Hi let's talk about Pcb manufacturing and how you can easily come a gutter. And there's a real trap for young players in terms of the manufacturing tolerances and manufacturing specifications for Pcbs and possibly to do with our Gerber generation as well. And this comes about uh, from a discussion we had on the Amp hour hasn't been released yet by the time this video comes out. probably will be uh, released as an Empower episode.

So let's take a look some Pcb design stuff. And yes, due to popular request, I have green t-shirt floating Dave Head let me know down below. if you like this, I think it's a bit weird. I think I've got a bit far.

I said I should write a script to like, uh, randomly, like, like make my head just float around like you know. listen, just pattern. That'd be nice wouldn't it? So let's talk about when you get your Pcb manufactured. let's go over to Jlc Pcb here, only because that's uh, the one that was, uh, discussed in the Amp hour and somebody came a gutser on this.

I won't mention who, but anyway, it's it's a real easy trap and you're almost gonna certainly cop this if you, uh, like, push the envelope. In terms of clearances and and Pcb specifications, you're doing really fine. pitch Bga stuff you need to route stuff out very finely. then anyway, you can really come together.

I'm sure I've covered in previous videos. One of the first rules of when you start laying out a Pcb, you know you've done your schematic and then your import, all your footprints and your net list and you're ready to start routing. You set up all of your uh clearances, you set up your trace widths and you know other sorts of you know, trace to via things in your via hole sizes. and yeah, you know you set up all this stuff first before you start routing and you base that information all the track and space and clearance and design rule Drc checking stuff on the capability of the Pcb you're getting manufactured.

especially if you're going after one of these cheap five dollar prototyping services and you need to do something really fine like find traces and and clearances and things like that. Uh, this is where you can come and guts are. So normally you go down here and you go: Minimum trace width and spacing. Every Pcb manufacturer will have their capabilities page, so you go over here.

Minimum trace, track width and spacing. This is the main one you want here, and the Pcb in question was a four layer Pcb, so they actually have a better specification here for uh, four layers. They actually have 3.5 mil or 3.5 thou, which is equivalent supposedly to 0.09 millimeters for your four and six layer boards. It's not as good for your one and two layers.

they're a bit more loosey-goosey on those. that's you know, five thou uh clearance, but 3.5 thou clearance sounds like oh, you know, that's that's heaps. I can do anything with that. Well, then let's have a look at that, shall we? But the first thing to note is, 0.09 millimeters here.

Does that actually equal 3.5 mil? Let's get our confuser and check. So 0.09 millimeters divided by 25.4 millimeters because they actually at one point can forget the date. But to find it spot on as 25.4 millimeters is there. It is.

Oh, it's back to front. Sorry that. yeah, the camera is back to front. Oh, I'll just read it.

3.5433 0708 7. Foul. But they've rounded it to 3.5 thou here. so they've whereas it's actually 3.54 thou.

So you might say, Well, what's the big deal with that? It's close enough. Round it off. Well, aha, Here's where you can come in gutter because you're only paying five bucks for your board or whatever you're sharing a panel with like a hundred other designs. They don't want to dick around and spend time and treat you special just for your 100th of that one board, right? So they have these limits for a reason, and if you have a look at everything else, everything else seems to be like in millimeters.

We've got clearances. Here we go. Clearances: Everything's in millimeters, but they gave you the value in Thous. So if you like laying out your Pcbs as I do with all your traces and spaces as thous and there's nothing wrong with that, then you can come a gutsy if you go in into your Pcb software and set your limit as 3.5 mil or 3.5 thou, you're actually going to be under that 0.09 millimeters.

So they're gonna or their software. Their Gerber uh checking software will automatically reject your boards. They won't just automatically manufacture, they'll come back to you as the example on the Amp hour They come back to you and said hey, sorry, you don't need our specification But then you go to them and say oh, but look, it's on your website 3.5 mil. Well, 3.5 mil is actually different to 0.09 millimeters and it looks like the manufacturing engineers at the Pcb company they sort of looks like they're using millimeters metric for everything.

