Assembling the first EasyBright

EasyBright components

Last week while watching Mannequin (a very young and fresh Kim Cattrall, a goofy plot, and music by Starship — what could be better? okay, if it had John Cusack and were set in Shermer, Illinois, yes, that would be better) I split all the EasyBright components into a parts bin for easy access and portability.

Saturday afternoon I put together the first sample.

EasyBright-3L constant-current LED string driver PCB with solder paste

This is waaaaaay too much solder paste for 0603 parts and 1/40″ IC pin spacing. I had to remove several solder bridges from the IC, and the passives had solder mounds instead of fillets. I took the picture specifically to record how much paste I used so I could adjust on the second attempt.

EasyBright-3L constant-current LED string driver, front

Here’s the cleaned-up board, front side.

EasyBright-3L constant-current LED string driver, back

Back side, with hand-written labels for the current rating and the serial number (S00). The “permanent” marker comes off easily with rubbing alcohol — I need to get some clear nail polish to seal it in.


Even before assembly, I had made notes about (and started implementing) things to fix whenever I print the next boards:

  • Change the IC’s ground connection from a via outside the IC footprint to a trace going straight in to the heatsink pad. I had routed that connection before I confirmed with Maxim that the pad is okay to connect to ground — it’s just not okay to be the only ground — and then forgot to go back and change it. Removing that via gives me a little more room to route the bottom-side LED power traces cleanly, and also:
  • Increase the pad size on the optional through-hole current-sense resistors. This, believe it or not, is EAGLE’s default pad size, and I think it’d be challenging to solder without a good, narrow-tipped iron.
  • Increase the trace isolation on the solder-side ground pour. There’s no reason to have it that close to the pads.
  • More subtle, I spaced the 2-pin connector pads an extra .02″ apart to see whether I could get the connectors to friction-fit for ease while soldering. They don’t quite. Either change the library footprint to space the pads a little further apart or just get used to pinching the leads together before stuffing the parts and soldering, which works better than I had expected.

I’m still delighted!

7 Responses to “Assembling the first EasyBright”

  1. Rob says:

    What method did you use for soldering? I’m guessing you just used a regular soldering iron as I’m sure you would have mentioned if you were using a hotplate, oven or hot air.

  2. Keith Neufeld says:

    Rob, for me solder paste == hotplate unless I specifically mention that I’m using my new hot-air pencil (as I will do when soldering the FTDI chip onto my x0xb0x, more to try it out than because it’s too hard to solder by hand).

  3. Patrick says:

    What is the reason that you have all the pads offset a little bit to the left and right? See purple line here:

  4. Asm says:

    Congrats on getting the boards and getting started making drivers!

    Shame about the $50 charge due to the resistor wiring issue, though.

    Anyway, have you considered using stencil? I’ve been using solderpaste in a syringe myself, and found it tedious (plus it tended to separate… but then I was using cheap chinese paste). is pretty cheap ($21 for a 21x22cm stencil), and stencilling onto small boards looks much quicker (plus it’s much more repeatable). I think Sparkfun did a tutorial on it.

  5. Keith Neufeld says:

    Asm, I’m definitely interested in stenciling in the long term. I didn’t order one yet because

    I knew I could ramp things up faster with the syringe and then switch
    I want to get feedback on the design and be sure the board layout is finalized before ordering a stencil
    I have the impression it’s easier to stencil a slightly larger area than such a small one but I don’t really want to have to depanelize the boards myself

    I’d be particularly interested in hearing from someone with experience stenciling tiny boards like this — and I should probably review the SparkFun tutorial.

  6. Keith Neufeld says:

    Patrick, the alternating-offset header pads are my copy of SparkFun’s “locking connector” idea — it allows the connectors to stay in place by friction when you turn the board upside down to solder, without making the through-holes too small for good solder flow. Huge credit to Pete Lewis at SparkFun for coming up with the idea — it’s fantastic and it really works!

  7. Magnus Falk says:

    Hey Keith, how do I get my hands on the EasyBright then? The LED calculator looks like something I would want as well!

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