Hi welcome to the Eev blog an Electronics Engineering Video blog of interest to anyone involved in electronics design. I'm your host Dave Jones hi just a quick one. This is not actually going to be part of my soldering tutorial. I just so happened to be playing around with a little three AIS accelerometer and I want to hook it up to a microchip pick uh chip and I thought uh I would just show you uh, just the process of actually soldering this thing dead bug style I've talked about this before.

uh because these uh, 3axis accelerometers uh, they're not really available in they've discontinued all of the usable uh packages like uh for basic soling or the so uh type packages and even dip type packages. You can only get them in these tiny little um LGA or other type surface mount packages now and they're real pain in the ass. but I thought I'd just show you I was just going to uh hook one up to this uh pick demo board so I can play with it uh and do some software and I just uh thought I'd show you soldering that chip So let's go. here's the Pck kit uh demo board I'm going to use I just had this lying around and just so happened to had a reasonable pic chip on it and a prototyping area here.

And here's my little tiny LGA package uh, accelerometer 3 mm x 2 mm and I'm going to solder onto here dead bug Style And here's the actual LGA type package. it's called, it's a 14 pin LGA and uh, as you can see, it's 5 mm x 3 mm in comparison to a standard quar wat resistor. Here it's It's not overly tiny in uh, the scheme of things for surface mount stuff today, but it still is a real pain to sold up because as you can see, um, it's it doesn't have the uh pads extending down the side of the case so you can't really. once you lay this thing down on the board, these pads are not directly accessible with the soldering iron.

So really, these chips are only designed for a Reflow soldering process. They're not really designed for hand soldering, so that's why today I'm going to actually flip it upside down like this and then I'm going to individually wire tiny little Bond wires over to my prototyping area here. So I'm going to sit it on here and I'm going to all the individual pads over to a larger footprint which then I can, um, access via hand soldering. This is an example of dead bug style construction.

Now the term dead bug actually comes from. um, actually tur in something like a dip package. upside down on its back like that and it looks like a bug with its legs on its back Dead with its legs sticking up in the air like that. And that's where the term comes from.

So even though this little LGA package does not have uh legs sticking up in the air, you would still I would still call this dead bug style construction. So you flip it on the back, you actually glue it down and then you individually solder almost like, um, almost like what's what happens inside an IC itself. they the machines automatically insert Bond automatically wiring little Bond wires to the pads which go out. if you actually opened one of these uh dip chips inside you will find like a silicon uh a can Dy like that with little Bond wires going out to these larger legs and that's pretty much exactly what we're going to do here today.

now. I'm pretty confident of doing this one because it has a 0.8 mm Pinto pin pitch and that's uh, reasonably large. The pads on there are reasonably large in the schema thing, so I shouldn't really have too much trouble I don't think, um, actually wiring this one up it? uh, we should be able to do it reasonably easily using a bit of magnification. I could probably do it by I as well, but we'll actually use some magnification today.

Just start two and a half times or something like that just to help us in actually uh, soldering onto the pads and making sure we don't short things out. And there's the device that we're going to solder. It's the Uh MMA 745 3axis Accelerometer. It's from uh, free scale and that's the LLG 14 pin package Now as you can see uh over in that little uh the bottom left corner.

There, it does have a little Pin One marker. It's important for us to actually get that correct when we flip it over so we know exactly what pins what. It seems to have another little uh marker there if you can see it, which uh indicates that it's the same side, but you just have to remember uh, which one is actually pin one? Okay, we want to add a tiny little drop of super glue down in here just so that we can hold that chip in place. There we go.

We've just, uh, tacked that in place it. This stuff sets almost instantly of course, so you've got to be very, very careful. but uh, that will just hold our chip in place while we solder it because you don't want the thing moving around. Okay, the first thing I'm going to do is I'm going to apply some flux from this flux pen just across the Uh main pads there and also on top of the device as well just so we can get some good wedding onto those Uh pads.

And what I'm going to use to make the connections is some wire wrapping wire. solid Core 30 AWG Uh, tinned wire and this is really useful stuff I Highly recommend you get some. It's quite fine. It's great for uh doing mods like this and in fact it is called uh Mod Wire and it comes in various colors and uh there's the actual um, it's an okay Industries uh brand 130 AWG and and using my chisel Point iron and my46 mm solder I'm going to Tin these pads.

um I've already tinned a couple and that didn't unfortunately I didn't press the record button. oops and uh, this is not my finest work because I am trying to do this under the under the uh camera so the angle of the iron is not um, ideal to how I'd normally do it. but uh, you can just tin these pads like that and then we will, um, solder the wires each individual Bond wire onto those and take them out to the individual pads. Let's try and solder a wire onto there.

um, it can pay. It can pay you to actually tin these wires first. Um, just so that they wet a bit better. But there you go that first one is attached and then we will just get in there and we'll actually uh, cut that and we'll get in and we'll push that down so it contacts one of the pads.

Let's say that one there and then this one will go to that pad. That one will go to that pad and so forth now I need to add some more solder to these pads in here because it the last process just uh sucked a fair bit of that away. So we'll get in here with our wire again and I'm doing all this through the camera. LCD I can't actually uh, see the board here so this would just be just like working under a microscope.

really. except I haven't got much in the way of magnification here, but there we go. Now what I'm going to do here is I'm going to Tin the Uh wire cuz this is a fairly, uh, fairly important step. although this is already tinned copper wire.

um really, that? uh, you got to add some flux on there, clean it, get some fresh solder on there to just to make sure it really takes. and after I do that I'll clean my iron on my sponge and hopefully if there's enough solder on the Uh pad on the chip that will be enough to Reflow onto my what my already tined wire and yep, there it goes there. Made an attachment nice and quick, easy and a good quality joint and this one here. I've got to bend a bit further over and don't bend it down directly because you don't want these to short because they aren't insulated uh wires.

but it's pretty easy to solder them onto a smaller um, well, a larger sorry, uh diameter um pad. So later on I will actually solder uh. flying leads directly off these pads. Here onto my pig chip and there's my completed dead buug chip.

It's uh, not my finest uh work. It is surprisingly difficult um to do on on a shallow angle. uh when you've got the camera in the way, but uh, bit harder than usual, but that only took me like 5 minutes or something. Something like that.

It wasn't hard at all. and I've now converted that um LGA package chip into a much more uh, usable pitch that I can actually come along and now, um, solder on some of this uh mod wire. I'll just solder them onto each of those and then over to the specific pin on the P chip which I need simple so that should work a treat. Uh, I'll have to do some, um, more up close visual inspections under the microscope, but that looks fine to me.