Cu/LCP Laminated Materials for New Generation FPC

As future materials for flexible printed circuits (FPCs) with high performance, we have studied copper clad lamination (CCL) materials of liquid crystal polymer (LCP) on copper (Cu) foil using a new laminating process, so called, surface activated bonding (SAB) method [1-5]. In previous report, it was found that the loss of peel strength during the heat-resistance test was improved by using copper-0.02% zirconium (Cu-Zr) alloy foil and a thicker sputter of copper-45% nickel (Cu-45Ni) or nickel-20% chromium (Ni-20Cr) alloys [5]. These improved materials showed excellent interface conductivity at high frequency and etching property. In this report, we tried to produce more improved materials with different sputtering metals and investigated various characteristics of the laminated materials such as scattering parameter (S21), etching property, and dimensional stability for the FPCs. It was clarified that the sputter metal of higher nickel content alloys prevented from the interface oxidation of the Cu-Zr alloy foil/LCP film laminated materials (Cu-Zr/LCP materials) after heat-resistance test. Especially in copper-80% nickel (Cu-80Ni)or nickel-10% chromium (Ni-10Cr) alloy, the peel strength of the laminated materials kept around 500N/m even after 144 hour heating. The S21 of micro-strip line of the laminated materials showed half attenuation when comparing with that produced by the conventional heat bonding method. It is also shown that the Cu-Zr materials produced by the SAB method (SAB material) have excellent etching property and dimensional stability.