Thanks Martin Very detailed. Much appreciated.
Ian > On 20 May 2022, at 19:00, Dekatron42 <martin.forsb...@gmail.com> wrote: > > > If I remember correctly my colleagues spoke about the normal capacitor > reforming by applying voltage to them after long storage (1-2years or more in > storage) and also the "resetting" that they are subjected to when soldering: > https://ec.kemet.com/blog/mlcc-dielectric-differences/ > > " Ceramic Capacitor Aging > Aging is another characteristic exhibited by ferroelectric, or Class II and > III dielectrics. While manufacturing the ceramic capacitor, the dielectric is > exposed to temperatures more than 1000°C. For Barium Titanate devices, the > Curie temperature can be in the range of 130°C to 150°C, depending on the > particular formulation. When exposed to the Curie temperature, the > crystalline structure aligns to a tetragonal pattern. Once cooled, the > ceramic’s crystalline structure changes to a cubic change. As this structure > changes, so does the material’s dielectric constant. > > Over time, the capacitance will continue to decline. It is possible to reset > this aging cycle by “resetting” the material, by exposing it to its Curie > temperature this usually occurs during re-flow. Typically, you can find the > aging rate in the catalog for a particular part type. Below is an example of > aging rates:" > > Our problems started when capacitors started to break and/or fall of the > circuit boards even though our designed were approved by the capacitor > manufacturer! We also experienced the problems with degrading capacitance in > MLCC capacitors but it was even worse with self-healing polypropylene > capacitors as it affected the smart-meters power supplies - it all turned out > to be manufacturing problems of the capacitors due to moisture in the > materials. > > https://www.researchgate.net/publication/348506751_Analysis_of_Failure_Mechanism_of_Smart_Meter_Capacitance > > "In practical applications, smart meters will fail, and even have batch > quality problems. In addition to the sampling inspection of the arrival > quality of smart meters, the analysis of the failure mechanism of smart > meters has become an important and long-term task. This article mainly > analyzes the component capacitance commonly used in smart meters, and > analyses the failure of chip multilayer ceramic dielectric capacitors from > appearance observation, electrical parameter testing, metallographic slicing, > and at the same time from electrolytic appearance observation, electrical > parameter testing, X- RAY, SEM and EDS for failure analysis. The results of > failure mechanism research not only help to improve the reliability of the > domestic energy meter manufacturing level, but also can save energy meter > maintenance and transformation costs, and have very important practical > significance for the construction of smart grids." > > /Martin > > >> On Friday, 20 May 2022 at 07:27:22 UTC+2 iavine wrote: >> Could someone explain what the reforming involves ? >> >> Thanks >> Ian >> >>>> On 20 May 2022, at 06:12, SWISSNIXIE - Jonathan F. <jfre...@gmail.com> >>>> wrote: >>>> >>> I've used a MAX1771 with ceramic capacitors a while ago for a >>> pandicon-circuit and a smaller nixie project. Both consume less than >>> 15mA@170V. Not sure how the circuit would behave at more current. >> >>> >>>> On Thursday, 19 May 2022 at 20:03:18 UTC+2 Dekatron42 wrote: >>>> A few other things that I experienced at my previous employer was that >>>> larger (sizewise) MLCC capacitors easily developed cracks, came loose from >>>> the circuit board and also needed reforming after storage. >>>> >>>> /Martin >>>> >>>>> On Thursday, 19 May 2022 at 05:01:25 UTC+2 mo...