Bond Head Alignment Using a Universal Reference Plate
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Solution Overview
Problem
Existing die bonding technologies face challenges in maintaining precision and accuracy due to image shifts caused by factors like module deformation and thermal drift, leading to reduced camera calibration accuracy and optical aberration, which affect alignment.
Innovation Solution
A method and apparatus using a collet with a see-through portion and transparent glass plate, combined with multiple cameras and a reference plate, to determine and correct alignment offsets by viewing collet and semiconductor die positions relative to a fixed reference, allowing for precise alignment adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional vision systems are used to capture images of bond head and semiconductor die, then alignment offsets can be determined, but image positions shift due to module deformation and thermal drift, reducing camera calibration accuracy and optical aberration
Solution Approach 1:
A reference plate with fiducial markers is introduced as an intermediary between the vision system and the bonding objects. The reference plate remains stationary during bonding operations, providing stable reference points that do not shift with thermal drift or module deformation. This mediator allows the system to maintain accurate calibration and measurement precision even as other components move or deform.
Solution Approach 2:
The reference plate is pre-positioned and calibrated before bonding operations begin. Fiducial markers are pre-established on the reference plate at known positions, allowing the vision system to perform preliminary calibration and establish a stable coordinate system. This preliminary action ensures that subsequent measurements remain accurate despite thermal drift or deformation during operation.
2Manufacturing precision
If a vision system with small numerical aperture and large depth of field is deployed to view semiconductor die and substrate in the same image, then alignment can be achieved, but bonding speed must be lowered to ensure higher bonding accuracy
Solution Approach 1:
The vision system is segmented into multiple specialized camera systems: one optimized for viewing the semiconductor die with high precision, and another optimized for viewing the substrate. Each camera can use optimal optical parameters for its specific task without compromise. This segmentation allows high-speed operation while maintaining high bonding accuracy, as each camera operates in its optimal performance range.
3Measurement precision
If bond head positioning is adjusted to achieve high precision alignment, then alignment accuracy improves, but the system remains sensitive to tilting of bond head or optical systems and inherent optical distortion
Solution Approach 1:
The vision system continuously monitors the positions of fiducial markers on the reference plate and provides feedback for real-time correction of alignment offsets. This feedback mechanism compensates for tilting of the bond head or optical systems, as well as optical distortion, by dynamically adjusting the positioning based on actual measured positions rather than relying solely on pre-calibration. The system detects and corrects deviations caused by these harmful factors during operation.
Data Source
Figure 1A~1B
Figure 2A~2C
Figure 2D~2F
AI summary
A semiconductor die is picked up with a collet, which is then located between first and second camera systems. The first camera system views the collet and a reference plate, and the second camera system views the semiconductor die and the reference plate, in order to determine a position and orientation of the semiconductor die relative to the collet and the reference plate. Thereafter, the collet is moved to a position above a bonding position on a substrate, and the first camera system views the bonding position so that the position and orientation of the semiconductor die may be adjusted before the semiconductor die is bonded onto the bonding position.