Silvered Mica and Capacitors

SILVERED MICA AND MICA CAPACITORS
Silvered Mica Plates Cut condensor films are thoroughly cleaned with the help of de-greasing agents and are then silvered on both sides by screen printing process. There is perfect adhesion between mica and silver which results in optimum performance of the plates. Variations on thickness of the silver deposited affect the dissipation factor of the plate, while the overlapping print area of the silver (electrode) and the thickness of the mica (dielectric) control the capacitance of the plate. Individual plates are used in the manufacturing of single film mica capacitors, whereas multiple pieces are used for all other types. These plates are printed for multiple patterns to reduce the manufacturing cost involved therein and in the onward processes.	Mica Stacked Units Multiple layers of parallel printed silvered mica plates interleaved with foil, usually of tin/lead, are used for the manufacture of the stacked units. The capacitance per plate is calculated and a pre-determined number of plates are stacked together to arrive at the required capacitances for the finished capacitors. Thick pieces of plain mica is used as backing on either side to reinforce the units. The finished units are then dipped in varnish and subjected to pressure with heat to make the units compact.
Stacked Mica Sections The individual pieces of stacked units are cut into sections with the means of a saw cutting machine or a gang cutting machine. The cut units we get after the cutting are literally the capacitors themselves, apart from having the terminals and the coatings. All the processes for testing of the various electrical properties are carried out at this stage on the unit.	Sintered Chips In this type, multiple layers of over-the-edge printed mica are stacked together. These units do not have any foil but use the silver itself for the purpose of termination. The units are edge bonded using high content silver paste on which the terminals are directly soldered.
Terminated Units The cut sections or the sintered chips are attached to terminals. In case of the sintered chips, the terminals are directly soldered on to the edge having high content silver paste. In case of cut sections, these units are clamped together with the means of metal clamps. The metal used for this process is normally copper with tin coating or steel with copper and then tin coating.	Moulded Mica Capacitors The units with terminals are moulded with electronic grade epoxy. The process used is that the units are placed in specifically designed mould boxes and liquid epoxy is poured into these boxes. These are then cured in air circulating ovens. The resultant product is a hard epoxy coated capacitor. This is specially needed where the terminals are of axial version, which cannot be dip coated, and also for very high voltage transmitting type capacitors.
Terminated Units The cut sections or the sintered chips are attached to terminals. In case of the sintered chips, the terminals are directly soldered on to the edge having high content silver paste. In case of cut sections, these units are clamped together with the means of metal clamps. The metal used for this process is normally copper with tin coating or steel with copper and then tin coating.	Moulded Mica Capacitors The units with terminals are moulded with electronic grade epoxy. The process used is that the units are placed in specifically designed mould boxes and liquid epoxy is poured into these boxes. These are then cured in air circulating ovens. The resultant product is a hard epoxy coated capacitor. This is specially needed where the terminals are of axial version, which cannot be dip coated, and also for very high voltage transmitting type capacitors.
Dipped Mica Capacitors The clamped units having radial terminals are powder coated with electronic grade epoxy. These units are hung in a device, brought to a heating station, heated at about 240° C and then immersed in epoxy powder. The process is repeated a number of times, to achieve the desired dimensions and complete encapsulation of the product. Click Here for Mica Capacitors Specificatios and Data