Cutting tool angle adjustment method

A cutting tool adjustment method includes lowering a cutting tool on a transparent Mylar to produce an indentation before an actual scribing operation; picking up the image of the indentation; using a numerical analysis method and a set formula to automatically calculate a correction angle and position so as to adjust the angle and position of the cutting tool subject to the calculation result; and repeating the calculation and adjustment procedures, if necessary.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cutting tool angle adjustment method and more particularly, to such an efficient cutting tool angle adjustment method practical for use to adjust the angle and position of the cutting tool of a fragile material scriber/breaker.

2. Description of Related Art

In a fragile material scriber/breaker, for example, wafer scriber, a cutting tool (for example, diamond cutter) is used for scribing wafers. This cutting tool has a cutting edge. During scribing operation, the cutting edge is lowered and pressed on the wafer.

Further, the cutting edge of the cutting tool must be adjusted to the desired angle and position before scribing, so that a good cutting indentation can be achieved (seeFIG. 8E). Without proper adjustment before scribing, the cutting indentation thus produced may have an angle of deviation or uneven width (seeFIGS. 8A through 8D). Therefore, the operator must adjust the angle and position of the cutting edge of the cutting tool before scribing.

Conventionally, the operator adjusts the angle and position of the cutting edge of the cutting tool of a wafer scriber/breaker subject to his (her) experience and skill. This conventional adjustment method wastes much time and may produce an error, thereby affecting the productivity of the wafer scriber/breaker.

Therefore, it is desirable to provide a cutting tool angle adjustment method that eliminates the aforesaid drawbacks.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a cutting tool angle adjustment method, which accurately adjusts the angle and position of the cutting tool with saves much adjusting time, thereby improving the productivity.

To achieve this and other objects of the present invention the cutting tool angle adjustment method includes the steps of:

(a) providing a transparent Mylar and suspending a cutting tool above the transparent Mylar, the cutting tool having a center axis, a transverse axis, and a cutting edge, the cutting tool having a predetermined specification;

(b) lowering the cutting tool vertically to the transparent Mylar to make an indentation on a top surface of the transparent Mylar by the cutting edge of the cutting tool;

(c) picking up the image of the indentation on the top surface of the transparent Mylar;

(d) digitalizing the image of the indentation into an image range of n*m pixels, and then figuring out a top edge proximity line and a bottom edge proximity line of the image of the indentation by means of a numerical analysis method;

(e) calculating a top angle of deviation θ1between the top edge proximity line and a reference line, and a bottom angle of deviation θ2between the bottom edge proximity line and the reference line; and

(f) calculating a angle of correction θTof the transverse axis and a angle of correction θAof the center axis subject to the formulas of:
θT=f1(θ1−θ2), and
θA=f2(θ1+θ2),

in which f1and f2are correction parameters corresponding to the predetermined specification of the cutting tool.

In general, the present invention is to have the cutting tool be lowered and pressed on a transparent Mylar to produce an indentation before actual operation (scribing), and then to pick up the image of the indentation, and then to use a numerical analysis method and the set formula to automatically calculate the correction angle and position and to adjust the angle and position of the cutting tool subject to the calculation result, and then to repeat the calculation and adjustment procedure if necessary. Thus, the cutting tool and its cutting edge can be accurately adjusted to the correct angle and position to obtain a precise indentation. Further, by means of automatic adjustment of the cutting tool, the present invention saves much adjusting time, thereby improving the productivity.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1is a schematic view showing the structure of a scriber according to the present invention.FIG. 2is a schematic view showing the relationship between the cutting tool and the Mylar according to the present invention.FIG. 3is a flow chart of the present invention. As shown inFIG. 1FIG. 3, a scriber9is shown and which is provided with a transparent Mylar1, a cutting tool2, and an image pickup device4. The cutting tool2is suspended above the Mylar1, having a center axis (A-axis) and a transverse axis (T-axis). According to this embodiment, the image pickup device4uses a CCD (charge-coupled device) to pick up images, and the cutting tool2is a diamond cutter having a predetermined specification (step SA).

Referring toFIG. 4andFIG. 1˜FIG.3again, after installation of the transparent Mylar1and the cutting tool2, the cutting tool2is lowered vertically to make an indentation3on the top surface11of the transparent Mylar1by the cutting edge21of the cutting tool2(step SB). Because the cutting tool2is not held in the correct angle and position before adjustment, the indentation3may show any of a variety of uneven patterns. For example,FIG. 8AthroughFIG. 8Dshow four different, non-horizontal, uneven indentations produced due to biasing of the cutting tool2. In actual practice of the cutting tool2, it is expected to produce a horizontal, even indentation as shown inFIG. 8E. Thus, when driving the cutting tool2to make an operation, for example, scribing work, a horizontal, even, and accurate scribing line can be achieved.

