Instructables

Hand-soldering teeny tiny chips!

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Have you ever looked at a chip that's smaller than your fingertip, and has no pins, and wondered how you could ever possibly hand-solder it? another instructable by Colin has a nice explanation of doing your own reflow soldering, but if the your chip is not BGA, and you want a technique that's quicker and won't put as many poisonous fumes into the air, read on...

p.s. here's what you need:
- soldering iron (fine tip)
- microscope (or very, very good eyesight)
- some flux will help (flux pen)
 
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Step 1: Check out the chip

Make sure you know which orientation the chip is supposed to go on the PCB. In this picture, you can see the little dot to the left of 'CYG'. The convention for chips is that that the little dot indicates the top-left corner of the chip, and you can have a look at the PCB layout diagram to figure out how the chip is meant to be oriented on the board.

Step 2: Tin the pins (and maybe the pads)

Turn the chip upside-down, and melt a little dab of solder onto each of the pins. You can do the same for the board too, if you want. Make sure you heat the metal of the pad enough to melt the solder itself, rather than melting the solder with the tip of the iron directly. After you tin all of the pads, use a flux pen to put some flux onto the board where the chip will attach.

Step 3: Put the chip in place

Turn the chip right-side up, and gently nudge it into place with a pair of tweezers until it's centered on the spot where it belongs.

Step 4: Connect top to bottom

Now comes the fun part. One by one, you need to heat the balls of solder that you've created, so that they become connected to the chip *and* the board. You can do this by touching the pads/pins from the side with the soldering iron tip, and sometimes wiggling it up and down to encourage a connection to form. A nice trick for the first pin that you solder (can be any pin, it doesn't really matter which) is to hold the chip firmly in place with a pair of tweezers (pin it down to the board), and touch the hot iron to the pin/pad in one corner until the solder bridges the gap. With any pin, you may need to wiggle it up and down, or add a little more solder (see the picture) to get it connected. But don't add too much, or you risk bridging pins underneath that shouldn't be bridged. With even just one connected pin, the chip will be stable enough that you can do the rest without having to keep it pinned down. You can work your way around the chip, connecting each pin to the board until you've got them all. See the next step for how to make sure you've connected everything successfully.

Step 5: Check your work

Now you can tilt the chip up on and look at the connection points, to see if you've made all of the connections successfully. Zoom in enough that you can see if the solder is going all the way from pin to pad or not. For the ones that are not, add a little more solder to the pad and wiggle the iron up and down until you get it to bridge, like a stalagtite meeting a stalagmite.

Step 6: Go for it!

Once it all looks good, give it a try! With a microcontroller, the first thing to do is to try programming it and see if it responds. From there, you can test if it can interact with the things that it's connected to (LED's, sensors, actuators, etc). Happy soldering!
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Orngrimm2 years ago
I prefer to presolder the chip (Like you did here), but then after the positioning (and securing), ill take my heatgun, set it to 410°C and quickly solder all points down in a few secs. No additional solder is needed and the result is much less excess tin around the pads.

I succesfully soldered this way down to 0201-sized SMD-Items. Havent had to solder 01005 (Fortunately) but who knows...

Anyway: Your instructable is nice and explains the process quite well and also does note the important part of checking the solderpoints afterwards.
Nice instr.!
Wouldn't the use of a hot air gun be detrimental to the chip? (obviously not, as you have used it) Whenever I use mine for whatever task (shrink shrinktubes, bend plastic) it will burn stuff very very quickly.

Hot air gun is the right translation I think :-) I just call it an 'Hete lucht pistool' :-)
My Hot Air Gun is not a cheap one with only ON/OFF but with a digital part with sensor and stuff. Costs over 100 Euros.
You can set the temperature and air-flow and oh-boy does it regulate the temperature well! We measured it against a calibrated PT100 and it came out in just around 2% error. Not bad!

