Today this is not a problem to get a Linux based development board really cheap. Raspberry Pi or Beagle Bone are the first that come to mind. Having those on your desk you wouldn’t think about building one by yourself. Unless you want to challenge yourself. Henrik thought it would be fun to build a Linux board with BGA processor. We all know that soldering BGA at home can be tricky, but doable. So he’s chosen cheap ARM processor with memory management – AT91SAM9N12. It comes in 217 BGA package with 0.4mm balls and distance between 0.8mm. Next to it he added DDR2 RAM which also comes in BGA package.
Another challenge was to find PCB manufacturer which would make small pads and vias reliable and cheap. OSH Park seemed to be right choice. Once boards has arrived, next step was to solder chips and other SMT parts. He applied soldering paste with stencils and placed chips. He had to be careful because even 0.4mm error would cause row offset of ball array. Obviously soldering was done with reflow oven which did job pretty good. Other components like NAND flash and large components were soldered by hand. Then he configures Linux system which had to be loaded in to memory and magical screen appeared. This is amazing what can be done with home conditions and some knowledge today.