Dual-Encoder Die Bonding for Thermal Drift Compensation
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Solution Overview
Problem
Conventional die bonding systems suffer from placement inaccuracies due to thermal expansion of encoder scales and carriages, as well as scale engraving defects, which are critical for achieving the precise positioning required in hybrid bonding applications.
Innovation Solution
A die bonding apparatus utilizing a linear motor-driven carriage with dual encoder heads and a controller to align the bond-head with a target location, compensating for thermal expansion and scale defects by measuring and adjusting encoder head alignment errors, ensuring accurate die placement down to ±50 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single encoder head is used to measure carriage position, then the device complexity is low, but thermal expansion of the encoder scale and carriage causes placement accuracy degradation
Solution Approach 1:
The single encoder head is segmented into two separate encoder heads (first encoder head and second encoder head) positioned at different locations on the carriage. This segmentation allows independent measurement of thermal expansion effects at different positions, enabling compensation for thermal distortion of the encoder scale while maintaining system manageability.
Solution Approach 2:
The controller receives position information from both encoder heads and uses the differential measurements to detect thermal expansion of the encoder scale. The system automatically compensates for thermal effects by calculating and applying correction factors based on the relative position changes detected by the two encoder heads, creating a closed-loop feedback system for thermal compensation.
2Ease of manufacture
If the distance between camera and bond-head is measured using encoder during carriage movement, then the measurement process is simple, but scale engraving defects directly impact placement accuracy
Solution Approach 1:
The second encoder head acts as an intermediary reference point between the camera and bond-head positioning system. By measuring position relative to this intermediate reference and using differential calculations, the system compensates for local scale engraving defects, as errors at one location are offset by corresponding errors at another location when the same physical distance is measured through the intermediary reference.
3Device complexity
If conventional single encoder head positioning is used, then the system structure is simple, but thermal expansion causes direct impact on distance measurement between bond-head and camera
Solution Approach 1:
The positioning measurement function is segmented between two encoder heads, with the first encoder head providing a reference measurement and the second encoder head providing a compensated measurement. This segmentation allows the system to isolate and compensate for thermal expansion effects on the encoder scale, maintaining accurate distance measurements between the bond-head and camera despite thermal conditions.
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
The solution provides highly accurate die positioning, insensitivity to thermal expansion and scale defects, making it suitable for hybrid bonding applications with improved placement precision.
Implementation Method 1
a linear motor and a carriage arranged to be driven by the linear motor along a traveling direction
Implementation Method 2
A linear encoder comprises an encoder scale extending along the travel direction of the carriage, first and second encoder heads mounted on the carriage
Implementation Method 3
a camera configured to detect a target location for positioning the die and for measuring an alignment error between an optical axis of the camera and the target location
Data Source
AI summary
A die bonding apparatus including a linear motor and a carriage, the carriage including a bond-head configured to pick up a die and a camera configured to detect a target location for positioning the die and for measuring an alignment error between an optical axis of the camera and the target location. A central axis of the bond-head and the optical axis are distant from each other by a first distance. The apparatus includes a linear encoder with an encoder scale, first and second encoder heads mounted on the carriage, and a controller arranged to move the carriage as a function of values read by the first and second encoder heads to align the bonding head with the target location. The first and second encoder heads are distant from each other by a second distance corresponding to the first distance plus an alignment error.