Ceramic Capacitor Failure
in [Design]
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From: Archimedes' Lever on 31 Mar 2010 20:23 On Wed, 31 Mar 2010 10:52:29 -0700, qrk <SpamTrap(a)spam.net> wrote: >The capacitor is a simple decoupling >>cap for a logic IC. Once removed, the board behaves nicely again. Is this a >>common failure mode for ceramic caps? How was it attached? By hand? Then yes, MLCCs can be put in jeopardy of infant failure modes by the application of excessive heat. If you glue it on and wave solder that side of the board, you can also do it. Then, there is brand name. Independent of materials used in its construction, buying from a not so well known "maker" can yield very poor lot-to-lot quality consistency. Stick with Vishay, who bought up a lot of the other makers. Philips is another good one. there are, of course others that are just as good.
From: JosephKK on 1 Apr 2010 08:24 On Tue, 30 Mar 2010 15:50:59 -0500, "eeboy" <jason(a)n_o_s_p_a_m.n_o_s_p_a_m.jasonorsborn.com> wrote: >I've got a situation where boards are being returned all of the sudden. >This particular board has been in service well before my time so it seems >as if it is perhaps related to a particular batch. The problem is with an >0805 ceramic capacitor. The same capacitor seems to have failed on each. >The result is a 56 ohm DC resistance. The capacitor is a simple decoupling >cap for a logic IC. Once removed, the board behaves nicely again. Is this a >common failure mode for ceramic caps? What's the probability that we simply >got a bad reel of the component? What potential causes are there for this >failure? > >I can rule out over voltage. The cap is rated at 25V but the maximum >voltage it would see during operation is 5V. I think I can rule out ESD as >there are many more sensitive components that would have fried before this >cap. The circuit is a low power logic circuit... no large switching >currents. > >Any thoughts? > >--------------------------------------- >Posted through http://www.Electronics-Related.com With the rather minimal data presented it sure sounds like bad parts. Admittedly it was ~20 to 30 years ago I did space qualification testing of MLC capacitors.
From: Bob Eld on 1 Apr 2010 10:53
"Archimedes' Lever" <OneBigLever(a)InfiniteSeries.Org> wrote in message news:bgp7r5hu6m3273g5s0r8f40tb6r6lf69k3(a)4ax.com... > On Wed, 31 Mar 2010 06:51:16 -0800, "Bob Eld" <nsmontassoc(a)yahoo.com> > wrote: > > > > >"Tim Williams" <tmoranwms(a)charter.net> wrote in message > >news:houcs9$ksg$1(a)news.eternal-september.org... > >> Z5U at 10kV? Wow, it might actually make a good bypass down under 100V > >;-) > >> > >> Tim > > > >That's Z5R > > > Google Z5R and find NOTHING. Google Z5U and find that it is an IEDC > Class 2 dielectric medium. > > Maybe you should "try again". > > Z5U is a common HV cap dielectric. Never heard of Z5R. Well then, since you can't find it on the internets, it must not exist! Idiot! Z5R is a 10deg C., to 85 deg C, +/- 15% Class 2 dielectric. Table 3 EIA Codes For Non-Temperature-Stable Ceramic Capacitors (Class 2 and Higher) Low Temp. Limit: High Temp. Limit: Capacitance Change over Range: X -55C 4 +65C A � 1.0% Y -30C 5 +85C B � 1.5% Z +10C 6 +105C C � 2.2% 7 +125C D � 3.3% 8 +150C E � 4.7% 9 +200C F � 7.5% P � 10% R � 15% S � 22% T +22% -33% U +22% -56% V +22% -82% |