BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a processing apparatus including a chuck table for holding a workpiece and processing means for processing the workpiece held on the chuck table.

Description of the Related Art

A plurality of devices such as integrated circuits (ICs) and large-scale integrations (LSIs) are formed on the front side of a wafer so as to be separated from each other by a plurality of division lines. The back side of the wafer thus having the devices on the front side is ground by a grinding apparatus to thereby reduce the thickness of the wafer to a predetermined thickness. Thereafter, the wafer is divided into individual device chips by a dicing apparatus. The device chips thus obtained are used in electrical equipment such as mobile phones and personal computers. The grinding apparatus is composed generally of a chuck table for holding a wafer and grinding means having a rotatable grinding wheel (tool) for grinding the wafer held on the chuck table, whereby the wafer can be thinned to a desired thickness (see Japanese Patent Laid-open No. 2010-052057, for example).

The dicing apparatus is composed generally of a chuck table for holding a wafer and cutting means having a rotatable cutting blade (tool) for cutting the wafer held on the chuck table, whereby the wafer can be divided into individual device chips with high accuracy (see Japanese Patent Laid-open No. 2010-173002, for example).

SUMMARY OF THE INVENTION

Each of the grinding means and the cutting means includes a spindle for mounting the tool and an air bearing adapted to be supplied with high-pressure air, thereby supporting the spindle in a noncontact condition. That is, the spindle is rotatably supported by the air bearing in the condition where frictional resistance is almost zero, so that vibrations are suppressed to allow high-precision grinding and cutting. However, in the case that external dust, water, etc. may enter an air supply passage for supplying the high-pressure air to the air bearing or an air discharge passage for discharging the air from the air bearing or in the case that the air supply passage or the air discharge passage may be clogged with foreign matter such as water generated due to a change in pressure or temperature, the high-pressure air cannot be sufficiently supplied to the air bearing. As a result, the noncontact condition of the spindle cannot be maintained to cause the occurrence of galling in the air bearing, so that there is a possibility of damage to the grinding means and the cutting means. Further, also in the case that air leakage has occurred in the air supply passage or the air discharge passage, a similar problem is caused.

It is therefore an object of the present invention to provide a processing apparatus which can prevent the occurrence of galling in an air bearing for supporting a processing tool.

In accordance with an aspect of the present invention, there is provided a processing apparatus including a chuck table for holding a workpiece and processing means for processing the workpiece held on the chuck table. The processing means includes a spindle; a spindle housing for rotatably supporting the spindle, the spindle housing having an air supply passage, an air supply port connected to the air supply passage, an air discharge passage, and an air discharge port connected to the air discharge passage; an air bearing defined between the spindle and the spindle housing, the air bearing communicating with the air supply passage and the air discharge passage to support the spindle by using high-pressure air; a tool mounted on the front end of the spindle; a high-pressure air source for supplying the high-pressure air; an air supply line for connecting the high-pressure air source to the air supply port; a pressure gauge provided on the air supply line for detecting the pressure of the high-pressure air in the air supply line; and a flowmeter provided on the air supply line for detecting the flow rate of the high-pressure air in the air supply line. A first allowable value is previously set for the pressure to be detected by the pressure gauge, and a second allowable value is previously set for the flow rate to be detected by the flowmeter.

Preferably, when the pressure detected by the pressure gauge has deviated from the first allowable value or the flow rate detected by the flowmeter has deviated from the second allowable value, a warning is given to an operator. In particular, when the pressure detected by the pressure gauge is maintained at the first allowable value and the flow rate detected by the flowmeter has become less than the second allowable value, abnormality that the air supply passage or the air discharge passage has been clogged with foreign matter is informed as the warning. Further, when the pressure detected by the pressure gauge is maintained at the first allowable value and the flow rate detected by the flowmeter has become greater than the second allowable value, abnormality that air leakage has occurred in the air supply passage or the air discharge passage is informed as the warning.

According to the present invention, the air to be supplied from the air source to the air bearing is managed not only according to the pressure detected by the pressure gauge, but also according to the flow rate detected by the flowmeter. Accordingly, in the event that the pressure of the air to be supplied to the air bearing is maintained at a desired pressure, but the flow rate of the air to be supplied to the air bearing is insufficient because the air supply passage or the air discharge passage is clogged with foreign matter such as water, possible galling in the air bearing can be predicted to thereby prevent damage to the processing means having the air bearing, such as grinding means and cutting means.

Further, when the pressure detected by the pressure gauge has deviated from the first allowable value or the flow rate detected by the flowmeter has deviated from the second allowable value, a warning is given to an operator. In particular, when the pressure detected by the pressure gauge is maintained at the first allowable value and the flow rate detected by the flowmeter has become less than the second allowable value, it is determined that the air supply passage or the air discharge passage has been clogged with foreign matter, and this abnormality is informed as the warning. As another case, when the pressure detected by the pressure gauge is maintained at the first allowable value and the flow rate detected by the flowmeter has become greater than the second allowable value, it is determined that air leakage has occurred in the air supply passage or the air discharge passage, and this abnormality is informed as the warning.

The above and other objects, features and advantages of the present invention and the manner of realizing them will become more apparent, and the invention itself will best be understood from a study of the following description and appended claims with reference to the attached drawings showing some preferred embodiments of the invention.

