Re:Hand solderable 1GHz ARM Cortex A8 in TQFP package
by mbell on Thursday April 26, 2012 @11:51PM
(#3897435)
Honestly the price differential is very small between 4 and 6 layers now-a-days. In mass pro that is, they will still charge a solid premium for 6 layer at many quick turn / small batch PCB manufacturers.
The biggest savings comes from avoiding blind and buried vias which are still expensive to use but often required for dense BGAs. You can also usually get away with a larger minimum feature size (trace width) with a QFP which can also be a nice cost savings in the PCB construction.
The real advantage here is not the savings in the soldering soldering but the savings in PCB complexity and cost. A small BGA with a few hundred pins will need at least 6 or more layers to be able to "break-out" all the pins from underneath the chip. With the TQFP package, all the pins are already at the edge of the chip, so it's possible to use a 4 layer PCB.
It's an exciting time when more people can have access build thing using this level of hardware. Now the next thing we need is decent documentation to go with these chips.