Here’s a demonstration which proves you don’t really need special tools to populate a surface mount PCB. We’ve seen this board before, it’s the glass PCB server which [Cnlohr] developed and demonstrated by connecting the real world to Minecraft. It’s a tiny board and we were happy to have the chance to see his method for populating the parts before reflow soldering.
In the video after the break [Cnlohr] starts by dispensing a glob of solder pasted from its storage container. He mentions that as long as you store the stuff in the refrigerator it’s rather easy to work with. Because most of his projects are single boards it’s not worth it to have a solder stencil produced. Instead he picks up a bit of the solder glob on the end of a toothpick and applies it to each pad.
This isn’t really as bad as it sounds. The fine pitch TQFP footprints can just be dragged with a bit of the paste. After this application — which took around seven minutes — he grabs some tweezers (not the vacuum type) and begins placing each component. If he missed some paste he’ll discover it in this step and add where necessary. The last step is a trip through his toaster oven.
Continue reading “Populate SMD boads using a toothpick and tweezers”
Everything you need to build a vacuum tweezers is laid out in this image. The parts should run you about $20 and when you’re done you’ll have the perfect tool for placing very small surface mount parts for reflow soldering.
This project uses the same concept as other fish pump tweezers projects but builds upon them with some interesting additions. The first step in the conversion process is to tear down the aquarium pump to reverse its flow. There are several steps but all-in-all it’s not very difficult. With the source of vacuum established [Technically Artistic] begins work on the business end of the tool. This is where the array of different pens see some action. The large blue one is the outer assembly, with the others combining to help connect it to the plastic tubing. The business end is made from a needle adapter for an air compressor, with an alligator clip cleverly modified to serve as a valve to release the parts from the tip.
When dealing with surface mount components, a manual pick-and-place machine is certainly a helpful device to have. Unfortunately, they can be quite expensive, so [Vassilis] came up with his own solution.
While commercial setups can cost upwards of a thousand dollars, this setup was made for less than a tenth of this cost. This one uses a simple setup of sliders and bearings available from a local hardware store. A cheap vacuum pen is used to lift the components, using an aquarium pump in reverse to generate suction. Finally, a USB microscope is used to make sure everything is placed in the correct position.
Plans are available on the site in DXF format, so you can build your own. The setup is reminiscent of a DIY CNC router, like this one that we featured a while ago. We could even see something like this serving a dual role with interchangeable heads for whatever you happen to be making that day!
Update: [Vassilis] published an video demonstration. See it after the break.
Continue reading “An Inexpensive Manual Pick-and-Place Machine”
[Zach Hoeken] has the answer to assembling multiple surface mount PCBs in the home workshop. It’s certainly not for everyone. But if you’ve ever thought of marketing your own small runs he has the equipment and methodology you need.
He had tried using hacked together equipment, but after encountering a range of issues he finds the investment in a few key items saves time and money in the long run. The first is a precision tooling fixture block; that metal plate with a grid of holes that makes up the background of the image above. It comes with machined pegs which fit the holes perfectly, and as you can see, his panel of 16 boards include tooling holes that line up with the fixture. Once in place, a steel solder stencil is aligned with the board using its own tooling holes. The alignment of the stencil and its uniformed thickness ensure that the perfect amount of solder paste is easy to apply with a squeegee. [Zach] hand places his components but he did invest in a proper reflow oven to make the soldering a set and forget process.
For those that have always felt a bit treppidatious when approaching SMD, you can relax. Here’s a simple guide to walk you through your first shaky steps into surface mount devices. Distributed freely under the creative common license, the Manga Guide to SMD is an 18 page comic that has a goal of making SMD producers out of all of us. There’s a good visual explanation of what SMT is and why we use it, as well as a thorough walk through of how to solder the tiny devices with your soldering iron. They don’t go into dealing with a small reflow oven in this issue.
If this fits well with your learning style, you might also be interested in the Manga Guide to Electricity.
[Adam] was tired of plopping the same components over and over into his Arduino-based designs. He spent part of his weekend laying out a small board that would host everything he needed and could be built as a single component for all future projects. Above you can see the project he calls SMDuino, an Arduino clone that can be used as a surface mount part.
The contacts on four sides of the board break out the pins. They’ve been designed with 0.1″ pitch which means they will work with standard pin headers. But since they’re plated through from top to bottom they are easy to solder to surface mount pads as well. The project is open source, so you can order your own boards (he used DorkBot PDX) or email him if you want to get in on a pre-order. That is for unpopulated PCBs only. But there’s few components used here so it’s pretty inexpensive to throw together. You’ll need four caps, four resistors, a crystal, an LED, the ATmega*8 of your choice (an ATmega328 is used here), and a low dropout regulator. Of course it is possible to go without the crystal oscillator.
Does this remind anyone else of the Basic Stamp 2?
We try to stick to the 0805 parts because they’re still big enough to solder by hand. But [Scott] shows us that it doesn’t take too many special tools to reflow fine-pitch components at home. In this case he’s using 0402 resistors, a footprint that we consider functionally impossible to solder using an iron.
The two parts of the equation that he spent some money on are professionally produced PCBs and a solder stencil. The stencil is laser-cut from Kapton, which is heat-resistant so it doesn’t warp during the cutting process. An acrylic frame holds the PCB in place, and he just tapes the stencil over it and uses a chunk of acrylic as a squeegee to evenly apply the solder paste. Splurging on the PCB and stencil means you’ll achieve tolerances which lead to success.
The next issue is placing the components. [Scott] shows off some vacuum tweezers he built using an aquarium pump. Watch the video after the break to see how small those 0402 parts are when he extracts one of the resistors from the tape packaging. With the board manually populated (check everything twice!) he moves the board to a completely unaltered toaster oven for reflow. We have seen a lot of projects which add controllers to these ovens, but he really makes the case that you don’t need it. Instead, he uses a thermocoupler read by a multimeter just to let him know what’s going on with the temperature. He uses a smart phone as a timer, and switches the oven on and off to match the solder’s heat profile. Continue reading “Fine-pitch SMD soldering with minimal tools”