How to neatly solder (without loads of wires!) decoupling caps on SMT microcontrollers.

This instructable is written to teach you how to use a neat and tidy method of prototyping with SMT microcontrollers (or other devices) on an adaptor board.

After struggling to make a neat job of effectively decoupling the power pins on my PIC18F I decided something needed to be done!

This instructable shows what I did.....

This is my first instructable (I thought it was time to give something back!) so go easy on the comments ;-)

S.

The first picture (below) shows the completed board - looks neat (apart from the burnt flux!) doesn't it....read on!

Step 1 Lets begin...

The first step is to solder your device onto the adaptor board as can be seen in picture below.
I find that the best way to solder these fine (ish) pitch devices is to use plenty of good flux and some leaded solder (dont tell the environment though ;-) !).

Comments

[M4industries]

(removed by author or community request)

[TheWaddleWaaddle]

I hate to be the one correcting the Grammar Nazi, but your suggestion is incorrect. If you remove the parenthesized words, it spells the 100% gramatically accurate sentence of "How to neatly solder decoupling caps on SMT microcontrollers.", rather than your suggested "How to solder neatly decoupling caps on SMT microcontrollers.", unless he is using a special form of decoupling capacitors called "neatly's" which I have yet to hear about. You could also add the parenthesized words at the end of the sentence, which would read "How to neatly solder decoupling caps on SMT microcontrollers without loads of wires!", which is still 100% gramatically correct... Now I feel like the Grammar Nazi :-(

-TheWaddleWaaddle

[M4industries]

I posted this more than a year ago, and I have since then learned a bit more about grammar. I saw that I was wrong a little while ago, but never really cared to take the comment down.

[ciroman]

And thus you got owned for posting a comment before thinking it through. Good job.

[omnibot]

Good ible. Also I have the same multimeter.

[ste5442]

Thanks!
The DMM is actually pretty good for the price - DMMs are usually only used for indication only and not for accurate absolute measurements so I dont care if the measurement accuracy is 1% or 5%.
Ballpark is fine in most instances (for me anyhow!).

S.

PCBPolice

[omnibot]

Same here. Been thinking of getting something a bit better later on but currently it's all I need.

[rachel]

This is super clear about how... but as a fairly new electronics hobbyist, I'm not at all clear about Why. What's a decoupling capacitor and why do you need them on smd components?

[osgeld]

i suggest you read this

http://en.wikipedia.org/wiki/Decoupling_capacitor

it basically acts as a noise suppressor

[ste5442]

Eeeeeexactly ;-)

S.

PCBPolice

[Whatnot]

Copper tape eh, yeah I'll get some at the copper-tape emporium on the corner.

[ste5442]

Oh, but dont buy it from a garden centre - they charge a lot for it. Grab some from Farnell, RS, DigiKey etc ;-)

S.

PCBPolice

[ste5442]

Most garden centres sell it for the top of plantpots - apparently it keeps slugs off them!

S.

PCBPolice

[osgeld]

very handy trick, and it does look nice and neat thanks for sharing!

[ste5442]

Thanks Osgeld!

S.

PCBPolice

[ste5442]

Hi All,

Please note that although this method looks nice it does also have some advantages over wiring each decoupling capacitor seperately (which is what you have to do with these adaptor boards normally).
Using this method you obtain a nice low-impedance ground connection for your decoupling capacitance. If you were to use wires for each ground connection you are effectively adding inductance (and resistance) to the ground leg of each decoupling capacitor - this adds to the capacitor ESR and reduces its effectiveness.
Inadequate decoupling can cause all kinds of strange behaviour so when grounding decoupling capacitors its best to use nice, low impedance traces ;-)

S.

PCBPolice

[jeff-o]

Shame they didn't just slap a ground plane on the back of the PCB for this purpose! For an even more rugged solution you could glue a thin piece of PCB to the back instead of the copper foil.

[ste5442]

The cost saving from switching to a single sided copper PCB (with non-PTH's) from a double sided, PTH PCB means they can make the boards for much less than half the price. But yes, it would have been nice of them to do that ;-)

S.

PCBPolice

[jeff-o]

You forgot to mention that a decent soldering iron is also required. Something with a nice fine tip and ideally temperature control.

[ste5442]

I agree, a decent iron is something everyone (who is into electronics) should own. Many cheap irons are simply too hot and totally unusable with small surface mount devices.
To save your sanity and your components it is best to make the investment in a decent iron with a nice tip and at least some level of temp control.
A very capable iron can be bought for less than £100 or even less from eBay. Second hand irons from eBay should not be ruled out since you can always buy new tips - the heating element, PSU and handle are pretty rugged and should last well.
If your pockets are bulging with cash why not check out an iron from Metcal :-)

S.

PCBPolice

[jeff-o]

Mmmmm, Metcal are nice - we have them where I work. Also lots of nice Hakko stuff. I'm spoiled! All this nice stuff makes it hard to go back to my $40 Weller at home...

[osgeld]

we have Hakko's at work, i get home and look very mad at my radio shack el cheapo, hoping one day it will morph but after after a decade with that RS i can work some magic with it, but its still tricky

[ste5442]

Hi Jeff-o and Osgeld,

I know how you both feel - I have a cheap no-brand Maplin iron which was about £25. It does have a temp control but it ranges from 'blast furnace' to 'surface of the sun'! Also, nobody sells any small tips for it :-(
But....I do get by with it very well and regularly solder 0402 devices with it without any tears :-)

S.

PCBPolice