This invention relates to a thick film electronic circuit and more particularly, to a thick film electronic circuit having a plurality of printed capacitors.
Printed capacitors are generally formed on an insulating substrate such as alumina by a method of printing process comprising forming a lower electrode, forming a dielectric layer on the lower electrode and further forming an upper electrode on the dielectric layer. The dielectric layer thus formed by the method of printing is typically porous and has low moisture resisting properties. Accordingly, a glass coating as a moisture-proofing protective film is often deposited on the capacitor. Since pin-holes and cracks are likely to occur on the glass coating, however, moisture may penetrate into the dielectric layer, reducing the dielectric characteristics and rendering the printed capacitor defective. It is often therefore necessary to inspect the insulation resistance of all the printed capacitors formed on the thick film electronic circuit. If a resistor 2 is formed in parallel to the capacitor 1 in a thick film electronic circuit such as shown in FIG. 1, however, it is not possible to measure the insulation resistance of the printed capacitor 1. To solve this problem, a conductive portion 3 may first be cut off so as not to form a circuit loop between the printed capacitor 1 and the resistor 2, and the insulation resistance of the capacitor 1 can then be measured and thereafter the cut portion 4 may be soldered. In FIG. 1, reference numerals 11, 12, 13 and 14 represent a lower electrode, a dielectric, an upper electrode and a glass coating, respectively. Since the cut portion 4 must be again connected by soldering, the conventional method has the shortcoming that the number of production steps increases to render the fabrication of the thick film electronic circuit all the more complicated and the production yield is eventually lowered.