[SI-LIST] Re: [SI-LIST]: Embedded capacitance on Flex..??

Larry, they are fun materials, aren't they?

Best Regards,

Steve.
At 05:42 PM 8/23/2005 -0700, Larry SMITH wrote:
>Steve - Yes, we have sampled both DuPont and 3M.  Dupont is very
>flexible, almost like saran wrap.  The 3M material is good for hard
>boards but is about as flexible as a potato chip.  Snaps like one too, I
>tried it..
>
>regards,
>Larry
>
>steve weir wrote:
> > Larry, DuPont and 3M both have thin dielectric with elevated Ers that is
> > nice stuff.
> >
> > Some caution is warranted though depending on the specific
> > application.  High Er material can do good things as you said.  For a 
> given
> > skin and dielectric loss, the peak magnitude of the parallel resonant peak
> > falls approximately as the inverse square root of Er.  It tends to be even
> > better than that as higher dielectric loss pulls down the peak as
> > well.  But there are some potential rocks in that stream:
> >
> > 1. Reduced board modal resonant frequencies, good for damping, potentially
> > bad if too low
> > 2. Reduced board to discrete capacitor parallel resonant 
> frequency.  Can be
> > a good or bad thing.  Introduces more variables to discrete bypass design.
> > 3. Increased risk of quarter wave resonance within power delivery band
> > between discrete caps and IC die.
> > 4. Much higher material cost.
> >
> > Best Regards,
> >
> >
> > Steve.
> > At 01:24 PM 8/23/2005 -0700, Larry Smith wrote:
> >
> >>Virendra - I believe that Dupont has some thin, flexible dielectric
> >>that can be loaded with ceramic to bump up the dielectric constant.
> >>
> >>We have found that the best value comes from thin dielectric because
> >>it both reduces inductance and increases capacitance resulting in
> >>lower impedance.  The lower power plane impedance produces more
> >>damping, which is a good for reducing power plane resonances.
> >>
> >>By increasing the dielectric constant alone (no dimensional changes)
> >>the capacitance per square area is increased but it turns out that the
> >>capacitance available to a power consumer with in a given time frame
> >>(i.e. 1 nSec) is the same.  This is because the velocity of
> >>electromagnetic propagation goes down with increasing dielectric.  The
> >>cylindrical wavefront that goes out from a disturbance "uncovers" the
> >>same amount of capacitance per time, independent of the dielectric
> >>constant.
> >>
> >>So if you are looking for high frequency capacitance to satisfy those
> >>fast edges, thin dielectric is good, high dielectric constant is
> >>neutral.
> >>
> >>regards,
> >>Larry Smith
> >>Sun Microsystems
> >>
> >>Ray Anderson wrote:
> >>
> >>>Typically the way I've seen it done in the past is to use a very thin
> >>>dielectric material (~2 mil thick) to achieve the higher than usual
> >>>capacitance.
> >>>
> >>>Most hi-k materials are loaded with some sort of ceramic material which
> >>>tends to make them somewhat less than flexible which could be an issue
> >>>with a flex board.
> >>>
> >>>Note that the materials people are always developing new and innovative
> >>>solutions, so what was true a couple of years ago when I looked at the
> >>>issue may no longer be the case.
> >>>
> >>>-Ray
> >>>
> >>>-----Original Message-----
> >>>From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
> >>>On Behalf Of Virendra
> >>>Sent: Tuesday, August 23, 2005 12:11 PM
> >>>To: si-list@xxxxxxxxxxxxx
> >>>Subject: [SI-LIST] [SI-LIST]: Embedded capacitance on Flex..??
> >>>
> >>>Hello All,
> >>>Does anyone have experience with embedded capacitance
> >>>(wih high K) on a flex circuit board? If yes, are
> >>>there any issues with bending the part of the flex
> >>>with the high k material..?
> >>>
> >>>thanks in advance,
> >>>
> >>>virendra
> >>>
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