Method for aligning the bondhead of a Die Bonder
In order to eliminate the inclination of a semiconductor chip picked by a gripper, the height of at least three points on the underneath of the semiconductor chip is determined in relation to a reference surface and from this the inclination is calculated. Determining the heights takes place in that the semiconductor chip is lowered until the semiconductor chip comes into contact with a needle.
1. A method for adjusting the bondhead of a Die Bonder, whereby the Die Bonder comprises a bondhead with a gripper deflectable in a predetermined direction in relation to the bondhead, comprising the following steps:
a) Picking a semiconductor chip or a plate with the gripper of the bondhead;
b) Moving the bondhead to a position characterised by co-ordinates (x 1 , y 1 ) that is determined so that the semiconductor chip is located above a needle;
c) Lowering the bondhead whereby the gripper is located in a bottom limit position in relation to the bondhead and monitoring the output signal of a sensor the output signal of which is dependent on the degree of deflection of the gripper in relation to the bondhead;
d) Determining a height z 1 (x 1 , y 1 ) taken up by the bondhead at the time when the semiconductor chip came into contact with the needle from the output signal of the sensor;
e) Repeating steps b to d for at least two further positions characterised by co-ordinates (x 2 , y 2 ) and (x 3 , y 3 ) and determining the corresponding values z 2 (x 2 , y 2 ) and z 3 (x 3 , y 3 ) that again correspond to the heights at positions (x 2 , y 2 ) and (x 3 , y 3 ) taken up by the bondhead at the time when the semiconductor chip, on lowering the bondhead, came into contact with the needle;
f) Determining two angles α and β from the values z 1 (x 1 , y 1 ), z 2 (x 2 , y 2 ) and z 3 (x 3 , y 3 ), whereby angle α designates the angle by which the semiconductor chip is rotated on a first axis in relation to its ideal position, and whereby angle β designates the angle by which the semiconductor chip is rotated on a second axis in relation to its ideal position;
g) Adjusting the bondhead according to the angles α and β determined in step f.
2. A method for adjusting the bondhead of a Die Bonder, whereby the Die Bonder comprises a bondhead with a gripper deflectable in a predetermined direction in relation to the bondhead, comprising the following steps:
a) Picking a semiconductor chip or a plate with the gripper of the bondhead;
b) Moving the bondhead to a position characterised by co-ordinates (x 1 , y 1 ) that is determined so that the semiconductor chip is located above a needle;
c) Lowering the gripper and monitoring the output signal of a sensor the output signal of which is dependent on the degree of deflection of the gripper in relation to the bondhead;
d) Determining a height z 1 (x 1 , y 1 ) taken up by the gripper at the time when the semiconductor chip came into contact with the needle from the output signal of the sensor;
e) Repeating steps b to d for at least two further positions characterised by co-ordinates (x 2 , y 2 ) and (x 3 , y 3 ) and determining the corresponding values z 2 (x 2 , y 2 ) and z 3 (x 3 , y 3 ) that again correspond to the heights at positions (x 2 , y 2 ) and (x 3 , y 3 ) taken up by the gripper at the time when the semiconductor chip, on lowering the gripper, came into contact with the needle;
f) Determining two angles α and β from the values z 1 (x 1 , y 1 ), z 2 (x 2 , y 2 ) and z 3 (x 3 , y 3 ), whereby angle α designates the angle by which the semiconductor chip is rotated on a first axis in relation to its ideal position, and whereby angle β designates the angle by which the semiconductor chip is rotated on a second axis in relation to its ideal position;
g) Adjusting the bondhead according to the angles α and β determined in step f.