Soldering Tiny SMD Components the Easy and Fast Way (with a Hotplate)

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Introduction: Soldering Tiny SMD Components the Easy and Fast Way (with a Hotplate)

About: I'm a Dutch guy doing things with music and technology. At the moment I'm finishing my MSc in Industrial Design. Not limiting myself to any genre or discipline, I like to work on anything related to music, d...

I've being doing electronics for a little while and while SMD components seemed to provide a lot of advantages, I was intimidated by their small size; "how the hell do I solder that?" But as I wanted to use a specific tiny accelerometer for my project, which only came in the minuscule 2x2mm (about 150 of these fit into an M&M!) I was forced to learn it. And to my surprise, it was even more easy an foolproof than normal soldering! This Instructable shows you step by step the process of soldering a small SMD PCB. Total time of doing it is under 5 minutes, even less when you get some practice.

For this Instructable I skip the part of designing the PCB and sourcing the parts, just to focus on the soldering part. If you have any questions on design, manufacture or sourcing, don't fret to ask! And if this Instructable helped you, don't forget to vote ;)

Step 1: Gather Parts

Before you start, make sure you've got all stuff you need:
  • A hotplate that can be set to a temperature of 150-300ºC (I was very lucky to have access to a Weller station, but anything with an adjustable temperature range will work)
  • Solder paste
  • (Flux is not necessary as its already in the paste, but it can make fixing mistakes a lot easier)
  • Precision tweezers
  • An object to apply the solder paste with, this can be anything thin and rigid, I chose to use a jumper wire
  • All of your components
  • The PCB to put everything on

Step 2: Dispense Some Solder Paste

Now find a (discardable) piece of plastic and put a little blob of solder paste on it. A blob the size of a 3mm LED was enough for my board.

Step 3: Apply Paste

Use your 'applicator' of choice (the jumper wire in my case) to grab a tiny bit of solder any apply it to one of the solder pads on your PCB. To make things a bit easier, I chose to start from the centre of the board outwards and with the biggest parts before the smallest. The amount of solder paste needed is very little, but make sure there definitely is a little blob standing up on the pad.

Step 4: Add the First Component

Now grab your tweezers, grab the component for you pad you just applied solder paste to and drop it into place. Gently push it into the paste to be sure it won't move. Be careful that you oriented the component right!

Step 5: Repeat

Now simply repeat the previous steps for all the other components. Whether your apply all the solder paste first and then place all the components at the same time or apply and place for each component individually is up to you. To keep things interesting, I like to take a group of components of a similar size and place those at the same time. I work from the largest to the smallest components, which allows me to gradually increase precision and concentration; when I arrive at the really small components, I've already practiced on the large ones!

Step 6: For the Really Tiny Parts

One of the components on my board is a 2x2mm accelerometer with 10 pins. The pins were so small that I was not able to individually dip the pads. After some trial and error of having to little or too much solder I figured out an (almost) fail-proof method. You take a tiny bit of solderpaste and apply it in between and on the sides of the pad. The capillary action when soldering will make sure that all the solder is pulled onto the pads and you're sure that you didn't add too much solder. To help this action, I like to apply a little extra droplet of flux. This really makes the component float and pull towards the right pads.
When the solder and flux is in place, simply put the tiny part in place and you're ready to do the actual soldering!

Step 7: Soldering

Everybody who has ever tediously soldered a complex strip-board design will love this step. Set your hot plate to the right temperature, I chose 270ºC, but depending on you components and solder paste you might want to use a different temperature.

Carefully put your board on the hotplate with tweezers, making sure the components don't move. Now the magic happens! After a little while you can see the solder paste becoming fluid and really grabbing the parts into place. Check if all the components are in the right place while the solder is still fluid, and if they're not (like with the tiny parts being just one pin offset) push them into place with your tweezers.

Once you're sure everything is in place, carefully take your board with tweezers and put it on a heat resistant surface.

Step 8: Test and Cheer!

After the board has been cooled, test it! If everything went right and the board programs and/or the LEDs light up, you'll be very happy! If it does not work immediately, take a good look at all the solder pad and use a multimeter to figure out if any connections shorted or didn't connect at all. If this happened you can simply put the board on the hotplate again and add/remove some solder on the place an error occurred. Something you need to look out for is that the PCBs will slightly warp from the heat, this means that the second time you put a PCB on the hotplate, the edges might not touch the plate and it will take longer for the solder to heat up in those areas.

I was very happily please with how easy and error-free this process went and I hope this Instructable will help you as well!


Edit:
As some of you have noted, the Weller soldering station and hotplate I used in the photo's, is not really in the price range of most hobbyists. But there is no need for such fancy equipment. Sparkfun swears by their skillet, Hobbytronics makes use of an electric stove and at Reprap they use a cheap cooking hotplate.

Also, I don't have a clue on what makes a good solder paste/flux and which one you should buy. Some of them have a syringe attached for easy application. Maybe an expert could chip in on this part?

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    42 Discussions

    Thank you for your Insights...your knowledge and expertise is greatly appreciated!

