Attention has been given to magnetic grinding as a replacement technology for the mask process used for solder printing. The stainless steel mask used for the process is drilled using a laser, causing a deficiency of the printed solder if a trace of the laser is left on the hole's sidewall. Conventional methods to eliminate the laser trace are buff abrasion and electrolytic machining. However, electrolytic machining presents the problem of damage to the mask surface. In contrast, laser drilled mask processing using magnetic abrasion has the merit that partial repair is possible. By polishing the mask using a magnetic abrasive, KMX, the laser trace was nearly eliminated and the sidewall surface became smooth.

View full abstract

Adhesion of DLC/CrN multilayered coatings onto stainless steel was evaluated using three adhesion tests: the scratch test, HRC indentation test, and microindentation test. In the DLC/10 μmt-CrN/SUS304 sample, the critical load (L_c) by scratch test improved to 28 N. In a SUS304 substrate reinforced by sulphonitriding, it improved to 52 N.
The HRC indentation test revealed cracks and delamination of the DLC coating around the indentation hole. The force-depth (P−h) curves in the microindentation test showed a few discontinuous behaviors (pop-in) accompanying DLC delaminations. Cross-sectional images under the dent were obtained using FIB observation, showing that pop-ins occurred at the interface between DLC and the Cr-C gradient layer. In the DLC/2 μmt-CrN/SUS304 sample, no delamination of DLC was observed in the microindentation test, although DLC varied with plastic deformations of SUS304 substrate in the microindentation test, and DLC delaminations were observed at the DLC − Cr-C interface.

View full abstract

Supercritical fluids are high-pressure media possessing both high diffusivity and solvent capability. Metal thin films can be deposited in supercritical fluids from an organometallic compound (precursor) through thermochemical reactions. In this study, copper thin films were deposited in silicon microholes of 10 μm diameter and 350 μm depth to the fabricate through-silicon vias (TSVs) used in three-dimensional silicon integrated circuits. The fabrication temperatures and pressures were varied respectively within 180−280°C and 1−20 MPa, respectively. The maximum coating depth decreased with deposition temperature, although a peak maximum of the depth was observed at around 10 MPa. The dependence of temperature and pressure on the coating depth was discussed using a Thiele model, which describes the balance between diffusive transport and consumption of the precursor. The model results and experimental results showed good agreement. Diffusion constants of the precursor in the silicon microholes were estimated from the observed maximum coating depths.

View full abstract