My First: Surface Mount!

[iamdarkyoshi]

I bought 50$ of soldering supplies. An old used digital iron, multicore desoldering braid and solder, electrolube flux and thats it. My first job was a repair of a 6ch. reciever that uses surface mount class D amplifiers. It has a 0.65mm pin pitch and it worked on the first try! Thanks dave for the suggestions on brand name stuff. WELL worth it. Also, if you have .7mm dia solder, you can load it into a 0.7mm mechanical pencil. Bit more precise.

[Howardlong]

How are you soldering passives? Don't put the solder on to the iron, melt the solder on to one pad, then melt that and position one end of the component on the pad. Then solder the other end normally.

I'm usually holding the passive in place and putting the soldering iron onto it with a small blob. It's the only way it works. My iron doesn't get hot enough to be able to touch-melt solder once it's on the board. I have to tin the tip so it allows for better heat conductivity to the solder on the board, else it takes about 20 seconds to start melting. I need temp. control on my iron, to be honest.

You definitely need a better iron if it won't heat the pad up enough so you can flow a bit onto the pad. And do yourself a favour and get some full fat solder. I don't understand why Maplin don't sell it these days.

Applying solder by putting it onto the iron first is a no-no as others have said, the flux will have burned off before it hits the pad for a start.

[IanB]

Going to echo lots of previous comments here.

1. Don't use lead free solder for hand soldering. Always use tin/lead solder (63/37 or 60/40).
2. Solder doesn't ball up on a clean tip. If solder makes a ball you have dirty surfaces or insufficient flux.
3. The Antex XS25 tends to run hot. No way is it "not hot enough".
4. If you can't melt solder within a second of touching the iron to the joint, it's not a temperature problem it's a dirt problem. Clean surfaces with IPA and then add liquid flux before soldering.
5. If you melt capacitors you are taking far too long to solder them. The iron should be touching for 2-3 seconds at most. Clean the pads, use liquid flux, clean the iron tip better. Make sure the iron tip is shiny before you start making a joint.
6. A good technique for SMD soldering is to place the solder wire between the joint and the iron. This way the iron will melt the solder, which will then conduct heat into the joint, which will flow to form a fillet. Watch tutorial videos for a demonstration.

[Electro Fan]

Two questions/requests:

Any links to preferred flux (liquid or otherwise)?
Any links to especially good videos on Surface Mount soldering techniques?

Thx

[IanB]

Two questions/requests:

Any links to preferred flux (liquid or otherwise)?
Any links to especially good videos on Surface Mount soldering techniques?

Thx

Here's an expert at work:

https://youtu.be/5uiroWBkdFY

[JackP]

I've seen that before, shows great methods that aren't shown in most tutorials. If you haven't, check out Dave's tutorial on the subject, IMHO MOST others are generally flawed in some way, but Dave shows good technique along with step-by-step instructions; you know someone is not lying to you when they leave in their mistakes for you to learn from (and gives justifiable reasons for them, like not having practised). He also has some hot air and oven reflow videos out there.

[tautech]

Trouble is most people have a wide range of kit and little of it may be well suited to SMD work.
Then general soldering experience has a lot to do with success.

If one thinks they will do a good amount, best they bite the bullet and get a rework station.
Get a couple of chisel or hoof tips and one I find very handy from time to time, the 45 degree knife tip that can bridge 2 pads on many passives. Great for rework.

But hang on to your big old iron, just yesterday I needed it for modding leads from a ATX PSU where a dozen leads came from one pad. Even the hot little Antex like the OP's wasn't up to that task.

[nanofrog]

Any links to preferred flux (liquid or otherwise)?

MG Chemicals Rosin Flux 835 is a reasonably priced, quality RA flux that comes in hobbyist friendly sizes. 

Any links to especially good videos on Surface Mount soldering techniques?

PACE SMT Video Database

Pace Inc. SMD soldering and desoldering (10 lesson playlist from Marc Siegel's YouTube page).

[miguelvp]

Two questions/requests:

Any links to preferred flux (liquid or otherwise)?
Any links to especially good videos on Surface Mount soldering techniques?

Thx

Here's an expert at work:

https://youtu.be/5uiroWBkdFY

Weird that @0:55s they don't mention flux and they are indeed using it.

[savril]

Contrary to previous comments, I don't agree with some of the Pb free bashing. I agree than 10 years ago, Pb free was much harder to use than lead solder but things have changed. I did my first SMD soldering few weeks ago (after 10 years without soldering) with Pb free solder and it went relatively easy, up to 0603 and SSOP (if I forget 2 pad lift  ).

But I was in a better condition of success than you :

• I used rosin flux (and it really help a lot, especially for ICs)
• I have a quality solder (with Ag), much easier to use than the Pb free I had 10 years ago
• I have a temperature controlled iron

From comments I had seen in this forum, this trio seem to be the condition to Pb free quality soldering.
However it ask for a certain amount of money (Ag is not cheap). If you can't get these, it's probably better to get lead solder... But more important, use flux. It really helped me a lot.
A temperature controlled iron is probably a good investment too. As SMD have a lower thermal mass, they can burn more easily.

There is also the fact that the PCBs I used had a solder mask which can help. For my first SMD soldering, I used a 1,2 mm chisel tip for components and a 2,2 mm for drag soldering ICs. If you get pins shorted, just apply more flux and drag the solder to the outside, so easy with flux.