[Jack Gassett] is developing a new breakout board for an FPGA. The chip comes in a ball grid array (BGA) package which is notoriously difficult to solder reliably. Since he’s still in development, the test boards are being assembled in his basement. Of the first lot of four boards, only one is functional. So he’s setting out to rework the bad boards and we came along for the ride.
To reflow the surface mount components he picked up a cheap pancake griddle. The first thing [Jack] does is to heat up the board for about two minutes, then pluck off the FPGA and the FTDI chips using a vacuum tweezers. Next, the board gets a good cleaning with the help of a flux pen, some solder wick, and a regular soldering iron. Once clean, he hits the pads with solder paste from a syringe and begins the soldering process. BGA packages and the solder paste itself usually have manufacturer recommended time and temperature guidelines. [Jack] is following these profiles using the griddle’s temperature controller knob and the timer on an Android phone. In the video after the break you can see that he adjusts the timing based on gut reaction to what is going on with the solder. After cleaning up some solder bridges on the FTDI chip he tested it again and it works!
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Get out the soldering iron and clear your schedule, it’s going to take you a while to assemble this 8x8x8 LED matrix which contains a total of 512 LEDs. We’ve looked in on a 3x3x3 cube, and [Chr], who is responsible for this one, has assembled a 4x4x4 cube before, but this one is quite a leap in complexity. It isn’t just physical assembly problems that increase with scale, you’ll need to consider a power supply too since one layer of a 3x3x3 cube would need at 90 mA, but a single layer of the cube above requires 640 mA to light all of the diodes. Multiplexing is handled per-layer, controlled by ICs which share 8 data lines and are latched by a shift register. This means the display only requires 11 microcontroller pins for addressing. It is striking how well [Chr] explains the design process, and how cleanly he builds the driver circuits on protoboard. There’s a lot to look at and a lot to learn, not to mention the stunning results which can be seen in the video after the break.
Continue reading “512 LED cube”
Ditch that old toaster oven and move to the next level of surface mount soldering with this vapor phase reflow method. [Ing.Büro R.Tschaggelar] put together this apparatus to use vapor phase reflow at his bench instead of sending out his smaller projects for assembly. It uses the heating element from an electric tea kettle to boil Galden HT 230 inside of a Pyrex beaker. There’s a copper heat break part way up the beaker to condense the chemical and keep it from escaping. When a populated board is lowered into the heated chamber, the solder paste reflows without the need to stress the components with unnecessary heat. Better than traditional reflow? At this level it’s hard to say, but we do find his method quite interesting.
The application of Solder Paste is an essential part of short run manufacturing and prototyping. After getting back bare boards from a PCB shop, its time to get down to business and populate those boards. This new tutorial set assumes you have access to things such as stencils for your boards, but does mention a couple of resources on commercially available ways to purchase stencils. Of course, if you have a laser cutter, we can help you out. After getting your solder paste chops down, make sure you check out our guide to toaster oven reflowing.
[Thanks to P. Torrone]
Take a few minutes to watch this amazingly informative video on how to solder QFN or MLF components without solder paste. The quality of the video and the information within is quite nice. Even if you don’t intend to work with these parts, you could pick up some tips for soldering with hot air.
[Luciano] didn’t want to drop a lot of cash into a flux and solder paste applicator so he built his own for about $5. He re-purposed a hot glue gun which you can usually find at a dollar store. After removing the heating element he inserted the body of a syringe. The plunger has been modified to use a knitting needle inside of some plastic tubing. After taking the picture above he made an improvement by adding a milliliter scale to the plunger, allowing you to meter out the paste and also gauge how much remains.
Do you have access to a laser cutter? If so, you can use [Riley Porter’s] method to cut your own solder stencils. He starts with the Eagle files and exports the Dimension and tCream layers to a PDF. That file is then processed using Ghostwriter, Gview, and finally, Corel draw. The result is a 1200dpi file to feed to your Epilog laser. Now you’re ready to stencil on the solder paste and populate the PCB.
[Thanks Travis Goodspeed]