1. Field of the Invention
The present invention relates to a wire bonding device, in particular, to a wire bonding device in which relative positional deviation of a capillary with respect to an object of bonding is caused by changes in temperature.
2. Description of the Related Art
To assemble a semiconductor device, wiring is automatically performed on an electrode pad of a semiconductor substrate. For such wiring, an automatic bonding device is used. An automatic bonding device is equipped with a horn device for applying an ultrasonic wave to a bonding line paid out from the capillary. A bonding target point of a semiconductor device is monitored by a camera. Such an automatic bonding device is disclosed in Japanese Patent Application Laid-open No. Hei 01-161727. In such a well-known device, there are provided, in order to perform bonding positioning with high accuracy, a temperature detection means for detecting a temperature of a horn, and a correction means for obtaining a change in a length of the horn due to thermal expansion based upon a detection result of the temperature detection means to correct a previously set relative distance between a capillary and a camera.
When coefficients of thermal expansion and dimensions of the support means for securing the camera in position and the horn and the relative positional deviation between the camera and the capillary from the initially set state due to changes in temperature are not taken into account, it is impossible to eliminate the positional deviation factors due to thermal expansion of the mechanism parts as a result of temperature change, and further, it is impossible to correct the deviation of the reference bonding position of the semiconductor device which is the object of bonding. The above-mentioned well-known technique does not teach any correction means for correcting thermal expansion of the support means for securing the camera in position, nor does it suggest the importance of such correction. Further, the thermal deformation of the object of bonding is not taken into account at all.
It is required that the absolute positional deviation of the camera should be taken into account and that the positional relationship between the camera and the horn should be corrected. For a future semiconductor device, there is also a requirement for a further improvement in the accuracy of the bonding position, which is to be attained by taking into account the thermal expansion/contraction of the object of bonding.
It is an object of the present invention to provide a wire bonding device in which the absolute positional deviation of the camera is taken into account and in which the positional relationship between the camera and the horn is corrected.
In accordance with the present invention, there is provided a wire bonding device comprising: an XY table (2), a first holding member (8) supported by the XY table (2), a camera (9) supported by the first holding member (8), a second holding member (5) supported by the XY table (2), a capillary (7) held by the second holding member (5), a stationary base (3) for securing an object of bonding (4) in position, and a driving amount calculating unit (13) for computing the driving amount of the XY table (2) on the basis of the positional deviation of the camera (9) with respect to the origin of the XY table (2) due to temperature change in the first holding member (8) and the positional deviation of the capillary (7) with respect to the origin of the XY table (2) due to temperature change in the second holding member (5).
In a coordinate system in which the camera (9) and the capillary (7) are caused to move integrally by the XY table (2), the first holding member (8) and the second holding member (5) undergo thermal deformation independently, with the result that a minute deviation is caused in the positional relationship between the camera (9) and the capillary (7), and this minute deviation is calculated, correcting the position of the object of bonding (4) detected and calculated through imaging of the camera (9). On the basis of the positional deviation of the capillary (7) held by the second holding member (5), the moving amount of the XY table (2) is corrected, whereby the deviation of the bonding position due to thermal fluctuations is eliminated, making it possible to realize a bonding of high positional accuracy. The relative positional deviation between the camera (9) and the capillary (7) due to thermal fluctuations can be physically calculated by detecting the temperatures of the holding member (8) supporting the camera (9) and the support member (5) supporting the capillary (7).
There is further added an expansion coefficient calculating unit for calculating the expansion coefficient of the object of bonding (4). In this case, the driving amount calculating unit (13) performs calculation by adding the positional deviation of the bonding point of the object of bonding (4) with respect to the stationary base (3) on the basis of the expansion coefficient, to both of the above-described positional deviations. By adding the positional deviation of the bonding (object) point due to the expansion of the object of bonding (4) to both of the above-described positional deviations, it is possible to perform bonding position control with higher accuracy.
The expansion coefficient can be calculated on the basis of a reference distance (L) between two points (24-1 and 24-2, or 25-1 and 25-2) of the object of bonding (4) and the present distance (L+xcex94L) between the two points at the present time (24xe2x80x2-1 and 24xe2x80x2-2, or 25xe2x80x2-1 and 25xe2x80x2-2). When the temperature is known, it is possible to calculate the positional deviation of a local point of the object of bonding on the basis of the known expansion coefficient of the object of bonding. Direct measurement of the expansion/contraction of the distance between the reference points of the object of bonding by the camera (9) makes the detection of the positional deviation amount more accurate.
It is possible to further provide a temperature detector (18) for detecting the temperature of the second holding member (5). In this case, the driving amount calculating unit (13) calculates the positional deviation of the capillary (7) based on the temperature. It is possible to provide a first temperature detector (16) for detecting a first temperature of the first holding member (8) and a second temperature detector (18) for detecting a second temperature of the second holding member (5). In this case, the driving amount calculating unit (13) calculates the positional deviation of the camera (9) on the basis of the first temperature, and calculates the positional deviation of the capillary (7) on the basis of the second temperature. In this case also, the expansion coefficient of the above-mentioned object of bonding (4) is taken into account.