Hi just a quick video because I was just assembling my new Uh micro Supply prototype PCB that I got from Uh Pcbz on.net or uh Circuit Laabs in New Zealand and I was soldering the components on here and I thought well I've gotten to this little Um Mop 8 package and I just thought I'd show you how I'm going to solder this onto here because it's not just a regular Uh package, it's got a thermal pad on the bottom so let's go now. the chip I'm going to uh solder on here is uh, this little one with the thermal pad on the bottom and it's an Sc Uh 4501 DC Todc converter. Now as you can see, I've already sold it an Mop Uh pocket package on here with a smaller Uh pin pitch actually and I just did that using uh drag soldering. just use my chisel chip tip solder in I put the solder on the bottom and then just drag the solder off the pins done in a few seconds.

you see me do that in previous videos but uh I thought well I've got a solder this one onto here and we've actually got this thermal pad on the bottom and I've shown you one way to do this before with u uh solder paste and put it down on there and then use hot air but uh I'm going to use a different technique today so I thought I'd show you that where I'm actually going to apply the heat from the bottom of the board and I specifically laid out my board so I could do this Now this is a not point uh, 65 mm uh pin pitch mop. It doesn't matter what the pin pitch is, really what we're doing here is um I'm going to show you how to get the thermal um because you need solder under that pad down there to thermally bond it to the chip and then all of this copper around here of course is used as a heat sink to get the Uh to get the heat out of the dye inside the chip and all those uh vs. there. they all go down to the bottom layer, which um acts as a bigger heat sink as well.

So let's give this a go. Now the key to doing this is actually Um in the layout of the board of course I've left the solder mask off there to uh attach to so that solder can attach to the Uh bottom of the thermal pad on the chip of course, but on the reverse side of the board I've also added here it is a solder mask cut out as well. so I can apply a big chisel tip on there and uh actually Heat this chip up from the bottom you need a a decent thermal capacity iron. So I'm going to use my JBC iron today with a fairly big chisel tip and if we apply solder through the bottom like that while that chip is sitting on top there, uh, solder will actually flow through those vs there and should contact our pad on the bottom provided we use flux of course.

Now you've seen me use my electral lube uh flux pen before, but I'm not going to use that one today. I'm going to use my Um flux gel. This is from um Aim solder in uh Australia You can get it from where components and other places. This is an NC 254 type uh flux gel so it's not like the liquid uh type flux.

it's more of a gel type. So going to apply that um on there and on the bottom of the chip as well. It's important to apply it to both surfaces and then we'll see if we can Reflow this thing from the bottom. it's not the easiest.

It's not as easy as the uh liquid stuff to apply this gel typee one, but we'll put it, that will probably be enough and we'll smooth that around the bottom. We'll smooth that around there. In fact, we can do that with our chip so I don't actually have to apply it. if I was using my flux pin, I would have applied it to both sides of the chip.

Hang on! I'm trying to get the bloody chip here with the tweezers. real pain in the ass but uh uh, we should be able to. Let's in fact make sure I'm getting pin one. In the right orientation.

you can see the dot up in the corner of the chip. There's my pin one up there with the square pad and the indentation up there. So really, what we want to do is uh, you can see that that's really is very. it is very much a gel.

very sticky, kind of uh gel. Certainly different. much different to the uh to the liquid type one you get in a pen. So if we get our chip on there now, we put it down in place.

we don't have to hold it exactly cuz our chip should self Center on there. but we've applied our liquid flux on the bottom. The chip is around the right way I hope and uh, we should be able to heat this thing from the bottom and we should be able to Reflow it. Let's give it a go now for this.

I'm going to use my JBC solder in Iron cuz it has a much bigger thermal capacity than my hoo uh, Fx8 here. So I'm definitely going to give this a to go. It's got a, you know, a fairly wide uh, chisel point on there I'm currently soldering at about 310. Probably want to bump that up a little bit because there's a lot of thermal Mass on the bottom of that I don't know, let's go 330 something like that, but it shouldn't have to.

maybe set it this. High um I'm still not intimately familiar with this JBC it'll probably do it at Uh 300, no problems, but eh, you just want to compensate a bit. Not taking any chances. it's whack it up.

The 330 shouldn't need to keep, but there very long. large thermal Mass soldering iron large thermal Mass Tip: I won't touch it cuz that's the hot pointy end folks. and uh, the idea is I apply solder to the Uh to the Chisel chip down here and I just get up under the bottom there hit that bottom pad and that chip. The solder should uh flow through the pins in that and it should just self Center and attached to the bottom of the chip.

