Fine-pitch SMD soldering with minimal tools

We try to stick to the 0805 parts because they’re still big enough to solder by hand. But [Scott] shows us that it doesn’t take too many special tools to reflow fine-pitch components at home. In this case he’s using 0402 resistors, a footprint that we consider functionally impossible to solder using an iron.

The two parts of the equation that he spent some money on are professionally produced PCBs and a solder stencil. The stencil is laser-cut from Kapton, which is heat-resistant so it doesn’t warp during the cutting process. An acrylic frame holds the PCB in place, and he just tapes the stencil over it and uses a chunk of acrylic as a squeegee to evenly apply the solder paste. Splurging on the PCB and stencil means you’ll achieve tolerances which lead to success.

The next issue is placing the components. [Scott] shows off some vacuum tweezers he built using an aquarium pump. Watch the video after the break to see how small those 0402 parts are when he extracts one of the resistors from the tape packaging. With the board manually populated (check everything twice!) he moves the board to a completely unaltered toaster oven for reflow. We have seen a lot of projects which add controllers to these ovens, but he really makes the case that you don’t need it. Instead, he uses a thermocoupler read by a multimeter just to let him know what’s going on with the temperature. He uses a smart phone as a timer, and switches the oven on and off to match the solder’s heat profile.

Comments

  1. Sven says:

    “In this case he’s using 0402 resistors, a footprint that we consider functionally impossible to solder using an iron.”

    You what? There is absolutely no problems in soldering 0402, i do that daily at work.

    0201 is very tricky but doable, 01005 is possible but completely impractical and messy with an iron.

    Btw. i do this without magnification.

    • nes says:

      I agree. 0402 is no problem with a < 2mm tip and a pair of tweezers.

      0201 is the size you often find in cellphones? They are quite doable with an iron too I find. Flux is key though.

    • Squirrel says:

      agreed. The one thing is that you _do_ need to have a relatively decent tip. If the tip of your soldering iron is over 3x the size of what you’re trying to solder and horribly corroded, good luck.

      So basically, what I’m saying, is that you’d want is something along the lines of the Aoyue 936 or 937 (they’re around $50, temperature regulated, fairly decent tips.)

      Granted in my own designs I stick to the >=0603 form factor.

    • jack says:

      yeah, as long as you have some decent tweezers and a fine tipped iron, >= 0201 is doable.

    • Jordan says:

      I couldn’t agree more. Though the trick we use on 0402’s (occasionally 0201, but for res. and caps. we just use a chisel tip and hit both pads at once) is “dueling irons”. Lay out the parts on the board (or run a bit of flux for re-flow) and go in with an iron in each hand. Super efficient and makes placing parts a reasonably quick job.

    • Mike says:

      I too can solder 0201s all day long with a $100 temperature controlled iron. The comment that 0402 are impossible to hand solder is ridiculous, after soldering 0201s they look huge. All it takes is some dexterity and a bit of practice :)

    • JB says:

      “Btw. i do this without magnification.”

      Aaaahhh… to be young…. I am 49 and can’t do that without my trusty magnifying lenses anymore. I started using them 5 years ago.

  2. svofski says:

    0402 is perfectly solderable and you don’t even need any special superfine tip. It’s just more convenient to use larger parts when you assemble everything by hand, or/and when you have to experiment a lot.

    I wonder if SMD could be more popular by this time if not for these FUD articles that claim that you need special tools or skills to work with them.

  3. Eric says:

    “In this case he’s using 0402 resistors, a footprint that we consider functionally impossible to solder using an iron.”

    … without tweezers.

  4. Kuy says:

    I also routinely solder 0603 and 0402 with lead-free solder by hand and without magnification with a very modest temperature-controlled iron. I think it comes down to the tweezers and method you use but any amateur should be able to do it. Stop scaring readers and hobbyists off! :-)

  5. eddie says:

    OK me too.
    I haven’t done 0402 but 0603s are very easy.
    I’d bet I can do 0201s by hand.

