Demand for mechanical solderless chip connection methods using anisotropic conductive particles has increased in the field of electronic devises. In this study, the preparation of conductive resin particles (5 to 10μm in diameter) by electroless nickel plating and the surface morphology of nickel film were investigated. Since the surface area of particles are much larger than in a bulk substrate, a batch-type electroless plating bath is unstable. Therefore, we applied the continuous dropping method to improve the stability of the Electroless nickel plating. The surface morphology of the deposited nickel was greatly influenced by the complexing agent used, the bath temperatrue and solution pH. Uniform deposits on the particles were obtained at pH 5 by using ammonium acetate as the complexing agent. In contrast, extraneous deposits were recognized at pH 5 when using sodium tartrate as the complexing agent and in baths at pH6. This extraneous deposition could be decreased by lowering the bath temperature.
Electroless copper plating has been used in through hole and via hole plating on printed wiring boards. Build up has become an important production technique in preparing printed circuit boards as via holes have become more dense and miniaturized. Electroless Cu plating solution transportation and circulation in via holes become increasing difficult as holes have become smaller. Via hole deposition uniformity is decreased and electrical reliability between each layers deteriorates greatly. Accordingly, the uniformity of electroless copper plating was investigated using circuit boards contain via holes 20-200μm in diameter and 30-230μm deep. Uniform deposits are obtained by selecting parameters related to required deposition characteristics. Via filling using electroless Cu plating is also discussed.
The effect of Ti film inserted as an adhesion promoting layer in a Cu/Ti/TiN structure was studied. A Ti film 15nm thick clearly promoted adhesion, to a level four times that of a Cu/TiN structure, but the effect of a Ti film 80nm in thickness was not clear. The difference in effectiveness appears to be related to the structure of the Ti. The hydrogen included in the annealing atmosphere was occluded in the 80nm Ti, leading it to change to Ti hydride; TiH1.924. Ti hydride is known to be a brittle material. Even though it includes hydrogen, however, the 15nm Ti film does not change to Ti hydride and has a fcc structure, according to the results of high resolution TEM and electron diffraction. The 15nm thick Ti is thought to have an extremely strong effect as an adhesion layer, because Ti hydride is not generated in the Ti film.
A series of chromium nitride coatings with different nitrogen contents were deposited on Ti-6Al-4V substrate by the arc ion plating method using a Cr target and nitrogen as the reactive gas. At nitrogen pressures below 027Pa, the deposited coatings contained 20 to 27 at% nitrogen and mainly consisted of the Cr2N phase. Above this pressure, coatings contained more than 35 at% nitrogen and consisted of the CrN single phase. The dissolution rate of the Cr-N coating in pure molten aluminum was drastically decreased above a nitrogen content of about 35 at%, which corresponds to the transition point from Cr2N to CrN. In TEM observation, it was found that a thin (∼50nm) reactive layer confirmed to be as wruzite type AlN formed in the interface between the CrN and Al after Al immersion. It was concluded that this AlN acts as a protective layer for the molten aluminum. In heat cycle testing, formation of heat cracks was significantly suppressed when deposited on Ti-6Al-4V in comparison to deposition on conventional tool steel. This behavior agrees with the results of thermal stress calculations for both substrates.
Electrodeposition of Nb-Sn alloy from ambient temperature molten salt electrolytes, i.e., an SnCl2-NbCl5-BPC (1-butylpyridinium chloride) system and an Sn-NbCl5-BPC system, by pulse electrolysis was investigated. The Nb content in the Nb-Sn electrodeposit was effected by the pulse period, current density, and duty ratio. Decreasing the duty ratio and increasing the current density increased the Nb content in the Nb-Sn alloy deposited from a 28.6mol%SnCl2-14.3mol%NbCl5-57.1mol%BPC bath. An Nb-Sn alloy containing 44.3wt% Nb was obtained from this bath at 60mA·cm-2, T=50ms, and a duty ratio of 0.2, An Nb-Sn alloy containing 41.3wt% Nb was deposited from a 7.7mol%Sn-15.4mol%NbCl5-76.9mol%BPC bath at 60mA·cm-2, T=10ms, and a duty ratio of 0.2.
The lightly tin coated steel (LTS) developed for welded cans is widely used. The composition of the chromate film during passivation treatment is the key to achieve both good lacquer adhesion and weldability. XPS analysis applied to the lacquer fractured interface and the LTS surface under various passivation treatments showed that lacquer fracture is caused cohesive failure in the thick tin oxide that grows during lacquer curing baking treatment or during storage. The metallic chromium content, in the passivation film was also found to play an important role in suppressing the growth of tin oxide and to ensuring good lacquer adhesion.
We investigated the 200°C annealing effect on high-resistivity electroless NiPC film containing 2.8at% carbon. In the step stress test for thermal stability, Film B of NiPC annealed at 200°C was 1, 280μΩcm, and showed almost no change in resistance even at low annealing temperature.