Probe Card Alignment via Gravity Center Coordinate Correction
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Solution Overview
Problem
Existing testing apparatuses face challenges in achieving high positional accuracy when moving a wafer to contact a probe card, due to distortions caused by changes in the center of gravity and temperature-related expansions, leading to misalignment issues.
Innovation Solution
The apparatus includes an alignment stage, a pogo frame, reference and wafer alignment cameras, and a controller that determines and corrects the contact coordinates by calculating the card gravity center, alignment, and wafer gravity center coordinates, and adjusts the alignment stage to ensure precise contact with the probe card.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the alignment stage is moved to position the wafer for contact with the probe card, then the testing process can proceed, but positional accuracy deteriorates due to center of gravity changes and thermal expansion
Solution Approach 1:
The system performs preliminary coordinate measurements and calculations before the actual wafer-contacting operation. The contact coordinates are calculated in advance based on measured positions of the probe card, alignment stage, and wafer, allowing the system to pre-determine the correct positioning target and compensate for potential drift before it affects testing accuracy
Solution Approach 2:
The patent replaces direct mechanical positioning reliance with a coordinate-based computational system. Instead of depending solely on mechanical alignment stage precision, the system uses coordinate obtaining units to measure positions and calculates contact coordinates through coordinate transformation, substituting mechanical precision requirements with computational accuracy
2Device complexity
If coordinate systems are not aligned between the alignment stage and pogo frame, then the setup is simpler, but contact position accuracy deteriorates
Solution Approach 1:
The patent introduces a reference target as an intermediary element that connects the alignment stage coordinate system with the pogo frame coordinate system. This reference target serves as a common reference point that allows coordinate transformation between the two systems, mediating the relationship between them and enabling accurate contact positioning without requiring direct mechanical alignment
Solution Approach 2:
The system creates a coordinate representation (copy) of the physical arrangement through coordinate measurements. By obtaining coordinates of the probe card, alignment stage, and wafer in their respective coordinate systems and transforming them to a common coordinate system, the system creates a computational model that accurately represents the physical contact geometry without requiring direct physical alignment
Data Source
AI summary
A testing apparatus includes a first coordinates obtaining unit, a second coordinates obtaining unit, and a controller that performs determining card gravity center coordinates of a probe card held at a pogo frame opposite to an alignment stage, determining reference coordinates in a target coordinate system of a reference target at predetermined coordinates, determining alignment coordinates when the first coordinates obtaining unit is aligned with the second coordinates obtaining unit, determining wafer gravity center coordinates of a wafer, and calculating contact coordinates by using the determined card gravity center coordinates, the determined alignment coordinates, and the determined wafer gravity center coordinates. The controller further performs determining actual contact coordinates at the calculated contact coordinates, calculating reference contact coordinates based on the determined reference coordinates, and correcting a position of the alignment stage based on a positional difference between the determined actual contact coordinates and the calculated reference contact coordinates.