    NOW I have to try this. In the 70's as a teen, projected like crazy. then came family. now am retired and finally getting into the box of old parts again, got my first raspberry pi from my nephew for christmas. I'm all excited to start soldering smaller stuff. knew about heatguns, this is so much better. THANK YOU. I love the new tech, so many more possibilities. like being a kid all over again.

    Awesome work. And as you wished, I have voted you in all three contests ;)

    Please see my instructable for a hot plate every bit as good as the Weller but you will get change from $20 for the parts! https://www.instructables.com/id/Heating-Plate-for...

    My preferred method is to heat the plate to 150C, place the PCB with solder paste and component(s) in place and then use a hot air gun (board still on the hot plate) to do the final bit of the heating.

    For solder paste I use standard paste from Farnell (Newark) etc but transfer it into a 1mm syringe with a fine needle. I also keep it in my fridge (suitably double wrapped) so it lasts longer. Mike

    used a old creepy crawler hot plate, cheap small and easy

    I was unable to find a hotplate so I Came up with my own technique to solder small parts and since I don't have 3 hands I used the device with the magnifying glass that the call a 3rd hand to solder the tiny resistors on a PCB. I used the alligator clip to hold the solder I then positioned it over the pad that I needed to solder and once one side is soldered in then it's easy to straighten and solder the other side, I used a rotary tool to grind a tip down to a very fine point as well and of course antistatic tweezers. It took me a fairly long time to figure this out and this is how I found this article in the 1st place, I didn't have the needed items and that's when this idea came to me. The 1st thought I had was to try and get something to hold the iron kinda like a spot welder but it wouldn't have worked, there is another way as well you can drop a bit of solder on one of the pads then you use the tweezers to hold the part heat the solder and position the chip in place this works fairly well but you have to have a small tip. Note: if you do try using what I refer to as teh presoldered pad only do it on one side and don't put too much solder on the pad all you want is enough to tack it down then solder the other side and add more solder to the pre-soldered pad if necessary. if you put too much solder on the pre-soldered pad it will make placing the chip or resistor straight and flat against the pcb

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    BasD3

    2 years ago

    Great tutorial.

    Anyone thinking of using conventional cooking appliances, sure they work but DONT use them for cooking afterwards. Ever.

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    tym3k

    3 years ago

    Is it possible to use a 3d printer heatbed for smd soldering? Like this one:
    http://pages.ebay.com/link/?nav=item.view&alt=web&id=281541422180

    Is there any reason that, once you have finished soldering, you couldn't just turn the hotplate OFF instead of moving the PCB off of it? That way you don't risk bumping or jarring the board and moving the parts while the solder is fluid. Just a thought....

    Nice instructable!

    2 replies

    Seems perfectly logical to me... although if you're doing batches then that wouldn't be possible. Then again, I don't personally have experience with this sort of thing (tiny components and using a hotplate to solder, that is) so maybe not.

    My reason is that I'm making a small series of boards and the hotplate is only big enough to fit two boards on. Your way might just be superior as the fast heating/cooling could have the small chance of putting undesirable stress on the components and damage them.

    Thanks for reading the instructable!

    Very impressive - I was just recently wondering how hard it would be to solder those miniature surface mounted components. It still doesn't look too easy, but perhaps some practice (and hotplate) would help.

    How sensitive are those tiny chips to static electricity? Did you use any anti-static precautions?

    Thanks!

    2 replies

    SMD components are just as sensitive to static as DIP components. I would use a grounded wristband and make sure any line-powered tools are fully grounded (they have a three-wire cord) - especially soldering irons! An anti-static mat couldn't hurt either.

    I didn't take any precautions except for working with quality tools and components. Using an anti-static wristband might actually be a good safety measure next time. Actually one of the accelerometers failed to connect on the end product for reasons unknown; it might as well have been damaged by static electricity now I think about it...

    K type thermocouple thermometers are available on eBay. I got one from sinedy for less that 4£ with 2 fibreglass insulated probes with plugs. just clamp the little blob at the end of the cable, and control the temperature manually. I am going to cut the flat bottom from an electric kettle and attach a k type probe. for less than £2 they also sell a 2kw triac module, just set it to give a stable temperature. If you want to be really fancy a pid temperature controller (k type) can be bought off eBay for about £10, though set up might take some skill, time and patience. get one that comes with its own SSR(solid state relay) to be sure its suitable. all this smd came along after my time but I'm getting back into it.

    You can, but this way, you can fix mistakes while it is still hot, instead of needing to reheat for rework. Also, your pizzas won't smell like solder ;)

    A lot of amateur radio homebrewers (ham speak for DIY) are fans of Cash
    Olsen's solder paste which he sends preloaded in a syringe with a tip for $5 + $3 shipping and handling. You can
    find it at www.kd5ssj.com He uses a beverage warmer that he got at WalMart for $1.87 as a heat source. Some use an alternative technique using an embossing gun (about $15) at craft stores to supply the heat which allows more control of time, location and amount of heat on the board.

    Nicely done 'ible.