EEVblog #1306 (2 of 5): PCB SMD Hand Soldering & Assembly

hi this is part two of the paduk three cent micro controller programming series where we build up open source uh programmer hardware and install the open source software to program these three cent micro controllers so part two here is just going to cover assembling this pcb so there's lots of like soldering and assembly tips and stuff like that let's go a little while later all your stuff just magically appears pcbs and all your parts are baggied straight from willy wonka's chocolate factory all right let's have a look at our pcb here using our tagano and we're in like flynn check it out all right doesn't that look neato unfortunately of course there's no silk screen overlay so we have to uh like use an overlay diagram if we're going to assemble this sucker and let's just uh check we didn't get any of that gold flash rubbish so let's just go in and check out the alignment on the solder mask expansion you can see we've got our solder mask going between pads there no worries that's pretty good that's a reasonable alignment for a proto like this no problems whatsoever there's no you know they're not overhanging the pads or you could argue and there's a little bit of overhang on the pad there but you know nothing near right home to your mum about for however couple of dollars we paid for these things um it's just yeah it's just fine and the registration on the villas hey look bang on look at that smack in the middle no wackers um and of course this board is uh has tented vias which means that the solder mask comes over the veal like that um no they're not actually plugged it's just that the solder mask happens you can't actually get plugged vias that's a separate process this is just the solder mask just goes over the top and sometimes you get it to like so is that got a little pinhole in it sometimes you get like complete coverage like that and these ones down here other times you'll get it you'll actually get a hole through there do we actually have a hole through there do we actually have light coming through that hole no i don't think so no anyway sometimes you get it going through and sometimes you don't just depends on how the dice rolls anyway that board looks pretty decent more than decent enough for a proto when i was a boy you couldn't even get something like this for a hundred bucks let alone a couple of bucks you know if you paid 100 bucks and you'd get a it was a miracle when paid 100 bucks and you could get like a tin plate board now this solder mask rubbish your tin plate so yeah anyway that's good enough for australia so what do we need for this well we need our schematic that's always handy then we need our overlay diagram yes the distortion in that uh barrel distortion there is caused by the lens on the tagana it doesn't go away unless i zoom you know all right it's still there still a little bit there but you know you zoom in near enough and then it's all right there we go zoom in a long way before it actually becomes fine that's to do with the lens that i've got on this thing because this thing's got like 30 times zoom it is huge i mean this is why i can go from a wide huge wide view like this with my hands to all the way in and this is not digital zoom this is optical zoom thank you very much and that's the price you pay for all that zoomty goodness anyway there you go gotta have our overlay and we got our bill of materials just in case you know you want to do some cross references and stuff like that um we don't actually have the designator in here so it's not entirely useful but anyway you might want to do a cross reference and the age-old debate of course whether or not you should actually put values on the silk screen overlay in this particular case um you didn't want this overlay because you wouldn't want to get this overlay printed because this uh the designator here would be smack on the pads and you don't want your um your silk screen overlay overlaying your pads that's going to ruin your day so like you know this has been optimized for not for printing on the board but it's been optimized for uh you know assembly but yeah there's a bunch of fan boys out there who love putting the component designator and the value on there and for assembly and for troubleshooting and repair and stuff like that good idea so with this board the first thing i'll put on because it's the biggest and it's just super satisfying to do it up front put the chippy on first and especially if you've got lots of parts like really surrounding the chips like this like close to the pins if you have lots of bypass caps there's not really that case here you could argue this one's a little bit close it's just that if you've got if you put all those passive parts on first around your chip then it can be hard to get in there and do you know get your iron in you've got to come in at a much higher angle like that rather than just rest your hand on the bench like that and come in at your normal angle you've got to tilt it right up and that can be annoying and that can impact your soldering technique all right there's our little chippy so we want it according to the diagram we want it like that up in the top right pin one up in the top right corner beauty all right before anyone asks i'm using my pace ads 200i in here because i just like it it's very nice and i'm using 0.38 millimeter uh tin copper i eat lead free solder so it's a 5 core flux multi-core brand and up i like using fine solder for surface mount stuff like this because you can just feed much finer control than if you use like point eight millimeter stuff like that you can just you know when you feed in onto the oh you can see the heat the shimmer