Adhesion and Interface Studies of the Structure‐Controlled Polyimide with Smooth Copper for High‐Frequency Communication

Abstract

Fan‐out wafer‐level packaging (FOWLP) is expected to become the dominating trend in millimeter wave and 5G communication. However, the reliability faces enormous challenges due to the inherent poor adhesion between the insulating layer of polyimide (PI) and copper wirings in FOWLP. Herein, adhesive polyimide (API) with improved adhesion on smooth Cu by the introduction of benzimidazole and siloxane structure is reported. The results prove that the adhesion strength is increased by 191.46% compared with the conventional PI, owing to the generation of Cu complexes by benzimidazole as well as the cooperation of the flexible siloxane segments. Besides, the APIs not only hold a proper coefficient of thermal expansion (CTE) of 6.28 × 10−6 K−1 matching with Si wafers (2.5 × 10−6 K−1), but also possess CTE (18.56 × 10−6 K−1) of API‐3 matching with Cu circuits (17 × 10−6 K−1), so that a low residual stress of −1.849 MPa is obtained. Moreover, superior mechanical, thermal properties are also obtained, of which the modulus and tensile strength are 6.31 GPa and 170 MPa, while Tg and T5% are as high as 474.6 and 524.57 °C, respectively. Therefore, the as‐prepared high‐performance APIs can be prospective candidates in FOWLP for high‐frequency communication.

Progress of research on the bonding-strength improvement of two-layer adhesive-free flexible copper-clad laminates

“…Thus, the peel strength can reach 1.1392 N mm −1 . 101 Fig. 6 shows that stripping occurs inside the molecular chains of the compounds made into membranes, i.e.…”

Design of metalized polyether-ether-ether-ketone based on semi-additive manufacture for 5G applications: from bottom-up assembly to selective electroplating

“…To improve the interface adhesive performance, Zhong et al 16 reported an adhesive polyimide (PI) via the introduction of benzimidazole and siloxane structure adhered with smooth Cu, and the adhesive strength increased by 191.46% in comparison with that of the conventional PI. However, this manufacturing process requires a specific substrate and is not suitable for general substrates.…”

A Novel Hydrophobic Polyimide Film with Sag Structure Derived from Multi‐Hybrid Strategy

“…[13] The intrinsic water contact angle (WCA) of pure PI films is low (≈50°-80°), unable to meet the requirements of hydrophobic properties for IC chip packaging and flexible wearable devices. [14][15][16][17][18][19][20] Therefore, it is necessary and meaningful to improve the hydrophobic properties of PI films from the perspective of intrinsic structure and surface microstructure design while ensuring excellent mechanical properties.…”