That's the plan. So here we go: I've got a large dollop of solder on my my iron tip and I'm going to apply it to the bottom down here now. I'll have to, uh, go off camera because I have got to see visually where I'm putting this thing. so let me give it a go.

but if we apply that there, yep, you see it bang and that should now be soldered to that thermal pad. too easy. Probably didn't even need to turn that up. the 330 we go in there, it'll still be hot by the way.

And this chip, ah bugger, it has moved I thought it's self-centered but it didn't. There you go, All right. Well, let's give that another go. I've applied some liquid flux this time cuz I haven't used that particular gel type one before.

was an experiment so maybe that's it. But let's uh, let's reheat the sucker up and uh, see if we can get that to flow. Oh, there we go. You saw it, just drag it back into place.

Look at that. It's even soldering the pads for us now. Beautiful. Look at that.

All right. I Think that folks is a winner. Their solder flowed through and it even reflowed some of the well looks like maybe attempted to do some of the pins there, but uh, it's definitely flowing through. and I think if that cools down cuz there will be still a lot of heat left in that so, but that should be in place folks and that is well and truly stuck.

Bingo We now have our chip solded onto that thermal pad down in there. Now let's watch this again in slow motion shall we? and you'll be able to see the chip self. Center Here it goes: Bang. That is actually the surface tension of the solder, pulling that uh chip back into the center of the solder.

Master Exposed pad under there. Now let's take a look at the solder reflowing on the these pins. Now this is not solder actually coming from the soldering iron up through the V's up under the board. It's actually the pins themselves.

When you buy these chips, the pins are already coated in solder. So what we're going to see here as you can see on the left hand side there the pins. As the heat flows up through the dye through the bond wire onto the individual legs, you can actually see the solder start to flow what looks like flowing from inside the chip outwards. But that's not.

That's just the heat radiating up that Bond wire through the leg and then down eventually to the pad. So obviously once you start seeing that solder reflowing on the pins themselves, you know that that heat has transferred through that thermal pad on the bottom of the Chip and actually got up into the bond wires. And yeah, it's really attached. so don't wait for the more to.

Reflow You know that thermal pad is definitely stuck. Get back in there. So maybe it was that gel flux? I'm not. Uh, sure.

maybe the liquid flux I've got is better. but let's just, uh, drag solder these pins. I've got a little bit of solder on the bottom of my chisel. Tip down in there and just get in there and go boing.

We can just drag those pins back out. Oh, got a short on that one. We can fix that up later. Not a problem, some solder.

Wick And it's really hard to do this under the camera. I Keep saying that folks, it really is. Trying to solder under the camera is infinitely harder than doing it with the correct angle seated standing up. But just drag those pins back, bang and we're solded like that.

Not a problem. So with that uh, shorted pin there, we can just get in there with a bit of solder Wick and Wick that off. or you can try and drag it off with the Uh pin as well. It's uh, it could work either way, but uh, this is real world example folks, this is not one of these perfect, uh soldering tutorials of of course you have these little uh issues when you solder these things in the real world.

It's just Wick There we go. Wick that little bit of solder left and you can probably, uh, retouch that back up. but uh, shouldn't need to. And yeah, it looks a bit messy.

There's a bit of flux residue there, but we can just clean that up and we'll have a perfectly solded, uh, thermal uh mop 8 chip. Beautiful. And to clean that up, we'll just use some of this. uh ELR Lube Flux Clean which, uh, somebody sent me in the mail bag, so thank you very much.

otherwise I'd just use my uh, isopropanol alcohol version. So here we go. We'll just squirt a little bit of that down, rub it around with the brush, or you can, uh, you should have one of these conductive uh brushes as well. These are quite, uh, neat, little bit harsher.

They got conductive uh, bristles so it doesn't generate any static charge. Really quite nice and you can clean your board up and that will be now. Beautiful. And there you have it folks.

there is our beautifully solded mop 8 uh., 65 mm pin pitch chip with the thermal pad on the bottom. and of course, the key to that is just leaving your solder mask off the bottom like that so you can apply the heat from the bottom and the solder flows through those uh VAs on the thermal pad and bonds your chip in place. So beautiful, just like a bought one. And of course, when you're doing boards like this, you can see these Um 0805 components around them.

You don't want to solder those on first, go in and solder all of your fine pitch uh chips first and then do your passives around them because if you got your passives in there, especially if they're very close like that, being able to drag solder out either whether you do drag solder out or drag solder across the pins like that. really annoying when you uh, try and getting if you already got these passives in place. and large components like there going to going to be a big huge inductor here and you know you might not be able to get his solar in iron in. So um, make sure you just do these chips first.

But there you go. That is, uh, almost trivial to do as you see. I used a um, a gel type flux I've never uh used before, it didn't quite uh, take on the first go. but then I applied some more uh flux from my flux pen which is a uh which is a liquid uh type flux and it worked.

uh, no problems whatsoever on the second pass. Very quick if you got a decent thermal Mass solder in iron and a chisel tip and you can see we got a bit of residual solder on various pads around here, but you know that's not really an issue that but that's going to happen. You know, if you're doing some drag soldering around here, you're just going to get some solder dags on these pads but not a problem. you need to apply solder to those anyway to uh hand solder those um passive components on later and as you can see, I've already solded my uh at Mega on there and what I'll do now is just solder this this uh T- So package once again 0.65 mm pin pitch.

Just as a bonus, we'll just do some uh drag soldering onto here. Let's go again. Always flux is key to this so just apply some. There we go, you can apply some liquid flux.

you can never have too much flux onto my pins there using my flux pen. Not going to use that gel type again. not that it's any, it's not any good. um it's just that uh I've got my flux pen and we will apply our chip on there.

This is where you your 65 mm. You don't really need to work under a microscope, but like a nice little times 4 magnification or something really kind of helps. Um I'm just doing this one under the camera. and yeah, pin one pin one.

Not a problem. So let's go in there, do some drag soldering. I Just found something a little bit annoying with my JBC iron here. Um I had it in here and well I had it in the it goes to sleep when you put it in the stand.

uh, like this? There it is in the stand. there. you whack it in. You know it's got a sensor in there and it can detect when you put it in and instantly heats up.

Really quite neat. Um, but I tried to uh, change the temperature, hold the tool, change the temperature. You can't change it when it's in the stand. Hopeless and you so you've got to hold it.

but I'm holding it and it still doesn't look. there's some timeout thing. Oh, there we go. You got to press menu.

Enter: Oh bloody hell hopeless. We only need this on 300. Really? Uh, good thermal. Mass soldering iron.

Now as I said before. large chisel tip, solder in Iron Like this, we'll apply a little bit of solder to the bottom of that now. ordinarily um I'd recommend. Uh, just tacking down one pin there on the corner.

But if your um flux is actually, uh, tacky enough, it's going to hold the chip in place anyway. So I'm just going to go For Broke here and uh, get in there and drag solder. No, there we go. The chip did actually move a little bit bit of a fail there, so let's But the good thing is that effectively allowed me to tack one of the pins in place there.

So there we go. and then I can just drag solder the rest of these pins. Look at that done, one side complete and let's try the other side here. I've put a little bit more uh solder on my tip again and we get in there and drag it back.

and if some a lot of people ask, why do I shake when I solder I normally don't usually I'm extremely good at that, but I am standing up here leaning over my camera getting in at the wrong angle H it all has to do with uh, doing this on camera. Maybe that second pin up there I haven't looked at that. Maybe that and it just needs another. The go there.

there we go. look at that perfectly solded a uh 0 65 mm pin pitch? um T-t package in, you know, seconds. Really too easy. And of course you use exactly the same uh, drag solder and technique on a quad flat pack like this.

at Mega here, no difference whatsoever. Doesn't matter about the pin pitch, whatever, you can do it on. So8 Parts doesn't matter. Um, usually I prefer to drag outwards like that rather than along the pins.

Um, Well, I do do it both ways depending on the circumstances, but uh I Just find it's a little bit more controlled if you just pull the iron out from the pins like that. Um, but you can certainly just go along bang, drag it right along the pins like that. Not a problem. and the key of course is the solder mask between the pins and hopefully you can see that in there.

You can see the solder mask just go a little Slither of solder mask going between the individual pads there and that's the key to prevent uh solder bridges on these sorts of uh pads when you do drag soldering along the pins like that. So if you're doing a very fine pitch part, this one's a 65 mm which uh, you know isn't too bad. You can easily even a cheap uh PCB manufacturer can get the solder mask uh between the pads on there, but say if you got a 0.5 mm or something, you may actually not be able to. your cheap manufacturer of your board may not be able to get that solder mask between pins.

In that case, then do want to do that drag soldering out. The technique: I Just showed there dragging out from the pins like that. instead of dragging along like that, it just uh prevents uh helps prevent individual shorts between the pins. So there you have it.

There's our beautifully solded chip piece of cake. You can do it with any normal uh solar in Iron whatsoever. Just a decent chisel tip. So if you like these solar in videos, please give them a big thumbs up.

And if you want to discuss it, jump on over to the EV blog. Forum Can C you next time.