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ceramic cap crack

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#62083

ceramic cap crack | 19 June, 2010

Hi all, lately ofen I have problem with cracked ceramic capacitors.We use 0805 and 0603 cap. Samsung.ICT measure diferent capacity of nominal.If I tray to desoldering component , then component cracked.I think , that the reason is the moisture in component?

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#62086

ceramic cap crack | 19 June, 2010

Please describe the location and appearance of the crack

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#62090

ceramic cap crack | 21 June, 2010

We also encountered the crack case in multi layer Ceramic Cap,0603 after touch up. Most failure were on the terminals. Previously, we used 0805 instead 0603.that time, failure were very few.

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#62093

ceramic cap crack | 21 June, 2010

check your de-panelling process if you are using break-out tabs or V scoring.

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#62098

ceramic cap crack | 22 June, 2010

Dennis: These "terminal detach failures" probably are caused by thermal shocking of the components. * Preheat the components * Use a hot air pencil rather than a soldering iron

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#62104

ceramic cap crack | 23 June, 2010

Hi,

about location - components are in the diferent location on PCB.In the one PCB have 7 cap 560pF 0603 , and some of thenm are cracked, another are OK. When I look at 20x microscope , I can't see defect, but ICT measure from 200 to 350pf.When heat component with soldering-iron,its body cracked near to terminal.

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#62115

ceramic cap crack | 25 June, 2010

Hi iv40 Try with NIC ceramic capacitor that was tested in wet process. We hav succeed with these cap after we found some failure with Kemet ceramic Cap which tested in dry test process while manufacturing.

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#62117

ceramic cap crack | 25 June, 2010

Thanks, Dennis. That is a good idea, but I have problem :) - our logistic department lookig for cheap components...What other mnfg of cap you use? Regards,

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#62118

ceramic cap crack | 25 June, 2010

> Thanks, Dennis. That is a good idea, but I > have problem :) - our logistic department lookig > for cheap components...What other mnfg of cap you > use? Regards,

The capacitor dielectric material might be something you could look at also. COG,NP0 > X7R > Z5U,Y5V. If the cracking is mechanically induced, COG and NPO are the strongest where Y5V are the weakest.

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#62130

ceramic cap crack | 27 June, 2010

*** silly question deleted, there are no 100nF NPO ***

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#62187

ceramic cap crack | 6 July, 2010

Is the board a two sided smt board? If so, where are the standoffs (board supports) located during the second side run? The 0805 being thicker than the 0603 may explain why 0805 was cracked less.

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#62217

ceramic cap crack | 9 July, 2010

A couple of things:

Does the cap break if you try to remove it with hot air? If not, than you are breaking the caps do to mechanical stress. We have had similar issues. I don't think your board is suffering from mechanical stress from depaneling or other processes (unless they are all grouped together, perpendicual to the score lines, and near the edge of the board). If they are, then check your depaneling process. If the cap is cracked, I'm surprised that your ICT even reads any capacitance, much less up to 350pf. It sounds like you are using a cap with an X5R dielectric. These have a high aging factor (7% per decade) and wide tolerance. These are the scavangers of the capacitor world, bottom feeders, and there is a reason they are so cheap...because they are. Go with X7R, heck, Y5V would even be better. I have been forced to use X5R in production and we have tolerance issues with all three. I believe two are Kemet and one is Panasonic so it is not an issue with the mfg, but with the dielectric of the part.

Try this experiment: Gentley heat each side of the cap with an iron, but do not remove it. Put it back on the ICT and check the measurement. If its an X5R dielectric, the value of the cap will increase to nominal and stay there for another 6-12 months before it deages again (it deages logarithmically starting at 1000 hours after the deaging process). What you have just done is deaged the capacitor by realigning the crytalline structure within the dielectric and this is the recommended method from the mfg, if you can believe it. Tell your purchasing department to stay away from X5R, unless quality is not a concern.

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#62225

ceramic cap crack | 12 July, 2010

I had cracking caps from the ICT and a variation in the length of the probes (due to wear and tear) that press down the PCB. That put lots of mechanical stress on the PCB.

So have also a close look at the ICT, or another other test fixtures you use.

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