Referring toFIG. 1˜FIG.4again, after formation of an indentation3on the top surface11of the transparent Mylar1by the cutting edge21of the cutting tool2, the CCD of the image pickup device4is driven to pick up the image30of the indentation3on the top surface11of the transparent Mylar1(step SC). Thereafter, as shown inFIG. 4, the image30of the indentation3is processed into an image range of n*m pixels through a digitalization process, and then the top edge proximity line31and the bottom edge proximity line32of the image30of the indentation3within the image range are calculated through a numerical analysis method (step SD).

During the aforesaid calculation process, a conventional image analysis software is used to automatically digitalize the image30of the indentation3into an image range of n*m pixels. Within this image range, the value for the pixel in each block is determined subject to the status whether it is filled with the image30of the indentation3or not, i.e., the value for the pixel in a block filled with the image30of the indentation3is set to be zero; on the contrary, the value is set subject to the relationship between the proximity line selected during calculation and the image30of the indentation3.

In more detail, there are total 2*n*m proximity lines been figured out within the aforesaid image range of n*m pixels, i.e., total *n*m proximity lines will be figured out when calculating the top edge proximity line31, and total *n*m proximity lines will also be figured out when calculating the bottom edge proximity line32. For example, when one proximity line301of the total *n*m proximity lines is figured out during calculation of the top edge proximity line31, it shows an unequal space between the proximity line301and the image30of the indentation3. For example, there are two blank pixel blocks between the proximity line301and the image30of the indentation3in the left end, and the values for these two blank pixel blocks are set to be 1 and 2 respectively, and thereafter the pixel block value is set to be zero when touching the image30of the indentation3. Further, there is one blank pixel block between the proximity line301and the image30of the indentation3at the second row from the left end of the proximity line301and thereafter the proximity line301touches the image30of the indentation3, therefore the values for these two pixel blocks are set to be 1 and 0 respectively. And so on, use least square difference method of numerical analysis method to calculate the sum of the values of all pixel blocks of the proximity line301after the values having been respectively squared, and the value of the proximity line301is thus obtained. In the same way, calculate the values of proximity lines302,303,304, . . . in proper order. After the values for all *n*m proximity lines have been figured out, compare the values to find the proximity line having the lowest value, which is the one in most proximity to and conformity with the top border of the image30of the indentation3and recognized to be the top edge proximity line31of the image30of the indentation3. The calculation of the bottom edge proximity line32is same as the calculation of the top edge proximity line31. When there are two proximity lines having the same smallest value after calculation, the first one is recognized to be the top edge proximity line (or bottom edge proximity line).

Referring toFIG. 1˜FIG.5again, after calculation of the top edge proximity line31and the bottom edge proximity line32through the aforesaid numerical analysis method, the top angle of deviation θ1between the top edge proximity line31and a reference line and the bottom angle of deviation θ2between the bottom edge proximity line32and the same reference line can then be figured out by means of triangle function (step SE). As illustrated in the coordinates inFIG. 5, the top angle of deviation θ1and the bottom angle of deviation θ2show a positive value and a negative value respectively.

After having obtained the top angle of deviation θ1between the top edge proximity line31and the reference line and the bottom angle of deviation θ2between the bottom edge proximity line32and the reference line, the angle of correction θTof the transverse axis (T-axis) of the cutting tool2and the angle of correction θAof the center axis (A-axis) of the cutting tool2can then be figured out by means of the following formulas:
θT=f1(θ1−θ2), and
θA=f2(θ1+θ2),

in which f1and f2are correction parameters, which correspond to the predetermined specification of the cutting tool2(step SF), i.e., a different specification of cutting tool has a different correction parameter.

According to this embodiment, a standard cutting tool2was used for test, and the test result is shown inFIG. 6andFIG. 7. From the indications shown inFIG. 6andFIG. 7, the values for f1and f2are deduced to be (1/2.8) and (1/1.55) respectively, i.e., the aforesaid formulas can be changed to:
θT=(1/2.8)*(θ1−θ2), and
θA=(1/1.55)*(θ1+θ2),

Thus, the correction angle for the transverse axis (T-axis) of the cutting tool2and the correction angle for the center axis (A-axis) of the cutting tool2can be figured out for adjustment of the angle and position of the cutting tool2. In general, the present invention is to have the cutting tool2be lowered and pressed on a transparent Mylar1to produce an indentation3before actual operation (scribing), and then to use an image pickup device4to pick up the image30of the indentation3, and then to use a numerical analysis method and the set formula to automatically calculate the correction angle and position and to adjust the angle and position of the cutting tool2subject to the calculation result, and then to repeat the calculation and adjustment procedure if necessary. Thus, the cutting tool2and its cutting edge21can be accurately adjusted to the correct angle and position to obtain a horizontal and even indentation as shown inFIG. 8E. Further, by means of automatic adjustment, the present invention saves much adjusting time, thereby improving the productivity.