SMD Soldering Tips
From Zerobeat
User installed field upgrades may involve soldering SMD components. Here are some tips offered on the Elecraft reflector.
There is no need for a hot air rework tool unless you're working with QFP's
or BGA's or something like that. For SMT resistors you can do it with just
an iron and a bit of a quick job with a slight flick technique or even
better you get a cheapy second iron so you can heat both sides and lift it
off the board. If you're really into getting the right thing they sell
irons that work like chopsticks for the task but again not really needed.
I'd bet that Elecraft would replace the module if there was to be an IC
change (or they'd offer to do the mods for a nominal fee) but for a few R's
and C's being changed... I think that would be perfectly acceptable to just
be able to get a few parts from them (or just have the parts on hand) and
get a set of instructions.
The hard part about the jab and flick to me is to be sure that you get enough heat in there that you are lifting the part and not the pad/trace. Also you have to be careful that you don't get too much heat there as that can lift the pad/trace too... :) (Brett Howard)
The K3 mods are very simple...replacing single components with plenty of room around them...no IC removal, fine-pitch ICs, etc. I was somewhat surprised how much solder they were loading on the tip in that video sometimes. Less is better than more for SMD.
One change I would make to that video. Forget the loupe and get a headset visor...you will definitely need both hands free (one for the soldering iron and one for tweezers or whatever you use to hold the component in place). $10 visors from eBay work just fine (doesn't need to be an Optivisor but looks similar). The flux, Quik Chip, etc are nice but not really necessary for what you will need to do. (AD5SS commented that the flux is very important -- makes it much easier to solder with fewer solder bridges.)
After removing an R or C, you wick the pads clean and then apply the *tiniest* bit of solder to one pad. Then place the component on both pads, apply heat to the one with solder to anchor it, then solder the other side and then revisit the first with a little more solder. If you make a "mound" of solder on the first pad, the component will not fit on top of it very well and you'll have problems anchoring it flush to the board. "Less is more" when soldering individual components (i.e. you can't wick them like ICs because they are not flush with the board). (Bill W4ZV)
Well put. I do it a little differently. I clean off the pad so the SMD will sit flat on it, position the SMD and hold it with a tool (small probe or screwdriver on the body) while I touch one end with a soldering iron with a tiny drop of solder on the tip. That way there's no significant solder on the pad but the drop of solder will anchor the part well enough that I don't need to use the tool to hold it in place. .
Next I solder the other pad(s) properly, then go back and touch up the first pad.
You need TWO free hands to do this work. (Actually four would work better but my pet Octopus isn't interested in electronics.) I find a binocular magnifier (like OptiVisor) invaluable!
Humph! If that Octopus would get interested we could try SO8R contesting (single operator, 8 radios). (Ron AC7AC)
That's my way of doing it. Use good solder wick to get the pad as free from solder as possible. There is enough solder on the SMD component pads for it to stick. Then solder the OTHER pad of the component, before returning to fully solder the first pad. (Stewart G3RXQ)
There are several videos at howardelectronics.com
They also have a nice soldering station on close out for $79 So far everything I have bought from them is first class. If you only need to remove and replace one or two SMD devices the Chip-Quick removal method and the solder drag install method with the mini-wave soldering iron tip looks good. For real service work on a regular basis the hot air remove and drag method install would be a better way to go, but that requires more equipment and cash outlay. Look at the videos to see what I am talking about. I just bought the JBC DI3000 kit and this is by far the best soldering equipment I have ever seen or used but it is extremely pricey. I can only justify because I am in the business of SMD board design and assembly of prototypes. This thing is the most powerful and controllable iron I have ever used. It heats to temp in 2 seconds and you can change tips an be soldering again in 10 seconds. The smallest tips can solder something as small as a SMD cap and then solder two copper penny's together then back to SMD's without adjusting the iron. When you place the iron on the stand the iron goes to sleep at a low temp then when you pick up the iron it is back to the set temp before you can wipe the tip. (Don KD5NDB)
Another item that really helps SMD/T work and rework is a flux pencil. Mouser carries them and I'm sure others.
I use a wood toothpick to hold the parts in place while soldering.
Think the key to doing good work is taking one's time.
A good flip-down jewelers visor helps as well. Would like to find one of these with LED lamps to better light some of the boards and parts.
Poor vision and the jitters does make this work tough going, if not impossible to do. (Julius N2WN)
