Sprayable silver paste with good shielding characteristics in high frequency band

Abstract

Due to the increase of high frequency radio communication, the necessity of EMI shielding as a countermeasure against noise in high frequency band is increasing. We have proposed a method of forming a shield coating film by spraying on module parts and have been developing silver paste for that purpose. However, conventional pastes have an issue that the shielding effect decreases in the high frequency band. As a method to solve this issue, we have developed a silver paste for spray coating using a silver powder with flaky particles. This is enabled because the silver powder with flaky particles has low resistance value and the shielding property becomes good even in a high frequency band. When the shield characteristic was measured by the coaxial tube method, the 7 μm film obtained by spraying this paste on the polyimide base material successfully exhibited 70 dB or more over the entire range from 500 MHz to 8.5 GHz.