Hi quite often in product design, product manufacture, production repair, you might have to upgrade things In the field. you might find a Fault in your product after you released it, or you might want to upgrade its performance. You want to make some changes. Things like that.

There's plenty of reasons why you might actually want to modify an existing populated. PCB Not always can you just re spin the board as it's called. relay it out to add a new component at a different component. Something like that.

This is actually very common in the industry, and I've actually worked in large companies, defense companies in particular where they'll actually have specific component obsolescence engineers where you have to maintain this military equipment. very expensive equipment. existing boards out there that have already been manufactured. You want to do upgrades to them or a component becomes obsolete for example, and you have to replace it.

but you can't just to respin the board of remanufacture these things. The boards cost can cost you know, tens of thousands of dollars in many cases, and you just don't want to Reese pin those all their exhibit fitted to existing equipment, they've already been qualified, and stuff like that, You just want to make a small little change or upgrade or replace a component to a different package. for example, very common that components in certain packages go obsolete over years, or they might discontinue some sort of our programmable part. you have to replace it with another programmable part.

It only comes in a different footprint and things like that. So you want to actually upgrade these boards. How do you do it? So I Thought would take a look at it. because let's take this board as an example.

It's a ridiculously complicated board and would be seriously expensive to actually not only you know, manufacture the board from scratch, but if you've got a big stock of these blank PCBs for example, just the blank PCB can be seriously expensive so often it makes economic sense to do what's called a a mod board. A dotter board might be many other different names for a let us know in the comments if you and worked at companies that call it different things, but we'll just call it a mod board. So it makes sense just to modify these boards with a little mod board. And of course, you might have to modify your boards of any complexity just to attest that your new modification works.

So typically you'll you know your hand solder that there'll be little mod wires going everywhere. It'll be really ugly. but you don't necessarily want to do that in a production environment. Or you know, if you've got a thousand boards you're manufacturing in new production.

Ten thousand a hundred thousand. Or if you've got boards out in the field, you don't want to the repair text to go out there and have to put in mod wires, cut and strip wires and individual parts and bend them over and put electrical tape in there, and just all sorts of dodgy stuff like that. So you want to do a nice, simple mod board like a professional solution for modifying a it doesn't have to be this complex I'm even relatively cheap and simple boards. If there can be lots of economical or other sort of logistical issues why it's better to actually do a mod Boards I Think is an important skill to have.

Not only know that mod boards like this and this is a very simple example, but even more complicated ones like you might be familiar. For example, if you're into like gaming consoles, a lot of those illegal mod boards and things like that you can buy a lot of people fitted them in themselves to you buy him as a kit. they might come on a little board that sort of, you know, weird-looking board that's convoluted shape or whatever to fit around existing components. That's a classic example of a mod board to an existing product that really, there was no other choice to do it.

and you want a professional solution that's easy to use so that people can install it. They don't want to have to run wires and strip wires everywhere. It's better if it's a professional solution on a board something like this. So it's really important to know that a you can do this sort of thing and that this is a professional solution.

So a really important topic. I've actually got a mod board here which will take a look at and this is for the 121 GW multimeter. We upgrade one of the parts in it so I thought yeah this is a good excuse to do a video on this. So I will take a quick look at this and may another example of a production mod to a real expensive pity key.

Let's go Now here's an example of a mod board on a real expensive board. This is from one of the Lacroix oscilloscopes you remember. I did a couple of videos trying to repair this thing but it was unfortunately BER beyond economical repair. And can you spot spot the mod board? Where's wally? it's there somewhere if you're watching in 4k.

I'm sure you can spot it. Yep there it is down there. right on the front end like that you can see I've got this board with a whole bunch of components and they've even like a double stacked of them else you know. I'm a male fanboy so I'm real excited about the double stack in there, but a little mod board that they've obviously put on this board.

now, whether or not this was done at the production stage or whether or not it was like an upgrade or you know something like that or they released it and they found an issue out there and they wanted to, you know, fix it or whatever. If you do know the details of this particular mod, then please leave it down below. But anyway, the fact is that they have actually modded that front end. You'd see that they've got a little board here obviously snapped off from a panel which will go into detail a minute and also will go into detail of these little cast elations on the side here of the board where they've actually soldered it down to like existing components.

