Ultrasonic Bonding Quality Control via Tool Tip Velocity
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Solution Overview
Problem
Current methods for monitoring the quality of ultrasonic wire bonding are inadequate, as they fail to accurately assess bond quality due to insufficient correlation with physical processes and lack of consideration for essential variables like tool tip speed and friction, making them unsuitable for reliable quality control in fully automatic bonders.
Innovation Solution
A method that generates quality indices by analyzing multiple variables, including wire deformation, electrical admittance, and friction, using feature extraction and weighting techniques to create a more precise assessment of bond quality, allowing for real-time control and regulation of the bonding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If multiple measured variables (current, voltage, deformation) are used for quality assessment, then the quantity of information increases, but the reliability of quality determination deteriorates because these variables do not sufficiently correlate with physical processes in the connection zone
Solution Approach 1:
The patent extracts and isolates the specific measured variable that directly correlates with bond quality - the force acting on the bonding tool during ultrasonic bonding. By taking out this specific force measurement from the complex set of electrical and mechanical variables, the system achieves reliable quality determination without being overwhelmed by irrelevant information from current, voltage, and deformation measurements that do not directly reflect the physical bonding process.
Solution Approach 2:
The patent introduces force measurement as an intermediary variable that directly connects the ultrasonic bonding process to quality assessment. This force measurement acts as a mediator between the physical bonding processes (tool tip speed, friction) and the quality evaluation, providing a direct correlation that electrical variables like current and voltage fail to establish.
2Difficulty of detecting and measuring
If electrical variables (current, voltage, admittance) are used for monitoring, then measurement is easier to implement, but the precision of quality assessment deteriorates because electrical resonance does not correspond to mechanical resonance
Solution Approach 1:
The patent replaces electrical measurement systems with a mechanical force measurement system. Instead of using electrical variables (current, voltage, admittance) that require complex electrical resonance analysis, the system directly measures the mechanical force acting on the bonding tool. This substitution eliminates the disconnect between electrical and mechanical resonance, providing precise quality assessment through direct mechanical measurement.
3Device complexity
If only one measured variable is used for quality monitoring, then the device complexity is reduced, but the reliability of quality control deteriorates because single variables cannot capture the complex bonding process
Solution Approach 1:
The patent extracts the single most critical variable - force during bonding - from the complex set of potential measurement variables. By focusing on this one extracted variable that directly correlates with bond quality, the system achieves reliable quality control without the complexity of multi-variable monitoring systems. The force measurement captures the essential physics of the bonding process without requiring simultaneous measurement of multiple parameters.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables more accurate monitoring of bond quality and improved control over the bonding process, ensuring consistently high-quality bonds by integrating essential physical variables and adapting to changing conditions.
Implementation Method 1
a transducer-bonding tool unit and an ultrasonic generator are used and in which, during bonding, measurement signals from one or more parameters that are variable during bonding
Implementation Method 2
Bond Process Monitoring via Self-Sensing Piezoelectric Transducers
Data Source
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AI summary
The invention relates to a method for quality control in ultrasonic bonding, in which a transducer-bonding tool unit and an ultrasonic generator are used, and in which, during bonding, measurement signals of one or more parameters that vary during bonding are acquired by means of one or more sensors to assess the bond quality and/or to influence the bonding process. As an advantageous further development, it proposes that, during bonding, at least one velocity profile measurement signal representing the time-velocity profile of the tip of the ultrasonic tool in its direction of oscillation is acquired. The invention also relates to a bonding device suitable for carrying out the method. The invention further relates to other methods for quality control in ultrasonic bonding and bonding devices suitable for carrying out these methods.