EEVblog #127 - PCB Design For Manufacture Tutorial - Part 1

hi welcome to the EEV blog and electronics engineering video blog of interest to anyone involved in electronics design I'm your host Dave Jones hi now I know a lot of you out there like designing your own products and that's fantastic now let's say you've come up with this great new design okay you've got this one off you built it works great you've debugged it fantastic and you want to make 50 on a hundred five hundred a thousand think big ten thousand hundred thousand what do you do how do you take your project from a one-off through to volume production well I'm glad you asked what I'm going to do today is take you step by step through the processes both thought and design processes you need to do to take a one-off project through to volume manufacture let's go what I'm going to concentrate on today is just the board level stuff okay so I'm not going to get into housings and you know designing the overall look and feel of the product that requires a whole separate blog so this will just be the board level how you can design and manufacture a high-volume PCB now let's start by taking a look at something like this okay it's a through-hole board traditional through-hole okay Green solder mask a pretty basic traditional board now is this suitable for high-volume manufacture well yeah you can get it done but it's not going to be very cost effective and for high-volume manufacture that's what it all comes down to manufacturing cost and complexity now if you've got a through-hole board like this it's just not going to cut it these days okay too expensive to manufacture sure you can labor still a bit cheap in China but trust me it's not going to be as cheap as surface mount so the first thing you want to look at is converting your through-hole design like this into something more like this with mostly in almost the goal is to go entirely surface mount because as you'll see that'll save you the most amount of cost it'll reduce your assembly time and everything will be sweet so look at converting every component in your design into our surface mount now I know this can be almost a total redesign and that's why I've mentioned this before in the blog during your entire design process even if you're doing a one-off prototype if you think there's even a remote possibility of making this into a volume product in the future you need to put a lot of thought into what components you choose for your board but trust me even if you do have to reto talir ear design your entire board from through hold it through the surface mount or just change half the components on there to lower the cost whatever as you'll see it'll be worth it so go to the extra effort upfront if you're going to make more than say 50 boards or something it's worth putting the effort in to redesign it properly now the difference between through-hole and surface mount is pretty obvious here's some video of a through-hole assembly line and as you can see the workers sit there they manually install the components and well that takes time effort and labor and you want to avoid that if at all possible whereas here is a modern pick-and-place machine placing your components from reels and tubes of components onto the board automatically and this can churn out boards much much quicker with less effort you set it up once and you push the button and it's all automated and your boards magically spit out the other end that's the ultimate goal for high-volume manufacture as little labor as possible one of the first things you do is go through every component in your builder materials in your design and you look at it is that component are easily manufacturable by the supplier I'm going to choose to assemble my board because not all assembly houses are the same they have different requirements they have different pick-and-place machines with different capabilities and not all of them can do what you want so basically you want to stick if you can stick to our large common components because that means every assembler out there will be able to do it do it cheaply now that might mean okay Oh 402 size resistors and capacitors for example there are some assembly houses out there that don't have the new machines that can handle components that's small so think about oh six oh three instead of o4o to think about quad flat-pack our packages instead of BGA or something like that BGA is going to be a little bit more touchy harder to inspect yields not going to be as high more critical pad dimensions all that sort of stuff so stick with the common package as I say Oh 603 and up Oh 402 is okay you know it's stick with the 0.5 millimeter pin pitch or larger on your sio type packages and your quad flat packs and stuff like that and you'll be fine with high-volume manufacture you're going to have to spend a bit more money on components than you anticipate if you're making say a hundred boards well you can't just go to digi-key and by a hundred resistors loose on the tape like that the assemblers are going to hate you for it trust me because they may not say so okay but they ought to charge you more because they may have to manually put these on to what's called reels okay this is what you need to buy for all your components are all of your SMD components now reels come in different types this one might have five thousand resistors but they're very cheap so there's real might only cost of five or ten bucks or something like that you can get little mini reels like that or they come in huge reels like this okay or when you're talking about ICS you might they might come in that tubes like this and these automatically slip into the pick-and-place machine and the chips shoot out like that okay you don't just want to buy them loose in your little digi-key pack it like that that otherwise I if you do that they'll have to hand solder them the efficiency is going to drop they're going to