SMD Soldering

[SquishyIce]

Hey everyone,
I need some input on what type of iron I need to solder SMDs. At the moment I only have a standard iron from RadioShack that can switch between 15W and 30W. However, I have heard that irons with adjustable temperatures are far superior. I've also heard little snippets about hot air irons, but I'm very unfamiliar with these. Any links to store pages for recommended products would be greatly appreciated.

[Michael Hill]

Check out this video. It's got a pretty good intro into SMD soldering: http://www.youtube.com/watch?v=b9FC9fAlfQE

[anthonyttu]

When it comes to soldering especially at the component level you get what you pay for in terms of irons. The adjustable irons are useful but doesn't mean they are good quality. In my opinion good tips are far more important especially with the small SMD components. Most of the Wellers from Frys or Digi Key can do the job, just be sure replacement tips are available. There are a few models with tips that are difficult to find. If your doing a massive amount of surface mount parts you should look in to using solder paste and a heat gun/oven (don't use your oven in the kitchen, once you use a oven for soldering you should never use it for food again).

[Michael Hill]

Originally Posted by anthonyttu

When it comes to soldering especially at the component level you get what you pay for in terms of irons. The adjustable irons are useful but doesn't mean good quality. In my opinion the tips are far more important especially with the small SMD components. Most of the Wellers from Frys or Digi Key can do the job, just be sure replacement tips are available. There are a few models with tips that are difficult to find.

Ya, this is important too. I like the wedge tips for SMD work. The conical tips they usually come with aren't usually very good. The chisel tips give you more contact with whatever you're trying to solder.

[SquishyIce]

Originally Posted by Michael Hill

Ya, this is important too. I like the wedge tips for SMD work. The conical tips they usually come with aren't usually very good. The chisel tips give you more contact with whatever you're trying to solder.

How pricey should the tips be? I just saw that the ones for the Hakko FX-888D cost around $10 or so. (2.4 mm chisel tip is $8.58)

[anthonyttu]

Originally Posted by SquishyIce

How pricey should the tips be? I just saw that the ones for the Hakko FX-888D cost around $10 or so. (2.4 mm chisel tip is $8.58)

It depends on the name brand my Metcal uses $25-50 tips my weller at home uses $5 tips

[jvriezen]

I've never done any SMD / SMT work myself, but folks who run a local hacker space do it all the time-- and they don't use a soldering iron:

http://tymkrs.tumblr.com/post/794649...nna-solder-smt

[VacioArconte]

The way we solder our RN42s down, you probably don't need any fancy equipment. We put some double stick tape on the bottom and generously apply flux paste. This method works great for lining up but you can't be too overeager with the solder as the tape creates a small gap that can cause shorts underneath the board. The most important thing with SMD soldering is having the component lined up properly. As long as it is lined up, you shouldn't have any difficulties.

[dyanoshak]

Originally Posted by VacioArconte

generously apply flux paste.

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

[svenw]

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.

[Loxmyth]

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

[asid61]

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).

[SquishyIce]

Originally Posted by Loxmyth

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

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.

[dellagd]

Originally Posted by SquishyIce

How pricey should the tips be? I just saw that the ones for the Hakko FX-888D cost around $10 or so. (2.4 mm chisel tip is $8.58)

That is the normal cost for the genuine Hakko tips.

I actually just purchased one of these irons and let me tell you, after owning the one you said you have for years it was an absolute dream. You get fine temp control, a great iron holder, and tips that last, but the immediate difference I felt was the cord. Its extremely flexible, as opposed to the radioshack one, and will let you solder at whatever orientation you want.

Honestly I find soldering so relaxing now. Some people get a massage, I go into my basement and solder up a board...

[efoote868]

I own one of these:
http://www.amazon.com/Aoyue-968A-Dig...dp/B006FA481G/

I bought it for my senior year at Purdue, which made doing senior design much easier since I didn't have to share this with other people.

I did 90% of the surface mount soldering and debugging (there were a handful of caps and resistors that another team member did). The temperature control is really nice, the hot air is superb (had many people asking me to help with their projects since what I had was nicer than most of the equipment in the lab), the smoke absorber is a really nice feature once you get used to it (the extra hose makes the cord a little less flexible).


The smallest thing I've successfully soldered was a 10 pin QFN with a footprint of about 2mm x 2mm using a reflow technique.

I've heard toaster ovens can also work if you don't have hot air..