| Summary: | 博士 === 國立交通大學 === 材料科學與工程系 === 87 === A series of fully aromatic thermoplastic polyimides(TPI) films were prepared with various of aromatic diamine monomers and dianhydride monomers. The relations between the critical surface tension(gc) , glass transition temperature (Tg), thermal properties, adhesive strength and the molecular structure of the TPI were investigated. It is found that the gc of TPI and the peel strength between the TPI film and alloy-42 plate are higher, and the Tg is lower when the amine groups are situated in the meta position as opposed to the para position. As ether linkage is introduced in dianhydride and diamine, the peel strength between the TPI and alloy-42 plate can be improved . The peel strength of 3,3￠,4,4￠-benzophenone tetracarboxylic dianhydride(BTDA)/1,3-bis(3-aminophenoxy)benzene(m-BAPB), ODPA/
2,2￠-bis (4-[3-aminophenoxy]phenyl)sulfone(m-BAPS), and 4,4￠-oxydiph- thalic anhydride(ODPA)/m-BAPB, is10.5, 12.2, and 13.2 N/cm respectively, which is higher than the requirement of adhesive strength,10 N/cm, between the adhesive tape and leadframe(metal) in integrated circuit(IC) package.
Siloxane modified polyimides, called poly(imide siloxane)s,(PISs), were also prepared. The dependence of morphology of the (PISs) on the solubility parameter of unmodified polyimides and the molecular weight and content of a,w-bis(3-aminopropyl)polydimethylsiloxane (APPS) has been studied. The effect of the morphology on the mechanical properties is also under investigation. The domain formation in the PISs with the APPS molecular weight Mn = 507 g/mole is not found until the mole ratio of APPS/PIS 3 0.5% in the pyromellitic dianhydride / p-phenylene diamine (PMDA/p-PDA) based PISs and at mole ratio 3 2.7% in the BTDA/m-BAPS based PISs. As the APPS Mn = 715 g/mole, the critical APPS concentrations of the domain formation in both types of PISs are equal to 0.1% and 1.1%, respectively. The critical concentration is equal to 0.6% in the BTDA/m-BAPS based PIS film with the APPS Mn = 996 g/mole. The isolated siloxane-rich phase in the BTDA/m-BAPS based PISs becomes a continuous phase as the mole ratio of APPS/PIS 3 7.7%, 10.0% and 16.6% as the APPS Mn = 996 g/mole, 715 g/mole, and 507 g/mole, respectively.
The effect of surface characteristics and morphology of the PIS film on the true interfacial adhesion between the PIS film and alloy-42 substrate has been studied. The effect of viscosity of PIS film and the surface treatment of UV/ozone ( UV/O3 ) on alloy-42 plates on the peel strength of PIS films/alloy-42 joints is also investigated. The gc of the PIS film decreases with the content and the molecular weight of APPS. The BTDA/m-BAPS based PIS films with the APPS molecular weight Mn = 996 g/mole (PIS9Siy) show two phases in all compositions and linear dependence of the gc on the surface concentration of silicon, [Sisurf], on the PIS films. The PIS film with the APPS Mn = 507 g/mole (PIS5Siy) or Mn = 715g/mole (PIS7Siy) exhibit the morphology change from homogeneous phase to inhomogeneous phase starting at the mole ratio ( y ) of APPS/PIS = 2.7% and 1.1%, respectively. The curves of gc dependence on the [Sisurf] discontinue or deflect at these two compositions respectively. The treatment of UV/O3 on alloy-42 plates improves the wetting on the alloy surface and promotes the peel strength between the PIS films and alloy-42 plates by a magnitude of 3 20%. It shows that the flowability of the same PIS films bonding at different temperatures significantly affects the bonding strength of the joints, but the flowability of different PIS films bonding at the same temperature, e.g. 400℃, is not the key factor governing the bonding strength of the joints. The true interfacial adhesion of the PIS5Si0.6/alloy-42 joint is of 80% higher than that of the unmodified BTDA/m-BAPS based polyimide film/alloy-42 joint. However, zero true interfacial adhesion is obtained between the PIS9Siy films and alloy-42 plates. The wetting kinetics study shows that the higher the siloxane content in the PIS, the higher the activation energy for the adhesive bonding process. And the phase separation significantly increases the activation energy. The scanning electron micrographs of the peeled-off PIS film surfaces from the PIS/alloy-42 joints reveal the rougher surface morphology from the sample with a higher interfacial adhesion.
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