Monday, August 13, 2018

UPDATE: 3D Printed Solder Fume Extractor & Reflow Soldering

Here are a couple of smallish projects I have just completed:

3D Printed Solder Fume Extractor

A while back I made a solder fume extractor which overtime had become a bit too bulky for my table, plus it was only using an activated carbon filter.

Turns out if you want to do any real filtering/removal of fumes you need to use a HEPA filter as this is capable of actually capturing the 0.5µm - 1.0µm particles rather than just removing the odor.

Also if you really want to get fancy you could have a multi-filter setup. For example you could have a pre-filter/HEPA/activated carbon combo, here your pre-filter enhances the lifetime of the HEPA filter, the HEPA filter removes the super small particles, while the activated carbon filter removes the volatile organic compounds that cause odor.

As size was a key constraint for me I had decided to just use a HEPA filter with a powerful computer fan (DELTA PFB1212GHE). To generate the PWM signal which controlled the fan I used an ATtiny13. As this MCU does not have as much grunt compared to say an ATtiny45/85 you have to get efficient with your code, here is a good tutorial on this. Come to think of it, an easier way to control the fan would be by using a 555 timer circuit.

With all that said, if you want to make/modify one yourself you can get the CAD files here.


UPDATE: Have made an attachment that holds an activated carbon filter, so now the fume filtering is a 2 step process. The CAD files link has all the relevant info


Reflow Soldering

If you recall my 2018May10 update I was in the process of designing a supa sekrit board. Well not long ago the PCB, paste stencil, & parts have finally arrived. So here is a quick overview of how the assembly went down.

1. First off the board was cleaned with some IPA and wedged between a couple of vero/strip-boards to make sure it didn't move around:

2. Then I aligned the Polyimide Film stencil (OHS Sencils). The board is mostly 0805's with the most complex component being a 0.5mm pitched QFN. First time working with Polyimide Film too, next time will probably get a Stainless Steel stencil to make alignment and paste release easier.

3. The solder paste I used was the Chip Quick SMD4300AX10 (leaded), this was deposited with the I-Extruder to minimize waste.

4. To level the paste I used the provided spreader which was basically a plastic card:

5. Lifting off the stencil. Most pads have good coverage, only the 0.5mm pitched QFN had issues as we will see later on:

6. Finally all components were loaded and solder paste reflowed on the ReflowR:

Here are some closeups of the joints as well. I have a feeling my temperature profile is a bit too high, as using leaded paste should give a shinier finish. Also a few of the QFN pads were a bit low on solder paste, suspect this was because stencil was not aligned (see the solder balls between pads):

Doing a quick functional test shows that the circuit is working, just need to delve a bit deeper into it and capture some waveforms and what not

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