Electroless copper deposition has been widely used in the manufacture of printed circuit boards with plated through-holes. Intrinsic contaminants originating from the mixed PdCl₂/SnCl₂ catalyst may be present in the plating bath. In this study, the effects of Pd²⁺ and Sn⁴⁺ ions on the rate of copper deposition and the mechanical properties of the copper films were investigated. An excess of PdCl₂ makes the bath unstable, leading to a reduction in the apparent deposition rate, but the appropriate amount of Pd²⁺ ions not only decreases lattice strain but also improves the elongation of the copper films. In the presence of both Pd²⁺ and Sn⁴⁺ ions, internal stress in the copper films was reduced, and the elongation of copper films was significantly improved by synergism between the two different ion species. Electrochemical analysis of electroless copper deposition elucidates that the presence of Pd²⁺ and Sn⁴⁺ ions not only decreases the amount of the methylene glycol anion adsorbed on the electrode surface but also prevents the inclusion of hydrogen into electroless copper films.

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Electroless nickel plating on aluminum substrates utilizing a nickel displacement process has been investigated.
A zincate process is in general use before electroless nickel plating on aluminum substrates. It has been confirmed, however, that the film of deposited nickel exhibits higher adhesion strength if a nickel displacement process is used instead of the zincate process, and that adhesion strength depends on the rate of the displacement reaction, which can be controlled by changing the kind of complexing agent and the plating conditions in the displacement bath.
In addition, fine bumps are required in the TAB or flip chip bonding methods and straight-walled bumps approximately 20μm wide and 15μm high can be formed by electroless nickel deposition utilizing the displacement process.

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The electrical contact properties of electroless deposits of Ni-Cu-P alloy containing metallic copper of low electrical resistance, and of Ni-Sn-P alloy containing metallic tin, which had aroused interest in the electrical resistance of its oxides, were investigated. The wear resistance of the deposits was also investigated using reed awitches.

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Mechanical rubbing of polyimide (PI) films is used to homogeneously align liquid crystal molecules on the surface. The chemical structure of aromatic PI surfaces subjected to rubbing has been analyzed by X-ray photoelectron spectroscopy, and the frictional charging and surface states of the PI films have also been investigated by measurements of surface potential (SP) and photoelectric emission (PE). Six kinds of PI films were prepared by reacting two diamines containing CH₃ and CF₃ functional groups with three tetracarboxylic dianhydrides. Rubbing of the films caused the O content to increase, while the N and F contents decreased. The fraction of the two oxygen components (-O- and C=O) of the films was changed by the rubbing. The films with CF₃ groups exhibited much more negative charging (negative SP) than those with CH₃ groups. It is suggested that the order of the charging of the films with CF₃ and CH₃ groups closely depends on the ratio by which the F and N elements, respectively, were reduced by the rubbing. Both with and without rubbing, the films with CH₂ groups gave a considerably larger PE level than those with CF₃ groups. This suggests that the electron trap levels responsible for the negative charging in the latter films make virtually no contribution to PE.

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