So you are using a bare attiny85 in your next project but don’t have room for the programming header, What do you do? I came up with the idea of using pogo pins layed out on A PCB so that they will sit on top of the Attiny85 legs. I used standard male jumps at each end of the chip to help line it up.
So when I was into using just a atmega328 dip chip I make a programmer header for it that also had a crystal and the capacitors need to make it function. I wanted to do the same for the attiny85. As you know you have to use a ISP programmer to flash the attiny85, This requires you to look up the pinouts and get a bunch of jumps out to wire it up. I wanted to eliminate all of this.
We’re used to reflow soldering of our PCBs at the hacker level, for quite a few years people have been reflowing with toaster ovens, skillets, and similar pieces of domestic equipment and equipping them with temperature controllers and timers. We take one or two boards, screen print a layer of solder paste on the pads by using a stencil, and place our surface-mount components with a pair of tweezers before putting them in the oven. It’s a process that requires care and attention, but it’s fairly straightforward once mastered and we can create small runs of high quality boards.
But what about the same process at a professional level, what do you do when your board isn’t a matchbox-sized panel from OSH Park with less than 50 or so parts but a densely-packed multilayer board about the size of a small tablet computer and with many hundreds of parts? In theory the same process of screen print and pick and place applies, but in practice to achieve a succesful result a lot more care and planning has to go into the process.
This is being written the morning after a marathon session encompassing all of the working day and half of the night. I was hand-stuffing a row of large high-density boards with components ranging from 0402 passives to large QFPs and everything else in between. I can’t describe the board in question because it is a commercially sensitive prototype for the industrial customer of the friend I was putting in the day’s work for, but it’s worth going through the minutiae of successfully assembling a small batch of prototypes at this level. Apologies then, any pictures will be rather generic.
Some of you reading this will now be asking “What on earth are you doing making this run of boards by hand, you should be doing it with a pick-and-place machine, or you should be hiring a specialist company!”. The answer to that isn’t really mine to give as the boards weren’t commissioned by me, but in reality it’s a nuanced decision based on a combination of cost, number of boards, and the eventual customer’s deadline for a trade show. Setting up a pick-and-place for a very large job is a performance in itself, and for a very small run of boards there is a hard financial decision to make over whether it is justified.
So there we were, setting out to make a batch of eight prototype PCBs. The story didn’t start on the build day, instead a few weeks ago the Bill Of Materials, or BoM, was exported from the CAD package, and the task of sourcing all the components began.
It stands to reason that the complexity of component sourcing increases with the number of individual component lines in the BoM. If your design consists entirely of generic components that every supplier has by the reel then sourcing is as simple as making the order, but sadly very few real designs are like that. So this step became an involved trawl through an array of suppliers for the elusive parts, sometimes ringing company reps to beg a few free samples.
The Great Gathering of Components
In the days running up to the build, a variety of packages arrived containing the components. There began the second major task, that of collation. It’s necessary to both ensure that everything has arrived and is the right component for the job, and to index and array them in a form such as to make the placement on the boards as easy as possible.
We started with a storage box of the type designed to hold hanging files. Each hanging file was labeled with a range of numbers corresponding to BoM lines, so 1 – 5, 6 -10, 11 – 15, and so on to the end of the BoM. Every line on the BoM spreadsheet was checked, that the component was present, was it compatible with the package it should be on the board, and was it present in sufficient numbers to populate the boards. Its line number from the spreadsheet was written on the label, and the spreadsheet was updated to show that it was present. The numbered bag of components was then placed in the appropriate hanging file for its line number, and the process was repeated with the next line number and so on until the whole BoM was covered.
At the end of the component collation, we had a box of hanging files containing numbered component lines, and inevitably there were a few lines which either weren’t quite right or hadn’t arrived. Some last-minute overnight ordering was in order, followed by collation steps for those parts.
It might seem like a lot of work to put in before making any boards, but this couple of days getting everything in a row will save you time when it comes to populating the boards, and will in turn result in better quality final prototypes.
On the day of the build, our components were all collated and were handed a stack of bare PCBs from the board house. We set up adjacent workstations for the two of us, and set to work.