  6. paranoid says:

    I’ve used the reversed-aquarium-pump as a vacuum source, and a bent basketball-inflator needle as the vacuum tip – not quite as fine diameter as the one shown, but you can get a pack of three of them for like $10 at the sporting goods store.

    A good stereo microscope makes a lot of this stuff so much easier to do. I use this one (admittedly not cheap.) http://www.opticsplanet.net/konus-microscopes-crystal-pro-stereoscopical-7x-45×-5424.html

  7. Requiem says:

    Considering I just got done soldering about 15 – 20 0603 components with a RadioShack station using what I imagine was about an 8mm tip. Easy. No magnification, just a lot of flux, a steady hand, and a Panavise Jr.

  8. charliex says:

    i bought anexpensive zephyrtonics vacuum pen, its basically a fish pump diaphragm motor and a tube with a lock pickup on the end. doesn’t work that great either.

    and yes, 0201’s are where it starts to get tricky.

  9. Sven says:

    By the way, i did the following as a joke to stick in the faces of people who say that 0603 is impossibly small.

    http://donkey.vernier.se/~ghlargh/01005/index.html

    This is really messy, but note that the components are 0.2×0.4mm and i did this with no magnification and a standard fine tip iron, no hot air.

    (if this is a double post, i reposted because the href tag didn’t seem to work)

  10. Taylor Alexander says:

    +1 for “You gotta be kidding me”.

    0402 is easy with just an iron and some tweezers. You do have tweezers don’t you? I consider those to be “standard tools” for soldering.

    Here’s how I do it:

    Apply some solder to one of the pads, keeping the other one clean.

    Apply some flux to said pad. I typically always use no-clean flux as it seems to work fine, and as the name states, does not require cleaning afterwards. (Or at the least, not as much cleaning.)

    Grab the component with tweezers, and bring it close to the soldered pad. Then touch the iron to the pad and put the part into place. The flux should allow the solder to stick to it nicely.

    Now let the solder cool, and the part is held in place nicely by the one pad and solder. You can now solder the other pad, and you’re done. You may want to touch up the first pad. You may also want to use flux when doing so.

    Just keep in mind that these small parts will conduct heat across to the other pad, and if you spend more time than necessary on one pad with the iron, it will melt the solder on the other side and the part will come free. Spend just as much time as necessary and then back off.

    • Taylor Alexander says:

      Oh and I forgot, you can save a step if you flux the pad, apply a blob of solder to your iron, put the part down (holding it with tweezers) and then dab the pad with your solder-blobbed iron.

      Honestly I just use paste and a heat gun for everything so I forget exactly how to do everything with an iron.

      Hand application of paste is incredibly easy and works great – no stencil needed. Just squirt the right amount of paste out onto the pads. Sometimes it doesn’t stick, but usually its fine. Then stick all your components down, melt it all with heat, and then touch up any bridges with an iron, if necessary. Its very, very easy to do surface mount soldering with trivial components and minimal cost.

      • MysticPixel says:

        @Taylor Alexander: first post is good, same method I use. But I have to say, just dabbing the pad with the solder-covered iron (as in your second post) is a good way to get cold joints. It “works”, kind of, because of the flux, but you gotta keep it there for a few seconds to heat up the pad/component properly. (Luckily the pads/parts are tiny so they heat up fast. But if you’re too timid it’s easy to end up with a bad joint.)

        Also, joining the “0402 parts are doable with a good tip/iron” wagon.

      • Pat says:

        You’re right in general, but when you’re talking about 0402s (and even more so for smaller) unless they’re directly connecting to a plane without thermal relief (which can be avoided in design), touching the pad with a clean tip is pretty much enough to heat up the pad/component to get the solder to flow well.

        Especially for really tiny guys, holding an iron there for a few *seconds* can be pretty dangerous, because the pads are so small that that amount of heat can lift them pretty easily.

    • macegr says:

      In the video, you can see Scott has a whole stack of PCBs to assemble; each of the PCBs is fairly large and appears to have quite a few components. Hand soldering SMD as you describe is how everyone else does it, but it’s not feasible when you want to make 20 of something. Solder paste stenciling is not always a requirement, but it is a time saver.

  11. Hackerspacer says:

    Kapton. Heat resistant. EXCEPT WHEN LAZERED.

  12. n0lkk says:

    Evidently few aren’t considering that the time saved by using this process over using tweezers and a soldering, is something Scott feels to be beneficial for him.

  13. Sven says:

    Of course solder stencils and ovens are time savers when making several boards, i was just pointing out the false statement in the article.

    Every step you take towards higher technology should save you time or give you a better result or you’re doing it wrong.

  14. Indyaner says:

    Great! Now I only need a Lasercutter that cuts tiny holes into a mask-layer to screenprint the flux on it =/

  15. ScottInNH says:

    One of the problems with SMT and novices is that there are very few “kits”. A lack of SMT kits implies truth to the FUD. I got a couple of kits from smtboard.com and I found the 0603 not difficult at all, and I haven’t been soldering as a hobbyist for more than a couple of years (and my eyes aren’t great either).

    That said, it’s worth pointing out that SMT isn’t just small legs, LEDs and resistors. There are some interesting parts out there which have pads underneath the chip, so reflow is absolutely required. Linear has some new and interesting dual-channel DC boost chips for example and they’re only available in such packaging.

    The other thing that’s mildly discouraging is the investment in SMT. You can get a PTH resistor assortment cheap from Jameco, Futurlec, etc. but no such cheap/starter assortments exist for SMT. And then if you’re building SMT on other people’s PCBs, you’d be using their SMT package size so now you need multiple SMT resistor kits.

    But all that said, it’s NICE to etch a board, drop on SMT parts, and not needing to drill and break drill bits.

    • Chris says:

      I have to disagree with you about the investment.

      Maybe the major US-based distributors don’t have good SMT assortment kits, but China does. I bought an SMT kit of 2,000 assorted resistors and 1,000 capacitors on Ebay. For one order and $10 shipped, I’m pretty much set; I spent much more money and effort putting together a good collection of PTH equivalents over the years.

      One thing I never stocked a good assortment of is PTH inductors, due to their price. I didn’t find any appealing SMT inductor kits on Ebay, but was able to put together my own from Newark from individual values. $11.57 got me 10 each of 22 different values. So much cheaper than PTH equivalents, that I’ll solder leads on them to make them PTH if I ever need to. ;)

      While I was at it, I spent another $30 or so, getting a fair quantity of various low power bipolars/jfets/mosfets, switching/schottky/zener diodes, TL431’s, ferrite beads, trimmers, LEDs, and other useful basic components.

      So for about $50 total, my parts bin is well stocked with darn near anything SMT except ICs.

      Now you’re right that you’ll often need other package sizes when building someone else’s PCB design, but typically then you’ll need to order an IC, or something else you don’t have on hand in any size. So the other components can be ordered at the same time. Kits are best for your own projects, which you can design to use your preferred sizes and parts you already have.

      • Indyaner says:

        Do you have a favorite seller on ebay for those sets? Please share if you do.

      • Chris says:

        Indyaner: I pulled up my copy of the invoice. It’s titled “(SMD 0805) 50 Value Resistor + 32 Value Capacitor Kit” from seller “anna758595″, and that seller still has the kit listed.

        But go with any seller you like, taking the normal care for any Ebay purchase. Read feedback. Make sure the description is clear, and English at least good enough that you can successfully communicate in case of questions or problems. All parts should be clearly labelled.

        For capacitors, dielectric types should be specified; which makes a difference in how much the value changes with temperature. NPO is the most stable common dielectric and best for small values, but limited to how much capacitance it can provide in a tiny SMT package. So at some point in ascending value (depending on package size), it typically switches to X7R, then Y5V for the largest ones (100nF and above). And for resistors, remember that SMT has a smaller maximum power dissipation than PTH. 0805 is rated at 1/8W max. 0603 is 1/10W if I remember correctly, and so on. Both are good reasons apart from ease of soldering to go with larger SMT sizes as your standard kit, as they’re more stable and versatile.

