Eagle Cad autorouter on fine pitch SMT

That first design may be an anomaly, so I tried a couple more designs.

Eagle Cad autorouter

In EEVblog #93, Dave Jones rant's that "PCB Autorouters Suck". Especially for beginners, and most definitely in cheap tools.  

I happen to agree.  So I tried a little experiment.  My results surprised me.

Eagle CAD versions

CadSoft recently released version 5.8 of their EagleCAD schematic and layout software.  They have a free version that is limited, but popular with hardware hobbiests.  Now they also have a "Freemium" version that is less limited, yet, too limited.

Hand soldering QFN

I tried last night to hand solder another 28-pin QFN part.  A QFN part has no leads, but rather copper pads are built right into the package.  And the leads are tiny and closely spaced.  On top of that, many QFN parts have a big ground "paddle" under the part.  This should be soldered down.  Atmel FAQ explains why.

So I'll give you the summary right up front: use reflow soldering for QFN.

How to waste 2 weeks

Inspired by a class I took from the author of Extreme SMT Instructable, I decided to set up a SMT reflow soldering system.  Although his hotplate technique works well, it isn't as repeatable as I would like.  Recently, he added a follow-up instructable that adds a PID controller to the hotplate system, which should make the process repeatable.  But I didn't see that until I was already committed to the toaster oven system (parts had been ordered). 

And the hotplate technique still bothers me.  The heat is applied to the insulating FR4 fiberglass, so only convection heat is getting to the solder joints.  The bottom of the PCB tends to discolor slightly, so who knows what this means for long term reliability.

Reading several DIY guides, I became convinced that the way to go was to buy a PID temperature controller and a powerful toaster oven.  Why duplicate something you've seen work when you can try to do it "better"?  (hint: This is especially not a good idea when you are under a tight deadline, like I am right now.)

In the Final 10

I got the word on Feb 12th that I made it into the final round of the Atmel SMART design contest.  I was too excited to post about it right away.

I sent out my three PCB designs in a local group order.  Got a great price and quick turn around. The boards literally arrived the same day I heard I was in the final round.

Phase 2 is complete

I worked until 5am Friday morning completing the information I need to send in for Phase 2.  I got up after a nap and was preparing to email what I had done the night before.  In my email was a note saying that since they wouldn't start judging until Monday, we could submit our material through Sunday.

While I was pleased that I had another 2 days, I was disappointed they waited until the last moment to let us know.  I could have done with more sleep.

Universal PCB design rules

I just went through the design rules of just about every prototype PCB house I know of to determine what my design rules should be so I have complete freedom of choice.

It does get easier, honest

After designing 3 boards (well, actually one of those was a complete redesign after a failed attempt) with Eagle CAD, I have re-learned it's crazy interface.  The fourth board I did today in about 3 hours, from beginning the schematic capture to completing the board layout including passing DRC, and even the silk screen layer done.

Re-learning Eagle CAD

Eagle CAD's free version of schematic capture and board layout is a great tool for hobbyists. Full featured, lots of parts libraries available, and it does a decent enough job for designs that will fit on a 2-layer board up to 4 x 3 inches.

But the user interface is arcane. It takes me a day to remember how to use the darn thing when I haven't used it for a couple months. Yesterday, I spent 2 hours on a 1 page schematic. That was easily twice what it should have taken, but I was re-learning the UI.