In this article we review a couple of SMT prototyping boards from Schmartboard.
Sooner or later you’ll need to use a surface-mount technology component. Just like taxes and myki* not working, it’s inevitable. When the time comes you usually have a few options – make your own PCB, then bake it in an oven or skillet pan; get the part on a demo board from the manufacturer (expensive); try and hand-solder it yourself using dead-bug wiring or try to mash it into a piece of strip board; or find someone else to do it. Thanks to the people at Schmartboard you now have another option which might cost a few dollars more but guarantees a result. Although they have boards for almost everything imaginable, we’ll look at two of them – one for QFP packages and their Arduino shield that has SOIC and SOP23-6 areas.
QFP 32-80 pin board
In our first example we’ll see how easy it is to prototype with QFP package ICs. An example of this is the Atmel ATmega328 microcontroller found on various Arduino-compatible products, for example:
Although our example has 32 pins, the board can handle up to 80-pin devices. You simply place the IC on the Schmartboard, which holds the IC in nicely due to the grooved tracks for the pins:
The tracks are what makes the Schmartboard EZ series so great – they help hold the part in, and contain the required amount of solder. I believe this design is unique to Schmartboard and when you look in their catalogue, select the “EZ” series for this technology. Moving forward, you just need some water-soluble flux:
then tack down the part, apply flux to the side you’re going to solder – then slowly push the tip of your soldering iron (set to around 750 degrees F) down the groove to the pin. For example:
Then repeat for the three other sides. That’s it. If your part has an exposed pad on the bottom, there’s a hole in the centre of the Schmartboad that you can solder into as well:
After soldering I really couldn’t believe it worked, so probed out the pins to the breakout pads on the Schmartboard to test for shorts or breaks – however it tested perfectly. The only caveat is that your soldering iron tip needs to be the same or smaller pitch than the the part you’re using, otherwise you could cause a solder bridge. And use flux! You need the flux. After soldering you can easily connect the board to the rest of your project or build around it.
Schmartboard Arduino shield
This is the AD5204 four-channel digital potentiometer we used in the SPI tutorial. It sits nicely in the shield and can be easily soldered onto the board. Don’t forget the flux! Although the SMT areas have the EZ-technology, I still added a little solder of my own – with satisfactory results:
The SOT23-6 also fits well, with plenty of space for soldering it in. SOT23? Example – the ADS1110 16-bit ADC which will be the subject of a future tutorial:
Working with these tiny components is also feasible but requires a finer iron tip and a steady hand.
Once the SMT component(s) have been fitted, you can easily trace out the matching through-hole pads for further connections. The shield matches the Arduino R3 standards and includes stacking header sockets, two LEDs for general use, space and parts for an RC reset circuit, and pads to add pull-up resistors for the I2C bus:
Finally there’s also three 0805-sized parts and footprints for some practice or use. It’s a very well though-out shield and should prove useful. You can also order a bare PCB if you already have stacking headers to save money.
If you’re in a hurry to prototype with SMT parts, instead of mucking about – get a Schmartboard. They’re easy to use and work well. Full-sized images available on flickr.
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The boards used in this article were a promotional consideration supplied by Schmartboard.