Thermomechanical and Electrical Properties of the $\text{SiO}_{2}/\text{ZrW}_{2}\mathrm{O}_{8}/\text{Epoxy}$ Composite

Epoxy resin (ER) is commonly used in the insulating dielectric substrates in circuit boards for various devices. However, its coefficient of thermal expansion (CTE) is mostly above 100 ppm/K and seriously mismatched with the connected materials, such as copper (CTE of 17 ppm/K), which usually causes several defects such as cracks, delamination, and warpage in the dielectric layer and then the service life of the devices is affected. Here we report a strategy to reduce CTE of the epoxy based film by using $\text{SiO}_{2} / \text{Z r} \mathrm{W}_{2} \mathrm{O}_{8}$ particles as low/negative CTE nanofillers. For comparison, epoxy composite films separately filled with the $\text{SiO}_{2}$ and $\text{ZrW}_{2}\mathrm{O}_{8}$ were also prepared. As the film was filled with both $\text{SiO}_{2}$ and $\text{ZrW}_{2}\mathrm{O}_{8}$ at a ratio of 8:2, the CTE achieved a reduction of about 52% compared to the pure epoxy films and was lower than either $\text{SiO}_{2}$ or $\text{ZrW}_{2}\mathrm{O}_{8}$ single-phase filled composite film with the same loading (75wt%). At the high frequency of 5143 MHz, the dielectric constant of the $\text{SiO}_{2} / \text{Z r} \mathrm{W}_{2} \mathrm{O}_{8} /\ \text{epoxy}$ composite film was 3.73, slightly increased by 29% compared to the pure epoxy film (2.89). The dielectric loss of $\text{SiO}_{2} / \text{ZrW}_{2} \mathrm{O}_{8} / \text{epoxy}$ composite film was 0.017, which was decreased by 29.2% of the pure epoxy film (0.024). The performance of low CTE, low permittivity and low dielectric loss is expected to be applied in printed circuit boards for electronic devices.