EVALUATING METHOD OF QUALITY OF ELASTIC SURFACE WAVE ELEMENT

PURPOSE:To make it possible to easily evaluate the quality of elastic surface wave element in a short period of time, by measuring electrostatic capacity between an electrode and a stem of an elastic surface wave element and determining whether it is acceptable or not by magnitude of the value of the electrostatic capacity. CONSTITUTION:An input electrode 1 and an output electrode 2 of an elastic surface wave element are opposite to each other on the surface and formed into a comb-like shape, and a piesoelectric substrate 3 is attached onto a metallic stem 4 by an adhesive 5. Correlation-ship between the electrode-stem electrostatic capacity and the trap level is checked in advance specifically by grades of the elastic surface wave elements, and electrostatic capacities corresponding to prescribed trap levels are sought in advance. And, by measuring an electrostatic capacity between an electrode and a stem of a specimen elastic surface wave element, and also by comparing it with the electrostatic capacity of judgement cryteria, acceptability of the frequency characteristic based on a prescribed trap level is judged. It is possible, by doing so, to eliminate necessity of measurement of passing characteristic in frequency of checkpoint at many places and also to determine acceptability easily.