[Russtafarian]

Any recommendations on tools and techniques for desoldering and soldering SMD components.  I'd like to swap some op amps and am a bit intimidated by those small delicate traces.  I have a board to practice on before I go after a working component circuit board.  any help would be appreciated.

Russ

[ctviggen]

Get a nice solding gun with a fine tip. Get some nice tweezers. Here are some other, better tips:

http://www.infidigm.net/articles/solder/
http://poeth.com/smtmfg.htm

Actually, a google search of "soldering smd components" turns up quite a few results.

[JoshK]

I am not very experienced with smd desoldering, although I have done some soldering.  With soldering, there is a cheater trick that really makes it a lot easier to manage.  It is hard to hold the component with tweezers, the soldering iron and apply a bit of solder all at the same time.  Instead heat the pad carefully and put a small dab of solder on the pad directly and only one pad for your device.  Then hold the component with the tweezers and reheat the solder while pressing the component onto the pad till it flows.  Voila, only need two hands this way and the rest of the contacts can be soldered without having to hold the component with the tweezers. 

[ctviggen]

Good point, Josh.  Also, use desoldering stuff (what's it called?  it looks like metal mesh and wicks the solder?).  That's very helpful, although I like the technique of putting a lot of solder on the leads and then lifting the component while the solder is hot.  That way, you could just suck up the solder after the component is off the board. 

[JoshK]

The method I read about using a hot air gun to desolder smd parts seems easiest, but you must be careful that your board is completely flat and doesn't move since you are likely to loosen/desolder other nearby components as well. 

Bob,
I've never had much luck or consistency with desoldering using the mesh wick.  I invariably end up lifting a pad 10% of the time.    If it is a cheap part, I cut the pins and desolder one pin at a time.  I'll have to try the add more solder way.

[JoshK]

Your first link Bob is great! I knew only a couple of those methods.  Now I have a few more.  My method was the small package method...the second described.  Works really well.  I even do that when I am trying to solder fine gauge IC's and such. 

[gitarretyp]

For soldering the components, JoshK described the most reasonable method. For removing components, i either heat it until it breaks free or use Chip Quik if i want to keep the component or it has multiple legs, eg ICs. It's essentially a low melt point solder that you add to solder joints. After you've added it to the joints, re-heat them and you should have plenty of time to safely lift the component from the board. Then, remove the chip quick with a flux coated Q-tip, clean with alcohol, and attach the new component.

For typical through hole components, i use a desoldering pump to clean the joint. The Chip Quik works well for stubborn through hole items, too.

[Russtafarian]

Thanks for the help.  Time to pick up a few supplies.

Russ

[Wayne1]

THE MOST IMPORTANT TOOL FOR SMD WORK IS A LIT MAGNIFYING LENS!!!

You can use desoldering braid and almost any sized tip IF YOU CAN SEE WHAT YOU ARE DOING.

I routinely replace smd DAC chips in the SB. Once you have some experience in the unsoldering, it isn't too hard.

A 4X magnifier is an absolute necessity for these 52 year old eyes.

[Gordy]

Randytsuch sent me some smd links a while back, here's two that haven't been listed.

A method using solder paste, sounds easy but haven't tried it yet... http://www4.head-fi.org/forums/showpost.php?p=1725176&postcount=7

Here's a couple download tutorial films...  http://tangentsoft.net/elec/movies/

[ohenry]

I just noticed that 41Hz.com has surface mount soldering practice kits that come with a practice board and components.  I've seen a few inquiries over the past several years asking how to learn.  This looks to be a very inexpensive way to get experience with no risk to your audio toys.

[Folsom]

This guide sort of sucks...

http://www.infidigm.net/articles/solder/

0805 capacitors... The way you are suppose to remove them is with two soldering irons.

SOIC removal... If you simply DO NOT CARE about the part there is a much better way. Get a sharp pocket knife or razer blade and cut all of the leads as close to the SOIC itself as you can. Then you just dip your soldering iron in the solder and wick out the remaining chunk of lead. This is very easy as it will stick to your soldering iron. Then to install the next part you can clean the board off or just slowly heat and push it in if you do not have any methods of cleaning. This tool kicks ass by the way...

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=370-325

If you do choose the flood method... You need to scrape under the chip for any resin, and then use a stiff brush (I use a toothbrush) with some isopropolyne alcohol to clean it up after. If you do not and you replace the chip then there is the possibility of shorting one side out to the other via resin that conducts (good resin does).

When ever you solder something like a SOIC that has leads that are very close together you need to use a pocket knife or razor blade to cut and scrape out inbetween the leads as best as possible, and then use isopropolyne alcohol and a stiff brush to clean up the resin that comes off. Again if you have good solder you will have resin (WBT or Cardas). Also if you get too much solder on (two leads connected), use a solder sucker to take up some. Then reheat both sides, and if you removed enough the solder will seperate to each lead and not connect in the middle. At this point scraping out inbetween is a must.

Careful technique to apply that is almost plain nuts... If you are touching a SOIC lead what you can do is have the soldering iron fairly straight up, and rather than trying to push the solder directly onto the lead, inbetween the soldering iron and it, put a VERY small dab on the soldering iron so it barely touches the lead. What will happen is it will bead on the soldering iron, but as soon as the lead is hot it will fall onto it and around it. This is TRICKY and does not always work in the way you hope. There are times when you need to add more solder. The point of this is to prevent a cold solder joint (BAD thing). A reason to do this is because unless you got a magnifing glass it might be HARD to see the solder "fall" into place (signifies just enough heat) on the leads when you pushed it on.

Tools I want in the future... Soldering iron forks with 8 leads for SOIC opamps, and then maybe a couple more semi-standard sized IC ones. It would looks crazy but it is possible. What would make it the best is if the fork could have a closing mechanism so you just press and grab all eight leads and lift! well it sounds like fun