 So today I'm presenting about my DIY solar reflow oven, which I built because I was fed up with soldering 2FN and EGA using hot air reflow oven, so yes, I just built a bit of solar reflow oven as well. So first things first, how do reflow ovens actually work? So basically they use a bunch of heating elements in a controlled environment like a box basically, and then they simulate a very, they actually simulate a reflow curve which is specified by the solar paste manufacturer that you're using. So depending on which solar paste manufacturer you use, there will be different specifications for what kind of reflow curves that you want to reach and follow, so yeah. So this is a picture of a solar paste, which is basically just blocks of solar and bunch of flux on, yeah. And that's what they use in industry to actually apply solar paste over a famous steel stand zone onto your boards. And that's actually a picture of a reflow oven that they use in like the real big ones in the industry. And yeah, this is a very quite a typical reflow curve for that free solar paste, and you see it consists of a few main zones, the pre-heat zone, the soap zone, and the reflow stage basically, and then after that will be the cool off stage. So really, why would you want to like make something like this? Well firstly because you want to get a reflow oven without paying for the huge one there, so that's why you would DIY one up, and it's actually not, it's particularly not that hard, but you won't get the accuracy that you get from industry ovens. And also you want to be able to solder small batch components much faster. You could use a hot paper, I'll explain that later on. So yeah, this is also an article on Hackaday, and they actually talked about making, a lot of people actually talked about making DIY solar reflow ovens, yeah. And it's actually very popular in the hobby. So first up is to choose a toaster. So my advice is not to lose this link if you're looking for anywhere. So it's just get the cheapest one you can buy, because anyway you're going to be hacking it, and the more complex, the more expensive it is, the more complex the internals are going to be, so it's going to be harder to re-engineer the insides of it, so just get the cheapest one. And generally the cheapest one actually works on bi-metallic strips, which is just through temperature regulation based on, you know, when it goes above that temperature, then the bi-metallic strip will disconnect and the heating element will turn off and such mechanisms. And basically you also remove everything inside it, including the towels, because you'll never use them. Unless you want to use the towels, of course, which can be used, but I use the single button on the face, so it's fine. So this is the internals of the toaster, yeah. And yeah, you can see the bi-metallic strip right there in this side, yeah. And that's a very typical toaster from like Giant, I got for $30, so yes, it's actually reasonably cheap, and you can get it cheaper online. So in terms of components that you're going to need, it's pretty bad, won't you? You may probably just need a microcontroller, or you'll need a thermal couple to measure the temperature that the inside of the oven is, and you also need some relay to switch on and off the heating element, so they can control the temperature. And then optionally, I mean, you kind of actually need this for use at the day, so yes, you'll need a button and LCD, or you can just use a button and you know, you wouldn't have no control over what peaceful curves you're going to follow and stuff. And yes, I got stuff from Spark Fun, which is a terrible idea, it's very expensive. So yes, I regret that. But yeah, type K thermal couple, I think it's a MAX3155, if I'm not wrong, I've made her MF11 the part number. Yeah, I think it's right. And also a Nokia 510 stream, which is a pretty standard, it's actually one of those old phones that people just throw away and Spark Fun is apparently just taking them and reproversing them to just get LCD to taste. And then any microcontroller, I use the Arduino because I wanted to put it inside the oven and it's very small and yeah, so in terms of electronics, wire up is actually just both the LCD and the thermal couple, both of the SDI. So I use chip select by some people using double software SDI, but I never understood why do you use software SDI because SDI is kind of meant to be used in trips of any way. So I never understood that. So yes, and for the power, it's just 2M50 PSD charger that I had lying around and it was just some random 5-ohm thing that I had lying on. So it works for you. That's what it looks like. So that's the LCD, but you can see a red button there and then I painted the reflowern to be black, so of course it looks cooler. And then all the electronics in the cardboard box, I actually got the cardboard box first of all later. Okay, software. This came out prepared for a terrible cold. I colded this in 10 minutes and I'm going to provide a better, get out of the classroom for some better cold. Okay, so to prevent cold reflowern, you need to follow the reflowern as I mentioned at the beginning. So you need to keep the temperature at the step, temperature for that specific time. And so that requires some amount of regulation. So I didn't use any PID loops. It was just simple logic. We just say if it goes above the temperature, turn the heating elements off. It goes below, turn it on. And that turns out to not work very well, especially when the oven has a lot of thermobasks and it takes