A new inorganic-organic polymer for the passivation of thin film capacitors

Inorganic-organic polymers with barrier properties against water vapor , excellent electrical data and good adhesion to various substrate materials have been developed. Tailored modifications of these materials provide an excellent protective coating for thin film capacitors. Several mm thick , expensive , encapsulations could be replaced by thin coatings. The polymer coating allows the use of thin film chip capacitors in surface-mount technology. As a measure for the efficiency of the coating , the capacitance decrease under controlled humidity has been used. The influence of the material composition , the type of catalyst during sol-gel processing and the curing conditions have been studied. Adhesion and water vapor permeation properties of the polymers and rheological properties of the coating solutions have been investigated. A protective coating is developed , which increases the withstandnesss of capacitors against humid conditions by a factor of about 30 (compared to uncoated capacitors) and shows no crack formation during thermal cycling.