So even though they've you know just tried to be nice and given you in this in 3.5 mils. Just be aware there is going to be a rounding error here and you can fail your their automatic check-in and then you might have to go in and redo your entire board because they're not going to be flexible enough. for five bucks, they're not going to be flexible. They're going to say sorry, your board's rejected.

Please meet 0.09 millimeters. Doesn't matter what it says on the website. So first rule is beware of companies that mix their units like this. So if we're in our Pcb software and we're in like, you change between inches and millimeters here.

I'm using keycad by the way. If you go into inches mode and then You set up your board, you know you're about to lay it out. and you track width. Here, you've set it to precisely 3.5 mil.

So aha, I'm I've obviously met this specification. No worries, she'll be right. And then you go in there. But if you switch to millimeters and you lay out your whole board, you can spend a whole week laying out your board.

Go to get it manufactured and then what They say, sorry, we're not going to touch that with a barge pole because it's slightly under and they do care. All it is is a go no-go thing. Does it meet their 0.09 millimeters? Well, if you switch to millimeters mode. oh, we're not.

.0889 millimeters now one want one, Hang on so and there's no point, are you in with them either. They're not going to argue with you. As I said for their five bucks board or whatever. If you're paying for the whole panel.

like if you're paying hundreds of dollars tool in charge and you get in the whole panel right, they'll bend over backwards to accommodate you. If you're getting these cheap boards like that and you're one of a hundred different designs on a panel, they're not going to care. You're under the 0.09 millimeters and you've come a gutser and they're not going to make your board so you might have to go in there and then change all your traces. and then you might find all the clearance.

Look in here. Let's say you widen that to like four mils. Something like that. Oh look, see, we've violated our clearance rule in here for, um, the spacing between the pad and the trace here.

Aha, we've got different specs for that. So if you've gone in there and gone, oh, okay. I've changed all my traces to four Mils. Yeah, no worries.

Uh, let's run the design rule checker and you run your Dlc and you go track too close to pad because that's their minimum specification for the like. A distance between the track and the pad like that and you've just just a smidgen over. Only needs to be a smidgen over. Remember, this is software doing this right.

Humans aren't going to over ride this unless you're paying them money and then they'll rub their chin and go. Oh yeah, yeah, she'll be right. No worries, you know. But no, they're just going to automatically reject your board because it's you know, 0.01 millimeters over the you know, the tolerances that they specify.

Let's go back to the website here and trace width and spacing is not the only thing you need to look at. You would think that Okay, the minimum spacing is three. you know, 0.09 millimeters. So you set that and you're good to go.

Uh-uh look at this right. these are their minimum. They've also got minimum clearances for all different types of geometries and they can be out by large values too. Let's have a look at this.

so let's have a look at the difference. Uh, the minimum spacing between a track and a pad. Which is actually what we've got here. We've got a a pad and a track on our Bga chip.

Naught point. Two millimeters. So much for your 0.09 millimeters you can only do in look. They they could reject your board because it's only.

uh, you know if you're closer than 0.2 millimeters. Wow. So let's go into our board setup here. Let's go into our nets.

Uh, 0.15 millimeters clearance? Well, what did we say? It's 0.2 right? That's what we need between a pad and another trace, right? So you might have. you would have to net classes. You would have to set up different net classes because we have different specifications. or you might run your Drc twice for example, and then have uh, differences between trace to trace specification which is 0.09 millimeters and a trace to pad which is 0.2 millimeters.

So if you go in there, I've got a 0.1 millimeter grid here, right? So 0.1 0.2 millimeters. That's the absolute minimum that they will accept for pad to trace. You know, if you've got a Bga chip here, right? You can't route out these traces like this. Uh, this.

Just assume that this trace is actually connected up there. I can't do this because I don't have a schematic. there's no netlist, and it looks like in keycard, you can't manually input a netlist like a generator new net on the Pcb to join this track to this track manually. Anyway, doesn't matter.

so just assume that that's that. You wanted to route these traces out here between the pads like this. You couldn't do it on that Jlc four layer board. They could actually completely reject your board.

