NEW DIAMOND GRINDING WHEELS WITH ELECTRICALLY CONDUCTIVE CUTTING EDGES
The application of an electrically conductive diamond material to a new type of grinding wheel whose cutting edges possess electrical conductivity has been tried in this research work. Firstly, electrical discharge machining is applied on a solid surface of an electrically conductive CVD diamond film to create protrusions like cutting edges. Secondly, it is confirmed that the EDMed surface of the diamond material has an ability of stock removing when used in the form of a small lapping wheel. Thirdly, two different types of grinding wheels for micro grinding, i.e. i) a V-shaped profile wheel and ii) a micro mounted wheel, have been manufactured. And it is found that very fine V-shaped grooves can be made on a cemented carbide workpiece by using those wheels with very small wheel wear.
Improvement of precision grinding performance of CVD diamond wheels by micro-structured surfaces
Abstract Chemical vapor deposition (CVD) diamond grinding wheels are used in precision and ultra-precision grinding owing to the high grain density, uniform dispersion of abrasives, and excellent wear resistance. However, the small chip space on the CVD diamond abrasive surface easily interrupts the grinding, which limits the practical applications of these wheels. In this paper, a novel micro-structured CVD diamond wheel was presented for precision grinding of optical glass, to improve the grinding performance. First, continuous and clear micro grooves of 4–6 µm width and 8 µm depth were ablated on the surface of a CVD diamond by a pulsed laser. Different from the conventional structured wheels, the grain size of the CVD diamond was refined from 10 to 20 µm to 5–15 µm by laser micro-structuring. Second, the effect of the micro-structures on the grinding force, force ratio, and ground quality were investigated for optical glass. The normal forces decreased by 48–65%, whereas the tangential force dropped by 25–54%. The normal-to-tangential grinding ratio also clearly reduced owing to the increasing abrasive edges and change in the rake angle of most grains. The measurement results of the ground surface showed that roughness R a decreased by 5–20% and subsurface damage depth reduced by approximately 25%. In addition, the wear morphology exhibited that abrasion flattening occurred not only on the CVD diamond grain tips but also on the side edges of the micro grooves. This implied that the micro-structures effectively participated in the grinding process, and thus, resulted in an increase in the grain density and enhancement of the cutting effort.
Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review
Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.