charge you more than going to take longer to assemble them poor it's hopeless so you want all your components now chips need to be an either choose or they need to be on you can get chips on reels as well or they need to be in what's called trays now here's a out of the trees trees generally aren't as good because a lot of machines can't support trays so they'll want everything on reels or tubes so just be careful there let's do a search on digi-key for a part to see if we can get it in real or a partial reel or something like that see what our options are now let's take an example of the ZX ety one double O nine and let's do a search for that and as you can see three options here are popped up we want the SOT 23 version which is here ok but look it's got three lines it's got three different rows there it's got three options for the same part check out the quantity over here 114 thousand parts they've got in stock so that's fantastic okay but as you can see they're all the same quantity available so that tells you it's exactly the same part exactly the same stock but three different procurement options now the second the second row here as you can see just here it says it's available in cut tape now that's the version you'll typically get it says minimum quantity over here of one okay now that's the one you typically get when you buy prototypes okay you only want five parts for a prototype so you buy five they cost you a dollar and nine sets each you know and you pay five bucks and and that's it okay nice and cheap four prototypes but we want let's say we want to manufacture a hundred boards okay you wouldn't buy you wouldn't buy that cut tape version you wouldn't buy that part number because it comes on the cut tape it doesn't come with a reel and it doesn't come with the leader tape attached which the manufacturer your assembly house needs to put that into the pick-and-place machine so that's pretty useless to your manufacturer now if you look at the top row up here as you can see minimum quantity of 3,000 so that's obviously it that says tape and reel okay so that is one reel of parts but you've got to buy five 3,000 of them minimum to get that one reel and they're 43 cents each let's go look at that price sorry forty cents each at three thousand but that's one thousand two hundred and nine dollars you'd have to spend 1,200 nine dollars there just to get your hundred parts needed for your hundred boards so that the assembler can assemble them that's just crazy okay so what you want is this third option down here now this isn't available for all parts oh really this is you have to choose your parts that go into your design carefully if they have these options if you're only going to make a hundred of them or or even you know five hundred and you want them on a real they offer what's called a digi real option now that is the same as the cut tape as you can see you can only buy you can buy just one of them but they will actually charge your fee and they'll put it on a reel for you with the leader tape exactly what the manufacturer it needs but you can order any quantity you want so let's go in there and calculate that price and let's say we only wanted to build our one hundred boards so we go down here we type in one hundred and we go calculate and instead of playing that over a thousand dollars we had before our total extended price is 84 dollars plus plus here it says a $7 reeling feel fee will apply to each reel audit but that's cheaper okay you're still only paying less than $100 for your hundred parts as opposed to over a thousand dollars for the three thousand minimum so just be careful when you're designing your product make sure these not only are the parts in stock but they're available in suitable quantities even reels or tubes or partial trays or something like that for your particular design it's very important so you can spend a lot of time just mucking around on digi-key finding your mouse or or it's the same on Mouser element14 and the others they all have the same service you can spend ages just doing this to optimize the manufacturing for your little board for your hundred or five hundred boards it's crazy so yes if you're going to make a hundred boards you might have to buy 500 ICS you might have to buy a thousand resistors something like that that is the price you pay for going to high-volume manufacture essentially so if you want to get a hundred boards made upfront then you need to do the costume based on your entire reels of components just assuming you're only going to make 100 if you're going to make another thousand down the track right you'll have most of the reels components on the reels left over but you have to amortize that cost in to your hundred boards now the other important thing to remember is that the pick-and-place machines can only support a certain number of these at any one time so a machine might only be able to support 20 reels or 30 reels that means you can only have 20 or 30 different components on your board if you have to do more than that then they need a second machine either inline with it and the board goes through the first machine on a conveyor through to the second machine not many houses will have that set up the smaller houses won't have that so they'll have to put your board through a second time reset up the machine so if you're manufacturing one hundred or a thousand boards I put it all through once and when they finish they rip off all the reels they change them over they have to put your boards all the way through again and that cost you money try and avoid that so go through your design component by component and see if you can consolidate the number of components do you really need a 15 K pull-up resistor if you've got a 10k resistor somewhere else on your board use a 10k for the pull-up consolidate those values if you need a 20k resistor on the board it might be better to put two 10k resistors in