LOL! What was I thinking?

[DZ]

Oh, and solder paste you can get cheap on dealextreme...

Wow, that is cheap! Thanks tocket, just ordered some of it!

Thanks for the link Troy, I went through the way the solder soic parts, it looks simple enough, I'd hate to get the wick stuck though!

[chad]

If i make a suggestion. If you are planning on doing more surface mount you have to get one of these, a hot air rework station, it changed my world.

http://madelltech.com/m3.html

Surface mount is so easy with it.
You need to get one of those $45 kestler syringes, don't worry it will last you years, Going on 4 for mine. Then just squeeze a little blob on each pad, place the components, fire up the hot air and wave it over the parts. You don't need to be too acurate with the parts placement. With the hot air both sides of the part will melt and the part will auto center itself from the surface tention of the solder. Really cool first time I saw it.
If you are doing one or two it isn't worth it but if you are doing any quanity you will thank yourself later.

chad

[mixedgas]

you know you can have a stencil made to put the solder down cheaply, and then another low cost high temperature rubber one that positions the parts, right?

Then go over to sparkfun.com and get a toaster controller.

I made the mistake a while back of ordering 680 pf SM caps, I can just see them without a microscope. I thus share your pain.

Steve

[Things]

Ive had to solder one of those before, it was my first SMT soldering!

It was actually quite easy. Tin the pad with abit of solder first, get some tweezers, and hold it in place, tack the tab on the side you tinned with solder, and then you can let go of the component, solder the other side (Quickly, since they are soo small they cant heat up and melt the other solder very quickly) and your done!

I personally dont like the idea of toasting circuit board either, especially with components that can be soldered with a regular soldering iron.

[Pitts]

Interesting isn't it.
A lot of my daily work involves SMT of this size.
WE do use magnfying glasses and microscopes.. helps a lot at my age.
Regularly do 100+pin Ic's.

I have found there are few key things...

First, middle and last is CLEAN CLEAN CLEAN.....

Make sure your PCB is clean, if its a re-work real important.
Use solder wick (under one of its many names, one of the best is SoderWick)... its like a braiding comes in different sizes. About 2 - 3mm is fine for mosr SMT stuff.
You can also use this to pre-clean the pads Tin and remove excess.

Clean pcb with ISA first...

Carefully align onto pads and tack down in a couple of corners.

When you get good at it you can get a "blob" of solder running along and if you use liquid flux (NOT plumbing liquid flux (like Duzzal.. bad bad bad its an acid) .. don't laugh I have seen it done) prior to starting you won't even need to mop it up with solderwick.

Luckily I have the Haako hot air soldering tool as well and this is very good for a reflow and "tidy Up" if needed.

Be careful with SMT 's they can fool you it looks OK but the pads / feet are not soldered but look like they are. That's where the reflow idea works.

Believe ot or not pissing about with a smaller iron and "hanging in there" will do far more damage to the PCB than using a suitable iron with plenty of heat and "get on wth it"...
Its like watching the guy who plasters your ceiling he makes it look so easy and fast then you have a go and you piss about and piss about until its a real mess, well I do anyway. soldering smt is like that

Then after clean again...
so..
Clean the PCB
Clean the pads
Clean the soldering iron tip (water on a sponge not isa)
Apply the flux to the pads
Position the IC (or whatever)
Apply the flux again over legs this time lightly.
Tack down the corners lightly ensure pads / legs are lined up.
Get the small solder ball rolling (takes practise)
Tidy up any bridges. Remove any blobs (shouldnt be any if you did it right.)
Clean again with isa
Check carefully all pads and legs look nice and shiny not dull, crinkly or flat.

Your done.

Just some thoughts....

Used to do about 20+cell phones a day most needing this process.

Cheers

Ray

[heroic]

Interesting isn't it.
A lot of my daily work involves SMT of this size.

So does mine, and that was good advice, but there's another obvious one that people always seem to forget:

Wet your sponge! Use it regularly!