You see, they've already got an existing component there that just soldered that over. and here's the blank space where it actually went. and this wouldn't have been designed at the production stage because if they were laying out this board and clearing that space in there and they would have just put the parts in there. So obviously post-production kind of thing or some sort of upgrade or something like that because this is a real huge expensive board.

And as I said, even if you've got the blank board, stock can be very expensive. but let alone a populated boy, you don't want to scrap a populated board. It can cost thousands and thousands of dollars. Or even as I said, some of the stuff I've worked on many tens of thousands of dollars, even into the six-digit category for a board is not unheard of.

so they obviously like got a little bit lucky because there was some space available, but you can always put it on top of the components really. And the fact that it was a square board that fitted in there quite nicely. So yeah, sometimes you get lucky. Other times as I said, you know, if you need to connect, say you know this spot here over to like over here.

You might need some convoluted board that sort of runs around this chip here because it's got this tie-down point here so you might need you know and you don't want to. You want access to the pot so you might have to do some weird thing. you might even have to do some flex solution or something like that. But yeah, you can see how you just tie a mod board into existing components like that.

It's nice and simple, professional, and it allows repair. Tech's in the field to actually upgrade these things which is important or just easily solder them down in production. or or as we'll see in the minute, actually treating them as a pick-and-place component and reflow solder in them. So here's an example of a mod board panel.

In this case, it's for the 121 GW multimeter where we wanted to upgrade an existing part on some already populated boards. So it was an SMB part that we upgraded to 223 parts like this. So how do you do it? Well, let's take a look at the details because this is just one example. There's many ways to do it, but there's lots of issues which go into making a board like this.

Unfortunately, this is not the full panel as you can see, it's been broken off here, and as you can tell by the fiducial marks up here and the rounded and the tooling holes here, the panel is actually this width here. It's not hugely big, but it obviously extended down here like this and this is how you want to do it. You want to manufacture these in panels like this with either break off tabs or Vee scoring or something like that, so you can easily cut them out at a later stage because the last thing you want to do is get a tiny little board like that and give that to you. Pick in place, assembler and go assemble that board.

please. They'll just roll their eyes and charge your fortune and probably just end up hand soldering anyway. So how do you make a nice panel like this one? Well, I've done a penalisation video which is very popular. I'll link that in at the end and down below if you haven't seen that.

Highly recommended. Lots of detail on how to do routing and Vee scoring and that's what we've got here. We've got a combination of routing and V scoring so let's have a look. You can see that obviously they've got they've routed out this point like you didn't have to add this little like sham fur in here like this.

It's not necessarily important to do that, they've just decided to do that no problems whatsoever. But anyway, you just route like that like a two point four millimeter routing tool might be like a standard diameter. As I said, look at that penalisation video I've done and I've got a combination of V scoring like that and I'll show you up close. But as per regular panels, of course you want your fiducial alignment marks.

You want your tooling holes on your outer strip like this so that it can go through the conveyor machine in the pick and place. So they'll have a rail up here and another rail down here and your board passes through the passes into the pick and place machine gets picked in place and then it goes out on those rails out in via these our tooling holes which move it along and it goes out to the reflow oven. So you want to automate that sort of process. Now you can see that all the copper fill has been left on here.

it's not on the bottom of the board because we don't actually want copper underneath here. There's just no reason to have it, but like there's being copy infill like this, just floating copper like that and the reason to do that is just so. It's nice for the PCB manufacturer so that they don't have to etch away all the copper. so you might as well just leave the you know, leave the copper on there to make the etching nice and easy.

We've got a combination of routing slots a V grooving top and bottom or V scoring as it's called. going across the panel here you might be able to see the detail in there I'll show you in a sec. And also we've actually got what's what Accord our cast elations or Halfmoon pads going right across the score in here. That not only allows for the boards to be individually snapped and cut out of the panel easily, but then it allows you to actually solder these down as a surface mount component Because as I said, in this case, this little mod board here is actually replacing an SMB footprint part with 2 in this case, 2 SOT 23 transistors.

