Compliant motion servo

Force applying apparatus comprising:

• a carriage movable in a first direction,
• a tool mounted to the carriage for relative motion in said direction,
• means for resisting said relative motion,
• drive means for moving said carriage toward an object to which a force is to be applied by said tool, thereby moving said tool into contact with said object and causing said tool to move relative to said carriage,
• command means for generating a force signal indicative of a force to be applied to the object by the tool,
• sensor means for generating a feedback signal indicative of position of said tool relative to said carriage, and
• force control means responsive to said feedback and force signals for applying to said drive means a force error signal indicative of the difference between said force signal and said feedback signal.

An ultrasonic wire bonder comprising:

• a support,
• a work table connected to the support for carrying an object to which a wire is to be bonded,
• a bonder frame,
• means for mounting the frame to the support for motion in a first direction,
• a transducer support
• a transducer carried on said support,
• a bonder tool connected to the transducer,
• means for mounting the transducer support to the bonder frame for motion relative to the bonder frame in said direction,
• spring means for resisting said motion of the transducer support relative to the bonder frame,
• sensor means for generating a tool position signal indicative of position of the bonder tool relative to the bonder frame,
• motor means for moving the bonder frame relative to the support toward and away from an object carried on the worktable,
• force command means for generating a force command signal, and
• force control means responsive to said force command signal and to said tool position signal for energizing the motor means and moving the bonder frame so as to decrease the difference between said force command signal and said tool position signal.

In an ultrasonic wire bonder wherein a bonding tool is mounted to a transducer support frame for motion relative to the frame and is resiliently restrained against such motion, wherein the transducer support frame is mounted for motion toward and away from a workpiece under control of a drive motor, and wherein the point of contact of the tool on the wire is subject to displacement toward or away from the frame, apparatus for providing a substantially constant force between the bonding tool and wire to be bonded, said apparatus comprising:

• servo means for maintaining a predetermined position of said transducer support frame relative to the object, said servo means comprising means for actuating the drive motor to cause the frame to follow motion of said point of contact, said means for actuating comprising:
• means for sensing position of said bonding tool relative to said transducer support frame and generating a feedback signal,
• means for generating a force command signal, and
• means responsive to the difference between said feedback signal and said force command signal for driving said motor in a sense to decrease said difference.

A method of contacting an object by a tool with a predetermined force comprising:

• mounting a tool to a carriage for motion of the tool relative to the carriage in a first direction,
• resiliently resisting relative motion of the tool and carriage in said direction, and
• maintaining a constant force between the object and tool by a closed loop servo that causes the carriage to follow displacement of the object relative to the carriage to thereby maintain the tool in fixed position relative to the carriage, said step of maintaining comprising:
• generating a force command signal,
• generating a feedback signal indicative of position of said tool with respect to said carriage, and
• moving the carriage relative to the object so as to decrease the difference between said force command signal and said feedback signal.