[SI-LIST] Re: Buried capacitance materials


Our raw boards are Hipot tested to 1 kV, and in the past we have had
instances of dielectric breakdown (Prepreg 2.8 mils +/- 1 mil), causing
short between 12V and GND plane.  I just want to make sure that BC-2000 can
withstand this.

Regards, Ravinder
PCB Development and Design Department
IBM Corporation
Email: ajmani@xxxxxxxxxx
***************************************************************************
Always do right.  This will gratify some people and astonish the rest.
.... Mark Twain


                                                                                
                        
                      Mike Brown                                                
                        
                      <bmgman@xxxxxxxxx        To:       Ravinder Ajmani/San 
Jose/IBM@IBMUS             
                      t>                       cc:       si-list@xxxxxxxxxxxxx  
                        
                      Sent by:                 Subject:  [SI-LIST] Re: Buried 
capacitance materials     
                      si-list-bounce@fr                                         
                        
                      eelists.org                                               
                        
                                                                                
                        
                                                                                
                        
                      09/24/2002 07:56                                          
                        
                      PM                                                        
                        
                      Please respond to                                         
                        
                      bmgman                                                    
                        
                                                                                
                        
                                                                                
                        




In most applications, hi-pot ought not be an issue for BC.  Hi-pot
applies between  primary and secondary wiring.  The copper on each side
of the BC material  is at secondary potential in most applications.  Or
so it would seem to me.  The bypass caps between the two copper layers
are probably rated at no more than a few x the operating voltage, and
you don't consider hi-pot ratings for those.  I rest my case.

Mike

Ravinder Ajmani wrote:

>
>That was an excellent summary on buried capacitance materials.  I will
>appreciate if someone can provide me the information about Hipot rating of
>BC-2000.
>
>Regards, Ravinder
>PCB Development and Design Department
>IBM Corporation
>Email: ajmani@xxxxxxxxxx
>
***************************************************************************
>Always do right.  This will gratify some people and astonish the rest.
>.... Mark Twain
>
>
>

>                      Greg.LINK@topsear

>                      ch.com.hk                To:
sunilb@xxxxxxxxxxxxxx
>                      Sent by:                 cc:
si-list@xxxxxxxxxxxxx
>                      si-list-bounce@fr        Subject:  [SI-LIST] Re:
Buried capacitance materials
>                      eelists.org

>

>

>                      09/19/2002 03:59

>                      AM

>                      Please respond to

>                      Greg.LINK

>

>

>
>
>
>
>
>All are FR-4 compatible, but only BC-2000 is used in volume.
>
>BC material is very reasonable but the licence to use it is expensive.
The
>other have so little use that the cost is not the relavent concern.  Emcap
>died as a project with Hadco but 3M is retrying with others.  The
>advantange of Emcap is a very high Dk 5X over BC-2000.  The disadvantage
is
>a 4 mil thickness (higher inductance) and a hard to process Ceramic core.
>Dupont's capacitor material is a double screening process but is only
>suited for descrete capacitance and inductance needs, so it's area is very
>small.  Here are 2 helpful equation in looking at the effects:
>C = 225 x Dk x A / t    L = a constant x t / W
>C=Capacitance, A=area, t=thickness, L = inductance, W= width
>
>Talk to your PCB supplier about design requirements, assuming us use
BC2000
>(the "only" available material), you should balance the construction but
>keep the BC cores near the components to limit through hole inductance
>Layers 2/3 and N-1/N-2 is common.  The more BC planes you get into the
>panel the better.  If you have a 12 lyr structure you might have 3 BC
>(power/ground) planes.  Area is very important.  Keep the surface
>Ground/Power planes as large and full of copper as possible. Copper
>thickness is not relavent but 1oz/1oz is easier to transport for your PCB
>supplier.
>
>Current carring capability can also be an importance consideration.  The
>very thin dielectrics can run into problems at not being able to handle
low
>current.
>
>Greg Link
>Processing Engineering Manager
>Topsearch Printed Circuits (HK)
>
>
>
>
>Sunil Kumar <sunilb@xxxxxxxxxxxxxx>@freelists.org on 09/19/2002 05:17:15
PM
>
>Please respond to sunilb@xxxxxxxxxxxxxx
>
>Sent by:  si-list-bounce@xxxxxxxxxxxxx
>
>
>To:   si-list@xxxxxxxxxxxxx
>cc:
>Fax to:
>Subject:  [SI-LIST] Buried capacitance materials
>
>
>
>Hello everybody,
>
>I am planning to use FR4 compatible buried capacitance (BC) laminates for
>power planes in a high speed board. I have come to know about the
>following materials:
>
>     1. BC2000 (Hadco)
>     2. BC1000 (Hadco)
>     3. EmCAP (Hadco)
>     4. C-Ply (3M)
>     5. HiK (Dupont)
>
>Except BC2000, I could not get much details about these materials. I have
>the following questions:
>
>Q1: Are all of them FR4 compatible? (I know that BC2000 is FR4
>    compatible.)
>
>Q2: How much costly are these materials?
>
>Q3: What precautions do I have to take in the layout of the board when
>    using these materials?
>
>Q4: What are the other BC materials available?
>
>
>
>Thanks,
>
>Sunil Kumar
>Senior Research Engineer
>ATM Group, Switching-B2
>Centre for Development of Telematics (C-DOT)
>Bangalore-52
>INDIA
>
>
>
>
>
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