Polyimide (PI) has been extensively used in 5G microelectronics however the relatively high dielectric constant (∼3.5) and moisture adsorption have greatly limit its practical applications in high-frequency region. Here hydrophobic PI/SiO composite films with low dielectric constant and excellent thermal stability were synthesized by dispersing methyl modified hollow silica nanospheres (MHS) into polyamic acid solution prior to imidization treatment. Comparing with unmodified hollow silica nanospheres (HS), the MHS obtained through methyl modification can disperse uniformly in the PI matrix. Thus, the relaxation and orientation polarization of the PI chains as well as their electron migration are suppressed, resulting in a significant decrease in dielectric constant. The PI/MHS-10% film exhibits a stable low dielectric constant (1.9–2.3) in the high-frequency range (8.2 GHz–12.4 GHz), meanwhile maintains a high breakdown voltage (192 kV/mm), mechanical properties (64 MPa) and an excellent thermal stability ( = 546.5 °C; = 589.0 °C). Moreover. PI/MHS demonstrates much lower linear expansion coefficient of 25.0 ppm/K that better matches the substrate. The surface contact angle of PI/MHS increases from 73° to 110° and the water absorption rate decreases from 3.1% to 1.6%, effectively avoiding the moisture adsorption. This work provides a simple method to prepare high-performance composite films for 5G practical applications.

中文翻译：

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通过简单改性获得具有优异介电性能和热稳定性的疏水PI/SiO2复合材料

聚酰亚胺（PI）已广泛应用于5G微电子领域，但相对较高的介电常数（∼3.5）和吸湿性极大地限制了其在高频区域的实际应用。通过在酰亚胺化处理之前将甲基改性空心二氧化硅纳米球（MHS）分散到聚酰胺酸溶液中，合成了具有低介电常数和优异热稳定性的疏水性PI/SiO复合薄膜。与未改性的空心二氧化硅纳米球（HS）相比，经过甲基改性得到的MHS可以均匀地分散在PI基质中。因此，PI链的弛豫和取向极化及其电子迁移受到抑制，导致介电常数显着降低。PI/MHS-10%薄膜在高频范围（8.2 GHz-12.4 GHz）内表现出稳定的低介电常数（1.9-2.3），同时保持高击穿电压（192 kV/mm）、机械性能（64 MPa）和出色的热稳定性（= 546.5 °C；= 589.0 °C）。而且。PI/MHS 表现出更低的线性膨胀系数（25.0 ppm/K），与基材更好地匹配。PI/MHS的表面接触角从73°增大到110°，吸水率从3.1%降低到1.6%，有效避免了水分吸附。这项工作提供了一种简单的方法来制备用于5G实际应用的高性能复合薄膜。