Segmented Ultrasonic Transducer for Wire Bonding
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Solution Overview
Problem
Conventional ultrasonic transducers in wire bonding machines provide limited flexibility in scrubbing direction and energy delivery, leading to non-uniform wire bonds and potential pad splash issues, especially in sensitive applications like copper wire bonding on aluminum pads.
Innovation Solution
The use of piezoelectric elements with segmented electrodes allows for simultaneous application of multiple frequencies, enabling non-linear scrubbing patterns such as Lissajous or elliptical motions, which provide multidirectional vibrational energy to the bonding tool tip, reducing deformation and collateral damage while improving bond uniformity and shear strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional ultrasonic transducers with single-frequency operation are used, then the device complexity is low, but the manufacturing precision and bond uniformity deteriorate
Solution Approach 1:
The piezoelectric driver is divided into multiple independently controllable segments or elements, each capable of operating at different frequencies. This segmentation allows the transducer to generate complex multi-frequency vibrational patterns that improve bond uniformity while maintaining a relatively simple overall transducer structure.
Solution Approach 2:
The transducer system transitions from static single-frequency operation to dynamic multi-frequency operation. By continuously varying the frequency content and phase relationships between different driver segments, the system adapts to different bonding requirements, improving manufacturing precision through dynamic control.
2Reliability
If single-direction linear scrubbing motion is used, then the ease of operation is high, but the reliability and bond strength deteriorate due to non-uniform energy delivery
Solution Approach 1:
The scrubbing motion transitions from one-dimensional linear movement to two-dimensional or three-dimensional non-linear trajectories (such as Lissajous patterns). By activating multiple piezoelectric segments with different phase relationships, the bonding tool tip traces complex paths that distribute ultrasonic energy more uniformly across the bond interface, improving reliability and strength.
Solution Approach 2:
The system employs periodic variation in scrubbing direction and intensity through multi-frequency excitation. Different frequency components create periodic oscillations that combine to produce complex periodic trajectories, ensuring uniform energy delivery throughout the bonding process and preventing localized overheating or insufficient bonding.
3Object-affected harmful factors
If conventional single-frequency ultrasonic energy is applied, then the energy delivery is simple, but harmful factors increase due to resonant vibrational effects and pad splash
Solution Approach 1:
The system changes the frequency parameters of ultrasonic energy delivery by applying multiple frequencies simultaneously or sequentially. This parameter variation prevents resonance with the natural frequency of the bonding tool or workpiece, reducing harmful vibrational effects and pad splash while maintaining effective energy delivery for bonding.
Solution Approach 2:
The system converts what would be harmful resonant vibrations into beneficial multi-frequency energy distribution. By deliberately applying frequencies that avoid resonance conditions, the harmful concentrated vibrational energy is transformed into distributed, controlled energy delivery that improves bonding quality and reduces damage to sensitive structures.
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 results in more uniform wire bonds with higher shear strength and reduced pad splash damage, aligning energy delivery with device geometries and reducing resonant vibrational effects, thus enhancing the wire bonding process.
Implementation Method 1
The transducer typically includes a driver such as a stack of piezoelectric elements (e.g., piezoelectric crystals, piezoelectric ceramics, etc.). Electrical energy is applied to the driver, and converts the electrical energy to mechanical energy, thereby moving the bonding tool tip in a scrubbing motion.
Implementation Method 2
Ultrasonic bonding energy is typically applied using an ultrasonic transducer, where the bonding tool is attached to the transducer. The transducer typically includes a driver such as a stack of piezoelectric elements
Implementation Method 3
Electrical energy is applied to the driver, and converts the electrical energy to mechanical energy, thereby moving the bonding tool tip in a scrubbing motion. This scrubbing motion of the bonding tool tip is typically linear motion along the longitudinal axis of the transducer.
Data Source
AI summary
A method of forming a wire bond using a bonding tool coupled to a transducer is provided. The method includes the steps of: (1) applying electrical energy to a driver of the transducer at a first frequency; and (2) applying electrical energy to the driver at a second frequency concurrently with the application of the electrical energy at the first frequency, the first frequency and the second frequency being different from one another.