Dennis, This is the second time in about a week that someone has suggested using "thermal" layers in addition to 'ground" layers. I responded to the last one suggesting they use the thermal layers as ground, but maybe I'm missing something. What is is it that makes you feel that a sheet of copper that you are using to conduct heat cannot also do the job of conducting current? Alan Hilton-Nickel NVIDIA Corp, Santa Clara, CA > -----Original Message----- > From: Dennis Tomlinson [mailto:det_werks@xxxxxxxxxxxxx] > Sent: Sunday, August 10, 2003 4:27 AM > To: si-list@xxxxxxxxxxxxx > Subject: [SI-LIST] Question regarding thermal layers > > > I am designing a conductin cooled module which will employ > thermal layers in the stackup and underfill on selected > devices. The thermal layers are DC isolated from circuit > ground. I am proposing the following stackup: > > 1. Signal + Comps > > 2. Thermal > > 3. Ground > > 4. Signal > > 5. Signal > > 6. Ground > > 7. Signal + Area Fills (1.8V, +5V) > > 8. Signal + Area Fills (-5V, 2.5V) > > 9. Power (3.3V) > > 10. Signal > > 11. Signal > > 12 Ground > > 13. Thermal > > 14 Signal + Comps > > My question is in regard to using the thermal layers as > signal returns. The dielectric between thermal and ground > layers is 5 mil core. I am contemplating the use of some > strategically placed bypass caps between thermal and ground > layers, as well as between thermal and 3.3V layers. Anyone > care to critique or comment on this plan? Would it make sense > to swap layers 9 (3.3V) and 12 (Ground)? Thanks in advance, > > Dennis Tomlinson > > > > > > ------------------------------------------------------------------ > 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