Hi just a quick video. Um I Got to solder on a tiny little MLF package on my new Uh micro supply project board here and I thought I'd Just uh, shoot a little quick video of just how to solder this sucker on. and if we take a look at the Uh footprint, it's absolutely tiny. I mean there's an 0603 resistor next to it there 0603 Capac are there so you can get a scale of the chip.

it's only 3 mm by 3 mm Square It's got a thermal pad on the bottom. um and it's a 12 pin MLF package. And here's the actual device here and it's a real pain in the ass package because if you look at the bottom of it, if I flip it over. By the way, this is a Uh Mcel.

um MI c253 DC Todc converter and if you look at the package down in there, hopefully I won't go out of focus there. and uh, look at the package. It is absolutely tiny and those leads do not come up the side of the package. so it's not like you can get your iron onto the pin of that package.

There's no way that you can actually uh, do that. So there's two options for soldering this chip. One is to, um, put solder paste. You know, a bead of solder paste or a line of solder paste along each row of pads like that, and solder paste on the bottom there.

and uh, then use a uh hot air gun to heat it all up to a uniform temperature while you're holding the thing down in the center and it should bang drop into place like that. That's one way to do it. The other way is if your pads are long enough, these ones the footprint for this is probably just long enough to do this. um is to uh put uh, if you don't have solder paste and you don't have a hot air gun is to uh put a uh some solder onto the bottom of there and uh, then you can put and um flux as well.

Flux is important. So you flux the whole thing up, you put some solder on the bottom of the pad, you heat it up and then you press the chip into place like that. and uh, once you've done that, then you can get your iron onto the little pad. Little very fine solder .5 mm or thinner solder.

Get right in there and hope that the solder takes that pad and then reflows under. and then because you got the flux on the bottom of those pads under there. Hopefully it'll adhere to the bottom of these pads as well. and uh, so you can actually do this um, using a conventional iron.

You don't actually need uh, paste or a hot air gun. And when you get these sort of parts from Digi key, they come in um what's called a moisture barrier bag where which actually uh keeps out moisture from the device cuz these are moisture sensitive and if you have a look on the back, there's a whole, you know there's a whole bunch of uh, info telling you how to use it and um, calculated shelf life 12 months in the bag at relative humidity? uh Peak body temperature 260 and all that sort of stuff. So really, once you take these things out of this bag, you should, uh Mount them within a certain amount of time and uh, in in the bag. It's got one of these uh, desicant uh things to soak up the moisture.

It's got a moisture indicator card to tell you if you know during transit or something that, uh, they were, you know that they were subjected, um and you know whether or not you have to bake the parts and uh, you know they can be a real pain in the ass. I Mean you know this is only warranted for production and stuff like that For one off protypes, you know you don't really have to worry too much about that sort of stuff, but uh, some of these parts are moisture sensitive and you got to be very careful with them during production because if you don't uh uh, bake the parts uh, before you, uh, place them if they've you know, expired and you don't bake the things properly, then you can lead you have all sorts of solder joint uh, problems and that can ruin your yield and ruin your day. Trust me. So I think we'll give the solder past method a try here.

and I've got some uh Australian made uh, solder past from uh Imim. it's uh, what is this um, uh, sn63 type and uh, it comes with a very fine screw on no puz so we should be able to get a very fine application. It's just a syringe, you know. So I I Don't have a past dispenser or anything like that that dispenses a measured amount of solder paste if you're doing this sort of stuff.

um, you know, seriously, you need one of those solder paste dispenser machines where it's actually an air compressor type thing and it, uh, basically does a similar thing. You hook it up to the syringe, but it dispenses a measured amount of pace. But I'll rely on my calibrated thumb here to, uh, dispense a measured amount of paste onto these solder pads and how much? Well, eh, how long's the piece of string we'll have to uh Wing It Basically, you don't want too much because if you get uh, too much on there, then you can short out your pads on your board and we don't want that. So I'll see if I can get this shot under the microscope for you now ordinarily I'd use my mantis uh microscope to do this.

Of course all my uh old uh Olympus SZ series solar in microscope with the light. but because I've got to get this on video I'm using my Um video uh, tripod my reverse Mount video tripod system which works pretty darn good. As you can see there, the working distance is, actually, you know, quite. uh, significant.

What's that? 100 mm, at least 120 mm, 130 more working distance. and uh, the zoom is really good. And I've done a video on this and uh, I'll provide the Uh link to that here if you haven't seen that video. How, um, easy.

I can assemble this in under a minute using uh, all offthe shelf bit. So anyway, this is what I'll use to uh, record the video. All right, let's give this a try. Using my calibrated thumb: I'm going to uh, apply just a little bit of solar paste in there.