series in your circuit because you've already using that component 20 times elsewhere on the board so just look at consolidating your components it's very important also think about pad sizes there's no point designing a fantastic board if you find that your manufacturer and their process cannot successfully load your component on the board they short together because they're the solder mask is too you haven't got sufficient solder mask between the pins of an IC for example and they put too much paste on it shorts out or a resistor tombstones because you don't have thermal reliefs on one pad ie you've got one pad connected this pad over here if your resistor connected to a big solid ground plane which sucks all the heat away and the other one just going off to a 5001 to stone look at things like that sometimes manufacturers will have their own preferred pad styles but usually if you say stick to the manufacturers recommended footprint or you use the IPC standard foot prints are you'll generally do okay but you also have to think about the size of the pads so on the IPC footprints for example come in three sizes nominal least and most so they'll put an n L or an M on the end of the foot print name in your library and what that means is that just the amount of pet the pad size are L is the least amount of pad size so the smaller so if you've got a very high density board with all the components stuff together they're not you'll want to use the least size pad the the smallest pad you can get but then you might find other then you can't probe them or you can't sort of rework them by hand if you have to or something like that so you've got to think about those sort of things normally you'd stick to the nominal size footprint but if you want something that's the flying test probes to come down which is another aspect of your design you're going to think about testing testing and programming your board can be a big thing now if you've got a microcontroller on there for example and you've got a program it well how do you do that ok it was fine in your design you might have used a socket for a dip chip but if you've got surface mount now well you can program out the chip before you put it on there before you give it to the manufacturer but that's hard and difficult it's much better to actually um solder your microcontroller for example on to the board and then provide an in circuit programming header so you've got to make sure that is designed into the board you've got to make sure it's accessible where you can program it and if you design it a little bit of nails which comes down here's a over typical better nails for a board then you bring it down and you want to be able to get those pogo pins onto those test pads or onto that in circuit programming header so you've got to think about that sort of stuff when you're designing the board up front and we haven't even gotten to penalisation in the high volume manufacture yeah for one of the most useful things you can do when you're designing a high-volume product is to get a spreadsheet of all the components your entire build materials into a spreadsheet put them in the the descriptions the footprints the quantities and the manufacturers part number and then the supplier part number and usually an alternate supplier part number so you might put in the digi-key part number the mouth so the element14 part number or something like that as your supplier and then you'll have it might have another column based on how many components are on a real for example there's 5,000 per reel so if you go to the effort and an cost as well you put the item cost you can total them all up see what it's going to cost you to manufacture a hundred boards even though you've got to buy 5000 resistors in all these reels so a spreadsheet is handy putting the effort in upfront pays dividends in the long run trust me okay so you've done all the hard work you've got your board you've gone through all the processes I just mentioned and it's all ready to go well not sorry it's not if you just try and get one individual board like this or 100 or a thousand of these manufactured just on its own like that it's not very economical why the reason it's not economical to get just one board like this manufactured individually as big as well it goes through the machine the pick in place just does that one board and it spits it out and there's also two handling issues with the board as well as it goes through the machine and stuff like that so what you want to do is what's called penalize it and let's take your one design and step-and-repeat it onto a PCB panel such as this now there are certain that panel sizes which we'll go into but basically is on a step and repeat it like that so in this case we've got 12 boards on the one panel so they set up the Machine the board goes in and bingo they can assemble twelve boards at once well components have to be placed one by one but it just means it's much more efficient you can just churn multiple boards through the process much quicker and that adds up to real savings in high-volume manufacture now there's a conflicting requirement with panels because your bare board PCB manufacturer they will have standard panel sizes now it's very tempting to fit as many of your designs as you can onto that maximum size panel that they do but you have to be cautious doing that because you have to ask can my PCB assembler actually physically handle a board that big their machine their particular machines they use might have a limit on the maximum size of the board and it might be a lot smaller than the maximum panel size the piece of a manufacturer can supply now a typical Barre board PCB panel might be 18 inches by 24 inches or 450 by 600 millimeters now a lot of assemblers might not be able to handle that size board now I generally stick with like an a4 size panel because I find you know pretty much everyone can handle an a4 size but ask