Build-up electrical insulation material for high speed & high-frequency

The demand for high performance build-up electrical insulation materials, used in IC package substrates, is increasing due to ever-increasing speed signal processing and density of LSIs due to requirement for faster information and communication equipment in recent years. These LSIs with signal travelling at high speeds also causes GHz band signal to travel through the package substrate. If the dielectric loss tangent of the insulation material is large, not only will it lead to high signal losses, it will also cause other problems such as increase in heat releases. Furthermore, GHz band signal travelling at high speed causes large transmission losses at the surface of the conductor due to skin effect and this is especially true when the surface smoothness of the conductor is rough triggering a signal delay. To countermeasure these problems, build up insulation material that has both low dielectric loss tangent and enables smoother conductor surfaces after processing, was developed achieving very low signal loss of -1.38dB/inch at 10GHz using microstrip line. Here we report the result of the low transmission loss of the newly developed material by microstrip line and the successful result of isolating the effect of low dielectric loss tangent and conductor smoothness that affect transmission loss. Finally we report a novel insulation material that achieves further low transmission loss by having dielectric loss tangent of 0.004 level with conductor surface roughness of less than 100 nm.