@neonixie.com wrote: >>>>> Roger, >>>>> >>>>> Yes. Looks like the common dielectrics (X7T, X7R) available in the 250v >>>>> 1-3uf range suffer from a 30-80% reduction in capacitance at 180v. I >>>>> hadn't realized it was that high. >>>>> Thank you, I'll look at the polymer caps. It's my last remaining >>>>> electrolytic on my board and if possible I would like to use a solid one >>>>> instead. >>>>> >>>>> Regards, >>>>> -Moses >>>>> >>>>>> On Wednesday, May 18, 2022 at 7:54:10 PM UTC-7 Roger Brinkman wrote: >>>>>> Hi Moses, >>>>>> >>>>>> What David writes below about the capacitance reduction of ceramic >>>>>> capacitors is correct. >>>>>> I have experienced success using polymer aluminium electrolytics (solid >>>>>> electrolyte) to replace conventional low-ESR electrolytic capacitors >>>>>> that regularly fail in similar applications. >>>>>> You might like to experiment with these. >>>>>> >>>>>> Best regards >>>>>> Roger Brinkman. >>>>>> >>>>>>>> On 19 May 2022, at 12:42 pm, David Forbes <nixie...@gmail.com> wrote: >>>>>>>> >>>>>>> >>>>>> >>>>>>> I haven't tried it, but I can make some observations. The MAX1771 isn't >>>>>>> connected directly to the output circuit, so it's not likely to suffer >>>>>>> from a problem. The current flows through the inductor which will >>>>>>> accommodate a momentary short circuit caused by the capacitor. >>>>>>> In short, it shouldn't be a problem. >>>>>>> Bear in mind that the effective capacitance of a modern ceramic >>>>>>> capacitor is much lower with a DC bias near its rated voltage, so you >>>>>>> would need to use either capacitors rated for 5x the output voltage, or >>>>>>> about 5x the desired capacitance. >>>>>>> Some capacitor data sheets publish this reduction in capacitance as a >>>>>>> function of bias voltage, most don't. Look for it. >>>>>>> >>>>>>> >>>>>>>> On Wed, May 18, 2022, 6:49 PM Moses <mo...@neonixie.com> wrote: >>>>>>>> Before I let the magic smoke out of half a dozen MAX1771 ICs.. has >>>>>>>> anyone ever tried using ceramic output capacitors? It wants a low ESR >>>>>>>> capacitor, so ceramics may work well. >>>>>>>> >>>>>>>> The datasheet doesn't mention ceramics on the output side.. but then >>>>>>>> again it was written a few decades ago when the required >>>>>>>> voltage/capacitance probably was not readily available. >>>>>>>> >>>>>>>> Regards, >>>>>>>> -Moses >>>>>>>> -- >>>>>>>> You received this message because you are subscribed to the Google >>>>>>>> Groups "neonixie-l" group. >>>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>>> an email to neonixie-l+...@googlegroups.com. >>>>>>>> To view this discussion on the web, visit >>>>>>>> https://groups.google.com/d/msgid/neonixie-l/7ae38dca-64ca-459d-a1e5-283a062f8f9en%40googlegroups.com. >>>>>>> >>>>>>> -- >>>>>>> You received this message because you are subscribed to the Google >>>>>>> Groups "neonixie-l" group. >>>>>>> To unsubscribe from this group and stop receiving emails from it, send >>>>>>> an email to neonixie-l+...@googlegroups.com. >>>>>> >>>>>>> To view this discussion on the web, visit >>>>>>> https://groups.google.com/d/msgid/neonixie-l/CAPbqtvcg0ak%2BLMH_7JJ01eFnYjFzu38v2N59k8ZfoFxrRY3J_g%40mail.gmail.com. >>> >>> -- >>> You received this message because you are subscribed to the Google Groups >>> "neonixie-l" group. >>> To unsubscribe from this group and stop receiving emails from it, send an >>> email to neonixie-l+...@googlegroups.com. >> >>> To view this discussion on the web, visit >>> https://groups.google.com/d/msgid/neonixie-l/bb141fcc-15ab-45de-a7ae-c9b38a3710dbn%40googlegroups.com. > > -- > You received this message because you are subscribed to the Google Groups > "neonixie-l" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to neonixie-l+unsubscr...@googlegroups.com. > To view this discussion on the web, visit > https://groups.google.com/d/msgid/neonixie-l/828a3fd5-aef6-4dcf-b413-a9ac327471f9n%40googlegroups.com. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. 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