If you wanted to do that, you'd have to put a Vr in there and drop them out. So yeah, just be careful. Like rule number two is, look at all the different specifications. It's not just the uh, the trace width specification minimum traced with to space in.

you've also got all these other things and then they've got like you know, the the pad to the track and things like that via to uh, track and all sorts of other different specifications and they can be really tricky to actually program into your software. I don't know how you do that in keycard actually because I'm not a huge user of keycad, but they can reject your board just based on that. And imagine if you went to all the time and effort to lay out their board and find out you couldn't get your five dollar prototype or not all manufacturers are going to be. Uh, you know, like have these sorts of differences.

Some of them will. All they'll care about is trace width and spacing. And technically there's no manufacturing etching process reason why there should be a difference in the specification between the a track, a copper track, and a copper pad and two traces like this, just two traces separated apart. In fact, that technically the requirements more stringent for the two traces parallel like this, because you could have two traces running right across your board like that.

and they're only like, you know, a 3.5 0.09 millimeters actually between them and just going to etch out that little tiny slither of copper whereas a track to a pad is like, technically, it's only that one little bit there. So what's going on here is it must be uh, to do with drill tolerances because a pad A typically this shows a hole, so it's there's going to be drill. Torrences, drill, wander, and drill. Uh, tolerance? They can.

You know, Little skid off a little bit and you can potentially get breakouts in your pad. That's why you need minimum annulus rings on your vias and your pads and stuff like that. And really, if that wanders across and if this was only 0.09 millimeters away, then technically even though your pad would still be good, it might you know it. You could wander closer to the track and then if you tracks only three and a half thou, it might break it.

You know things like that. So, but technically copper to copper, there's no difference. That's why some manufacturers will only give you this um, track and space and that applies to everything. But Jlc have decided.

I like, you know, quite a few manufacturers do. They have different tolerances for different things. Definitely something to watch out for. And you'll see.

there's definitely a drill related aspect to this because it's got Pth which is plated through hole to track. This is just pad to track. I.e copper to copper. This is actually from the hole.

You'll see. it's it's not from the top here. it's actually from the hole over to the track just in case the drill wanders. You know, wiggle wiggle wiggle.

Yeah. And then you've got like totally contradictory stuff up here. Nothing to do with holes 0.127 millimeters for pad to pad clearance. pads without holes.

Different nets. What's the difference between that and the two traces down here, which are going to be different nets, huh? But it's there. Technically they can reject your board. you know you think you've got .09 But technically, if you've got two different nets with two pads 1.27 millimeters.

thank you very much. So yes, let's just look at the example here. This is a Bga. This is not a dense Bga.

Um, oh, a fine pin pitch. Bga This is 0.8 millimeter pin pitch. This is like, you know, almost positively enormous by my you know, compared to like this one over here. let's go over to this one.

This one is 0.4 millimeters. So this is half the pin pitch of this one over here. Look, this is the keep out that you need around that pad. In theory, from Jlc Pcb, you couldn't even route.

you couldn't even drop a Via down there on this. 0.3 Now, whether or not Jlc actually pushed that point, you know, actually enforce that point Two millimeters. Uh, and I had to or whether or not it's only through hole pads. Why that'd make a difference? I don't know.

Um, it had to trace because maybe they could. Uh, you know, the drill could slip and it could come near the edge of the pad or something like that and you could get a possible breakout and then that could potentially break through your trace or not. Maybe that's a that's a thing so they might not care. But hey, a Via is going to be a drilled hole unless you know all this laser, micro drilling and stuff like that.

But we won't go into details like even at 0.1 millimeters. Okay, look at that. Oh yeah, yeah, you'll just have a room for a Vr in there, maybe. But we won't go into the specifications for Vias and the annulus ring and you know all that, uh, sort of, uh, stuff.

So anyway, I'm sure I've done that in uh, previous videos, right? So let's just say that your manufacturer had a 0.15 millimeter clearance, for example, right? and you're trying to route out this Bga here and you set your trace to three and a half mil here. Three and a half thou. You know you've got a little bit. you've got a little bit of room left in there.

Don't push the limits of these specifications like I would go like, you know, can we go 3.7 Something Like Yet, we can easily go 3.7 And still, we're not going to come a gutter on those clearances. So don't push the limits just because the manufacturer says you can do 0.1 millimeter trace or three thou trace. Don't do it unless you absolutely have to. And you're absolutely careful about your metric and Imperial units and the conversion to and from now.