See 2nd image @ Amazon: http://www.amazon.de/STEiNEL-Hei%C3%9Fluftgebl%C3%A4se-HG-2310-LCD/dp/B000UXBMVS/ref=sr_1_1?ie=UTF8&qid=1349882910&sr=8-1

The trick is to set the temperature to just a few degrees above the melting-point of the tin or paste you use.
Normal Chips can witstand such temperatures without any problems for quite some time... I once tripple-re-Soldered an FRAM tis way... Took 5 Minutes of hot-airing in total for sure. No problem at all for the Chip...
I like the sound of a heat gun. Do you use a pencil style heat gun, or can a regular size heat gun work? Just blast it for 5 secs?
Unsure what it is called in english... Native swiss guy here speaking german ;)
I use this one: http://ch.farnell.com/steinel/hg-2310lcd-eu/heissluftpistole-230v-eu-lcd/dp/1712315 which is with 330 swiss francs a very expensive one...
Cheaper ones also work no problem... But i like the option to regulate the temperature to degrees and not only with "1-10" and also being able to adjust the airflow independent from the rest...

So yes: Large one; not stylus-type like http://ch.farnell.com/oki-metcal/hct-900-21/heissluft-loet-entloetstation/dp/1015504 as an example.

Heatgun may NOT be the term you use... In german it is "heissluftpistole".
Heissluft = hot air / heat
Pistole = handgun / gun
So heatgun seems to work... Also wikipedia knows it with this name:
http://en.wikipedia.org/wiki/Heat_gun
"They are also used in electronics to desolder circuit board components" is even listed in the wiki! :) And also there is a citation needed.. Maybe they want to link to here? ;)
cgosh2 years ago
Great Instructable, terrific photos! Thank you.

I like Caig Labs Circuit Writer, a pen-shaped dispenser that places a small dab of conductive glue that dries hard. For tiny connections, transfer it with the tip of a straight pin. No worries, no shorts, no heat. Clean surfaces, but flux is probably not needed. About $20, check Froogle.com

I've used it to place surface-mount capacitors, resistors, etc. directly to the pins of mini-DIP IC's and create power buss traces on the case, so I make tiny projects with no PC board, then encapsulate with clear epoxy or hot-melt glue. Use 40-ga. Kynar or "wire-wrap" wire for jumpers.

For a tiny solder pencil tip, file a piece of solid wire to a point and hold with pliers and wrap it tightly around the tip, then tin the wrap and the point. The common copper wire used for electric outlets is handy.

If your eyesight is lacking, try a pair of "readers" eyeglasses at any drugstore for a few dollars or get a set of magnifying glasses on a flip-up headband.

For a steadier hand, hold tools closer to the work, same as you were taught to choke-up on a baseball bat to improve control. Also hold your hand against a solid surface, same as steadying a camera.

The "ground" shown in the center of the chip above also acts as a heat sink, so heat will determine its need. Digital circuits rely on solid supply voltage and reliable ground. If either is the least bit flaky, odd results will occur, so make sure both are solid.
kc8hps2 years ago
I had a chip have crack issues on the joint/trace junction etc. I found that by using a flat nose 30 watt iron I could flow solder over all traces. some became joined but that is ok because your only half way there.

Take a piece of solder wick and lay over a line of connections. have a slight film of flux on your wick. heat it and any solder not attached to a trace/connection will be removed by capillary attraction to the wick, leaving nice chip to joint attachments. remember to lightly use some alcohol to (read Q tip) to remove excess flux as sometimes I can make a chip act funky.
beehard442 years ago
I have a different technique. I first apply some solder on 1 PCB trace, let cool. Place chip with a bit of downward pressure, make sure it's aligned, melt the solder. Then i just take advantage of capillary action and melt the solder on the traces and it'll just go to the pins. Too much=short though. Alot of flux helps.
Derin6 years ago
my friend said that he had a chip smaller than his thumb,I shoulda believed him!
Many chips are smaller than a grain of rice these days. Open up some broken electronics made in the last 5 or 10 years, I doubt you'll find chips with actual through-hole leads.
It's rather irritating when your parts *require* a custom etched circuit board to even be used.
tinker2343 years ago
wow that is small hey could i make a robot that small hmm i wonder
There is one huge problem with your method. You put solder on each pad, which has thickness. Then you melt only one pad, when you do this all the other pads will keep that one pad from properly seating. As a result the entire chip will not be seated properly. If you could heat all pads at the same time, then this would work.

