Jungihl Kim

Adhesion and interface studies between copper and polyimide

The adhesion and interface structure between copper and polyimide have been studied. Polyimide films were prepared by spinning a polyamic acid solution (Du Pont PMDA-ODA) in an NMP solvent onto a Cu foil, followed by thermal curing up to 400°C. The adhesion strength was measured by a 90° peel test. The peel strength of 25 μm thick Cu foil to 25 μm thick polyimide substrate was about 73 g/mm with the peel strength decreasing with increasing polyimide thickness. Cross-sectional TEM observation revealed very fine Cu-rich particles distributed in the polyimide. Particles were not found closer than 80-200 nm from Cu boundary. These Cu-rich particles were formed as a result of reaction of polyamic acid with Cu during thermal curing. We attribute the high peel strength to interfacial chemical bonding between Cu and polyimide. This behavior is in contrast to vacuum-deposited Cu onto fully cured polyimide.

Adhesion and interface investigation of polyimide on metals

The interface and adhesion of PMDA-ODA and PAA-ethyl ester polyimides to several metals including Cr, Ni, Cu, and Au have been studied by transmission electron microscopy (TEM) and a 90° peel test. The adhesion strength of polyimide on metals is generally very high compared with that of metals on polyimide. The trend in both cases is the same, i.e., Cr has the highest adhesion strength followed by Ni, Cu, and Au. Cross-sectional TEM studies showed that very fine particles were precipitated in the polyimide near the interface in the case of polyimide on Cu (or Ni). The precipitates were not found closer than 80-200 nm from the polyimide/Cu (or Ni) interface. Some large particles were identified as Cu2O (NiO in the case of polyimide/Ni) by scanning transmission electron microscopy and microdiffraction analyses. The formation of these particles was ascribed to a process involving first the reaction of polyamic acid with Cu (or Ni) to form a polyamic acid complex. During subsequent thermal curing, the complex...

Adhesion, Reaction and Stability of Metal/Polyimide Interfaces

Interfacial reactions of polyimide with several metals have been investigated by XPS and TEM to determine their effects on adhesion and long term stability. It has been found that the polyimide-on-metal interface and the metal-on-polyimide interface are intrinsically different; in the case of PI-on-metal interface, the precursor of polyimide, polyamic acid, reacts with the metal resulting in a strong chemical bond and therefore, higher adhesion strength than the corresponding metal-on-PI interface. Both interfaces are found susceptible to T/H environment, resulting in significant adhesion loss. The mechanical and electrical properties of polyimide may be altered as a result of the interaction with metals and therefore, great care is necessary to insure a stable interface and the reliability of devices.

Residual carbon detection in ceramic substrates by a nuclear reaction technique

Abstract In high-performance microelectronic packaging technology, multilayer ceramic substrates are used as multiple chip carriers by most of the mainframe computer manufacturers. Depending on the processing steps employed in the technology, varying amounts of carbon may be left in the substrates, which can adversely affect their electrical and mechanical properties, even at parts-per-million (ppm) levels. Of various methods capable of detecting trace carbon in ceramic materials, we investigated the technique based on a nuclear reaction, namely, the (d, p) reaction for 12 C.