in the video from the heat i love it anyway um yeah you can just feed in a more precise control over that solder so there we go it's maybe a bit more suitable although you can't use big tip no workers and no i'm not using any pcb holder or anything like that see even with this tiny solder look at the amount of solder that we've put on that pad already no i'm not using any uh pcb holder at all so there you go we've tacked wow a little bit off there you go that's a bit better it's a bit how you doing before there you go attack down one pin and then you just want to go in the opposite corner like this and tack that down as well just tuck that one down there like that and bingo chippity-doo-dah is not going to move anymore so now we can get in there and we can solder so i'll get my flux i just use a chem tools uh local brand no clean flux pen does the job some flux there we go we can go all the way around if you want just put some flux on there so that our joints are going to be cleaner all right should we do drag soldering or not oh yeah why not look i'll go to my well based tip and there we go you can see that's got a well in there and that helps the surface tension drag the solder away oh some daggies had some daggies hang on don't know where that came from there we go so we'll just feed some solder into there like that until it bulges out a little bit start on the unsoldered side shall we and there we go that is soldered got a little bit of dag left over there that'll just fall off no workers there we go fortunately our chippy's not perfectly lined up but anyway no workers that is actually soldered believe it or not it's terrible muriel let's put our solder in there and then let's just go along here and jump there we go that looks sweet as once again all those little dags will clean up later probably would have done better without the wheelbase tip i think i don't know soldering looks terrible up close like really magnified it's always better from a distance next up well and do the most prolific uh thing so 100 end capacitors i just yeah we've got 12 of them so just get 12 out of the bag and then go around and populate them and then if you actually count 12 then you can't i get it wrong if you've got one left over you know you missed one somewhere and be careful when you tip these out because these things can fling around everywhere and you can come a gutter you can lose one trap for young players so what you want to do now is go around and just tack one side of course the right hand side because i'm right-handed so i attack the right-hand side of all of the capacitor pads all 12 of them first and then because if you do it one by one it's just it's just much harder so yeah i believe that one there so just put a bit of solder on there is that one there in fact you could argue that it's uh best to just simply go and do everything really like go and do every single pad so then you'll be ready and rearing to place those components some people don't like to do that but once again components can get in the way well a little bit too much solder on the previous pad there rather than just try and find them all maybe just go in and do them all that was a thermal mass thing that was uh yeah the tip is actually too small but just be consistent if you're doing top side do top side for all the components and you know left for all the others etc oh oh no i gift it that one goes in that direction that one goes in that direction oops sometimes you do that that's what happens when you don't have your silk screen overlay you get your camera guts are you don't know what's the right way up we'll do that for our sop 23 package there no wackers even for our big daddy jobby up there and do that and these two tiny little tiny little deities itty bitty and uh we won't worry we are well okay yes we will we'll do a one pin on that us oh no that's uh do that usb is um it's got holes there a usb connector um shouldn't have done that oh well it doesn't matter and might as well do it for the inductor up there too now normally i actually wouldn't be uh doing this on the tagano with a digital um screen like this i'd ever be using my mantis or nothing at all um just be using my eyes my mark one eyeball but because i've got to shoot this video i've you know the the the tagano is the best way to do it the camera inside the mantis absolutely sucks for video so yeah the absolutely kills it so there we go i think we've got um solder on all our pads now we can go around and place some of our caps where do we want to go here where was one there was one c12 down here that's definitely one so we'll just place our cap on there like that i would go around and solder them all in one pass later and then do a second uh visual inspection uh pass after that that one's most likely a bypass cap because it's going to the ground plane there am i right c2 i think irma yep c2 no workers so let's get c2 there we go you can do this really fast if you know where they all are like if you're doing it like i am you've got to like punch hunt and pick uh to find the damn things c8 you know if you're assembling a whole bunch of boards you'd get used to what's what and there we go gotta have a pair of nice pair of fine tweezers and they've got to be wide enough like to place to get over chips like that as well by the way so you know um you've got to have multiple like get get different types of tweezers you need bent ones and all sorts of fancy pantsy ones yeah this um chisel this tiny little chisel tip i don't know like is it like half millimeter chisel or some point eight millimeter chisel or something it's probably like it's too small uh these are o603 uh parts and i just don't have the other one another one to hand i could find it and put it in there but oh maybe that one there is probably more suited i'd say that one is a 1 16 i don't know what's that in bloody metric almost tombstoned in there this is the problem with um like digital microscopes like this it's hard to see because they're not three-dimensional it's hard to see whether or not um components tombstone it's much better under a mantis or with your eyes okay sorry i'm not sure why the uh tagano capture froze there but anyway lost a bit of material now we'll do the s08 and i swear i've been spending at least half of my time just finding the location of parts wow those pads are big very generous um left a lot of uh generously left a lot of solder look and i still can't find where that 4.7 mic goes i swear like it'll come out in the wash but it's just it's really annoying to uh you know just have to spend most of your time just finding parts on the board where to actually place them and for something like this so-8 you wouldn't even bother to drag solder because it's so quick and easy just to do them one by one like that yeah i didn't put any flux on there either so i'm just relying on the solar flux anyway if you don't know um the the ip official ipc standards for footprints they come in um small normal and large size pads and basically it has to do with the you did the density of your board and if you've got a really dense board and it basically has to do with like how much pad like overlays like the end like this so that you can get your iron on and the good thing about having them extended long like this is that you can actually use this uh use this extended bit as a test point for a flying probe tester so they're actually very handy so if you've got the space and you know your board's going to be flying probe tested don't use like the small uh footprint pad which you'll have like you know they'll basically be no almost no pad extending over the end there they're just very small footprint very compact footprint so the uh flying protester will have to come down onto the leg of the ic and then it can slip off and short you know and do all sorts of things so uh yeah having larger pads like that is actually um can be rather uh handy it's you know it's a luxury if you can afford it and then the little sop 236 i have to tilt that you can see the tiny little dot in the top left-hand corner and that goes in there like that so yeah don't don't rely on the text uh always go by the actual dot and we've got our little diode and the end with the lines on it like that that is the cathode up and nicely there look at that beautiful now here's where you can really come a gutter with leads look at these little suckers always measure them there we go so the negative is i.e the cathode is the one that although this one has a green line that one necessarily doesn't but uh yeah so that end closer to the internal die there is the negative end now here's the interesting thing is that you can't tell from the overlay which way around that lead goes here's the three leds got a chamfer on there what does the chamfer mean well could actually mean don't rely on what that chamfer means because there is no physical embodiment of that chamfer on these leads right so on other types of other physical types of leads they may there may be so what does that sham for me and well you don't assume that it means anything what you do is you actually check out the pcb there's our three leds here's our three resistors and you see the series resistor is uh going up to the positive rail here so if we have a look at our schematic here you'll notice that there's the resistors up the top to the positive rail there's our anode there's our cathode cathode goes over to the chippy over here and you can physically see that embodied on the pcb so this would be our cathode going off to the chip and the anode goes over there so bingo i've got a flip because we said that in there was the cathode so i'm gonna flip it around focus your bastard all right so i flip that around like that and yeah we'll just take that over to there and we'll solder that in place be careful with leads they really don't like heat leads aren't very forgiving there we go and just for good measure for sanity check there you go make sure you got them in the right way it's so easy to come a guts especially you know if you go to nothing worse than going soldering down 100 leads and then realizing you've got them backwards it happens now it's time for some resistors now you should always put these in the same orientation so why just because it's good practice so that you can read and inspect later and some people like to actually solder them upside down like as in like like literally flip them upside down just for shits and giggles but there's actually a practical reason why some people will solder them upside down because when you pull them out of the uh tape like this they could land either way right so if they land like that some people just go oh bugger it just solder it in upside down i couldn't be bothered flipping the little bastard there it is like oh and it just so happened to flip in the direct orientation murphy must be asleep today but yeah and so if you ever see them sold parts soldered upside down like that you'll know why people just went screw it couldn't be bothered look at all the resistor values in here one two three four five six seven different resistor values did we really need all those different values like just ask yourself when you're actually designing yeah yeah it could be very good reasons for it but try to consolidate resistor values if you can it's really handy you know it just means one extra one less reel you've got to put on your pick and place machine and of course for a manual assembly point of view i've now got to um take open crack open seven different packets you know pull back the tape get out like this is a 10k resistor there's one of them on the whole board thanks all right let's try and flip six of these suckers what do we get oh five out of six ah close but no cigar all right i was just going to put down a couple of my last resistors and i found that one i was supposed to put down was already populated even this one this uh 20k one was actually in here and it made sense because all these 20ks were bundled together and maybe that's why i thought it was okay and i'm so glad i didn't solder the other end i'm going to do that as one last pass because then i had to take that out and move it over to there and it was trivial it took like two seconds to do that um but yeah you're eventually going to come even on a simple board like this with you know this is hardly any parts at all but with actually eight different types of resistors you know odds are you're gonna like you're gonna give one of them now here's an interesting thing look at these little diodes here little sod 523 packages real pain look at the size of them in the tape there and there's actually every second one in the tape which is interesting so the problem with look there's this board is not a dense board there's absolutely no reason to use such a tiny package like the sod 5 2 3 like this because you'll have trouble the little pick and place head will have trouble with these parts look oh six are these are actually smaller packages than o six o three they're kind of like down in the o four 0402 region then that's you know okay but there's no reason to use that and like some uh depends on your assembly factory some pick and place machines won't be as capable or most actually won't be as capable with o402s as they are with o603 so there's just no reason like you just get like a lower slightly lower yield oh some manufacturers might go oh we hate o402s or whatever you know like a real you know using real old gear or something like that there's no reason to use such a tiny little diode like that anyway can you see the my ah there we go if we zoom in we can see the marking on that there it is tying a little cathode mark on their little line but yeah zoom out like this is where you need like there's no way you can see that you know you probably can't maybe when i was younger i might be able to see that with my with my eye but like if you get the light at the right oh yeah i can it's i'm just getting glare uh just the lights at the right angle i can't see diddly squat when i'm using this uh the this tagano microscope i've got actually look at the microscope because the angle of the light comes down like this it's up in here it's up in here and it shines down and then it's the perfect angle that it just gets in my eyes and i can't like i can't see any of the markings on those resistors or anything it's hopeless that's not my eyes it's it's that it's just the angle all right i've gotten to the point where i've put in all of my passives now you don't want to put in something like a crystal and why they used a through-hole crystal there i don't know everything else is surface mount use a surface mount crystal doesn't make any sense um if you're going to oh no i just forgot three what happened to three resistors up the top there all right i know the reason why i missed those uh three 1k resistors for the leds is because i don't actually have them i can't find them here so i had all my resistor packets and i went right i've gone through all my resistor packets i assume i've placed all the parts and i come back and want one no um they're missing so maybe i didn't order them maybe they weren't on the bomb or whatever but um yeah yeah i definitely haven't placed them because there's three of the only three on the bomb and there's three i i'm missing on the board so um yeah i'm missing part it doesn't matter i've got a kit because it's a lead dropper resistor why use 1k um when like it's popular value so i'm going to use some 820 ohms no worries don't use those much so you don't want to run out of my 1ks so there we go 820 ohms make the leds a bit brighter all right now comes the time that we want to go in and solder the ends of them so if you've soldered like everything say on the right hand side if you're right soldered then you know you've got to get everything on the left hand side and if you sold everything from the top you know you got to get everything from the bottom so hopefully if you go through the board you should be able to just find them and tack them down just go systematically oh that was a shocker too much solder dave ah absolute atroci ah terrible muriel absolutely terrible anyway you don't need any uh flux um for doing uh the components just rely on the flux in the solder unfortunately because the angle of my eye and the things um focus in on my iron and hopefully if you go reasonably sister i'm i'm not i'm i'm not being systematic here here's where like real pain to get down into that diode down in there he's he's really trouble i've got to go near vertical on that iron to get down into that that's yeah that's really annoying you got to think about stuff like that for hand soldering matters and here's where i don't like these digital microscopes like you know you're looking down on it i mean look i can i can actually tilt this can actually tilt it on an angle like that i can tilt the tagana so it kind of gives you like a like a just just a different angle on the because when you've got like a top down view it's not that great and here's why i didn't solder in the usb connector by the way because then it would have been a pain to access those pads down in there oh that's a bit how you're doing that joint alignment on that resistor there that's a shocker absolute shocker and yeah it's it's just things look a bit distorted when you've got it like that but if you straighten it back up vertical and you're looking down you don't get any depth perception it's really you know it's really quite annoying anyway i think i'm done but this is where you want to go get them on an angle and go in there and inspect do that under the mantis mantis is better inspection microscope by far and even though i don't need to i'll just show you that if you are unsure about joints in there you can just go in and like systematically reheat like that you see that salt is actually flowing further up the leg there they're already soldered but you know if you just wanted to touch them up that's how you do it and oh one last inductor there because that is not going to work uh my um the dc to dc converter is not going to work without that inductor okay with these usb connectors i would actually recommend in just putting down some flux down on there because they can be a bit of a pain in fact probably even whack some on the pins if you're feeling lucky it's gonna be really hard to get the iron into these suckers so anyway i'm going to that doesn't protrude through the board so we can tack down one of those pins to keep it in place so there we go that looks right there we go i think she i think she flowed i think she flowed yep yep she's holding in place there you go there we go no yes they are supposed to be shorted beautiful you'll notice that there's no solder mask down between those pins either so you really want to uh be careful about bridging on these pins it's really tricky to get in there to the extra pin you almost have to heat up the one next to it i could have got my smaller conical tip but yeah should be right bobby dazzler look at that ah you could say that pin over there hasn't wetted actually now it has ah thing of beauty is a joy forever now the through-hole stuff and you'll see that the solder will wick down in there like that and it won't always go all the way through this one's actually going to require a fair bit of heat now you'll see the solder wick down through the board once it's gone through there we go it's gone a bit concave so has it actually flown through to the other side or almost almost don't actually need to put any more on there that's more than taken up but that's now yeah like more than enough and same with those ones though flow down into there that looks a bit messy but should have actually flown a good lot of the way down in there yep so i put the tactile switch and a little pin header on there one tip with these you see how these aren't really as tight as a nun's nasty they're loosey-goosey in there and you can solder those at the wrong angle so just a little tip in there actually go and get a dip chip and actually insert it into there and that will physically hold them in place perfectly lined up while you solder them then you just lift the chip back out and just for a bit of street cred there you go a ui 709 texas instruments 37th week 1978. i just literally like that was just one of the first ones that came off my um sponge at my you know i like i obviously salvaged i desoldered this when i was a kid i would have desoldered this um still comes in handy just another tip when you're laying out boards like this look at the size of these annular rings i.e how much exposed ring there is on each pad it's not fall like why would you do that this is not a high density board there's absolutely no reason to do that whatsoever the thing about a small annulus ring like that is it's hard then to get your soul your eye your tip sorry you tip onto there to make contact with the pad so that you can then feed the solder onto it because you put your soldering iron on there first you heat up your annulus ring and your um component leg and then you solder that looks oh no that is that a trick no yeah that's a that that's a shadow trick it looks like there's a hole there but i don't think there is i think that's a light and shadow so yes bigger annular rings please there's absolutely no reason to go tight-ass i hate a small ring and there we go it's like a bought one just cleaned it up with some flux remover it's still got some resisue and stuff left on there so what we want to do now is um before we power it up just you know buzz a few things out to make sure like things like the power rail and stuff like that's not shorted so let's do that so first thing c6 sorry i don't have the schematic here to show you but this one here this is actually the input you can see it coming over there like that so this is actually the input cap make sure it's not shorted and it's not winner and a cap on the uh 3 and 3.3 volt rail c5 here there you go that one's not shorted either so both of our rails are not shorted so winner we can power that up oh did i say power that up well we can't because we haven't programmed the thing it's got nothing in it so yeah oops [Music] you

Channel: EEVblog

Views: 55,976

Rating: 4.9321213 out of 5

Keywords: eevblog, video, padauk, padauk microcontroller, padauk microcontroller programmer, programmer, github, pcb, bom, bill of materials, how to, tutorial, open source, open source software, microcontroller, jlcpcb, assembly, pcb assembly, pcb manufacture, surface mount, surface mount soldering, surface mount soldering 101, surface mount soldering techniques, smd, smd soldering, soldering technique, drag soldering, soldering tips, soldering tutorial, how to solder, circuit board

Id: VJJmtm0VmIs

Length: 33min 24sec (2004 seconds)

Published: Thu May 14 2020