Now you make this panel as large as your one, of course, subject to your assembler and how it fits in their machine and whatnot. Now this is a naught point eight millimeter PCB so it's pretty thin. There's no real need to have it at point eight millimeters in this particular case, but you can see that it's actually going to be quite flexible like that in both directions. You don't want to do it too far in that direction because you're going to snap off the V scoring along those boards.

But the problem is is that if you have one big panel like this and you stick it in your pick and place machine and it's only held with the rails at the top and bottom when you put it in like this and the pick and place head comes down to place paths. whoops, it's gonna. it's gonna walk in the middle like that. So boards like this: it's quite common for your assembler to actually manufacture a custom tray.

That actually this board just sits snugly inside the tray and it's fully supported over the entire area like that. So yeah, but your manufacturer will advise on that sort of stuff and often just handle that for you. They might do that without even telling you. You just say simple, my panel please and they'll go OK And they'll have like as part of the tool in charge will be manufacturing a holder for this particular board.

Now you can see the v-groove in across there. This isn't a particularly deep V groove. If you have a look down there, it's a in fact, bottom seems to have a different depth I Wonder if that's actually consistent across the board? Yeah, it seems to be I Think they've got possibly a sharper V groove on the bottom? Dude. I'm not sure if that's on purpose or whether or not.

That's just the way that the you know tolerance in how the Me the machine the V groove will was actually are set on the thing. And there's the bottom of the board. And this V grieving needs to be controlled. You know, fairly accurately at the factory, especially for a like a nought point eight millimeter.

our PCB like this one. the thinner your PCB gets the you know the more critical your tolerance gets on that V-groove cutting wheel and you need the case. There's more than enough our fiberglass left in there to hold this board together during not handling and whatnot, but it allows easy snap off so as you can see when you snap it off you might be left with a few DAGs and things like that in there, but this is fairly common. It's not generally gonna be an issue, so you left with the Halfmoon cast elation like that and which allows you to just easily solder that onto like existing pads onto the board and then when you snap it off you're left with a tiny little board like that and you can see how that is basically becomes a little.

A surface mount component is other ways you can do the cast elations and you know stuff like that. If you really want to get all fancy pantsy about it, but those half million cast elations work well, then you simply solder that as a component. In this case you would hand solder, but you could actually reflow it. But because this is a retrofit, generally a retrofit to an existing board although it doesn't have to be if it's a like an obsolescence component replacement or something like that, you can actually get this actually placed by the pick-and-place machine and reflow up.

But of course, like You wouldn't have it on any production reel or production tape or anything like that. so you might put it. Maybe you might do if you're like, really keen. you might do a specialized production tray for it or something like that that held it as a tray base component in the pick-and-place machine which could then pick it up just you know, using your existing nozzles on to the existing component and then lift it onto the board and actually place it and have it refloat.

And of course this is a real simple example. There's only two transistors in there replacing a single surface mount part. but like you can make these as weird and wonderful and convoluted as you like that could like read out over in your entire board. You can even do this as a flex circuit as well.

But the problem with a flex board is that you don't get the same kind of a cast elation hole on the end that you would on a fiberglass. PCB Like this, but yeah, you can have pads either on the top or bottom and whatnot and then just start solder bridge those on. No problems whatsoever. Both are valid techniques.

So in this particular case, we wanted to replace an SMB component with two SOT 23 parts and as you can see doesn't quite fit on there. You could sort of like stagger them a little bit so like this one went behind there. if you had the width like this which you didn't really have, but because we actually had two of them there and had an adjacent pad. sorry, you can't see under there, but normally there's a pad there and a pad there, then we can just have it going from that pad to that pad.

No problems whatsoever and this is just a real simple example, but it gets the point across so it's just real neat and tiny and it simply becomes just it looks like yet another part. In fact, you know if you zoom out of this like you're really like hard-pressed to tell that you know that's actually a mod board in there. Really? So I hope you found that video useful and if you did, please give it a big thumb up. And as always you can discuss down below or over in the Eevblog forum and if you like my content, you can always support me on Patreon links down below and I said cryptocurrency donation or what sort of jazz and as merch on my store? you know the deal.

Catch you next time you.