Using more layers is often a simplification. The 24 layer board of my last design completely avoided vias on the high speed signals (apart from the escape vias from the BGA pads). That also allowed me to match track lengths very accurately and to match differential pairs with the same accuracy. > Of course 20 layers does not mean 20 signal layers. Ground layers can = be > used with success for clocks, differential signals as well analog signal= s. > There isn't any BGA package yet from which you can't escape in max 10 > layers. The smallest pitch the biggest headache. 20 layers is legitimat= e > for NASA or for other people which don't want to get headaches during a > project design... > -- > http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive > View/change your membership options at > http://mailman.mit.edu/mailman/listinfo/piclist > --=20 __________________________________________ David C Brown 43 Bings Road Whaley Bridge High Peak Phone: 01663 733236 Derbyshire eMail: dcb.home@gmail.com SK23 7ND web: www.bings-knowle.co.uk/dcb --=20 http://www.piclist.com/techref/piclist PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist .