Surface mount electronics at home

Most of the coolest electronics parts are only available in surface mount (SMT) packages these days.  What is a modern maker to do?

I guess some folks start out with breakout boards and try to keep using their breadboards with SMT parts.  At some point, however, you’ll be ready for the next step.  And that involves designing your own circuit board and building your project.

When I was in college I used EAGLE for my electronics projects.  Even when I worked at Boeing we used EAGLE in our group, even though it wasn’t Boeing’s preferred package.  However, now I use KiCad and while it took a little getting used to, I love it.  Some of the features are way better than EAGLE and KiCad is free so how cool is that?

After your design is done you will want to have your boards fabricated, and I would recommend OSHPark.  Perfect…purple…prompt.  The cost is excellent for the quality and the delivery times keep getting shorter.  Awesome!

With boards in hand it’s time to start making!  We cut our own stencils in-house with a Silhouette Cameo.  With the Cameo and the gerber2graphtec code on GitHub you’ll be able to make your own stencils in no time.  We use 4mil Mylar as our standard for stencils.

The solder paste can be a little pricy, but if you don’t need much you can get a small tube of solder paste from Digi-Key.  Squeeze out a blob, smear with an old hotel key-card, and you’re ready to lay those tiny parts down.  To move the parts around by hand we use a set of vacuum tweezers.  The tips for the SMT parts are a bit pricy, so we just took the tip off of a mechanical pencil and use it as a tip.  Also, I highly recommend you watch the following for some awesome assembly tips:

After the parts are down, it’s time to put them in a convection toaster oven and get the paste to reflow.  Try to follow the reflow profile provided by the solder paste manufacturer.  You can monitor the temperature with a non-contact thermometer or with an Arduino and one of our RTD shields.

In minutes you’ll have your board made!  With just a few readily available tools, which really aren’t too expensive, you too can make professional circuit boards at home!

If you do decide to go this route, I would recommend getting a SMT hot air rework station as well.  Some of those SMD parts are expensive and if you need to do any rework, the hot air station will quickly pay for itself.  We use the Kendal rework station linked to above and it works great.  We don’t make much use of the soldering iron though so you might want to look for a station without the attached iron.

So?  What are you waiting for?  Go make something with surface mount parts!

FCC Regulations and Open Source Hardware

We’ve been doing some research into how we can sell our designs without needing FCC testing.  There are a number of exemptions called out in CFR47 15.103.

One of the more interesting exemptions is the one related to “digital devices in which both the highest frequency generated and the highest frequency used are less than 1.705 MHz.”  We’ve read some discussion forums where some interpret this to include harmonics generated by the oscillator, which would make this exemption quite narrow in application.  However, there is a FAQ page at bureauveritas.com that seems to interpret this to mean “digital devices oscillating below 1.705 MHz.  See here (cached copy)  Take note of the answers to the following questions:

  • Can’t I be exempt from FCC regulations?
  • What kind of digital consumer products get exempted?

I’ve sent them a message asking if they believe the harmonics are excluded under this exemption.  I’ll update the post with their reply.

Another good resource on the interpretation of Part 15 is in the FCC’s OET Bulletin 62 (cached copy).

Update February 25, 2013

The response from Bureau Veritas is probably what you would expect: cautious with a slant for testing:

Digital devices using oscillator frequencies of 1 MHz (or even lower frequencies) are not necessarily exempt from FCC requirements. As you indicated, the potential for harmonics extending beyond 1.705 MHz exists, and these harmonics could conceivably emit at power levels that would require compliance testing.

Obviously, specific product design will ultimately determine the level of concern, but it is not a safe assumption that the oscillator frequency alone will define FCC exemption.

Hello world!

This is our first posting. We can’t wait to look back at it a few years from now and reflect…

We’re really excited about what we’re starting here.  We hope we can help enable people do creative things while sharing knowledge and doing what we love to do: make playgrounds for electrons.