Process control for laser wire bonding
AssigneeInternational Business Machines Corporation
InventorsArunava Gupta, Brian W. Hussey
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Abstract
An optical process monitor primarily for use in laser wire bonding detects the reflectivity change of the wire being bonded in order to provide feedback control of the high power laser used for bonding the wire to a pad. A low power laser beam which is co-linear or combined with the high power laser beam is conducted to the bond site and reflected from the wire during the bonding cycle. The change in reflectivity of the wire during the bonding cycle is detected from the reflected low power laser beam. A signal commensurate with the detected change of reflectivity is used to control the power or duration of the high power laser during bonding.
Claims32
A device for monitoring the energy dissipated during laser bonding of a metal workpiece to another workpiece comprising:
- first means for propagating a first beam of energy to the metal workpiece sufficient to bond the metal workpiece to the another workpiece;
- second means for propagating a second beam of energy co-linearly with said first beam, said second beam being reflected from the metal workpiece in the bond region;
- detection means disposed for detecting the reflected second beam and providing a reflectance signal commensurate with the reflected second beam, and
- control means coupled to said detection means for receiving said reflectance signal and controlling said first means responsive to said reflectance signal.
A method of monitoring the energy dissipated during bonding of a metal workpiece to another workpiece by propagation of a first energy beam sufficient to bond the workpieces comprising the steps of:
- propagating a second energy beam, co-linear with said first energy beam, for being reflected from the metal workpiece in the bond region during bonding;
- detecting the reflected second energy beam;
- and
- controlling the first energy beam responsive to said reflected second energy beam.
A device for controlling the process parameters of a laser wire bonder while bonding a first metal workpiece to a second metal workpiece comprising:
- first laser means for propagating a first laser beam for bonding a first workpiece to a second workpiece;
- second laser means for propagating a second laser beam, co-linearly with said first laser beam, said second laser beam being reflected from the first workpiece in the bond region;
- detection means for detecting the reflected second laser beam and providing a reflectance signal commensurate with the reflected second laser beam, and
- control means coupled to said detection means for receiving said reflectance signal and controlling said first laser beam responsive to said reflectance signal.
In a laser wire bonding apparatus for bonding a wire to a pad by use of a beam of high power laser energy at a first wavelength, a monitoring device for controlling the high power laser energy comprising:
- laser means for propagating a beam of low power laser energy at a second wavelength, co-linearly with the beam of high power laser energy, for being reflected by the wire in the bond region during bonding;
- detection means for detecting the reflected low power laser energy and providing a reflectance signal commensurate with the reflected low power laser energy;
- and
- control means for receiving said reflectance signal and controlling the beam of high power laser energy responsive to said reflectance signal.
Dependencies are inferred from the claim text.