We don't really need much at all, just a tiny little amount because if that, when we press the chip down, if that oozes out to the side, it can short out to these pins over here and you don't want that. That'll ruin your day. So uh, now, I've got to apply paste. Here's the tricky bit.

the angle's not the not the greatest in here and I haven't practiced at all. You probably should practice uh first, on a small on a small. uh well, you know, a blank board or something like that. But let's let's get a tiny amount of paste.

don't need much at all. And the solder mask. Beautiful thing about the solder mask is that it will, um, stop the solder from shorting out to the pins next to it. That's why you can't have any gaps in your solder mask between pads, you've got to have what's called solder mask expansion.

I've talk talked about this in various videos. This is not easy, really. I'm just sort of. It's all.

It's like a dab. It's almost like a dab effort here, rather than a uh rather than a good continuous line of solder. Pace This is pretty poor. Quite embarrassed by this, but uh.

anyway, it doesn't matter. It'll uh, it'll get the job done. so that's H You know? Yeah, that's not. That's not by far my best effort at all.

but it should do. and uh, then all we've got to do is, uh, put the chip on here, make sure you get it around the right way of course, and uh, then we'll be uh, ready to use our um, hot air gun at uh, you know, uh, probably, uh, you know, 250, 260 or something like that. Um, and we'll solder that, uh, directly. Reflow that directly onto the board cuz what we're doing here is um, what's called Reflow soldering.

CU We've already applied the solder paste on the board which has the flux and and stuff in it. um, onto the board. and then we're reflowing that solder onto the pads. So pin one is down in this corner down here and have a look at the chip.

You can see the Pin One marker there. So let's and double check. Flip that over and you can see that the Uh pads on the bottom like that. So let's get our pin one in position and let's place this chip on these pads here.

Ah yeah, it's really. It's getting a bit tricky there. But the good thing about Reflow soldering is that it will effectively due to surface tension of the solder, effectively pull the Um chip into place and align it on the pads for you. So there we go.

Now let's uh, heat up the hot air gun to maybe, uh, say 250 and give this a try and see if that solder reflows you won't be able to see much unfortunately. Um, but anyway, um let's give it a go. Okay here we go. I'm going to use my Uh A10 858 d uh El Cheapo You know, $50 hot air gun here and let's give it a go.

Let's uh, there we go. You can see that solder in now. sorry I have to move the board around. Uh, but you can see the solder reflowing onto those pins and uh, hopefully the thermal pad underneath is done The same thing you have to assume if you get the chip up to suitable temperature bang.

There We go. probably didn't use enough. probably could have used some more solder paste. Actually bit disappointed.

uh with that. Yeah, probably could have used some more, but there you go. We've uh, successfully solded that device. nice And there we go.

Uh, if you get down in there, you can actually see the solder reflowed onto those pins of the device. Um, unfortunately the alignment of the chip is a bit off. it didn't uh, pull it in. uh, probably because of the uh thermal pad actually.

Um, that's an issue with those thermal pads, but have a look at the other side here. it's hard to get this under the camera. I'm going to have to use my mantis scope, but uh, there doesn't seem to be any excess uh, solder paste there. and that chip got pretty hot.

Um, just a bit of a warning when you uh, heat these things up. um, the board can actually get, uh, quite hot. It gets up to temperature of course and uh, if you got a lot of copper there, it can stay that way so it can be hot and dangerous. but there you go, there's a that will probably do the job probably.

I should have put a bit more solder paste on that. um I'm bit bit Rusty haven't done it for a little bit and uh, pays to practice first. but uh, it's better to have two little solder than too much because if I you know if I don't think that's enough. I can always get in there with a Uh with my solder in iron and just you know, touch up and Reflow those pads.

But pretty much what we wanted is the thermal pad on the bottom and those basic pins under there. So um, as long as we didn't heat it up too much, uh, we won't have destroyed the uh chip cuz they're designed to uh, survive. You know, going through these Reflow ovens at uh, uh, you know, a couple hundred degrees for uh, quite some time so should have survived nicely. There you go.

I uh hope you enjoyed that video on that's with like a $50 um you know A10 858d uh hot air gun. You know you don't need much and a you know, a tube of $10 solder paste or something like that. Really easy. but You' got to have a decent microscope to uh, inspect this sort of stuff as well.

Um, but you can um, easily do this if your pads were about long enough. You could do this with a regular solder in Iron as well. But I chose a solder paste method this time and I think that should work a treat. So what I should do now is actually, uh, go around each pin and uh, check to make sure it's not shorted to the thermal pad which is, uh, ground of course, course.

So um, you know, just as a, uh, double check, it's hard to hard to check that it's actually connected to the pin. You can sort of see the connections on the side there. Ah, it's You know it's really hard, but you just got to fire up the circuit and uh, try it basically. But there you go, that's solder in one of these pain in the ass 3 mm by 3 mm .5 mm pin pitch MLF packages.

They're a pain in the ass. Avoid them if at all possible. but uh, you know this uh chip I wanted to use the Uh Micrel uh w253 only comes in this package, unfortunately. not very hand solder friendly.

Anyway, if you like the video, uh please give it a big thumbs up and if you want to discuss it, jump on over to the EV blog. Forum Catch you next time.