This is the humble beginning of what will hopefully become a informative and thorough soldering guide. I've been motivated to start this guide in response to several misconceptions floating around about soldering. Many of the rules people are taught seem outdated, intended for an era of through hole components, and when extrapolated to modern surface mount devices (SMD) cause people to seek out expensive and fairly useless items which don't necessarily work any better.

Apply Solder to the Iron

Specifically I'm referring to ultra thin solder and ultra fine point soldering irons. There seems to be this wide spread misconception dating back to through-hole days that soldering electronics should be done by first heating the component and then feeding solder, not onto the iron, but into the joint. Don't get me wrong. This works. It's just impractical for a modern TQFP. This technique is directed towards preventing people from creating cold solder joints while using cheap five dollar irons, and in that respect, this rule does what it intends to do. For SMDs, the rule simply doesn't apply and adhering to it causes no end of grief.

Get a Good Iron

First, if you're trying to solder SMDs with a five dollar iron you should save yourself the trouble and give up now. It's doable. I've done it as a challenge. It requires quite a bit of skill which you learn by using much nicer irons. As an analogy, every once in a while, you hear about the heroic surgeon who saves someone's life on a plane by performing emergency surgery with a pocket knife sterilized with whiskey. That surgeon was able to pull off the surgery with a pocket knife because he had performed the surgery numerous times in a fully equipped operating room. If he had instead tried to learn to perform surgery with his handy dandy swiss army knife ....

Metcal: Smartheat

Soldering SMDs is hard. Don't learn with a pocket knife. I recommend a Metcal/Oki iron. I love them, and have had much better experiences with them than Hakko or Welder. For me, I think Metcal/Okis are just in a different league. They make a fairly affordable station, the PS-900 for around $200. I personally use the PS-800 with the cononical bent tip PHT-652327 in 650 degrees F. Hakko and Welder both make fine irons and they are definitely preferable to a five buck iron, but Metcal's smartheat irons for me seem to be distinctly superior. The tips seem to last forever. I've never needed to replace my tip. Initially I bought a spare tip thinking I would. Now 2 years later, the original one I got still seems fine. Although I have tips in other shapes and temperatures, I haven't used them other than to try them out. A good iron with a good tip really seems to be able to serve as an all terrain sports car - a tool with no compromise. From soldering 01005 caps to attaching USB connectors onto a ground plane, my single tip will do it all. I've also heard very good things about irons from Pace.

Temperature Dial vs. Temperature Controlled

A common misconception I've encountered is this belief that a soldering iron should have a temperature dial. This maybe a religious divide and being a Metcal adherent, I confess that I don't get the point. The idea goes something like this. If the thing you're soldering has a lot of thermal mass, you want to crank up the temperature of the iron to heat up the thing faster. The problem with this is that it also destroys tips and components and makes a mess. Your solder is going to melt at the same temperature no matter what you're soldering to. If it's SAC305 thats about 200C. A nice iron will respond quickly to attached thermal mass by pumping in a lot of heat until it can get its tip back to the spec temperature. There's obviously going to be some gradient but even at 600F which is around the lowest working temperature, that's still 315C which is a hundred degrees C hotter than the melting point of the solder. If you need to set your iron to 750F or 900F!!!, something is wrong and hotter is just not the right approach. Creating an improved heat conduction path should work better. In situations where a lot of heat is required, a small butane blow torch may be appropriate.


Flux!!! It is your friend. Seriously, don't bother trying to solder SMDs without flux. The lack of flux is what causes many to believe that SMD soldering is much more difficult than it actually is. Although through-holes could easily be soldered with just the rosin flux that comes in most solder, this doesn't work for surface mounts. Because you're using a lot less solder, there is also a lot less flux and the work time with the solder is equal or greater which means the flux will have largely burned off before you're done. For SMDs, you need a bottle of flux. For beginners, I recommend the rosin based RMA fluxes. The newer no-clean or water soluble fluxes have their purpose but the rosin works best all around and is the easiest to learn with. The only down side is it's messy. Really messy. Kester 186 is an example of an RMA Rosin based flux.

Cleaning Flux

If you decide to use flux, the next problem is cleaning up the flux. This is especially a problem if you decide to use the rosin based flux. The water based stuff should just wash off with water. A little soap helps. For Rosin flux, water is useless. But there's a fairly recent fad that has made this problem easier to deal with. "Hand Sanitizers" Specifically Purell. Both isopropanol and ethanol will work reasonably well. Setting a board in isopropanol is a tried and true solution to cleaning off rosin flux. For smaller areas, a bit of Purell and an old toothbrush works pretty well. Turns out, Purell is 63% ethanol. Other generic hand cleaners might also work. Check the ingrediants on the bottle to be sure.