On Mon, Sep 22, 2008 at 8:43 PM, Zik Saleeba wrote: > TQFP is just too big for the project I'm working on so I'm looking at going > to BGA for the first time. The process of breaking out those signals seems a > little tricky. The package I'm looking at has 100 balls with 0.8mm spacing > and I've been having some difficulty finding vias small enough to route the > signals out using conventional board processes. The vias are just too large > too allow enough clearance between the pads. A little reading around the web > seems to indicate that at this density I should be looking at microvias > rather than conventional vias. > I learned from our PCB designer that you need microvias for 0.8mm BGA. Not all BGAs are the same, some may not need microvias. As a matter of fact, I have a board infront of me which has a Xilinx CPLD in BGA packaging. It is only a 4 layer board with no microvisa, no blind/buried vias. Just some clearance between the CPLD and other components. This may help. http://www.ddiglobal.com/press/technical_bulletins/BGA_Guidelines.pdf http://wisconsin.cern.ch/ROD/ti_documents/spra429b.pdf http://focus.ti.com.cn/cn/lit/an/szza005/szza005.pdf And then I have another board with no BGA packages and no complex digital ICs but there is a complex planar transformer, I do not need microvias, but I need to use blind and buried vias and 8-layer boards because of the windings and isolation requirement and the density of the boards. Regards, Xiaofan -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist