Organic Substrate Material with Low Transmission Loss and Effective in Suppressing Package Warpage for 5G Application

The next generation communication system, which is called 5G, is coming. With the introduction of 5G, dielectric material with low dielectric constant (Dk) and low dissipation factor (Df) is required to reduce transmission loss. And, the substrate is also required to be thin with the performance of suppressing the package warpage. Therefore, the package substrate for 5G mobile device will be required to satisfy the low transmission loss and the small package warpage. Low coefficient of thermal expansion (CTE) is known to reduce package warpage, so the substrate material with low CTE is also required. In this research, the substrate material having low Dk and Df, and CTE has been developed. The base resin system consists of the polycyclic resin having the planer stack structure of aromatic ring. The strong intermolecular force between the stacks restricts the local movement of the resin system, which can contribute to the small CTE and the low Df. Besides, low or non-polarity component is a basic idea to design low Dk and Df resin system. In general, different polarity components have less compatibility each other. We have overcome the compatibility issue by introducing chemical co-crosslinking reaction modifying both the polycyclic and the low polarity components. Warpage behavior of the package was evaluated comparing with the conventional coreless thin substrate. The warpage value of the developed substrate material was 150 µm, smaller than that of the conventional substrate. Signal transmission property at 28 to 77 GHz was also evaluated. The loss values of the substrate at 28 and 77 GHz were 0.47 and 1.29 dB/cm, respectively. Those were smaller than the values of the conventional one.