        I’ve had very good luck ordering from China. Still, there are some particular parts I’m wary of. For low ESR electrolytics, I go only with known, major manufacturers, from regular domestic distributors. LEDs, especially high power ones, may have fudged specs or slight to major defects. I’ve also seen some ICs at a too good to be true price which I almost bought, until I noticed the manufacturer’s silkscreen logo wasn’t quite right. Avoiding these things, I’ve had only one order out of what must be around 50 so far that I wasn’t happy with, and wasn’t able to resolve with the seller.

        Hope that helps!

      • Pat says:

        There is almost *no reason whatsoever* to use Y5V class dielectrics anymore. You can find caps that are cheaper or equal price, and same voltage rating and capacitance (or larger!) in X5R/X5S/X7R/X7S (etc.) nowadays. If you can find a kit that avoids Y5V (or, god forbid, Z5U) you’d be better off.

      • ScottInNH says:

        I enjoy these exchanges, and it’s one of my favorite things about HAD. I hope these threads are not so off-topic that they bother other subscribers to the page.

        If I understand you @Pat, and I understand the capacitor specs correctly, you’re not saying there’s anything “wrong” with Y5V, you’re just saying it is wasteful to pay extra for it. Is that correct?

        (If yes, it’s good advice, but it probably doesn’t apply to @Chris ‘s suggestion, since his y5v caps came in a low-cost “kit”, and it’s probably still way cheaper than buying more typical caps standalone/each). If I understood this correctly, I’ll be going with Chris’s advice as that’s a good deal, and I’m just making hobbyist stuff. Cheers.

      • Pat says:

        The “what’s wrong with Y5V” is that it is ridiculously unstable with temperature (-20%, +80%). It can basically only be used for decoupling (where only the -20% matters), so don’t use it with anything else. The main reason it gets included in that kit is because the one place where Y5V still has an advantage is apparently ‘moderate case size, moderate voltage’.

      • ScottInNH says:

        @Pat – thanks for clarifying. I totally misread your first comment, but your second one set me straight. The wikipedia page on cap tolerances is pretty useless, so I’ll spend some time reading up on this.

  16. Burned Fingers says:

    I guess that we have a crop of mutants here, the Xmen movie must be based on real life…

    You need xray eyes and a steady hand and a third arm to use these parts. I have an issue even seeing these tiny parts, much less soldering them…

    If its not 1/2″ copper pipe and a blow torch, I’m screwed….

    Any suggestions for us old geezer’s with bad eyes and no hand eye coordination?

    • sneakypoo says:

      One of those lights on a boom with a magnifier in the center works decently. The cheapest ones have pretty bad distortion towards the edges so it’s best to check them out before buying IMHO. Also check that you can fit your iron under there.

      A head lupe can work well. You know the kind that you see all the jewellers use in the movies.

      “Dental loupes”. A variant of the above. Random pic from google:

      These guys can get pretty darn close to the parts while maintaining a comfortable working distance. I got myself a pair of 6x ones but I’ve never used them really. I felt the magnification was a bit too much. I’ve been thinking about getting another pair in the 2-3x range.

      I think I’ve seen people use cheap USB microscopes as well but I have no experience with that myself. I imagine working distance will be an issue.

      Then of course there’s the high dollar solution which is to get a proper stereo microscope on a boom but then we’re talking $$$.

      “Fortunately” for me my eyes are starting to fail me on the far away stuff. I can still jam my nose fairly close to whatever it is I’m doing and rarely need any additional magnification, even for the tiny stuff.

      Oh yeah, light, plenty and plenty of light is an absolute must.

      As for the shaky hands, well, I wouldn’t mind having less shaky hands myself… What I tend to do is steady my hand on the PCB/table/PCB vice or whatever is close enough at the time. Hmm, maybe a bean bag could be useful here, I’ll have to try that.

    • Steve-O-Rama says:

      +1 for the diopter (the arm with a large magnifying glass and a light), plenty of flux, lots of properly-aimed light, and lots of practice.

