[SI-LIST] Re: Chip caps vs. Tantalum

There are also issues of a similar nature with very large cap value
ceramics in small package sizes.  As capacitance goes up plate thickness
goes down, with a resultant decrease in reliability.  The problems are
frequently caused by silver migration, which requires moisture, and/or
plate porosity.  In principal ceramic capacitors should be "hermetic",
but it doesn't take much of a break in the surface to cause a problem.
A couple of lifetimes ago, we had some ceramic caps that were
affectionately known as "Blue Bombs" because a several actually
exploded.  Surge can be a major issue as well as very low supply
impedance.

---Bob Lewandowski
   Stratos Lightwave


> -----Original Message-----
> From: Michael_Poimboeuf@xxxxxxxxxxxxxx
> [mailto:Michael_Poimboeuf@xxxxxxxxxxxxxx]
> Sent: Monday, August 19, 2002 2:01 PM
> To: martin@xxxxxxxxxxxxxx
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Chip caps vs. Tantalum
>=20
>=20
>=20
>=20
>=20
> There are lots of factors favoring ceramic over tantalum - as=20
> well as some the
> other way round.
>=20
> The foremost factor in my experience is reliability and safety.
>=20
> Tantalum caps are more prone to failure due to surge current=20
> from fast turn-on.
> If you search
> the web for surge current failure modes in tantalum=20
> capacitors I think you may
> be able to
> track down the papers regarding circuit designs to limit=20
> inrush current for
> tantalum applications.
>=20
> For instance:
> https://www.onsemi.com/pub/Collateral/AN1542-D.PDF
>=20
> I was involved in an unpublished study regarding computer=20
> system failure,
> explosions, fire and
> so forth due to inrush current failure... In my study we=20
> found that the tantalum
>  capacitors failed
> because they were overheated by the contract manufacturer=20
> during assembly and
> rework and
> that inrush current caused them to fail (spectacularly) in=20
> the field afterwards.
>=20
> If chip caps give you sufficient Xc over the frequency and=20
> temperature range
> you're designing
> for, and if you can tolerate microphonic noise and other=20
> issues with ceramics,
> then ceramics
> are better.
>=20
> --
> Michael Poimboeuf
> mkp@xxxxxxxxxxxxxx
>=20
>=20
>=20
>=20
>=20
>=20
>=20
>=20
> "Martin Euredjian" <martin@xxxxxxxxxxxxxx> on 08/19/2002 10:37:46 AM
>=20
> Please respond to martin@xxxxxxxxxxxxxx
>                                                              =20
>                  =20
>                                                              =20
>                  =20
>                                                              =20
>                  =20
>=20
>=20
>                                                              =20
>                                                              =20
>                                                              =20
>  To:      si-list@xxxxxxxxxxxxx                              =20
>                                                              =20
>  cc:      (bcc: Michael K Poimboeuf/AM/Avid)                 =20
>                                                              =20
>                                                              =20
>                                                              =20
>  Subject: [SI-LIST] Chip caps vs. Tantalum                   =20
>                                                              =20
>=20
>=20
>=20
>=20
>=20
>=20
>=20
>=20
> I've been trying to figure out what the differences might be between
> large-value (1 to 100uF) chip caps and similarly valued=20
> Tantalums.  This, of
> course, as it pertains to PDS or switch-mode DC-DC converter design.
>=20
> When/Why might one choose a chip cap over a Tantalum?  What are the
> advantages/disadvantages in comparison?
>=20
> I've seen pictures of modern DC-DC modules that seem to use several
> large-value chip caps.  If that's the case, why did the=20
> designer go this
> route?
>=20
> Thank you,
>=20
>=20
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D
>  Martin Euredjian
>   eCinema Systems, Inc.
>        voice: 661-305-9320
>        fax:   661-775-4876
>   martin@xxxxxxxxxxxxxx
>   www.ecinemasys.com
> =
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D
>=20
>=20
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>=20
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> List archives are viewable at:
>           http://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
>=20
>=20
>=20
>=20
>=20
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>=20
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>=20
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>=20
> List archives are viewable at:    =20
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages=20
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>  =20
>=20
>=20
------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://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

Other related posts: