



PCB fabrication has changed a lot in the last couple of years, at least for me. Steel stencils, paste and reflow ovens used to be out of reach. Not any more! The construction steps for PCBs are: (If you haven't already backed it, this is your last couple of days to back SPIDriver on Crowd Supply . Today's update shows it driving the small LCD display that's included in the "Expert" pledge package. Please head over there are check it out! Thanks so much!)PCB fabrication has changed a lot in the last couple of years, at least for me. Steel stencils, paste and reflow ovens used to be out of reach. Not any more! The construction steps for PCBs are:

apply paste to PCB through stencil place parts by hand put it in a cheap IR reflow oven and press 'start' go for a 7.5 minute walk

Hand placement works surprisingly well. Surface tension works to your advantage, centering the parts on their pads. Companies like Sparkfun and Adafruit sell plenty of modules that are placed by hand. I've started doing this too, for short runs of modules. TermDriver is made in this way.Automated placement is an obvious next step, but right now there are few attractive choices for pick-and-place machines. Probably the liteplacer is the closest to a garage-budget machine, and it may be that at some point I'll be getting one.In the meantime, I've been looking at ways of speeding up hand placement.Placing large components is generally trickier than small ones. QFN packages have no exposed leads, so aligning them on the board is crucial. Typical lead pitch is 0.5 mm, so placement within about 0.1 mm is the goal. You peer down the microscope and nudge the part so it's lined up on each edge. Then you very gently push it into the solder paste without letting it move more than 0.1 mm. This is hard.Here's something that makes it easy.It's two acrylic sheets, sandwiched together. The lower is a frame for the PCB. The upper is a guide for the component placement. With the board pressed into the lower frame, the upper layer exactly places the larger components.Actually placing the parts is now laughably easy. The slots are precisely cut for each one, so it's not even necessary to use a microscope. It's possible to place 5 parts in a few seconds - not bad for a human!After placement the PCB pops out of the frame leaving the parts firmly stuck in place in the paste. While this setup has been working really well for large parts, small components haven't worked out -- they tend to get lost in the holes in the acrylic.The short script that converts an Eagle "mnt" file into an SVG for the laser cutter is here . That and some double sided tape is all you need to place components by hand with better than .05 mm accuracy.Thanks for reading! If you know anyone who might be interested, please encourage them to subscribe . And if there's something you want me to write about or feature, please let me know. Thanks again.