Grinding is a process for making board-shaped workpieces thin (approx. less than 1 mm thick) and flat by using a grinding wheel.
The grinding wheel is an abrasive which uses synthetic diamond. Wheel segments (thickness: several millimeters, height: 3 – 5 mm) are arranged along a ring-shaped wheel base. There are various types of grinding wheels which adopt different abrasive sizes, bond materials, segment thicknesses, etc.
The grinding wheel is attached to the processing axis so that it is parallel to the chuck table surface. It is pressed against the workpiece while rotating at a high speed in order to make the workpiece thin and flat. The grinding wheel has a diameter equal or larger than the workpiece, and the wheel is positioned so that half is overlapping the workpiece. Both the grinding wheel and chuck table are rotated during the process (infeed grinding).
During the grinding process, water (deionized water or city water) is supplied in order to cool the processing point and remove swarf. The chuck table is a slightly conical shape so that the contact between the workpiece and grinding wheel is only half of a circle throughout the process. Saw marks can be observed on the ground surface, and the surface roughness depends on the grit size of the grinding wheel.
The wafers are ground on the backside of the semiconductor circuit pattern, hence the name “back grinding” (BG) for this process. When processing down to a thickness of several hundred microns, more than 100 μm thick, the risk of wafer breakage is not so high. However, at a thickness of less than 100 μm, the risk of wafer breakage is high, so solutions such as modifying the substrate transfer method within the processing equipment and careful selection of the type of grinding wheel are essential to thinning.
Fully-automatic equipment for grinding wheels
Semi-automatic equipment for grinding wheels
The grinders currently available have various automatic functions. In particular, the machines are equipped with wafer handling, thickness measurement, and cleaning functions so that the machine can process the workpieces as a cassette. The optional thin wafer handling specification is necessary for the processing of thin wafers.
With this type of equipment, loading/unloading of the workpiece and cleaning are performed manually. A thickness measurement function within the machine can be additionally installed upon request.
・Grinding/thinning of semiconductor wafers
・Grinding/thinning of semiconductor packages
・Grinding/thinning of devices for electric components and optical components