Surface mount technology

[Dick.1]

I bought a kit of bits from fleabay to make a digi oscilloscope on a bit of a whim mainly because it was really cheap

When it arrived I was informed that it was upgraded F.O.C. to version 4K (whatever that meant)

Looking at the kit it means that I now have to solder about 10 of those miniature SM resistors that you can barely see & also a D.I.P. socket that doesn't seem too bad to do.

The rest of the parts are standard (although v small) with the main processor pre fitted.

Soldering these midget bits will be a good test to see if I can still hold an iron with a steady hand

Why o why do we buy these things

Dick

[AlanBeckett]

It's not too difficult.
I've got one of those 'On your Head' Magnifier' things.
Buy some Solder Paste in a Syringe. Put a dab on each Pad. Put the Component on the Pad and hold it down with a sharp Pointer - I use Tweezers.
Using a sharp Bit in your Soldering Iron to melt the Solder at each end.

Works OK.

Alan

[Murphyv310]

Hi.
That's the way to do it!!! It is a bit of a culture shock working with SMD if you've never done it before. Those headband magnifiers are the biz, if your long sighted get a pair that will allow you to wear your specs.
I did a lot of SMD work in Sony, we used liquid no clean flux and a tiny amount of solder on a very fine tip. Make sure your "board" is secure, there is nothing worse than it moving when trying to manipulate components or actually soldering.

[Mark Hennessy]

I've never found paste to be all that easy to use - plus it doesn't keep very long. Regular 60:40 solder, but the fine stuff, and a small conical tip works for me. You'll need a bit of desoldering braid to remove the excess, and liquid flux can help (clean it up afterwards - even the "no clean" stuff). Being able to see is the really critical part of the job - in addition to the earlier suggestions, those cheap plastic loupes are quite good for inspection afterwards. And USB microscopes can be good fun as well.

Lots of good videos on YouTube - there are many different approaches and it's fun to watch the experts at work. Ultimately, you'll develop your own way of working, so don't feel that you have to rigidly follow anyone else. Most importantly, don't be afraid of it - just give it a go.

[Dick.1]

Ah, so my favourite old copper chisel end "Tinmans" iron that I keep warm on the gas ring (that I use to warm up my cocoa amongst other things) might be a tad on the large side then ............

I'm on the lookout for some scrap boards with these on that I can practice on first as it's been a while since I worked on anything anywhere near this "small stuff"

Thanks for the encouragement folks

Dick.

[Mark Hennessy]

I'm on the lookout for some scrap boards with these on that I can practice on first as it's been a while since I worked on anything anywhere near this "small stuff"  

That's an excellent plan

On some boards, the components will be glued in place before wave soldering, so that makes removal difficult.

Others will have been soldered using "reflow", where the solder paste is applied to the pads, the components are placed on the board, and then the whole lot is put in an oven. It's fascinating to watch (check YouTube), as when the components are initially placed, they aren't done especially carefully. But as the solder melts, the components are brought into alignment by the surface tension of the molten solder. Magic!

Some folk have made their own reflow ovens using small toaster ovens and custom controllers. The hard bit is the "thermal profile", as the temperature has to be carefully regulated as it follows a carefully determined set of numbers during the process. Not something I've tried, but lots of info out there if you're curious...

"Reflow" obviously works best for boards that have the SMT parts on one side. Frequently, that is done first, with the SMT parts on the top of the board, and then the through-hole components are picked/placed and the board then goes for wave soldering.

So it's best to find a board like that, where there's no glue to get in the way...

[boater sam]

So my normal soldering method which I have used for 50 years needs updating?

40/60 wiping lead 1 lb bar.

Tallow and blacking paste

Mole skin

Max Sievert  blowlamp.

You live and learn.

[Murphyv310]

So my normal soldering method which I have used for 50 years needs updating?

40/60 wiping lead 1 lb bar.

Tallow and blacking paste

Mole skin

Max Sievert  blowlamp.

You live and learn.

Hi Sam.
You're reply made me laugh. The good old days to be sure.
Although I do SMD there's nowt wrong with fixing things the old way.

[Herald1360]

Max Sievert  blowlamp.

Would that be "The original and genuine Sievert Apparatus" by any chance?

I have a cane wrapped handle petrol one with the fuel tank stamped "For Benzoline". Works fine on unleaded now.