Become a Paste Aficionado
The first task when populating boards is to screen print the solder paste on the pads. We used the jig supplied by the board house for this task, with locating pegs fitted to align both board and stencil, and extra pieces of scrap PCB material taped down to support the stencil beyond the edge of the board.
Screen printing solder paste is in principle quite simple. Align the stencil with the pads, and using a scraper spread a layer of solder paste over all the holes. When you lift the stencil away the board should then be left with a uniform layer of solder paste on each pad, ready to have a component placed on it.
Describing this crucial step in those terms makes screen printing solder paste sound so easy, but of course it isn’t. The paste consistency is very important for a large board in the way it isn’t for a small one. The paste you print on the pads will spread out over time, and eventually your closely spaced tiny pads will be completely obscured by an amorphous blob of paste. If you have a small board you can get away with it, but on a large board it’s important to ensure that the spread is not too quick. You’ll then have a chance to place your components and reflow the board while the printed solder is still well-defined.
It’s best to describe the optimum solder paste consistency in terms of smooth peanut butter. Think of the perfect-spreading peanut butter, it’s not the runny stuff at the top of the jar where the oil has started to separate out, neither is it the stuff at the bottom of a jar that’s stood in the fridge for six weeks and goes all clumpy as you spread it on your toast. It’s the easy-spreading middle of a new jar, keeping its consistency and just about right for your knife. And so it is with solder paste, for a large board you need to very carefully ensure that your paste is well-mixed, and not dried out. Too runny and it will quickly spread out, while too thick and it may clump in the stencil and not stick to your pads. It’s something you gain a feel for with a bit of experience.
With the jig, stencil, scraper, and boards ready, and the correct consistency of paste to hand, there is one more step before spreading. Clean everything with IPA solvent; every single PCB, stencil, board, jig, the entire lot. It seems tedious, but it will make the difference between good and poor results. All drying paste residues, dirt, and oils can affect the quality of the job, and you need the best possible result.
After all that effort, the paste scraping itself is very quick. Make sure you have enough paste on your scraper, draw it across the stencil in one go covering all the holes with a firm pressure. Lift the stencil away, and inspect the quality of your paste printing. Don’t be afraid to clean it off and do it again if you aren’t happy with the results, we redid a couple of our board run.
Knowing Your Place
Towards the end of the morning then on our build day we had a row of boards ready screen printed with solder paste. They were lined up in front of my friend at one workstation, while at the other I had the box of parts and the BoM both on the computer and as a print-out. We both had large-scale print-outs of the component layout, and my job was to supply the tape of each component line in turn with the plastic strip ready lifted at the end, while he placed the components using a vacuum pencil and a magnifier. He has better dexterity for those 0402s than I do. The task of spotting component positions was shared, a game of Where’s Wally/Waldo on paper and computer, but without the stripey jumper.
Once you have started stuffing boards you are in a race against the spread of your solder paste, so there is no letting up until the task is complete. In our case the whole process took us all day and well into the evening, working through the BoM omitting any large components that would obstruct access for smaller one, then returning to fit them in a second pass. There followed a checking step during which a few inevitable omissions were rectified, no matter how hard you try there will be a few that you miss. Through all this process all that work collating components came into its own, when asked for any line I could pick it out in very short order, and I could return to it when any omissions were detected.
Bring the Heat
The final step was the reflow soldering itself, in this case with a small purpose-built reflow oven. Each run became a ten-minute anxious wait watching the display as the temperature cycled through its ramp, smelling the flux smoke and finally lifting the finished board from the drawer. There is something magical about the process of reflow soldering, watching messy spreading paste going in and bright well-defined solder joints come out. We examined each board as it came out, and it is inevitable that each one will require a small amount of reworking. There will always be a few bridges between adjacent pins or even components slightly off their pads, but this is the nature of prototype assembly.
After a very long day and a lot of preparatory work before that, we had a row of prototype boards. We should be able to commission them all as working devices, and from those my friend will have more than enough to satisfy his customer’s demand. All of the above describes a very long and tedious process but there is no reason why any Hackaday reader should not also be able to do a large board with a bit of practice. If we’ve inspired you to have a go at reflowing your own boards of whatever size then share the results with us on hackaday.io, meanwhile if you have any tips to further streamline the process with larger boards we’re all ears.
[Moony] thought that it was unconscionable that IR soldering stations sell for a few hundred Euros. After all, they’re nothing more than a glorified halogen lightbulb with a fancy IR-pass filter on them. Professional versions use 100 W 12 V DC bulbs, though, and that’s a lot of current. [Moony] tried with a plain-old 100 W halogen lightbulb. Perhaps unsurprisingly, it worked just fine. Holding the reflector-backed halogen spotlight bulb close to circuit boards allows one to pull BGAs and other ornery chips off after a few minutes. Voila.
[Moony] reasons that the IR filter is a waste anyway, since the luminous efficiency of halogen lights is so low: around 3.5%. And that means 96.5% heat! But there’s still a lot of light streaming out into a very small area, so if you’re going to look at the board as you de-solder, you’re really going to need a pair of welding goggles. Without, you’ll have a very hard time seeing your work at best, and might actually do long-term damage to your retinas.
So the next time you’re feeling jealous of those rework factory workers with their fancy IR soldering stations, head on down to the hardware store, pick up a gooseneck lamp, a 100 W halogen spotlight, and some welding goggles. And maybe a fire brick. You really don’t want your desk going up in flames.
This is 2016, and almost every hacker dabbles with SMD parts now, unlike back in the day. This means investing in at least some specialized tools and equipment to make the job easier. One handy tool is the SMD soldering tweezers – useful not only for manual soldering of parts, but also for de-soldering them quickly and without causing damage to the part or the board. Often, especially when repairing stuff, using a hot air gun can get tricky if you want to remove just one tiny part.
[adria.junyent-ferre] took a pair of cheap £5 USB soldering irons and turned them into a nifty pair of SMD soldering tweezers. The two irons are coupled together using a simple, 3D printed part. [adria]’s been through a couple of iterations, so the final version ought to work quite well. The video after the break shows him quickly de-soldering a bunch of 0805 SMD resistors in quick succession.
We’ve all had that treasured pair of headphones fail us. One moment we’re jamming out to our favorite song, then, betrayal. The right ear goes out. No wait. It’s back. No, damn, it’s gone. It works for a while and then no jiggling of the wire will bring it back. So we think to ourselves, we’ve soldered before. This is nothing. We’ll just splice the wire together.
So we open it up only to be faced with the worst imaginable configuration: little strands of copper enamel wire intertwined with nylon for some reason. How does a mortal solder this? First you try to untwine the nylon from the strands. It kind of works, but now the strands are all mangled and weird. Huh. Okay. well, you kind of twist them together and give a go at soldering. No dice. Next comes sandpaper, torches, and all sorts of work-a-rounds. None of them seem to work. The best you manage is sound in one ear. It’s time to give up.
Soldering this stuff is actually pretty easy. It just takes a bit of knowledge about how assembly line workers do it. Let’s take a look.
So what is enamel wire anyway? Enamel wire starts off as, typically, a freshly drawn copper strand so there’s absolutely no oxidization or surface film on it. It’s then immediately run through an enamel mixture (typically polyurethane) and dried. This results in a very thin, practically invisible flexible coating all along the strand. The coating isn’t exactly perfect, when looked at under a microscope there will be obvious thick sections along its profile depending on how it was wound, the speed it was coated, and how the coating was dried. Either way, the name of the game is to selectively remove this coating on all the little strands at once without removing any where you don’t want to.
Since this coating is so thin it doesn’t take much to break through and get to the shiny copper underneath. Going back to the assembly line, all it takes is a bit of heat and flux and you’re good to go. The nylon stranding can be safely ignored, it melts and floats to the surface of the solder bead during soldering. As long as you have flux it will keep the remaining organics from interfering. This is why you may see some black specs on the surface of a typical connection to enamel wire.
As for soldering the wire. The first step is to make sure you have a really clean cut into the strands. For this I recommend first carefully prying away a generous amount of shielding. Then, with a brand new blade on a utility knife, slicing the stranded ends flat against a cutting mat. Even with my nicest end cutters, the strands were just too thin to cut nicely.
Next, simply apply a generous amount of flux to the end of the enamel wire you’d like to solder. It doesn’t hurt to flux the tab or wire you’re trying to connect it to as well. Try to thread or intertwine the wire to its mating part without disturbing any strands. Then, use good solder and bond the usual way. The trick is to apply heat until you see solder just creeping up the enamel wire. It will be pretty hard to see as only the enamel closest to the joint will burn away cleanly enough for wicking to occur, so a magnifying glass is recommended.
For larger gauges of wire this technique will work too, up to a point. It’s only when you get to the serious gauges of enamel wire that a bit of sandpaper is productive. For the small stuff flux and heat is your friend.
The core of the build is a 16 bit microcontroller a dsPIC33FJ128GP802 from Microchip. It’s a humble chip to be doing so much. It uses a UBlox NEO-6M positioning module for the location and a custom built QFH antenna built after calculations done with an online calculator for the GPS half. The audio half is based around a VLSI VS1003b decoder chip.
The whole build is done with protoboard. Where the built in traces didn’t suffice enamel and wire wrap wire were carefully routed and soldered in place. There’s a 48pin LQFP package chip soldered dead bug style that’s impressive to behold. You can see some good pictures in this small gallery below.
The interface is a standard gLCD and an analog joystick with a click. The mp3’s and map data can be loaded with an SD card. There’s still a bit of work to be done, for example, he hasn’t figured out what to do about batteries yet. If you’re interested in more, there are a few videos dedicated to the build on his YouTube channel and there are likely to be a few more.
I guess it comes down to this: did [Brek] add a GPS to an mp3 player because he gets lost while listening to music, or did he add a mp3 player to his GPS because he likes listening to music while he’s found? Philosophy aside, it’s a beautiful build.
We’re all used to temperature controlled soldering irons, and most of us will have one in some form or other as our soldering tool of choice. In many cases our irons will be microprocessor controlled, with thermocouples, LCD displays, and other technological magic to make the perfect soldering tool.
All this technology is very impressive, but how simply can a temperature controlled iron be made? If you’re of an older generation you might point to irons with bimetallic or magnetic temperature regulation of course, so let’s rephrase the question. How simply can an electronic temperature controlled soldering iron be made? [Bestonic lab] might just have the answer, because he’s posted a YouTube video showing an extremely simple temperature controlled iron. It’s not the most elegant of solutions, but it does the job demanded of it, and all for a very low parts count.
He’s taken a ceramic housing from a redundant fuse holder, and mounted it on a metal frame to make a basic soldering iron holder into which the tip of his unregulated iron fits. To the ceramic he’s fitted a thermistor, which sits in the gate bias circuit of a MOSFET. The MOSFET in turn operates a relay which supplies mains power to the iron.
Temperature regulation comes as the iron heats the ceramic to the point at which the thermistor changes the MOSFET and relay state, at which point (with the iron power cut) it cools until the MOSFET flips again and restarts the process. You may have spotted a flaw in that it requires the iron to be in the holder to work, though we suspect in practice the thermal inertia of the ceramic will be enough for regulation to be reasonably maintained so long as the iron is returned to its holder between joints. Nobody is claiming that this temperature controlled iron is on a par with its expensive commercial cousins, instead it represents a very neat hack to conjure a useful tool from very few components. And we like that. Take a look at the full video below the break.
Those of us who have spent a lifetime building electronic projects have probably breathed more solder smoke than we should. This is not an ideal situation as we’ve probably increased our risk of asthma and other medical conditions as a result.
It has become more common over the years to see fume extraction systems and filters as part of the professional soldering environment, and this trend has also started to appear in the world of the home solderer. As always, where commercial products go the hardware hacker will never be far behind. We’ve seen people producing their own soldering fume filters using computer fans.
A particularly neat example comes via [Engineer of None], who has posted an Instructable and the YouTube video shown below the break for a filter mounted on a desk lamp. A toaster is used to heat a piece of acrylic. The softened plastic is then shaped to fit the contours of the lamp. The lamp’s articulated arm is perfect for placing light and fume extraction exactly where it is needed. It’s not the most complex of hacks, but we’d have one like it on our bench without a second thought. We would probably add an activated carbon filter to ours though.
We’ve featured quite a few fume extractors over the years, like this ducted fan, or this downdraught workstation. It’s safe to say though that many of them have been a lot more cumbersome than this one.