SMD solder mask stencil (BtM edition)

[xxv]

I’m finally taking the plunge and trying out solder paste reflow soldering for my surface mount electronics projects. It turns out, it’s pretty fiddly but not that hard. With practice, I’m sure I could do a pretty good job and make boards quickly.

Using suggestions from some other places, including this other topic of the same name, I put together a SMD solder mask stencil using 0.002" Kapton polyimide film and my Glowforge. Were I to do it again, I’d probably get a different material such as the 4mil mylar referenced in the other post as the Kapton is a bit flimsy and also expensive. It does work well aside from being a bit too thin, though.

The Kapton as it came out of the Glowforge:

After I rinsed off the char with water and dried it:

The power settings I used are:
Engrave (not cut) 1000 speed, power 80, 180 lines/cm, 1 pass.

Also at a suggestion from the other post, I cut a quick alignment sled out of 1/16" inventibles acrylic:

This let me tape down the solder mask with painter’s tape to help keep things aligned. Because the board is 1.6mm thick and the acrylic is 1.5mm thick, I left the paper backing on it to get that extra 0.1mm.

I created the stencil pattern in KiCAD 5 and just exported the solder paste layer as an SVG (without the page borders, but with the board outline that I then just used as an ignored reference in Glowforge). Amazingly, I could just load the SVG straight into the Glowforge without modifying it, as I cut out the perimeter of the design by hand.

[evansd2]

Outstanding… now I need a reflow oven.

[xxv]

I actually got a griddle that looks a lot like this:

(Presto 07061 22-inch Electric Griddle With Removable Handles)

And it seems to be working pretty well. It doesn’t seem to get much beyond 220°C at its hot spots, but that seems to work well enough to cause the solder paste to melt. I’m not sure it’s the best solution, but I do like that you can easily slide boards on/off. I’ve only really done test boards on it yet, so I’ll report back if it ends up being a good choice.

[cynd11]

Cool! Don’t forget to show us what you are making with these boards!

[evansd2]

Huh that’s a cool trick with the griddle. I never heard of that one.

[xxv]

It’s a motion-detector night light! It’s got two buttons on it which let you set the brightness and color. For good light quality, I’m using a SK9822 RGB and a separate warm white LED.

Where the board lives:

The housing, diffuser, and black grille with the firefly on it are all laser cut. The remaining parts are 3D printed.

[Jules]

They work great for pancakes too…(in case the tech doesn’t work out.)

Very cool firefly!

[xxv]

Haha, yeah, I don’t think I’ll be putting food on this one after boards with solder paste have been on it. But I was weighing the trade-offs before I put my first board on: solder reflow…or pancakes…

[cynd11]

Wow, thanks for showing it!

[ben1]

This is what I use. It works really well. I got a roll-top toaster oven to save space.
http://reflowster.com/

[karaelena]

Just about a year ago I used this, https://github.com/botletics/Reflowduino. I didn’t use his PCB, but ended up using his source and adapted it to the gear I had. The only modification I’ve done has adding a profile for powder coating and a ESP01 that sent push notifications via Pushover.