That sponge in the soldering iron stand is there for a reason. Keep it moist and dip yer bit in it. The bit should be shiny and clean when you apply solder (or paste) to it, otherwise all the activity of your flux is going to clean the iron, not to flow your joints!

[The_Doctor]

Not much I can add, but just a bit..
Like Pitts said, apply lots of heat fast, not a little, slowly. A fine tipped conical bit and some hair-fine solder is good for discrete connections, but here's my method for pin rows on IC's. This works for the finest spacing existing, so long as you actually HAVE leads that stick out for easy access. (Some IC's don't, and I won't even go there). I use a standard iron and bit (2 mm 'pencil' tip) and standard solder (rosin flux, NOT 'no-clean' or 'crystal'). That's it. But there IS a difference in use. I first line up the IC extremely carefully with a dab of solder in diagonally opposing corners to lock it down, and redo each if and as needed to get really tidy alignment as seen by lamp and magnifier. Measure thrice and cut once. When it's perfect I run a generous run of solder joining all pins on each row. Then I hold the board up, so that the rows are on the underside of a steep slope, and I tap excess solder off the bit into a tin can, then run the bit from the highest pin, slowly and smoothly down the row, watching as each pin appears bright and clean and isolated from those that are below it. Sometimes I have to tap off the solder collected on the bit mid-row. Sometimes the lowest two pins won't separate well and need a tiny bit of removal by wick, which I do by heating them (board is flat and upright now), then nudging the end of the braid up to the pair or trio of joined pins, and drawing it away just before removing the iron. This sounds fiddlier than it is, and gets way better joins than having to wick the lot, and it's faster. Gravity and heat together leave an ideal fillet with strong joins. Wicking all of them on the very fine pitches is an almost guaranteed recipe for dry joints and tiny splinters of copper caught between them. I tried all sorts of methods before I worked this out. I was getting returned jobs that had gone bad soon after use, and that stopped happening once I perfected this method.

Another thing I do after cleaning a new etched board is to wipe it with rosin flux diluted with IPA. This keeps it free of oxide, helps soldering, and helps retain parts in place while soldering.


Re wet sponges, I agree they do important things, but, I find a light brisk wipe on my jeans is even better. Doesn't cool the tip, and doesn't leave spidery strands of un fluxed solder on the edge of the tip.

The main flaw in my method is the tapping of solder off the tip. I use the edge of a tin can. Ideally, to protect the iron while still allowing this to hurl solder efficiently off the tip into the can, I ought to get a silicone cable sheath slit lengthwise and tucked over the rim to form a protective edge, but I never get round to it, I never have that silicone covered flex around except for special tasks.

[DZ]

Cool, thanks for all the tips guys. I've been soldering pin thru hole components since I was kid, I've desoldered some SMT stuff, but this is going to be my first at building something with SMT. I'm looking forward to the learning experience.

What do you guys think of this: http://www.engadget.com/2006/03/07/h...soldering-iron

[drlava]

Here's another tip: forget the $45 digikey stuff and get this:
http://www.dealextreme.com/details.dx/sku.7952
Keep it refrigerated, warm it to room temp for working, keep it in a syringe with a blunted needle/cannula for application. Solder smt like a pro!
You think that cap is small, try 0402 sizes

[DZ]

Here's another tip: forget the $45 digikey stuff and get this:
http://www.dealextreme.com/details.dx/sku.7952
Keep it refrigerated, warm it to room temp for working, keep it in a syringe with a blunted needle/cannula for application. Solder smt like a pro!
You think that cap is small, try 0402 sizes

Hey drlava, how does that paste compair to what tocket recommended? http://www.dealextreme.com/details.dx/sku.4711 About the same?

0402! Sheesh, I think 0805 is small enough for me! Thankfully 0805 is the smallest part on the board, though there are 12 of them per board. The rest of the parts are 1206 or larger which looks a little more manageable.