Fine metal particles can be formed on Si using electroless displacement deposition, by which Si wafers are simply immersed into a metalsalt solution containing HF. Depending on the kind of metal and the surface conditions of Si substrates, the particle density of the deposited metal varies widely. Especially, the Pt particle density greatly changes according to Si surface conditions. This study investigated the influence of Ar-plasma etching of Si on the Pt particle density. Single-crystalline n-Si(100)wafers were etched by Ar plasma using a radiofrequency glow discharge spectrometer. An amorphous Si layer was formed on etched Si surfaces. By immersing Ar-plasma-etched Si wafers in a H₂PtCl₆ solution containing HF, Pt particles with particle density four hundred times higher than that for non-etched Si wafers were deposited. The Pt particle density was decreased by removing the amorphous layer and by chemical etching of the single-crystalline Si wafer. Results show that the influence of Ar-plasma-etching extended at least 0.5 μm to the interior of single-crystalline Si beneath the amorphous layer.

View full abstract

This study was conducted to improve the corrosion resistance of electroless Au/Ni-P layers used in printed wiring boards(PWB) without degrading solder-ball bondability and wire bondability. We examined self-assembled monolayers(SAM) of n-alkanethiols as corrosion inhibitors. The n-alkanethiol adsorption was evaluated using the contact angle of water. Corrosion resistance was evaluated using the salt spray test. Results show that excellent corrosion resistance was obtained for long carbon chains and high concentration. After heat treatment of an Au/Ni-P substrate on which ODT-SAM had been formed, the Au-plated surface was measured using X-ray photoelectron spectroscopy. The diffusion of Ni was less than that obtained with an Au/Ni-P plated substrate on which ODT-SAM had not been formed. Therefore we infer that ODT-SAM functioned to seal pinholes. Apparently, the corrosion resistance in the salt spray test was improved because ODTSAM inhibits contact between salt water and the Ni-plated film. Furthermore, no deterioration of bondability properties was observed when solder-ball bondability and wire bondability were evaluated for an Au/Ni-P substrate on which ODT-SAM had been formed. Therefore, ODT-SAM is inferred as effective to improve the corrosion resistance of electroless Au/Ni-P layers of PWB.

View full abstract

Pulse plating was used to prepare nickel films from a Watts bath with no additives. The influences of the current pulse electrolysis parameters of duty ratio=0.03-0.33, T_on=0.1-5 ms, and I_av=2-10Adm^-2, on the hardness, texture, and crystal orientation were investigated. Those characteristics were studied respectively using a nano-indenter hardness tester, scanning electron microscopy, and XRD. Results showed the importance of I_av for obtaining high-hardness films. The highest value of hardness was 4.5 GPa at T_on=1 ms, duty ratio=0.1, and I_av=10 Adm^-2. Hardness is related closely to the texture. A Hall-Petch relation was observed between the hardness and grain size. The preferred orientation changed to the(311)→(220)→(200)plane with increase of the duty ratio when the pulse parameters were T_on=1 ms and I_av=5Adm^-2.

View full abstract