What I do is put solder on only one pad, then solder down that one pad. Then I head each trace and have the trace melt the solder. This will cause the solder to wick-up onto the pad. This way all the pads are properly seated.

I like your ideas of using the Flux marker, I didn't know these existed.

-Matt
Thanks for the good tips. I have never done anything before............I am starting out doing whatever I can do with electronic stuff, because I started with PCs...um, this is my project and after reading your post I may have a go at this 3rd generation ipod headphone to motherboard connecton repair job. Tricky because the wires on the "board" part are torn from the chip pins.
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Wesley6665 years ago
Just as a question, did you mean to buy a chip that small or were you just not paying attention? As well what are you building?
davidmerrill (author)  Wesley6665 years ago
I needed a chip that small -- I was building a little battery powered ring that could communicate using infrared, so everything had to be tiny!
Good answer! LOL
AtomSoft5 years ago
NO need for steady hands. Just get some Masking Tape and your set. Use a razor to cut a long thin strip and place over half the IC and then solder a few pins and remove tape and continue the rest.
Cheyyne8 years ago
Nice! Doesn't really address the major problem, though, and that's the requirement of VERY steady hands...
davidmerrill (author)  Cheyyne8 years ago
yeah, you might want to avoid having too many cups of coffee on the morning that you're doing this!
Take some dramamine before soldering (or dissecting tiny critters). Will steady your hands right up. lol People have been know to use this tactic to fool lie detectors as well. though at larger intake levels.
I took a developmental bio course once where we had to dissect zebrafish and mouse embryos and the prof made a point of telling us not to drink coffee on lab days =D
Grey_Wolfe6 years ago
I used to work for a company that made ery specialized computers. Since our order numbers typically were in the teens for a given year, we did everything by hand. There were only like two surface solder parts per system, but this is actually the same technique I used.
safdar6 years ago
whats the point?
g_c_c7 years ago
Another good tactic is to put a drop of solder on each of the pads, use a flux marker on them, then use a torch to heat a razor blade to red hot. I've only tried it once, and on larger parts than that, but- might be worth a try.
bfr8 years ago
Cool. I didn't believe this was possible when I first heard about it, but now I think it's just as easy, if not easier than soldering leaded packages since bridges are harder to make. I use paste rather than solder though which makes a big difference. I also remove the solder balls with wick first so the chip sits flat. A chisel tip also helps a lot, fine tips aren't that great unless you have a metcal :-)
wiml8 years ago
Nice howto. One quibble— the dot actually indicates where pin 1 is. For most chip packages, pin 1 is in the top-left, but that's not always true. PLCCs have in 1 in the middle of one edge, and the dot is there. (The even poorer man's reflow is solder paste and either an oil lamp or a stove burner. Tricky to get the temperature profile right, but it works. I recommend an aluminum heat-spreader plate. Actually, I recommend using better equipment. :-) )
bikeNomad wiml8 years ago
http://www.sparkfun.com/commerce/present.php?p=Reflow%20Skillet is a tutorial on using an electric skillet for reflow work.
chuckcolby8 years ago
If you put a piece of Kapton tape on the bottom of the chip and cut the tape so it is flush with the side of the chip, it will keep solder from going under the chip. This means less chance of out of sight shorts and it also makes it much easier to remove the chip by using Solder-Wick to remove the solder at each pad.
The tape won't work for this chip or any other center-pad QFN chip because they have to have their center soldered down for thermal reasons. Also, this kind of chip *should* to have solder underneath it, since that's where its leads are! If you solder without any going underneath, you'll have connections that will crack easily.
johnpombrio8 years ago
I wonder if there are sockets for these surface mount chips. I guess you could also solder leads to the pads then snake the leads through the thru holes on the board. I watched a factory worker repairing surface mount stuff and she had the finest tipped soldering iron and a big magnifier!
There aren't sockets for these chips (other than maybe test/programming sockets, but you can't afford them). For one thing, the center slug must be soldered down for thermal reasons. But look at http://www.schmartboard.com/ for easily-soldered boards for a variety of package styles. For instance, this 20 pin chip should work with http://www.schmartboard.com/index.asp?page=products_csp&id=74
Unfortunately, the chips that I've had to use in this kind of package (switching power supply regulators) can't stand the extra lead length.
davidmerrill (author)  johnpombrio8 years ago
I am thinking about making a little breakout board ("surfboard" as they are called sometimes) so that I can prototype with this chip on a regular breadboard.. I think that you *could* solder little "wire-wrap" wires to the leads, but they would probably keep breaking off due to the strain and small attachment area, and it would be very frustrating.
bikeNomad8 years ago
Instead of tweezers (which take a third hand if you're holding solder and an iron), you can do what I did and make a jig for SMD soldering out of a piece of wood and a piece of wire.
SMTSoldering1.jpgSMTSoldering.jpg
davidmerrill (author)  bikeNomad8 years ago
very nice!
This is a great instructable. Very useful. I would only suggest putting more emphasis on the flux. Effective use of of a liquid flux can make things MUCH easier. It helps get the pins and pads heated quicly, it also helps the soldier magicaly flow to the right places. The flux despenser I use has a little needle to release small drops of it for fine work like this. I hope you post more like this one, it may inspire someone to build something they otherwise would be afraid to.
davidmerrill (author)  kimota.nomis8 years ago
thanks for the feedback. when I first tried to solder little surface-mount stuff, I was really intimidated - it looked IMPOSSIBLE! But once you have some practice, and learn useful techniques like the one I've presented here, it becomes a tractable problem, and doesn't seem so bad after all. I hope others will be inspired by this, and believe that they can do it too!
The major problem with this technique is that the ground slug in the middle of the part usually needs to be connected to GND for properl electrical connection, heat dissipation, noise reduction (ground return current noise), and mechanical stability.

