[SI-LIST] Re: Question regarding thermal layers
- From: Ravinder.Ajmani@xxxxxxxx
- To: si-list@xxxxxxxxxxxxx
- Date: Mon, 11 Aug 2003 08:58:28 -0700
Dennis,
If you use sufficient decoupling between Thermal and Ground planes, you can
use Thermal planes for signal return. I will propose one change to your
stackup. You should switch layers 9 and 12. Layer 9 as Ground will
provide decoupling to -5V and 2.5V on layer 8. Also, if Thermal plane 13
is well connected to Ground (through capacitors), it will provide good
decoupling to 3.3V plane.
Regards, Ravinder
Server PCB and Flex Development
Hitachi Global Storage Technologies
Email: Ravinder.Ajmani@xxxxxxxx
Dennis Tomlinson
<det_werks@amerit To: si-list@xxxxxxxxxxxxx
ech.net> cc:
Sent by: From:
si-list-bounce@xxxxxxxxxxxxx
si-list-bounce@fr Subject: [SI-LIST] Question
regarding thermal layers
eelists.org
08/10/2003 04:27
AM
Please respond to
si-list
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
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