your manufacturer what they can handle because you don't want to get your boards manufactured and then find oops it's 10 millimeters too big for the machine you're screwed you've got to go to a more expensive manufacturer watch out for it let's take a look at a typical panel I've got one here now now there's many different ways to do a panel which we'll go into but a panel will have these basic requirements it will have what's called a tooling strip top and bottom this is this bit down here now what that does is allows the pick-and-place machine to actually grab hold of it can either sit in rails like this and it can go physically be are automatically move through the machine like that now what the tooling strip must have it by the way it should be about 10 millimeters wide top and bottom like that if it's any smaller than that then the machine may not be able to automatically handle the board the other thing you'll have and these tooling strips are the tooling holes now you typically have four of them like this a minimum of four and they're typically a four millimeter diameter hole and they're used to get a little arm there's little spritz cogs in there that physically move the board along the panel so it should have tooling holes the size isn't that critical but four millimeters is a bit of an industry standard tool in hole and it must have fiducials as well fiducials and marks as well which we'll go into in more detail later and a panel must also have a way to break the boards out so it must either have routing which is like this one with breakout tabs or v-groove and we'll go into those but they're the basic requirements of a panel now even if you've got a huge design like this one this one's almost a4 size and really as you can see only one of them fits on a panel now we can manufacture this is just an individual board or what's called a loose board or a fully routed board without any tooling strips but then yeah there's limits to how close you come components can come to the edge of the board because it needs to physically hold it so even with a board like this that's large you would still put tooling strips top and bottom and a way to break the board out and here's an example of a more advanced panel that has our three extra features which I'll show you one of them is a bad board marker now if you take a look here as you can see it's some it's just on the it's in the part of the Dead part of the panel but it's a marker that the assembler can actually mark that indicating when they do an automated test that this particular board is bad out of you know if you've got twenty boards on there that can be really important so you know don't bother using that board it's failed now another item at it's got is what's called an impedance test strip because this is a controlled impedance PCB so I'm in the tooling strip here we've added our an impedance test coupon it's called and what that does is just allows you when the bare boards manufactured it allows you to test that the controlled impedance is exactly what you want it to be the third item this board has is what's called a test stack now what this does is it brings the internal copper layers because this is an eight layer board I think it is it brings the copper to the edge now this could be tricky to try and get on camera here but as you can see the coppers right on the edge now you would probably need a microscope to look at that but what it just allows you to inspect the individual layers on that board after it's been manufactured so that and they're different lengths there's many different ways to do this but that's just an example of how you can inspect the board after it's manufactured now a lot of companies when they bare board manufacturers when they assemble your panel they will provide you with a what's called a core sample and they will actually cut off a part of one of your boards and they'll give it to you so you can actually inspect that under a microscope yourself but this just allows you to do that just in case they don't provide you with that core sample there's another important thing I forgot to mention not only for the individual bare board but it relies it has the same thing on panels as well now when you when you lay out your board you should add what's called pull back to the copper now as you can see the copper doesn't go all the way to the edge and that includes those internal layers as well if you've got an eight layer board don't bring your copper all the way to the edge because it can short out and cause all sorts of problems so have have say 1 millimeter pullback or something like that at least allow something so the copper doesn't go right to the edge there's one other thing you can do with panels where as well if you've got a lot of boards like this it's a fairly unique requirement everyone won't need it but I'll just mention it it allows you to actually see these little breakouts in the corner here okay you can actually route out you can actually route out tracks out of there and bring the tracks out of each panel so you might want to bring out our test tracks out of each panel like this and you might have a test connector on one side of your board or some interface for some sort of test jig and you might want to test all of your boards in situ in the one panel it's it it's not a common requirement but you can actually do that now let's get into how you break the boards out how do you get them out of the panel after they're assemble this has got four individual boards in it okay quite complex how do you break it out now there's two different methods to do it one is called V grooving which I'll show you up close and the other is called routing and breakouts with tab breakouts now this is an example of av grooved board as you can see it's got these score marks or what's called a V groove I'll show them up close later but a long like this and both vertical and horizontal now here's another board which is another example of V grooving as well okay now this works really well on completely square boards if your board is completely square and you don't have any components overhang in the end which can often be a problem because when you get this board after its assembled they have to break these out now normally what they do is they run along with a little wheel along there which actually top and bottom which then does a nice clean cut on it but if you've got components overhanging the edge for example like you like like you have a connector or something like that overhanging the board well you can't actually get in there to break it off so you might have to break it off by hand but what a V groove allows is allows you to easily just snap the board off and I'll show you here it is OOP see but what you get okay once you do that is you I probably can't show that on camera but you get a pretty rough pretty rough edge here's it gets and gets a little little fiberglass hairs on it and it's it's just not a very clean way to actually do a board but you can just snap them off even if they got component overhangs you can sort of wiggle them a bit and they'll come apart really easily that's V grooving now it's pretty hard to get in there and actually show you what a V groove looks like but what it basically involves is if your board is like this the drill actually drills down into your board like that that's the top of the board and this is the bottom of the board and it goes like that they drill at top and bottom okay and it leaves just a little bit of fiberglass actually connecting in the middle like that and that allows you to just snap the board's off really easily and that's V grooving now you can actually specify the angle of the actual groove in there like that if you want to get fancy and all you know if you're someone like Apple and you're really designing you know a million or a billion of these things then all that sort of stuff might actually matter but generally you just say I want V grooving please and they'll just do V grooving now I mentioned our copper pullback before now because AV groove actually has a distance between it which can be a bit variable then you have to be very careful to actually pull back your copper so that's not exposed when they do the V grooves so if you have continuous copper going across like this and you take it right to the edge of your board then well you're just going to get exposed copper when they go in and they drill it for the V groove just be careful of that now the other type of penalisation is what's called route in with these tab that's a tab breakout okay now you just specify the routing path around your board this is really good for odd shaped boards which I'll show you in a minute but basically there's industry standard tooling sizes for these routes now two point four millimeters is a standard routing tool with so you just specify that as an outline and they will do it you can actually tell them to do it but it's better to specify it yourself so you know exactly what you're going to get but these tab breakouts these can be a bit tricky these can be an art in itself now that this is this board is hard to actually push out by hand sometimes you can break the board and especially when it's loaded with components you don't want to do that so you might get in there with a pair of side cutters for example side cutters like that and actually cut the board out now you have to design these tag cut outs in such a way that it allows the board to be held in there fairly firmly okay because you can't if you've got a very large board like this which I'll go into you can't just have one on the corner over here one on here because the damn thing will warp so you have to have you might have to have multiple tab multiple breakout tabs along the edge you poured depending on how big it is and you have to make them so that they when you cut them out they don't have any burrs as well here's an example of a very wide breakout tab that supports a very large board such as this and it has multiple holes spreading an arc like that which allows you to actually break it out so you put these unplanted holes around there in an arc and it breaks out and it leaves just like a little indent in your board when you break it out here's a good example of a panel with an odd shaped board as you can see we've got the tool in holes the fiducials over here but it's got um it's routed out okay it's routed out around here now and all the way around like that now this is a good example because it has a combination of V grooving and routing so if you've got and you can see that the board has a weird shape on the on the bottom here and the top so you route out the weird shape ones but it's straight on the edges so you do V grooving on the edges like that so that allows you just not easily snap out that board while giving you the giving you the advantages of the odd-shaped board with the routing and this is just a fairly simple example actually there's much more convoluted ways you can actually do this and it's almost an art actually figuring out how to snap a board out of panel what combination of V grooving you use what combination of routing as well one very important thing to remember is how stiff is the board because often it will only be supported along the along the top and bottom edge here by the Machine and the pick-and-place machine comes in and it places the component down and you don't want this to happen what look at this board okay there granted this is a naught point eight millimeter board it's half the size of a stand at one point six millimeter board but look at how much that board what okay fantastic that's normal fr4 I kid you not okay but that's not point four millimeters that can make your seasick almost really okay so you've got to take that you've got to take the rigidity of your board into account when you're actually designing a panel and here's an example of a panel that just has a V grooving along the top and bottom edge and vertical route in like that once again you could have done that as a V groove but in this case we wanted to get a really nice edge because this is what V this is what routing gives you routing gives you a beautifully clean and smooth edge on your board with no burrs whatsoever whereas AV grooved edge will be it'll be sharp it'll be it won't be completely flat and it it's just you know it's not a clean edge at all you may even have to file it down afterwards so from that point of view routing is preferred but here's an example of a board that because there's no central support in here okay it's routed all the way from top to bottom like that okay this can actually this can warp as you can see when you place the components in the middle that board can actually warp like that so because there's no rigid support in the middle to actually cross brace it so in this board doesn't have components in the middle so you didn't have to worry about it they're only on the top and bottom but if you start putting it in the middle it can flex a lot and that can be a problem and here's yet another board where it's fully routed around and it's got tab breaks like that but in this case it's got the tab break in them in the middle as well so that helps form a rigid structure for the board so it's not going to warp nearly as much as that other board that didn't have any central support in it here's an example of a panel that has many different designs in it and generally this is okay for prototyping but for production are it's generally frowned upon you don't want to have to load multiple individual designs onto the one panel it just confuses things you can exceed the number of reels you've got and stuff like that so really you want to stick to one design per panel now that little thing there on the panel is what's called a fiducial mark now these are very important to not only put on your panel but on your actual board as well now as you can see this board will actually have actually four fiducials on the panel itself now typically you only need two you put them in opposite corners of the panel now the reason these are important is because when the board's manufactured it's dimensional tolerance ie from a reference point over here to over here may be slightly out now that's not a problem when they assemble a board they take a reference point which will be this fiducial mark down here what it does is a camera comes over and it looks at it looks at that fiducial mark now fiducial mark is typically one millimeter in diameter or a couple of millimeters in diameter it's copper with the solder mask pulled back now it's very important that the solder must pull back so there's a lot of contrast between the copper color on there and the surrounding solder mask but the reason you have to is they they align it down here like this at this point and then the camera goes over there and gets the other fiducial and it knows from the files you've given it how far that dimension and that dimension is and it actually can rescale the board to take into account any minor direction directional tolerances on the bare board manufacture if you've got fine pitch components like this BGA for example as you can see what you do is you put what's called a local fiducial into here so you see this little fiducial there and there's a little fiducial at opposite corners of this high pin count device so if you look at if you look at that device there's the little tiny there's the little fiducial there there it is and on the opposite side so you want to put those on very high density devices like BGA is typically for SI packages and everything else you just don't bother you just rely on the two fiducials on the panel but local fiducials can be important to get extra dimension in tolerance in that particular area of the board and one very important thing not to forget if you're loading components on the top and the bottom of the board make sure you add the fiducial marks on the bottom as well otherwise they won't be able to succeed they may not be able to successfully load that side of the board so make sure you do fiducials on both now I know what you're thinking why is this board gold wire is everything gold-plated all the pads and everything well not only does it look funky you know nice gold highlights around the edge but gold can be made extremely extremely flat surface so when you've got a high pin count BGA device like this it's it's very important in fact it's vital to use gold because if you use a solder or tin coated board sure they can air level them which is what's called hot air leveling on on a copper on a tinned finish it's going to be nowhere near as flat as this so it's very important for solder mask layering and for for the tolerances when the balls go on there and the solder reflow so I'd recommend even for simple boards gold plate doesn't cost that much extra I recommend you get gold plate I use them on all my personal boards as well cost a few cents extra now there are going to be times when well you just can't are penalize your board one example of this is my micro watch board which because it sits on your wrist and the board's exposed you can actually see it I wanted really nice cleanly routed edges I didn't want to have to v-groove it and then file I'm off to get a nice edge that sucks so I got them individually routed so this is what's called supplied loose or individually routed from the PCB supplier and that's great if you want beautifully milled and machined edges and that's okay if you have to just do an individual board like this it's fine they can what the piece to be as simple as can do they'll charge you for it though is they'll make up a custom little carrier module that's you know routed to the shape of your board and they will actually mount them in that there'll be an extra tooling cost but it might be worth it if you want to beautifully routed board now I'm sure everyone recognizes this it's the Arduino now did the Arduino guys actually get these assembled as individual boards or do they actually penalize it and snap it out later well there's a couple of telltale signs all you got to do is run your finger along there and you can tell it's as rough as guts that means it's been v grooved and snapped out on all four sides and if you actually get in there and take a look at it it might be hard to see it but it's actually a V it's it's actually a v-shaped edge on it you can see where it's been v grooved and snapped out but this bit over here has been routed check it out that's smooth as a baby's butt in the hair but it's rough up here so they routed out that little bit V groove everywhere else there you go okay now let's actually take a look at a board now assume this is your design okay and you've got it finished and you're proud of it and it's lovely and it looks great in 3d mode check it out there we go it does everything you want now what you have to look for is that a we talked about this before you pulled back the the copper from the edges of the board okay very important for when you do V grooving because we're going to v-groove this design because it's a nice square board so and we don't need fully routed nice clean edges we're happy to just v-groove it okay so what we do is we flip it over to our panel and we do a separate this will usually be a separate PCB and you've duplicated this board multiple times now this is our TM designer it'll automatically do this for you you can actually place multiple designs but as you can see we've created a panel size here we've created tooling strips top and bottom and we've actually put in the tooling holes there it is it's a 3.2 millimeter hole as you can see we've created the fiducial here like this which is basically just a pad with a this one has fiducials top and bottom but it's a pad that just has the solder mask expanded on it so if you go into 3d mode here let's check it out it all looks really groovy and you can see that the copper has doesn't touch between boards like that so there's enough room to actually do the the V grooving in there and you can actually see that the fiducial looks like a real fair dinkum fiducial it's got the gold and plated pad in there with the solder mask expansion so that will provide a nice high contrast there's the tool in holes up there and it all looks very good and penalized now if we go back to 2d mode what you do is you actually create you actually create a separate our well I call it fab notes but you can call it anything you like a separate layer that just has the particular tool in information you want in this case you just put a line in there that shows I want V grooving all the way down there and I want V grooving across the middle like that and it's easy and the manufacturer will just interpret that it's not actually aren't part of your board layer but it will appear on the Gerber files and that gives them the information they need to manufacture this panel with V grooving now an often overlooked aspect of board design it's not just our panel base but for any board but particularly when you're going to manufacture is you want good solder mask expansion around in your pads now this is a standard quad flat-pack 44 pin microcontroller with a Reasonable pin pitch but let's go to 3d view here and what you want there's the chip and you want the solder mask expansion between these pads you want you don't like this solder mask in here this little slither of solder mask to be so thin that actually disappears when they go to manufacture it there's a minimum width it needs to be and that's probably about four or five fell before it starts becoming unusable and it breaks if you don't have solder mask between your pins you end up you can get shorts easily on your pins so you want a reasonable distance a solder mask it's very important to check this before you send your boards out to be manufactured and then loaded now as you can see here we've actually got an expansion of 1.5 foul on or 1.5 mil as it's called 1.5 L on the solder mask expansion and that's what we get here now we can actually go in there and actually measure that distance between the measure that solder mask width in there and as you can see it's a 5.5 mil so this one is more than adequate to be manufactured that will be no problems at all we get good solder mask between our individual pins and we shouldn't get shorts there's a very low likelihood of getting shorts on though pins that's what you want so now you finished your power design it's all fantastic you've got your tooling scripts your fiducials and louder lalala you got it all what do you do well you got to supply the correct files to not only the bare board manufacturer but to the PCB assembler as well let's take a quick look at that okay so we've created our PCB panel now let's generate the Gerber's now as you can see I'm going to generate this is only a two layer board so I've got the top overlay I've got the top paste mask which will go to the assembler when you don't have to send that to the PCB manufacturer they don't care about the paste you've got the top solder mask top layer bottom layer bottom sodomize bottom paste bottom overlay if you've got an overlay on the bottom of your board I actually create a separate mechanical layer for the PCB boundary that's just the outline the outer outline of the board and I've got the fab notes as I said before now the fab notes can include all sorts of stuff about the detail a board like it's 1.6 millimeter fr4 and you want gold plate and yada yada yada and tented Viers and all that sort of stuff but this fab notes only just has the v-groove information because I'll supply a text file with all that other information separately so we'll just generate some Gerber's there and bingo it's done here it is and there is there's our Gerber information so it's got these are all supplied as separate layers so here we go it's generated all of the layers this shows them all overlaid but as you can see it will do it separately there's that separate V groove thing I showed you before here's the origin marker down the bottom that's the reference origin and these are the different layers there's my board outline there's my PCB that's the top and sorry the bottom solder mask and and that's the paste file but that goes to the assembler and there's the overlay and there's the top solder mask and the bottom layer and so forth so as you can see it just generates a information for the panel so that the manufacturer knows what to do they no you want V grooving all through that board and it's the same thing if you do routing now there's one other thing that you have to supply to the PCB manufacturer we've done the Gerber files but you need to supply the NC drill files now let's just generate those and bingo they're done and there they are there's all our different holes used in our design as you can see some of them are actually our slots there but others are these are supposed to be our square they it doesn't render properly but that generates a industry standard NC drill file which goes along with yogur burrs and that provides all the information the manufacturer needs in terms of drill sizes how many drills and where to drill them and of course there's one vital thing which the assembly house is going to need and that is the pick-and-place files to know exactly where to put what component so we can generate pick-and-place files here let's do it as a text file and here's the pick-and-place file which is generated this is a text one it can be a CSV or other formats as well manufacturers will can pretty much accept anything you give them here's the designator down in this column down here and then we've got the footprint and then we've got the actual location of the component relative to a particular reference point which is usually the bottom left-hand corner but it doesn't always have to be and this is the file that the manufacturer needs to feed into their pick-and-place machine to assemble your board and of course you would also give the assembler the overlay diagram as well showing where all the compartes go with the reference designators and also an important thing to also give them is a physical sample of the board exactly how you want it built because they aren't mind reader's usually they do a pretty darn good job they do know what they're doing but nothing beats them actually having a real physical sample in their hands that they can actually compare the board when it comes off the machine or when they're loading and setting up their machine and I to having gone through all that information you can just say well I don't want to do that just give your board and the just the Gerber's for the individual board the building materials everything else to the assembly house and some assembly houses will do all that penalisation and everything else is the fiducials the tooling and the pick-and-place and all that for you it's called a turnkey solution they will take just your individual board and you don't even have to send them the components you don't have to worry about the reels and all that sort of stuff getting them in tubes trays and quantities you just say I want a thousand of these please and they'll go yes sir no problem but they'll charge you a lot more money for it and you also don't keep individual control like when you do your own panel and you do everything yourself you supply the parts they might get the parts from the gray market who knows so just something to watch out for you can get the assembly houses to do the whole shebang but whether or not you want to I don't know it's up to you so there you go that's a pretty much a quick overview of how to design your product for high-volume manufacture and there's more that goes into it as well there's more smaller little things which are applicable to niche designs and stuff like that but the golden rule is talk do your PCB assembler first before you go and design your panel and everything else because you might put all the money buying your components designing your board and then find off might find hard to get an assembler or the assembler you like to do your board so just be careful and uh you will probably have to do a second spin as well or a third spin of the board it's not uncommon whatsoever so just budget that in you're not always going to get it even the professionals don't always get it right the first time catch you next time

Channel: EEVblog

Views: 682,819

Keywords: pcb, design, dfm, layout, tutorial, lecture, smd, construction, panel, manufacture, high, volume, gerber, files, altium, eagle, digikey, mouser, farnell, element14, component, purchasing, arduino, routing, v-groove, scoring

Id: VXE_dh38HjU

Length: 50min 45sec (3045 seconds)

Published: Sun Nov 14 2010

Reddit Comments

[u/nthdesign]

Dave Jones is also the co-host of the fantastic podcast, "The Amp Hour." He and Chris Gammell talk each week about electronics, hardware startups, and have guests from the field. Give it a listen if you haven't already. A good starting point is the recent episode with Jeri Ellsworth talking about her new augmented reality headset.

[u/fgriglesnickerseven]

does he ever get into testing/regulations? It seems that the cost even of a moderate production run (1k devices) probably is less than getting approval from various regulating agencies.

[u/kasbah]

Check out this StackExchange answer as well.

[u/BlueInside]

Anyone else know of other good tutorials/videos describing designing PCB's for eventual manufacture? thanks

[u/lordxakio]

One of the most informative and awesome videos i've ever seen. I loved it.. The accent and voice were clear and rad... i digged it! I learned quite a bit from him!