capacitors would not work.

For a decent sized P&P machine think 50 -- 500k$

Larger surface mount discrete components (0805 and bigger) are not too difficult to place and solder, and for hobby builds, there is no need to use a pick and place machine. Soldering can be done effectively by hand and a fine tip soldering iron and fine solder, or by solder paste in a toaster oven as already stated.

aha ok then if i wasnt to see a video on youtube about placing these tiny components by hand, what exactly do i have to search for, i mean what do i type in the search to find something about it ?

and about the heat and melt, i don't understand is this in the process of the machinery or the placing by hand ?

Remember youtube is google-powered, just typing in "manual pick and place" works fine. Without a vacuum pick-up nozzle you have to use tweezers, but the various machines for manual P&P help productivity. Of course without a solder stencil you also have to manually place solder paste first.

The umbrella term for all of this is SMT (surface-mount technology).

and about the heat and melt, i don't understand is this in the process of the machinery or the placing by hand ?

toaster oven, hotplate, whatever, you'll see the temperature profiles for soldering on every datasheet. The whole board is cooked at once, that's the easy part.

there is another option of PCB : it's when we draw the pcb design in a software and go to a shop who has machinery and we ask for it to be printed then we solder normal size components by our hands, i guess that can be commercial too right ?

look what this guy did !! very clever http://www.youtube.com/watch?v=YhavXauuWqY