Hi, It is correct that the layers should be symmetrical, to provide better copper balancing, Power planes are generally defined by power integrity / decopling requirement impedance requirement Routability Your stack up can be modified as follows 1)Top Signal 1 2)GND 3)Signal 2 4)VCC3.3 5)GND 6)VCC2.5 7)GND 8)Signal 3 9)GND 10)Bottom Signal 4 Routing, switch the signals between layer pair Top Signal 1 and Signal 2 or between layer pair Bottom Signal 4 and Signal 3 Don't switch over routing between Signal 1/2 to Signal 3 / 4 Incase of more routing layer requirement, make layer 4 & 7 also routing layer , make layer 5 split power plane of VCC 3.3 & 2.5, make layer 6 as GND Regards, Vasudevan D Technical Leader - PCB Design, CFT Philips Software Centre Pvt Ltd, Philips Innovation Campus, # 01, Murphy Road, Ulsoor, Bangalore - 560 008. India Tel: +91 80 5579 000 extn : 5030 fax : +91 80 5546 645 stephanie.goedecke+FromInterNet@ philips.com To: si-list@xxxxxxxxxxxxx Sent by: cc: (bcc: Vasudevan Duraiswamy/BTC/CFT/PHILIPS) si-list-bounce@xxxxxxxxxxxxx Subject: [SI-LIST] Re: 10 Layer Board Stack up Classification: 2002-12-02 02:48 PM Please respond to stephanie.goedecke+FromInterNet Hi, generally, the layers should be symmetrical. The details of the layout depend on the details of the board. Stephanie Goedecke Philips - SP3D Chip Design GmbH Petersbrunnerstr.17 82319 Starnberg / Germany Phone: +49-8151-270-160 Fax : +49-8151-270-200 Hi , In 10 Layer Board stack How Multiple Ground Plane Will be More effective and Why. Is there any Formula/Thumb rule behind this. most of my Critical Signal ( CLK) are Running at Signal Layer 1 and My Board Stack up is Top GND Signal Layer 1 VCC3.3 GND VCC2.5 Signal Layer 2 Signal Layer 3 GND Bottom Thanks in Advance. ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu