Understanding Surface Mount

Do you know what a MELF is (and, yes, it is safe for work to Google it)? What’s the difference between a QFP, and LCC, and a PLCC package? Do you need a 0603 resistor or a 1206 resistor?

If you are an old hand at surface mount devices (SMDs) you probably know the answers to most of these questions. But if you’ve done most of your work with through hole, it is a confusing mess of acronyms and numbers. Sure, you can Google and find out that at 0603 resistor is .06 inches by .03 inches. [TopLine] has a great booklet that pulls many common definitions in one place available for download that can help you make sense of different SMD nomenclature.

The booklet is more than just a chart or a table. It defines often confused terms like sweep and tweeze, for example. We did notice it lacks some of the newer packages like CCGA, but it is still a great guide to get started.

If you are still shy about building with SMD, you can look at some of the tools we’ve covered before . If you don’t want special tools, you can always try a toothpick (or try the simple method in the video).

30 thoughts on “Understanding Surface Mount

  1. I tried using a toothpick and I just couldn’t get the hang of it. I end up mushing the end of it so it becomes a sort of sticky sponge (soaked in flux) moving around the part and feeding the soldering iron. There was a video here a while back of Chinese assemblers soldering together USB controllers using bamboo sticks so there’s something to the technique.

    I find I can manipulate 0603 parts with ease using a #11 X-Acto blade doped with some dry flux. The shape of the blade lets me push and hold parts down with just the tip or grab and pick up the part with the broadside on.

    1. Other than rework, you really shouldn’t be hand-soldering SMD parts. And even for rework, hot air is much easier.

      I strongly recommend giving reflow a try. It’s easier than I thought it would be my first time, and the results look almost as good as manufactured boards.

      Disclaimer/ad: I sell toaster reflow oven conversion kits on Tindie.

          1. @Zaid, here was my documentation of my first attempt at a reflow.


            Honestly it wasn’t as hard as I though, I used an unmodified toaster oven from Goodwill (it had an internal fan, and I had a cheap IR thermometer for checking the temp), an acrylic stencil from the above mentioned site, and some general lead free solder from Sparkfun.

            Honestly you can do it without the stencil as well, its just harder to be efficient with your application and not apply too much. (Tried a stenciless test for a few resistors, worked good. Might be harder on chip packages) The stencil makes it really easy.

      1. yes more than anything I have to tell people to get a cheap Chinese hot air rig …. these days when I teach kids to solder at the local makerspace we start by removing some 0603s from some dead PCB with hot air and tweezers, then soldering them on to some scrap proto boards with an iron …. then we move on to thru-hole parts ……

        (keep all those unused proto boards for others to practice with)

        1. Personally I prefer the Edsyn for small hand work over the cheap hot air guns. However, they are pricey unless you can get a deal on a used/refurb. I do have both. The cheap Hakko clone is good when you want lots of air over a lot of area, but otherwise the Edsyn is much easier.

          1. I got the SparkFun one for Christmas a couple years back. I’m sure it’s a private labeling of someone else’s actual product, but it’s been absolutely ideal for me all this time.

      2. The annoying part about that is that if you don’t do it often, you’ll be throwing away a lot of paste. Regular old solder on a spool lasts “forever” while the paste goes to crap pretty fast.

    2. I use hot air with a low temperature paste and a toothpick with good results. I don’t go below 0805 ’cause of my 52 year old eyes and, quite frankly, when I look at the size of some of those packages I’m afraid I’ll inhale one :).

  2. Is it my imagination, or this document is already a little outdated? I am no expert, but the statement “Americans are slowly incorporating 0603 resistors and capacitors into their new designs.” does not feel right. Plus, some packages like PLCCs are not nearly as popular as they once were.
    Other than that, the document is actually a very good introduction to SMD components.

  3. I’ve has success reflow soldering with solder paste, a cheapo $30 hotplate from Target, and a $0.50 ceramic tile from Home Depot. Dab paste on all the pads, set the SMD parts in the paste, set the board on an aluminum foil raft for easy removal, set that on the tile on the hotplate. Turn on the hotplate and watch until the solder melts. Count to 8 or so, then remove the raft from the hotplate (and turn it off so you don’t burn down your house) and let air cool.

    The tile spreads the heat from the hotplate evenly so you don’t end up cooking the resin out of the PCB like I did the first time I tried the method. The hard part is figuring out how much paste you need. One board I used way too much, the next one (that worked other than using the wrong capacitors) I should probably have used more.

  4. I find that 0603 is slightly harder to rework than 0402 or smaller with an iron, as you can touch both terminals on the smaller parts with a reasonable iron tip. I will say that having a hot air tool on a flexible arm that can be locked into place is amazing. If nothing else it can heat up an area enough to make iron rework a piece of cake.

  5. That document is WAY out of date. Way way way out of date. No mention of all the BGA configurations. 0402 is in development? Machines aren’t available for them? 0402 looks like pepper flakes? 0201 and 0102 are commonplace. You would be better off profiling Jedec.org. A great place to start.

    Be smart and in all your designs stay away from custom footprints. This is especially true in LED’s. They tried and we pushed back. Now that most of the big boys cross license, you can do a design using a Cree LED and dump a Lumileds on with the same footprint.

    1. Yea 100um to 1mm is a pretty big step in the world of small. I’m shocked they messed that up.

      What I don’t get is why smd components are still using imperial. Metric is so much easier to visualize once I started using it.

    2. There are metric codes and I have order the wrong parts on digikey by accident because I did a search without rechecking. I have over 50+ passive parts for my HaD projects and thankfully only made 1 mistake so far. I managed to recalculate a different set of passives based on what I already have.

      Some of these can be pretty nasty surprises as the do look like the imperials.
      0201 (0603 Metric)
      0302 (0805 Metric)
      01005 (0402 Metric)

      Always order extras for SMT parts especially when they are 0402 or smaller to factor in losses due to parts flying off.

  6. A lot of boards now come with HASL rather than raw copper pads. How does that affect soldering – by drag method or reflow?
    I would imagine you need even less solder paste, or none at all…

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