Ok so the cover photo of this post is a bit strange given that the blog is about electronics and I’m from South Africa. The reason for it is that I’m going to move to Canada within the next few months. I’ve applied for a position at our Canadian branch and have gotten the job :). So this leaves me with less time for the project. Luckily we’re almost there. Over the past few weeks I’ve been busy redesigning the circuit boards, again, so that I can get it ready for production. As mentioned in my previous post, I’ve started collaborating with one of the blog’s readers, Mark. We’ve just had someone else go over my circuit designs and some errors were spotted which lead to the redesigning of the circuit. This has only been done for the Arduino shield version of the board and not for the stand alone version of the board. I’m going to focus on getting the Arduino shield version ready for production should anyone be interested in it.
I also had a little glitch with the code of the project which I’ve resolved today, I think (“,). Today I had a bit of time to also test the reflow process, to fine tune the timing of the curve and to get a feel for the process. So a bit more on that. I’ve produced two test boards to reflow in the week. Just to put some resistors on it to experiment. I don’t have any stencils as I’ve produced the boards myself. So when I started I added way to much solder paste resulting in a lot of blobs and messy soldering.
After the reflow process I tested the soldering and it was hard and not in paste form anymore. But I didn’t see the solder paste going to a liquid state like in some videos that I’ve seen on YouTube. So I adjusted my timing intervals and redid the process. As I only had two boards, so I’ve removed the solder by using a solder sucker and reapplied the solder paste.
Some of the pads were ripped of whilst sucking the solder from the board :(. Still good for testing though.
After the second run. You can see that the board got a little hot and discolored slightly. As you can see, I’ve again applied way too much solder paste and created some nice blobs :). But again the solder paste changed from a paste form to a solid state which is good. I still didn’t see what I was expecting to see referenced to the YouTube videos that I watched, so I’ve upped the reflow temperature from 210 °C to 225 °C and I thought now I must see what I’m expecting and again I didn’t.
So something I did notice is that I’ve baked my board nice and crispy 🙂 Again the paste turned from a paste to a solid but the process still didn’t show me what I was expecting to see. At this point I decided that I’ll put some resistors on the other board and reflow it with the same settings to see how it turns out.
Nice looking board with solder paste applied with a tooth pick.
When I started mounting the resistors I noticed that I was still using way too much solder paste by how much the solder paste was pushing out to the sides when I pushed the resistors down into place. So I took a lot of solder paste off the board with the toothpick again.
And from here I’ve reflowed the board.
After the reflow process was finished I tested the solder and it all held in place. So it works yeay but I still didn’t see what I was expecting. As you can see I baked my board again to a nice brown color which means that I’m applying way too much heat. I’ve taken videos of each of the runs that I’ve done and after I was done I reviewed the footage and eureka there it was. The reaction what I was looking was there all along except that it was happening a lot more gradually than I was expecting from the other videos that I saw. Maybe it is because my solder paste is also a bit old. I bought it last year somewhere but kept it refrigerated as the internet instructed :). Or maybe it is just the brand that differs slightly. I’m still not experienced enough to feel comfortable to reflow boards with ICs on it so I will make a few more test boards just to get the process of reflowing a board correct without crisping the board.
I will edit the footage that I took today and then compile a video that will show my reflow process and what was happening. Once done I will post it on YouTube and obviously embed it in the blog for you to view. So until next time. Please feel free to leave a comment if you like what I’ve done so far.