Die Bonding Position Determination Using Side-Look Stereo Imaging
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Solution Overview
Problem
Conventional die attach machines face challenges in accurately determining the bonding position of semiconductor dice due to uncertainties in die center calculation, which leads to misalignment and increased costs due to the reliance on bottom surface images, ignoring the shape differences between top and bottom surfaces of the dice.
Innovation Solution
The use of side-look 3D stereo optics and multiple cameras to capture images of the die's side surfaces, allowing for the calculation of the die's midpoint and eliminating variations from the sawing process, thereby eliminating the need for an up-look camera station and reducing cycle time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an up-look camera is used to capture 2D images of the bottom surface of the die, then the die center can be calculated, but the placement accuracy deteriorates due to shape differences between top and bottom surfaces
Solution Approach 1:
The patent transitions from 2D imaging (up-look camera capturing bottom surface) to 3D imaging (side-look stereo cameras capturing side surfaces). By adding the third dimension (depth/Z-axis), the system can calculate the die center based on the top surface geometry rather than the bottom surface, eliminating the accuracy loss caused by sawing-induced shape differences between top and bottom surfaces.
Solution Approach 2:
The patent uses stereo cameras to create a 3D digital model (copy) of the die's side surfaces and top surface. This digital replica allows for precise calculation of the die center and orientation without physically measuring the bottom surface, thereby avoiding the inaccuracies introduced by bottom surface deformation from the sawing process.
2Measurement precision
If an up-look station is added between pick-up and bonding positions, then die orientation can be measured, but the cycle time increases leading to throughput loss
Solution Approach 1:
The patent merges the measurement function with the bonding head itself. The side-look stereo cameras are integrated into the bonding head, allowing orientation measurement to be performed at the bonding position rather than requiring a separate up-look station. This eliminates the additional measurement station and reduces cycle time while maintaining measurement precision.
Solution Approach 2:
The patent enables continuous measurement and bonding operations by performing die orientation measurement during the bonding head's movement to the bonding position, rather than requiring a separate stationary measurement step. The on-the-fly measurement approach maintains continuous productive action without interruption.
3Device complexity
If the die center is calculated from 2D bottom surface images, then the process is simple, but misalignment occurs due to edge variations from sawing
Solution Approach 1:
The patent uses 3D side-look stereo imaging to capture the die's side surfaces and calculate the center based on the top surface geometry rather than the bottom surface. This dimensional change allows the system to ignore the deformed bottom edges caused by sawing while still achieving precise center calculation and bonding alignment.
Data Source
AI summary
The invention provides an apparatus for determining a bonding position of a die. The apparatus includes a bond head for picking up and bonding the die. The apparatus further includes a plurality of cameras positioned and configured for capturing at least a first image including a first side surface of the die, a second image including a second side surface of the die and a third image including the first and second side surfaces of the die. Further, the invention provides a method of determining a bonding position of a die. The method captures at least a first image including a first side surface of the die, a second image including a second side surface of the die and a third image including the first and second side surfaces of the die. The method further determines a bonding position of the die based on the captured images.