29
Dec 12

Reflow Toaster Oven: Conclusion

So the project is finally done other than cleaning up the box and making it look better etc.... The big question though, is, was this project really worth it? How well does this reflow toaster actually work? This is the answer.

The short answer is that this toaster works great. In fact, it works better than I though it would! The hard part here was applying the solder paste. Check out the pics below and then we'll discuss some things.

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This is the first part I tested. I ran this board through the oven with only the DPAK regulator loaded just to see what happened. It turned out to be fine, as you can see, the two small legs are soldered down really well. I didn't take a pic before it went through the oven for this part, but I did for the rest.

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This is a pic of the board and the syringe that i used to apply the solder paste. I figured it would be good to post this just so you can see what I was working with.

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At this point I'm confident in loading the rest of the test components. The above two pictures shows some of the solder paste on the board before soldering. The solder paste in the first picture looks pretty rough. This is because it is still too cold. I mentioned this in the video, you need to warm up the paste a little bit to get a decent application. When it's cold you end up just smudging it around everywhere and it will look like this. After warming up, the paste will stick to the pads a little bit. This is important because you can stretch out the paste line if your pads are small and close together. I didn't do this well, but you should still be able to notice it in the second picture.

As I mentioned in the video, my needle was pretty big. I'm not real familiar with these but it seemed like a pretty big needle to get stuck with. If you got a smaller one than you could lay a thinner line and eliminate the shorting between pins. Even with my application in the pic, the pins were not as bad as I expected.

Here is a pic of the board in the oven:

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The final product after reflow looks like this:

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You can see, I forgot that the plastic barrel plug would melt.

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The three passive components on this side floated into their spots and look pretty good. The amount of solder paste I used per pad varied quite a bit, but the parts came out well. Again, this was before I figured out the paste would be easier to apply once it warmed up. I'm not worried about this though, it will be easy to straighten out with practice. The second picture really shows how much my solder paste amount varied.

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Next are the two crooked resistors. These two are messed up in part because they didn't stick to the (cold) solder paste and when I put the board in the oven I think I bumped something and caused the resistor on the right to hit the one on the left. This screwed up both, but if the solder paste is warm the parts will stick to the paste and the paste will stick to the board. Basically, the paste will hold the parts in place and fend off little disruptions like this.

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The last part is the MOSFET. This is the smallest pitch part so I was curious as to how this would come out. As you can see, it is actually pretty good. Considering I used too much solder paste, causing the shorts, the pins are pretty clean. I would recommend a smaller needle, but I also think you could just get a better feel and spread it out. Either way, it isn't difficult and that is really all you have to do other than place the parts.

This wraps it up. I hope some people find this interesting/helpful. Feel free to contact me through the website or comment if you have any questions. I recommend no one try this at home.

Data Package:
Note-I haven't been able to get the python app packed up as an exe yet because of some technical problems, but when I get this figured out I'll update the package. The source code (python GUI and embedded C) is packed up as the aptana project and CCS studion project respectively. It should be simple to import these and check out the code. If importing doesn't work just check out the source files or create your own project and add the source files only to it.

Download Data Package