Semiconductor Chip Mounting Calibration for Height-Dependent Image Shift
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Solution Overview
Problem
The use of a Scheimpflug optical system in mounting apparatuses for semiconductor chips is prone to image displacement due to temperature changes, leading to errors in determining the target position, especially in stacked die mounting or 2.5-dimensional mounting where height variations occur, resulting in inaccurate placement.
Innovation Solution
A mounting apparatus employing top-view and bottom-view imaging units with Scheimpflug optical systems, a calibration controller to calculate and adjust for calibration values based on images from these units, ensuring accurate placement by aligning the focal plane with the target height and correcting for temperature-induced errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a Scheimpflug optical system is used to image the work target from an oblique direction, then the imaging speed is improved and movement errors are reduced, but temperature changes cause minute displacements of optical system elements that appear as displacements of the output image in the plane direction, resulting in target position calculation errors
Solution Approach 1:
The patent changes the imaging parameters by switching between different focal planes corresponding to different height positions. The imaging unit adjusts its focal plane to match the height of the placement surface, allowing accurate imaging regardless of the number of stacked semiconductor chips. This parameter adjustment compensates for the temperature-induced displacements by recalibrating the focal plane position.
Solution Approach 2:
The patent replaces the mechanical adjustment of the imaging unit's physical position with optical focal plane adjustment. Instead of mechanically moving the imaging unit to different heights, the system uses optical means to shift the focal plane to different height positions, thereby maintaining imaging accuracy without mechanical displacement errors.
2Adaptability or versatility
If the height of the placement surface changes due to stacked die mounting or 2.5-dimensional mounting, then the mounting capability is improved, but the amount of error in target position calculation differs for each height, making accurate placement difficult
Solution Approach 1:
The patent implements a dynamic focal plane adjustment mechanism that adapts to different placement surface heights. The imaging unit can dynamically shift its focal plane to match the current height of the placement surface, whether it's the first surface or a second surface formed after stacking semiconductor chips. This dynamic adaptation ensures consistent imaging accuracy across multiple stacking levels.
Solution Approach 2:
The patent adds the height dimension (Z-axis) to the imaging system's control parameters. By incorporating focal plane position in the height dimension, the system can accurately image placement surfaces at different heights without compromising horizontal positioning accuracy. This dimensional extension allows the system to handle stacked die mounting while maintaining precision.
Data Source
AI summary
A mounting apparatus obtains calibration values for calibrating a difference between coordinate values based on top-view and bottom-view images, for each assumed placement height of a planned placement area of a mounting body. A calibration controller calculates calibration values based on the top-view and bottom-view images from a bottom-view imaging unit and top-view imaging units employing a Scheimpflug optical system by imaging a calibration index matching the placement height. A mounting controller adjusts a position of a mounting tool so that a planned contact surface of the mounting body is at the placement height to recognize a reference position based on the bottom-view image, and adjusts positions of the top-view imaging units so that the focal plane falls on the same plane as the placement height to recognize a target position based on the top-view images of the planned placement area and the calibration values corresponding to the placement height.