Wire Bonding Offset Correction for Thermal Expansion
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Solution Overview
Problem
Variations in ambient temperature and heat generation from heat sources in wire bonding apparatuses cause thermal expansion differences between the capillary arm and the detection camera arm, leading to positional displacement of press-bonded balls, making it difficult to determine the exact center of the ball, especially when the ball's diameter approaches the wire diameter, complicating accurate bonding.
Innovation Solution
A method and apparatus that detect the distances between the pad edges and the press-bonded ball edges in both X and Y directions, compare these values to predetermined ranges, and correct the offset between the capillary and detection camera to ensure the ball is within a predetermined area, using a detection camera offset from the capillary, allowing for accurate positioning and bonding regardless of the ball's position relative to the wire.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the detection camera is positioned offset from the capillary to detect press-bonded balls, then the bonding position can be monitored, but thermal expansion differences cause offset changes and bonding position displacement
Solution Approach 1:
The system uses the detection camera to continuously monitor the bonding position and feeds this information back to the control unit, which automatically adjusts the bonding coordinates to compensate for thermal expansion-induced offset changes between the camera and capillary
Solution Approach 2:
The system dynamically changes the bonding coordinates based on detected positional displacement, adjusting the parameters (X, Y, Z coordinates) in real-time to maintain accurate bonding despite thermal expansion variations
2Manufacturing precision
If the press-bonded ball diameter approaches the wire diameter, then smaller bonds can be formed, but the ball edges become obscured by the wire making center detection difficult
Solution Approach 1:
The system detects edges of the press-bonded ball from multiple directions (at least three directions connecting the pad center and outer circumference points) rather than relying on a single view, enabling accurate center calculation even when the ball is small and edges are obscured
Solution Approach 2:
The detection process divides the ball into multiple reference points (pad center and at least three outer circumference points), detecting edges from different directional segments to calculate the center position accurately
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
This approach enables accurate correction of the offset, ensuring the press-bonded ball is positioned correctly on the pad, improving the precision of wire bonding by determining the ball's center and diameter, even when the ball's edges are obscured by the wire, thus enhancing the reliability of the bonding process.
Implementation Method 1
detecting a press-bonded ball at a bonding portion after bonding in a bonding apparatus including a capillary capable of performing bonding onto a workpiece and a detection camera disposed with a certain amount of offset from the capillary
Implementation Method 2
Variations in ambient temperature and operating heat generation caused by these heat sources produce a difference between thermal expansion of the bonding arm and thermal expansion of a detection camera holding arm
Data Source
AI summary
A detecting apparatus used in a bonding apparatus including a capillary and a detection camera disposed with a certain amount of offset from the capillary and capable of detecting a press-bonded ball at a bonding portion after bonding. For a pad in which two edges of a press-bonded ball corresponding to two adjacent sides of the pad are definite, the detecting apparatus detects the respective distances between the two sides of the pad and the corresponding two edges of the press-bonded ball, and compares the detected values to determine if these values fall within previously set allowable ranges; and if the detected values are outside the allowable ranges, the amount of offset is corrected so that the press-bonded ball comes within the allowable ranges.