On Sat, Feb 02, 2008 at 12:09:37PM +0000, ST de Feber wrote: > > Has any one of you designed a PCB with a 144 pin > QFP/TQFP package ? (with or without exposed die pad)
I just made a board with a QFP208 (0.5mm), 100 (0.65mm rectangular) and 80 (0.65mm square). > How many layers will such a board have ? It depends entirely on the function of the chips. If it's a digital chip and only uses a single power supply you might be able to use just two layers. If it's fast digital and/or analog and has multiple supplies you will probably need at least 4 layers. If it's an FPGA you can simplify your routing because most of the pins are interchangable. If it's a CPU you might need more layers to get the connections to the right places. I probably could not have routed my two SRAM chips on less than 4 layers (just too many power and ground pins plus the need to bus together the A and D lines) but if I'd only used one, larger SRAM I might have gotten away with 2. -- Ben Jackson AD7GD <[EMAIL PROTECTED]> http://www.ben.com/ _______________________________________________ geda-user mailing list geda-user@moria.seul.org http://www.seul.org/cgi-bin/mailman/listinfo/geda-user