Re: SMD Soldering
 

Dave give a very thorough explanation of how to solder SMD components.


With IC's, it works better to tack down two pins on opposite corners.

You can also get good deals from eBay on new and used temperature controlled irons. Look for Hakko 926, 936 or 937. Make sure you are getting the handpiece as well as the base. I find the newer Hakko's we have at work a bit flimsy.

An alternative to using the wire type solder is to purchase some solder paste that is loaded into a syringe. Make sure it comes with a plunger. Some of the solder paste syringes are meant to be used with automated equipment where the solder paste is pushed out by the machine. Squeeze out a tiny drop on each pad. Place the component on top of the solder paste and press down gently. The surface tension of the paste should hold the part in place. Heat up the pin/pad with the tip of the iron to melt the paste. Clean up with isopropyl alcohol (rubbing alcohol).

If you are going to be doing a fair amount of SMD soldering, you will eventually have to remove parts for one reason or another. It is easiest to remove two terminal SMD components using two soldering irons, one on each terminal (electric chopsticks). IC's are best removed by using two irons to "blob-on" enough solder to bridge all the pins on each side (as quickly as possible) and flicking the IC off the pads.

Re: SMD Soldering
 

Flux, flux, and more flux.

For either through hole or surface mount the key to good solder joints is heat flow.

One thing that can get in the way of heat flow is oxidation. Do you know what helps oxidation form? Heat, like all that heat in your soldering iron. That's why most solder that you buy is actually a tube with a goopy core of a chemical called flux. The flux melts as the solder melts and helps clean the joint of any oxidation, vastly improving the heat flow.

I've seen a lot of people "paint" with the iron. That is, flowing some solder on the tip of the iron, and trying to spread that solder blob onto the joint. This doesn't work because all the flux in the solder has already burned off and none is left to clean the joint.

This is why it is best to heat the joint with the iron and let the joint melt the solder. This ensures that the joint is at the proper temperature to melt and bond with the solder and allows the flux to do its job.

However, this is difficult for surface mount components. You need a third hand to hold the small component with tweezers in addition to the iron and solder.

Here is where flux paste or a flux pen comes in handy. First, apply flux to the pin and pad you want to solder. Then flow some solder onto your iron tip. Next, hold the part in position with some tweezers and paint the crusty blob of solder from your iron to the joint. The applied flux will magically breath life into that crusty solder blob and beautifully wick it on to the joint.

With lots practice, you can solder QFP packages in no time with plenty of flux and the drag method: https://www.youtube.com/watch?v=erb6-i54tbo

-David

Re: SMD Soldering
 

If you don't mind buying a used iron buy a metcal soldering iron (the ps2e power supply with hand piece and base can be had for around $100- $200 on eBay). The way the iron temperature control works is through the tip, so a brand new tip and you have essentially a brand new iron. The tips are a little bit more expensive (around $20 new) but you only need a few kinds and they last longer than any other iron I have uses.

As for soldering smd components just buy a good flux pen and make sure to use it. It will make a world of difference. Don't worry about getting a fine conical tip, as it will take forever to solder anything. You also won't be able to get enough heat down if you are soldering to ground planes. Instead buy a nice size (1/8") chisel tip and treat it with lots of care.

Re: SMD Soldering
 

I do soldering almost daily at work. The link below is what I use, I just picked up a second unit for the team this week too. Had mine for over 3 years. No problems yet and I still haven't had to replace the elements.

http://www.gqelectronicsllc.com/come...idProduct=4393

Re: SMD Soldering
 

For SMD parts, you could just make a reflow toaster.
Take a $20 toaster, a $10 Arduino clone, a $20 thermocouple, and a $10 relay. Or if you're cheap, a toaster and a seconds timer can work (although not as well as a real reflow oven will).

Re: SMD Soldering
 

I use one of these , it works great and usually comes with some extra tips. I like the soldering iron a little better than our Hakko F-888D and having the hot air rework is great for smd and other things like heat shrink, polycord welding .etc too.

We've also used a hot plate in a box to do some quick small batch reflow. Works quite well as long as you have a accurate thermometer to dial in temps.

Re: SMD Soldering
 

Honestly, I would shy away from the SMD toaster ovens. They're really just toys that kinda do the job. Heat distribution is terrible in them and even the metal grates you put them on can be disastrous. Plus, you still have to get stencils made, unless you want to try to put paste on the pads by hand (have fun with that).

Re: SMD Soldering
 

I have done the paste by hand. It's really not that hard for the standard types of smd stuff with legs and tiny resistors; just use a toothpick to apply. Unless you've got a ton of circuits to solder, in which case it makes sense to invest in a stencil.
I don't use the grate. I use a large metal plate that came with the oven, and that seems to do the job.
For stuff like QFN I would be worried about proper positioning, but you can hardly solder those by hand easily either.
I don't know about heat transfer, but I have done quite a few boards with my $20 toaster, including a sensitive high power LED board. With my shaky fingers I do not want to SMDs by hand (although I imagine it would involve a lot of cussing).

Re: SMD Soldering
 

This looks like a rather viable option. It also appears that the tips this unit uses are 900M (A rather standard size), so it would be easy to replace them.

Thanks for all the help so far, everybody! I never would have imagined that I'd get so many responses in less than 24 hours.

Re: SMD Soldering
 

I forgot to tell you, If you want free shipping, look for them on Ebay! Same company, same item.

http://www.ebay.com/itm/FULL-PACK-GQ...em3cc622 7884

Re: SMD Soldering
 

I find the most essential tool for SMD work is a good magnifier. I have used a binocular microscope in the past but I am using one of those dual magnifiers most of the time now.

http://www.mcmaster.com/#magnifiers/=va4pev