Fine Tuning of Reflow Soldering

Hello everyone

Things seem to be speeding up on this side. I had a bit of time to test the reflow oven again over this weekend after creating some new test boards in the week. So first things first, I had to setup my testing area:

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With a lamp to light up the inside of the reflow oven and my tripod with the camera standing off to the side πŸ™‚ So once the camera recording station was setup, I had to apply the solder paste to my boards. I do this with a lovely tooth pick since I don’t have stencils for these awesomely DIY test boards that I’ve made. This takes quite a while.

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I’ve also applied flux to reflow the paste easier but I’ve stopped using it in some of the later tests since it doesn’t seem as if it is required.

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Resistors nicely fitted πŸ™‚ I’ve done a bit more research on the process in the week and found that quite a few people advises you to put a test board underneath the actual board that your reflowing. This prevents the heat coming through the grid to toast your board being reflowed and allows for more even heating of the board itself. Hence, my previous two attempts became my heat buffer boards

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And then I put my actual board on the heat buffer boards.

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My initial tests resulted in the boards not being reflowed properly. I then went ahead with adjusting the timing of the various stages. But look at that color πŸ™‚ No real discoloration. Yes, my board weren’t being toasted anymore.

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Here is a close up of the soldering done, not to great:

IMG_0071But once again, look at that color πŸ™‚

So I repeated the process twice coming to three runs until I had the unit working perfectly for me. I did a fourth run to just double check it.

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So here is a photo of the first three runs that I did with the initial run from the previous week on the far top. Just above the reflowed boards are the test boards that haven’t been reflowed as yet to just show the initial color of the board. At this stage, my wife left for a party and promptly requested the tripod as well as the camera recorder.

Luckily I had a backup which was the powershot from Canon. I didn’t have another light stand but since my wife is a kick ass wedding photographer, she have multiple light stands of which I was only given one obviously ( I break things πŸ˜‰ ). So I had to setup my recording area again and this is what it looked like:

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Notice that the light stand is just a straight up stand and doesn’t have any left-right, top-down pivot control. My solution, tie it to the desk, worked perfectly πŸ™‚

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One thing I noticed on my final run was that the graphing function of the controller was a bit funky. Some quick thinking and inspection of the sensor inside the unit revealed that the tip of the thermouple touched the grid of the oven. This obviously grounded the thermocouple. So the thermocouple would try to get out a measurement but the then the signal would be grounded. As soon as I moved the thermocouple tip away from the grid, the unit was happy.

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A thermocouple generates a voltage because of the two different alloys that it is made up off. So when heat is applied the voltage increases. This voltage is a few milli Volts, so we need an amplifier to amplify it so that we can interpret it, this is where the AD597 comes in. Here’s the result of all the boards with resistors that I’ve reflowed over the past two weekends, I think that it looks good πŸ™‚

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Β So I’ve completed the redesign of the circuit, I’ve procured most of the parts and I’ve found a company to make the PCBs for me. I’ll be finding out what specific file naming conventions they use for the Gerber files and then I will have the boards within the next three weeks. Here’s the video of the past weekend’s testing.

I will then reflow these boards with the components using my prototype that I’ve developed and the fine tuned timing that I’ve finalized over the weekend. I hope that all of you are looking forward for the next post with new photos πŸ™‚ Until next time, have a good one.

 

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One comment on “Fine Tuning of Reflow Soldering
  1. Mike says:

    Hello – price please without thermocouple – K type ? and SSR

    thanks,
    Mike

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