Frequency Trimming of ZnO/Glass SAW Filters

In the process of producing ZnO/glass SAW filters, a desired frequency cannot always be obtained after sputtering ZnO thin films on IDT /glass substrates. It is therefore necessary to adjust the center frequency of each SAW filter within 0.05% tolerance after sputtering. We have developed a method to adjust the center frequency in a mass production process by overlaying organic polymer resin on the substrates. The frequency deviation then becomes very small not only in one lot, but also between lots, and the mass production cost of SAW filters can be reduced tremendously.