Injection molding of liquid crystal polymer on Al plate with anodic aluminum oxide structure for heterogeneous bonding

In recent years, 3C (Computer, Communication and Consumer Electronics) electronic products have gained market demands rapidly and these products need to have high heat-dissipating function. The general heat-dissipating components are usually bonded to the polymer components by gluing, cladding or riveting, however, these methods are prone to assembly cost and also aging damage due to changes in environment or long-term application. This study aims to develop a new heterogeneous bonding method to solve such problems of the traditional bonding. Experimentally, executing anodic aluminum oxide (AAO) process on the surface of aluminum (Al) plate could produce porous sub-micron structures. Heterogeneous bonding specimen with the AAO structure is made by insert injection-molding (IIM) process. After IM, applying mechanical adhesion test into the AAO structure has been performed for verification of the heterogeneous bonding of Al plate and polymer. Result confirms the presences of the heterogeneous bonding component. The AAO process of this study is the secondary forming method in which the porous structures are evenly distributed and can extend the diameter from 100 nm to 120 nm. The contact angle measurements carried out on the surface of AAO structure shows that AAO structure could reduce the contact angle of the droplet. Namely, the super-hydrophilic and higher surface energy state are achieved. After the AAO process has been executed, the Al plate with the AAO structure is put into the injection-molding machine as part of insert. The mold is filled with the liquid crystal polymer (LCP). Finally, the tensile tests have been carried out to find the bond strength (BS). Accordingly, the BS of the Al plate without the AAO structure and with the AAO structure was about 35.4 MPa, and 63.0 MPa respectively. It is found that the Al plate filled with the LCP can enhance the BS by the AAO structure. This study can be further applied to the application of heat-dissipating components by the heterogeneous bonding method.