Electroless thin film nickel / gold plating processes have been applied to fine copper pattern surfaces. Generally, a palladium catalyst treatment is used as a pretreatment of electroless nickel plating. As described in earlier reports, using an electroless nickel strike plating solution without palladium catalyst improved the solder ball shear properties. Complexing agent selection of nickel strike plating solution was examined in this study to improve solder ball shear properties because the nickel complexing agent in the electroless nickel strike plating solution influences them. Results show that complexing agents with high chelating activity for nickel ions such as citric acid exhibit excellent solder ball shear properties.
Atmospheric pressure plasma treatment and surface graft polymerization were applied to a polytetrafluoroethylene（PTFE）sheet to improve adhesion strength between the PTFE sheet and electroless-plated Cu film. The surface temperature of the PTFE sheet during plasma treatment was adjusted via applied radio-frequency（RF）power for plasma treatment. For applied RF power at 25 W, the maximum surface temperature was ca. 100 ℃. For applied RF power at 65 W, the maximum surface temperature was ca. 280 ℃, which is designated as “heat-assisted plasma treatment”. The adhesion strength between the plasma-treated PTFE sheet and electroless-plated Cu film was measured using a 90 degree peel test. The average adhesion strength of the plasma-treated PTFE at 25 W was 0.6 N/mm. In contrast, the adhesion strength of the plasma-treated PTFE at 65 W was 1.9 N/mm. This value was much higher than the target value（0.65 N/mm）for printed circuit boards. Heat-assisted plasma treatment drastically improved the adhesion properties of PTFE.
When coated steel sheets are used as a chassis for electrical equipment, electromagnetic waves are thought to propagate through the space formed by a lid and a flange. This study was designed to clarify characteristics of coated steel sheets that can affect electromagnetic shielding properties at locations where steel sheets overlap. The influence of resin coating weights of the steel sheets on the electromagnetic shielding property was examined. This study also examined the influence of steel sheet surface profiles on the electromagnetic shielding property. For this study, resin was coated on the steel sheets which have the same interval between peaks of a waviness curve, the arithmetic average roughness Ra and the different interval between peaks of a roughness curve（PPI）. For greater resin coating weights on the steel sheets, the electromagnetic shielding property was lower at the same steel sheet surface profile. However, with higher PPI on the steel sheet surface, the electromagnetic shielding property was enhanced at the same coating weight. The electromagnetic shielding mechanism of the coated steel sheets was discussed based on these results.