very long time to heat up and cool down. So that makes it, the regulation will be quite bad if you use my method. And yeah, mine was 10 minutes for testing purposes. Yeah, it's just that. But this is my method to follow reflow curves and it's also very bad. So I'm going to skip through this. And it works. Yes, it works. Yeah, a better implementation will be what is done by this slide. They actually use a proper PID controller. And they also have proper storing of multiple reflow curves in storage. And then they also have a nice 1.8 TFT of the, TFT is there that they draw beautiful curves on. Yeah, that's what it looks like. It's really nice in the face. So yeah, if you want to actually make a very, very nice oven with a really nice UI, then go with this one. It's really good. And they also provide very good instructions. So for some problems that I face, let me talk about that. I'll talk a few. First thing, installation is key because you want to be able to keep the thermobasks of the oven at where you want it to be. If you wanted to take too long heat up in Kona and for that installation, it's very important. Another area where you're installation is important is because when you're reflow, you don't want to reflow your control electronics as well. And because that will just destroy everything. So that's why I put it in a cardboard box, which kind of works. But I would rather actually, I would suggest using a five-linked, which I'm going to experiment with soon, to cover down the inside of the metal stuff inside the oven so that the heat doesn't come out and reflow your electronics. Also, chopper wires are annoying. I had to, I, first prototype was chopper wires and everything kept disconnecting so that's always with you. I soldered everything at the end. And then software bugs because my code is terrible and power system, I don't know why, but there's this weird problem with the LCD where it keeps going and it just keeps turning off. I have no idea why for that. It may be an issue with my power, but I haven't developed that yet. So in terms of testing, I've played with quite a few components, trying to improve them. So first thing I did was the Edison connector, because that's just annoying and I work with it quite frequently on my projects, because I do a lot of cool projects involving the Edison chip. So I had to try reflowing that. It's a .5 mm pin pitch component and so it's actually quite hard to solder by hand, but it's still possible. Ambrose managed to do it in like one hour or something. And I managed to do it in five to ten minutes. So that's what it looks like after it soldered. It's actually pretty decent. So yes, and that's when I half-light up the place, it's not visible. So I also, this is actually what I was actually working on at that time. I think I presented this a headway before. And you see, this board consists of a lot of O6 OJ components, a bunch of QFN accelerometers and gyroscopes also. So it's not very complex, but it's kind of okayish complex. And I also used the OJ stencils, new metal stencils, which is really nice. If you guys haven't tried it out, you should go try it out. That's what it looks like. And it's actually, it's more durable than the polyamide ones that they normally, that they normally sell, but the new ones are actually much more nice, they're nicer to use, especially when they're doing a lot of, I'm going to be doing five or ten in a while. So I'm going to be doing a lot more than five or ten in a while. So that'll be quite useful when that comes. And this is the board, so that it is pretty good actually, if you look at them. And these components, they take a very long time to solder by hand, but when you use a stencil and reflow them, they take less than an hour. So yes, it's kind of fun. So the question would be, why would you ever use a reflow when you can just use a hot day? Well, it's about the same. Main factor for me is reflowing looks way cooler. And also, especially when you're in an environment where there's, you know, you have wind or other stuff, then you get very uneven cooling on the hot day. So while you're reflowing, you'll kind of shield you from the wind. So in terms of uneven cooling, that's what I think the hot day will have problems with. In terms of using hot air reflowing, well, this is just way better from my experience, it just takes much longer to use hot air reflowing in my experience. And also, again, hot air reflowing I think is meant for more like rework. So it's more precise and takes longer because it's really each individual component and even each lead individually sometimes. So yeah, it takes much longer. So conclusion would be, it's a really fun project to try out when you're soldering a lot, especially. And if you do it, it will also be a very good installation to your bench. And some pros of this would be that you'll give you a more control environment, it'll be faster than hand soldering and yeah, a little cool. And some cons would be that if it's not insulated properly, you will still have some amount of uneven heating inside the oven because of the way that the oven itself is structured, especially when you don't have heating elements on both the top and the bottom or something. And also, in terms of price, it's not bad. It's still more expensive than a hot day. I can get a hot day from $30. This is about approximately $70 put in after components and toaster. So yeah, it has actually finally earned its place on my bench permanently. So yeah, I'm having quite a bit of fun using it. Thank you very much.