Hand Assembled SMD Board

I figured I’d post a photo of a board I’m working on.

It is an I2C to 20×4 LCD /keyboard  interface with support for an ESP8266-01 module plus the serial interface modules.

I ordered the solder paste screen from Elcrow and figured I’d give it a try. A couple years ago I picked up a convection toaster over from Walmart and modified it so the fan would run always on.

There are lots of tutorials and such about making a complex controller for “toaster oven reflow” but my approach is simple: I figured out the setting on the temperature dial so the solder melts then I made two marks on the dial: that point and a bit cooler.

I “pre-heat” the board at the cooler setting then move the dial to the “melt” setting for about 5 minutes, then move back to “pre-heat” after the solder melts, then after a couple minutes and shut the unit off.

This seems to work fine. My view is that the fixation with temperature ramps and the like is because those parameters are for volume production and that makes a huge difference if you are making a thousand units an hour.

This board was manually assembled using my technique. I had a bit of problem with the solder paste, probably because I used a silicone spatula (for cooking) rather than a proper spreader. The solder paste was about 3 years old but kept in the refrigerator.

DSCN0118

The picture was taken straight out of the oven, after I removed a bridge across Q1. The assembly is not perfect but that is mainly because of hand assembly and solder paste application, not the oven. In particular, I’d be happier if U4 was aligned properly but the soldering seems OK.

The board was designed and laid out with Kicad.

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