      If you’re in the US, you may want to try looking for a diopter at your local office supply stores (Staples, Office Max, Office Depot, etc.). I found a nice one for about $40 since it was on sale. I’d also advise getting one with LEDs, instead of a fluorescent or halogen bulb, since the latter get hot AND are expensive to replace. With LEDs, there’s no replacement, but they last nearly forever.

      Eye problems, such as cataracts and astigmatism, may contribute significant difficulty in soldering these parts, since visual clarity is vital for getting the parts and tools in the right place. They’re not insurmountable, though. :)

    • svofski says:

      Some time ago I bought a stereoscopic microscope with a wide field of view. It provides only 10x and 20x magnification, which makes it a huge loupe basically.

      It wasn’t expensive at all. And it’s one of the best tools I have in my “lab”. I can’t describe how incredibly precise human arms can be when the feedback loop uses some proper enhancements. It’s really important to have stereoscopic vision for this, I think.

  17. zappaknowsbest says:

    The most important part of SMD soldering is having a good pair of Zircon encrusted tweezers.

  18. wardy says:

    It’s not always the size of the component that necessarily defines how hard it will be to solder – sometimes it’s a ground or power plane that saps all the heat away from your (thin) soldering iron tip.

    When that happens your iron tip can stick to the board and you’re in trouble! Soldering iron tip selection is an art in itself.

    • Pat says:

      1) Thermal relief.

      2) If that’s not good enough, stick the board in an oven on the lowest setting for a bit, then pull it out and solder it while it’s warm. Doesn’t have to be that hot. Heat transfer is proportional in the temperature difference, so even having the board at, say, 150F (which isn’t too hot) would reduce the heat transfer by 25%.

  19. Reddy says:

    Nice idea i will try this next time. Thanx

  20. NewCommentor1283 says:

    its not about how skilled you are,

    its about how fine your tip is.

    its not about the tools you have,

    its about how long you can hold a soldering iron against your bare finger before the smell of burning flesh makes you feel (insert graphic word)

    smd is not difficult,

    ITS FRIGGIN PAINFUL !!!

    and it can STFU even if its possible, ive done it, only for mods,

    never ever ever ever for builds (%*&%$&*^%()

    • ScottInNH says:

      @NewCommentor1283 – You’re doing it wrong if you are burning bare flesh. I use tweezers. That only leaves 1 hand free, but a prior step is me tinning the pad. Then tweeze, hold, hit it with heat 3 seconds, remove iron, remove tweezers. NO BURNS.

      I’m not an expert with the iron. I’ve only done this a couple of years, as a part time hobby. I’m 42 and have had bad eyesight since I was 12. I did PTH parts then I got a couple of kits that used 0603 parts, which should be considerably easier than 08 or 12 sided parts. My results aren’t perfectly straight like a reflow would be, but they work.

      I suggest watching more youtube videos and attending a make workshop.

      I still think SMT is a pain in the ass, but so is drilling boards (probably more so).

    • Sven says:

      You really should use tweezers when holding SMD components for soldering…

  21. Luke says:

    I thought for a second there it said Krapton.

    Anyway, that seems like some fine stuff to me, but I’ve only used a solder iron about 5 times so…

    BTW, If your designing your own board (unless space is an issue) why not make it as easy a possible?

    Cost?

    • Sven says:

      I have taught people who have almost no experience, to solder 0805 and 0603 in about an hour, no problems.

      And i actually find it faster to solder SMD than PMD, you don’t have to fit the component through the board and hold it in place while soldering, you just tin one pad, tack it in place and finish. No flipping the board back and forth.

  22. Dave Thomas says:

    The McMaster probe you show in the video–do you also need to buy the metal tip, or is it included?

    (can’t tell from the catalog)

    Thanks,

    Dave Thomas

  23. scott says:

    Sadly, I’m not sure the part number in the original video is correct anymore. I believe you do have to buy the metal tip separately, but I’m not sure what that part number is. The tip used had an OD of .028″, but I don’t see that in the catalog.

  24. Andrew Coad says:

    How long does the solder paste stay moist after you have spread it on?

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