There's actually another way that you can come a gutsy here. And that's actually when you generate Gerber files. It's not really going to be a problem in Keycard here, but it can be in other software. When you plot your Gerbers.

most packages are going to give you the option. they call it the coordinate format, but really, it's it's resolution. It's how many digits of resolution you're going to export in into your Gerber files. now.

Keycard give you two only two options here, which is good as we'll see in a minute. Uh, 4.5 or 4.5 or 4.6 unit millimeters is it? I don't like the way they've named this because as I said, it's resolution. What 4.5 stands for is it's not not actually 4.5 It's 4 is the number of significant digits before the decimal point. So in terms of millimeters, you can have 99999 millimeters, right? That can be your maximum maximum number it can put in the Gerber file, then the dot five.

That means five decimal places. So with the reference to one millimeter, so effectively, this, uh, choosing this 4.5 option gives you a resolution of 0.0005 millimeters, which is more than enough. you're not going. You're not going to get why, have to worry about rounding errors Between uh, you know, Imperial and Metric and stuff like that, Doing that, and 4.6 that'd be 0.0006 millimeters resolution.

Got it? But other packages like Altium here. Uh, because you know Ltm's it's been around a long time, probably before you were born, And if we go to our fabrication outputs here and we generate our Gerber files, okay, they give us the option in inches or millimeters here if we go to millimeters. and if they don't use four point two, they use four colon two. So that means you know four significant digits and uh, two.

only two decimal places, four millimeters. So if you chose this four two option here, it would generate Go. It actually tells you here has 0.01 millimeter resolution. Four three has one micron because it's 0.001 Got it? But it varies with inches.

You saw that keycard. As far as I'm aware, it only has the option to output Gerbers in in Metric, whereas Altium can do it in millimeters and you could have the same thing with reference to one inch here. So if you choose two, three like this, it has a one mil resolution. one foul resolution.

If your trace is 10.5 mil, for example, right? 10.5 foul. When you actually render that, it's going to render that as uh, either 10 or 11 000. It's not going to give you your 10.5 thou. You're limited in your output resolution.

Okay, so what I've done is just placed some traces here and I've set them a different width. So I set it at 10.1 10.2 10.345 and 10.6 Now, let's generate the Gerber for this uh thing. and let's choose that. two, three, I, I eat one Mil resolution.

I warned you here. Um, two, four, and two five only need to be chosen if objects on the grid are finer than one mil or one thou. And we've got that. If you don't understand what this format is, you can kind of come a gutser.

Let's generate a top layer and Bingo! We've got our Cam file down here. Oh this. This camtastic curb of your Gerber view is awful. I'm going to something else.

So let's use the Gerber viewer in a keycad, shall we? Unfortunately, I can't get right on there, but you can see it's exactly the same. has it hasn't increased the resolution there. Unfortunately, I believe this is like the lowest grid. I don't believe you can set a custom or finer or non-snap grid in key Cad.

Please leave it in the comments down below In the Gerber viewer, you can do it a custom grid in the Pcb. but Gerber viewer seems to be different so it's somewhat annoying. So you know, please bear with me. But like you know, fair enough.

Good enough for Australia. There you go. That's eleven thou. Okay, it's jumped up to eleventh Hour.

You can see how just the resolution is not there. Let's just generate that again. But using two five so that'll give us a 0.01 foul resolution, right? Plenty. Absolutely plenty.

So let's do that. Bingo. We've generated that open Pcb2 now. Hopefully we've got different size traces here.

Oh, it's like 10 point. Let's call that 10.1 Anyway, you can see how that is over 10.2 there. That's just the resolution on here. You can see that just the Gerber viewer resolution is not there.

Let's go to the second last one, which is supposed to be 10.5 And yep, yep, there we go. 10.5 mil. Near enough because the Gerber view is not perfect. But if you had a perfect Gerber viewer that let you measure that exact, let me know.

If you can actually get the information, how to? can you just click on that object and get the width I don't think there is in? Anyway, you can see how that resolution option in generating your Gerbers can make a difference in roundings You thought you were safe with your three point five thou. Uh, you know, minimum or whatever and they reject your board and you're like, oh god, I can't. I'm gonna have to reroute this thing. Or like large parts of it.

Uh, because you were trying to push the limits of your Pcb designs. So there you go. There's three ways you can come and guts are there Actually, With uh, getting your Pcbs manufactured like this. The first one is the difference between the rounding errors between Imperial and Metric and how your particular manufacturer actually enforces those and don't expect miracles for your five buck board delivered or whatever it costs.

Um, yeah, if you're pony up the money, yeah, they'll bend over backwards. But otherwise, oh, don't get angry at them because all you said on your website, three Point Five Thousand. I set my thing to three point Five thousand. I spent a week laying out my board.

You damn well better manufacture it for five bucks. Like no, that's just going to tell you to bugger off. So yeah, just be careful. Especially when websites like do those conversions and they don't add up.

You know if they're going, uh, it's 0.09 millimeters or 3.5 thou. Same thing you go. Well, no, it's not. You should question.

Like, really question them, or simply don't push the limits unless you absolutely have to. And if you are pushing the real fine limits, probably you don't want to use the prototype services anyway. You know you might pay. You know, pony up a bit more and get you know, like better tolerances and more controlled and more flexibility in that sort of thing.

So the second one can be those differences between trace width and minimum clearance. Just like you know. really. Be careful.

take note of these. Don't just go by. Oh, it's three and a half hours. So it's it's four, four.

You know, good enough. I'll set all my traces to four and she'll be right. and you can come a gutsy with much larger specifications for other objects, various clearances, and things like that. And then you've got Bga clearances like this: minimum Bga, pad dimensions, and stuff like that.

These may conflict with these minimum clearances up here. Look at this point: Two, once again, 0.25 millimeters, four to see, minimum pad dimensions and stuff like minimum distance between Bga There you go: 1.127 and this figure here 0.127 millimeters. That's coincidentally the same as this pad to pad clearance up here. So different nets.

nothing to do with holes at all. So one of the issues here could be related to actually the solder mask which you wouldn't necessarily think of and solder mask alignment because you've got solder mask slithers. I won't go into it, but there's going to be a minimum thickness of solder mass you need, just like a trace width on your copper layers. You're going to have the same minimum, uh, you know, amount of sodamast sliver between your pads like this.

So you're going to be limited to solar mass expansion around, uh, your pad on your Bga, and then not only that, minimum, but then you also got the alignment as well. So maybe this is partially uh, related to the alignment of what they're capable of in their solder mask. Uh, alignment. Because then you start getting like solder mask over the pads overlaid onto the pads and stuff like that.

And that's not terrific. But you know, what do you want for your five bucks? And what do you know? They do have a solar mass section. Here you go. Uh, 0.2 millimeters.

Although that seems to be that's not the solder mask slither that seems to be pad to pad. So there you go. Solder Mask bridge spacing between copper pad edges must be 0.2 millimeters. Or does that mean that they'll touch your Gerbers.

and like, if you don't have the minimum solder mask expansion, they'll expand it for you or something like that. Or you've got too much and they'll reduce it. Don't like that. Don't like any company touching my Gerbers, but you may not have a choice when you're using one of these prototype service panels.

When you're paying for the whole panel yourself, you can demand things, but not when you designing, not when you use these. You know, five bucks for your five boards on your prototype panel No, you get what you get as we teach our kids in preschool. You get what you get and you don't get upset. So again, there's no actual process technology reason why there would be an electrical difference between a pad and a pad on a Bga.

I mean, technically, if they can do 0.09 millimeters here, technically they can do it here. so it's to do with other factors. Yeah, it's interesting. You've got different all these different options.

and then the third one, of course, is generating. uh, your Gerber files. The resolution, which you may not have known about before, but now hopefully you do so anyway. I hope you found that video useful.

If you did, please give it a big a thumbs up. Let me know about the Floating Dave Head Seven. I don't think I'll do the Seven Dave head. I'm not.

I'm not a fan of it. I don't I'm not liking it's it's it's greatly disturbing. It really is. Anyway, catch you next time you.