Okay, so I've got a new project that has some annoyingly conflicting requirements. I'm working on a processor module that needs to be both compact and inexpensive ( of course ). The processor is tentatively selected ( an NXP ARM ) and, as always, comes in two packages, each of which seems to support one of the requirements. In a LQFP-144 I would be able to use standard 6/6 board rules and, thus, be able to get boards made just about everywhere. The problem is that I'll shatter the desired size requirements ( by a factor of 2x or more ) if I go that route. On the other hand, there is a BGA package ( 100-pin, 0.8mm pitch ) that will make size constraints all but easy, except that I'd have to go, at least, to 5/5 rules with smaller than standard drill holes and a minimum of 4-layers. I don't have any experience with board houses to handle that sort of thing and, besides, we'll only need a half-dozen of the boards at the very most. The project is for a small University that sits in the middle of three of the five most impoverished counties in the state. Needless to say, there are not huge funds available.
So, I guess there are a few questions.
1) Any pointers on reasonable PCB fabs that can handle fine(-er) pitch design rules without the cost for prototypes becoming astronomical.
2) Ideas about the best way to "prototype" with BGA packages that require more signal layers and tighter design rules.
3) Any completely new ideas... The requirements are for:
2x I2C buses
1x CAN Controller
1x Device USB
>256MB Non-Volatile Memory
Computational loads are only moderate. The problem is the need for extensive storage and random memory access ( sadly, the XMega EBI only gets me within an order of magnitude for the RAM, 128Mb[its] vs the needed 128MB[ytes] ).
Martin Jay McKee