Multi-Harmonic Ultrasonic Transducer for Semiconductor Bonding
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Solution Overview
Problem
Existing ultrasonic bonding methods face challenges in increasing welding power at constant amplitude or reducing amplitude with constant power while avoiding transitions from static to sliding friction, which is particularly problematic for bonding sensitive semiconductor chips with multiple electrical contacts.
Innovation Solution
The method involves using a single ultrasonic transducer for multi-harmonic or multi-frequency excitation, combining first and second harmonic oscillation components with different frequencies and amplitudes to increase welding power and efficiency, allowing for larger areas to be bonded with reduced mechanical load on chips.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a single ultrasonic transducer is used for multi-harmonic excitation, then welding power increases, but device complexity increases
Solution Approach 1:
A single ultrasonic transducer is designed to generate multiple harmonic oscillation components (first harmonic, second harmonic, and higher harmonics) simultaneously, making it a multi-functional device that performs the work of multiple transducers. The transducer structure includes a piezoelectric element that can be excited at multiple frequencies to produce complex vibration patterns necessary for ultrasonic bonding.
Solution Approach 2:
The transducer operates by changing its vibration parameters (frequency and amplitude) dynamically. By controlling the excitation frequencies and amplitudes of different harmonic components, the system achieves variable welding power output. The piezoelectric element responds to multi-frequency electrical excitation by producing corresponding mechanical vibration patterns with different amplitudes and frequencies.
2Productivity
If higher harmonic components are added to increase welding power, then cycle time decreases, but mechanical stress on chips increases
Solution Approach 1:
The system dynamically adjusts the amplitude and frequency of different harmonic components during the bonding process. The first harmonic component provides the fundamental vibration motion, while higher harmonic components are superimposed with controlled amplitudes to increase welding power without creating excessive mechanical stress. This dynamic control allows optimization of both productivity and chip safety.
Solution Approach 2:
The patent utilizes mechanical vibration principles by generating complex vibration patterns through superposition of multiple harmonic oscillations. The tool tip performs a movement that is transmitted with contact to the component, creating friction welding through relative movement between substrate and component. The vibration pattern is carefully controlled to achieve welding power increase while maintaining acceptable stress levels.
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 higher welding power with constant mechanical load, reducing cycle times and increasing the distance covered by the tool tip per unit of time, thereby enhancing the bonding process efficiency.
Implementation Method 1
an oscillator arranged in the manner of a cross, each oscillating element being designed according to the piezo principle
Implementation Method 2
a metallic connection is produced by friction welding in the contact area
Implementation Method 3
the work done at the weld point during one cycle of the system's harmonic oscillation
Data Source
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AI summary
The invention relates to a method for ultrasonic bonding, wherein two longitudinal ultrasonic waves propagating in a common working plane oriented parallel to a substrate are induced in one or more ultrasonic transducers and are passed through ultrasound-conducting arms from different spatial directions onto a common connection point of the arms, and at the connection point cause an ultrasonic tool arranged directly or indirectly at said connection point to oscillate in two or three dimensions, wherein at least one ultrasonic transducer induces an ultrasonic wave with a first harmonic oscillation component and a second oscillation component.