In the last episode, we put our circuit boards through the reflow process. Unfortunately, it’s not 100% accurate, and there are often problems that can occur that need to be detected and fixed. That’s what the inspection step is for. One could insert an inspection step after paste, after placement, and after reflow, but the first two are icing on the cake — the phase where most mistakes can be caught is after reflow.
There are a variety of methods for reflowing a circuit board, but they all rely on a single principle: heat up the solder paste (a mixture of flux and solder) until the flux burns off and the solder becomes liquid, and then cool it down. Accomplishing this once or twice is easy; once you’ve played with a hot plate you’ll swear off through hole. Scaling it up and doing it repeatedly with high yield is extremely challenging, though. Continue reading “Tools of the Trade – Reflow”→
[Simon]’s solution fills that gap with one breadboardable design to handle all of your small-pin-count part needs. It accommodates SOT223, SOT323, and SOT23 three-pin parts like transistors or voltage regulators, and also has pads for all of the common two-terminal parts like resistors and capacitors from 0402 on up to 1206. You could build up a full voltage regulator circuit on one of these things. He’s even included some whitespace on the back for your notes.
SMT parts aren’t even the future any more. And with the right procedure, they’re not hard to hand-assemble. So the next time you have some extra space in a PCB order, toss in a couple of [Simon]’s breakouts and you’ll be ready for your next breadboarding session.
Fortunately (or unfortunately), [ucDude] has had the opportunity to try out a high quality video microscope while soldering some small surface mount components. He loved it, the problem was he had a hard time going back to using just his eyes. He wanted a video microscope but the cost for a professional one could not be justified. The solution? Build one!
[ucDude] called on one of his photographer friends to help. After discussing the project they decided to use a webcam and a lens from an SLR camera. Testing with the webcam resulted in an image that could not be zoomed-in enough, plus having to connect it to an external computer proved to be a bulky solution. They next tried a Raspberry Pi, camera module and zoom monocular. It worked great! The entire assembly was then mounted to a camera boom stand making it easy for the camera to be positioned over the work area and out of the way of hands and soldering irons. The Raspberry Pi’s HDMI output is plugged straight into an HD monitor. The result is exactly what [ucDude] was looking for. Now he can quickly and confidently solder his surface mount circuit boards.
My introduction to electronic manufacturing was as a production technician at Pennsylvania Scale Company in Leola PA in the early 1980’s. I learned that to work on what I wanted to work on I had to get my assigned duties done by noon or thereabouts. The most important lesson I had learned as a TV repairman, other than not to chew on the high voltage cable, was to use your eyes first. I would take a box of bad PCB’s that were essentially 6502 based computers that could count and weigh, and first go through inspecting them; usually the contents were reduced 50% right off by doing this. Then it was a race to identify and fix the remaining units and to keep my pace up I had to do my own desoldering.
It worked like this; you could set units aside with instructions and the production people would at some point go through changing components etc. for you or you could desolder yourself. I was pretty good at hand de-soldering 28 and 40 pin chips using a venerable Soldapulit manual solder sucker (as they were known). But to really cook I would wait for a moment when the production de-soldering machine was available. There was one simple rule for using the desoldering station: clean it when done! Failure to do so would result in your access to the station being suspended and then you might also incur the “wrath of production” which was not limited to your lunch bag being found frozen solid or your chair soaked in defluxing chemicals.
Pick and Place machines are one of the double-edged swords of electronics.They build your boards fast, but if you don’t have everything setup perfectly, they’ll quickly make a mess. A pick and place can’t grab a resistor from a pile and place it – so far only humans can pull that one off. They need parts organized and oriented in reels or trays.
[Parker Dillmann] had to load some parts, but didn’t have a tray for them, so he 3D printed his own. [Parker] works at a small assembly house in Texas. He’s working on a top secret design which includes FFC connectors. Unfortunately, the connectors shipped in pick and place unfriendly tubes rather than reels. If he couldn’t find a tray, [Parker] would have to hand place those connectors as a second operation, which would increase the time to build each board and leave more chances for mistakes.
Rather than place each part by hand, [Parker] got in touch with his friend [Chris Kraft] who is something of a 3D printing guru. [Chris] confirmed that a 3D printed tray would be possible, though the PLA he prints with was not static safe. That was fine for the connectors, but [Parker] was hoping to save some tray space by putting his PSOC4 chips in the printed tray as well.
[Parker] used SketchUp to design a tray that would fit his Madell DP2006-2 pick and place. He left .15mm clearance around the parts – just enough to cover any inaccuracies during printing, but not enough to throw off parts placement. He sent the STL file over to [Chris] who used Simplify3D to a create a Gcode file. [Chris] printed the tray at .2 mm layer height on his MakerGear M2 printer, and the results looked great. Would they be good enough for the pick and place machine?
[Parker] received the printed trays in the mail and loaded them with parts. The pick and place had no problem finding and placing the connectors, making this job a huge success. [Parker] even left room for the PSOC4 chips.He plans to paint the tray with anti-static paint before giving them at try.
[Matt] wanted his own light saber. You could argue that this is nearly as dangerous since you can’t see the beam and it doesn’t end a few feet past the business end of the grip. Plus there’s that who “not actually a Jedi” thing.
We don’t know if retro computing fans are going to love or hate this (translated). On the one hand it’s pretty cool to see a ZX81 clone up and running. On the other hand, an Amiga 600 case was sacrificed to serve as the body for the hack. [Thanks Juan]
Watchdog timer. If you know what that is your mind immediately says “good idea” when you hear the word. If you don’t know, you need to learn. Watchdogs are reset timers that are built into most microcontrollers. If your firmware gets stuck and doesn’t maintain the timer’s counter at a regular interval the watchdog it will perform a hardware reset and hopefully your hardware will start functioning again. Here’s a guide for using the watchdog in an Arduino, but the concepts are pretty much universal.
And finally, if you’re struggling with surface mount soldering we recommend grabbing two soldering irons. But in a pinch just grab some heavy gauge copper wire and wrap it around your soldering iron tip. It ends up being a two-point soldering iron set for the size of specific components such as 0805 resistors. [Thanks Rupert]