Yes, that’s right, the wait is over….. my PCBs from Dorkbot PDX have arrived in the post ! Here they are in all their purple loveliness.
Sorry about the photography, this is my electronics blog not my photography blog, so point-n-shoot camera came out and handheld “macro” mode with no flash was the chosen mode.
Man that MPR121 is a *small* package. It’s a QFN20, and a pad pitch of 0.5mm. It makes the pads on the .05” connector look huuuuuge !
When it comes to soldering the QFN20 onto the PCB, the fact that “QFN” stands for Quad Flat No-leads really becomes apparent. You can’t get your normal soldering iron onto anywhere that you could possibly hope to get some solder, the chip, and the pads to meet in that joyous harmony called “properly soldered”. So since I don’t own commercial wave-soldering machine, and I don’t have a toaster oven I could repurpose to be a reflow oven, and I didn’t have a spare frypan around that I could convert/sacrifice to be a soldering skillet, I whipped out the (new*, so far unchristened) Atten 858D+ hot air rework station, whacked a bit of solder paste on the pads, plonked the chip down, fired up the heat, and hey presto, a few minutes later the chip appears soldered to the PCB ! I guess we’ll only see once we get a chance to connect it up to my Fez Hydra and start looking at the driver (although luckily there’s at least one sample out there ). That maybe something for the weekend – bring on the weekend !
* Here’s a great plug for the eBay supplier of my new Atten 858D+. Looking around on eBay, I found lots of eBayers that ship from Hong Kong or China, and the buy-it-now price for this unit was around $59. Then I came across one located in Sydney, and wow, the buy price was only $63. Wow, a $4 “premium” for having someone in AU to buy from. Wow. (Yes, I was impressed). But that’s not where it ends. Clicked buy one afternoon, sometime about 3, and paid with paypal. Before the end of the day, I had an email from Aus Post that a parcel had ben dispatched to me, and it arrived at the PO Box by 8am the next morning. W. O. W. What a great eBay seller. If you’re in AU and want something fast and Carmates has it, my experience says you’d be lucky to find a better dealer.