A hot air pencil for plastic welding (such as the expensive Leister Hot Jet S http://www.malcom.com/products/hotjets.php ) with liquid flux makes this a very easy process. Tin the pads of the part and the board as evenly as possible. Place the part in the proper location with flux underneath.

Apply heat with heat gun until the part literally "sucks" into place. While reflowing give a gentle tap on the side of the part (with tweasers) to nudge the part out of place so that it will naturally rebound into the proper location.

With inexpesive boards such as the one shown in the above photos, multiple reflow processes will eventually cause the pads of the part to be lifted. For part removal, use the same process (lots of flux and gentle heat). Once you can tap the part out of position you're reflowing and can then pull the part directly off the board.

For an inexpensive heat gun, the major consideration is to not use too much heat, and to MINIMIZE the airflow (otherwise you'll blow parts off the board).
davidmerrill (author)  skipandmadge8 years ago
I have a labmate who claims that a heat gun made for melting heat-shrink tubing will also work for this..
Stereo Microscope would be nice but expensive so I bought handsfree magnifier glasses to fit into my head like a cap and with a hinge to push up the lenses. These are available at electronics hobby shops.
nv0u8 years ago
Reflow would work better, however instead of using a hot air gun (which could blow the thing off the board) try using an old convection oven. Set the temp to about 150F for 5 mins or so, then crank the temp up to 400F for about 1 minute max. Watch in amazement as all the parts seat themselves.
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