Ultrasonic transducer

Details Ultrasonic transducer Ultrasonic transducer

2000-03-24

2001-09-11

Dunn, Tom (Department: 1725)

Metal fusion bonding

Means to apply vibratory solid-state bonding energy to work

C228S110100, C156S073100, C156S580100, C310S311000

Reexamination Certificate

active

06286747

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to ultrasonic transducers.
2. Description of Prior Art
The invention relates more particularly to such transducers for use in bonding tools for connecting semiconductors to printed circuit boards for example. The bonding tools are used to apply pressure and ultrasonic energy simultaneously to miniature components for making electrical connections between them. The materials used in the driver of the ultrasonic transducers are piezoelectric ceramics. In different stages in the bonding process, there are parameters that must be monitored including the amplitude of the ultrasonic burst and its duration (bonding time). An optimized range of these bonding parameters which ensures the required bond quality is usually determined for each type of bonding machine. At present, all the bond parameter monitoring sensors are installed separated from the piezoelectric driver or may be attached to the ultrasonic concentrator.
SUMMARY OF THE INVENTION
It is an object of the invention to overcome or at least reduce this problem.
According to the invention there is provided a bonding tool for applying pressure and ultrasonic energy simultaneously to join miniature components together, the bonding tool comprising an ultrasonic driver having a plurality of thin piezoelectric wafers separated by planar electrodes and held together in a stack under mechanical pressure against one another, and a sensor mounted in the stack that comprises a pair of planar sensor electrodes separated by a piezoelectric wafer and insulated from adjacent electrodes in the stack, and means for measuring electrical voltages generated across the sensor electrodes.
Two or more sensors may be positioned in the stack.
The piezoelectric wafers are preferably cylindrical.
The piezoelectric wafer of the sensor may be made of one of a polymer, ceramic and composite material.
Each of the sensor electrodes may be made up of a plurality of conductive elements that are separately connectable electrically to the measuring means.


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