some customers ask us: he gong, may i ask why some of the high-voltage ceramic capacitors you provide have a line that is divided from the middle? can it be worn away? it affects the appearance!
i would like to introduce you to the knowledge of potting of high-voltage ceramic capacitors. generally speaking, after the chip of high-voltage ceramic capacitors is soldered to the electrode and oven, it is necessary to encapsulate the chip into epoxy resin. the epoxy resin must be professional. high voltage resistance, high and low temperature resistance. however, some technicians did not fully consider the strong pressure of epoxy resin on the chip, and took some wrong practices.
for example, some people use metal materials to make high-voltage capacitor potting molds. this is not a fault. however, if you simply make a capacitor shape in a metal mold hole, it is a big mistake. because of ceramic chips and epoxy resin. the thermal expansion and contraction are basically the same, but the thermal expansion and contraction of the metal mold is particularly obvious, so that the high-voltage capacitor made by a single mold looks good in appearance. the overvoltage test shows that the capacitor is broken. no high pressure. at this time we melted the resin and found that the strong internal stress crushed the hard ceramic chip!!
the potting module interface of the high-voltage capacitor will leave a line, as if the capacitor is divided into two halves.
why is there any problem with the use of metal for potting, and some people have been unsuccessful? the reason is that instead of using a piece of metal to make a mold, instead of using a piece of metal to synthesize a set of molds, when the capacitor is potted cooling down, you only need to separate the two halves of the mold, you can take it out. as shown above, there will be a line on the capacitor, you can clearly imagine the mold form. this two-in-one method effectively avoids the high-voltage capacitor in after the glue is applied, the chip is crushed. because "not a piece of iron." the internal stress has a place to vent.
in addition to the use of metal molds, there are a large number of enterprises using plastic molds. generally use plastic king, can successfully avoid the problem of internal stress extrusion high-pressure ceramic chips. because plastic king's thermal expansion and contraction effect is not obvious, can effectively protect high pressure the ceramic chip is not crushed.
regardless of the material used to make the potting mold for high-voltage ceramic capacitors, we must consider the above problems. in addition, we must pay attention to: the mold should be light, easy to dissipate heat and heat; the mold should be strong and effectively pressed the two poles of the capacitor will not cause the two poles to fall off due to thermal expansion and contraction.