And incidentally, you'll notice the largest solder pads on these outer pins of all of these chips. and they're uh, solder thieves. Uh, they go under various names, but this is designed to be wave soldered and you can tell this board has been uh, wave soldered instead of Reflow soldered. You know, if you look over some the power stuff over here, it's clearly you know.

had the molten wave just go right over this thing and the idea of these uh, so obviously all the components need to be glued uh down for that to take place. and then these, uh, just ensure that you don't get uh solder dags happening between pads. you just get as the solder wave goes over this thing, you actually get a larger pad on the end allows you to capture any excess solder that's coming off like that. You should be able to see there how the solder is all the way up these legs of all these parts.

So that's a dead giveaway. how you can tell that a molten solder bath has gone over this thing cuz it's just plated those legs right up there. Whereas if it was Reflow soldering, if you just had solder paste on the pads, you'd of course only get the Reflow down on the pins down there and you can see the glue oozing out the bottom of the package there holding the device down. So you just, uh, don't see boards like you know SMD boards like this.

Uh, wave soldered like this anymore. it's just all gone. uh, almost exclusively. uh Reflow uh, you know infrared uh or other Reflow Soling cuz it's much more controlled.

Much nicer when you got a hot molten solder bath just passing over this. All of these components just picture, you know, big blobs of molten solda just going right across the board like this and you end up with quite a a messy board. It's hard to get on camera, but you know all the joints are messy and and all the components have to be individually glued down. It's just, it's a really horrid uh process.

I'm glad they've done away with it. Now the idea with solder Fein Pads like these these larger pads on the outside. Let's say that the Uh board travels through the soldering wave in this direction. Okay, so the wave is coming across like this and then behind it.

it's bubbl in like this as it goes across and it's dragging the solder across all these pins. just like the drag drag solder in technique you've seen in the videos. and when it gets to this side over here, when the all the bubbling boiling solder is being dragged across these last two pins, if they're the same size pads then you can actually get a a you know, a bridge, a solder short between those two pins. But if this pin over, if this pad over over here has a solder Fe on it, it's a solder feing pad then the solder inherently wants to go towards that larger pad and stay there.

so as the board travels through like this, it ensures that there's no short between those last two pins there. So ideally, in this case, if the solder uh is flowing in this direction like this, or the board is moving in this direction so to speak, then you don't actually need the th in pads on this end. If you know the direction your board or your panel is traveling through the wave soldering machine, you only need those on one end. but just as a matter of course, they just put them on both ends just in case you want to whack the board around the other way.

But ideally, if you're doing this properly, you should know the direction or you're laying out your board for way solder. And you should know your direction of board travel whether it's this direction or that direction. Because ideally you want the pads to be in this direction. If this chip was oriented like that and you put your board through the wave soldering machine like this, that's not a good idea folks.

And same thing with your uh, surface mount components like this. You want them so you want your Ic's in this orientation so the solder drags over the pins like that. And ideally you also want your Um passive components like this mounted in the vertical Direction These ones here WS Necessarily solder as well and as consistently as one in this vertical orientation when the board moves through. W Soldering like that just because it forms a well, like there's a cavity behind it.

Like that when it travels through the wave soldering. as the last bit of solder goes over and it may, there's a chance very slight one. it may not take as well as it would on a vertical oriented passive component. And that's why if you have a look at the board, it's no coincidence that all of the chips are pointed in this direction like this.

none are mounted in the vertical direction. That means the board passes through the wave soldering process like that, and very often the designer of the board will actually, uh, put on the silk screen a big arrow pointing in the direction of board travel. but I can't seem to find any solder Direction marker there at all. If you actually have a look at some of these chips here, you can see that the right hand side pins actually have more solder on them than the left hand side pins there.

That means that this board has passed through the wave soldering process like this. So imagine the this is this Center marker. Here is the bubbling boiling wave solder. It's going here and these left hand pins are hitting the solder first and then they're dragging across like that and then you're you end up with via that process I Said earlier.

Where it you know you need a larger pad on the end of the chip to determine where the solder naturally uh, flows through onto that last pin so you don't get a short. Then that's why you get a little bit more solder on those pins at that end on the right hand end of the chip there. So clearly this board we know exactly which direction it's G through the wave soldering process. Neat.