Bond Pad Assessment via Indentation Depth-Force Profiling
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Solution Overview
Problem
Current wire bonding methods, particularly when transitioning from gold to copper wire, face challenges such as underpad damage, non-stick on pad, ball lift, and pad lift due to sensitive bond pad designs and non-optimized bonding parameters, which are difficult to address efficiently with existing methods that require extensive testing and analysis.
Innovation Solution
A method and apparatus using an indentation tool to measure depth-force profiles on bond pads, allowing for rapid determination of suitable bonding parameters by applying a series of forces and analyzing the resulting indentation depths, enabling accurate assessment of bond pad robustness and optimization of wire bonding parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If copper wire is used for wire bonding, then cost and electrical performance are improved, but work-hardening occurs leading to underpad damage and bondability issues
Solution Approach 1:
The patent applies preliminary action by performing an indentation test on the bond pad before actual wire bonding to assess pad robustness. This preliminary assessment allows optimization of bonding parameters (bond force, ultrasonic power, bond time) in advance, preventing underpad damage during copper wire bonding while maintaining bondability.
2Reliability
If conventional bonding parameter optimization is performed using multiple bonding cycles, then bonding results are improved, but time consumption increases significantly
Solution Approach 1:
The patent performs a preliminary indentation test to measure bond pad robustness characteristics before wire bonding. Based on the measured robustness, optimal bonding parameters are determined in advance, eliminating the need for time-consuming multiple bonding cycles while ensuring high-quality bonding results.
Solution Approach 2:
The patent replaces the conventional trial-and-error mechanical bonding optimization approach with a non-contact electrical measurement method (indentation test measuring current progression). This substitution significantly reduces optimization time while maintaining accuracy in determining bonding parameters.
3Measurement precision
If cross-section SEM/EDX analysis is performed to evaluate bond pad structure, then structural understanding is improved, but sample preparation difficulty and time increase
Solution Approach 1:
The patent replaces complex mechanical sample preparation (cross-sectioning for SEM/EDX) with a non-contact electrical measurement method. The indentation test measures bond pad robustness directly through current progression during indentation, providing accurate structural evaluation without requiring physical sample preparation or complex imaging equipment.
Solution Approach 2:
The patent creates an electrical signature (current progression curve) that copies or represents the bond pad's mechanical and structural properties. This electrical copy provides the same diagnostic information as physical cross-section analysis but without the complexity of sample preparation, enabling rapid assessment of bond pad robustness.
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 significantly reduces the time and cost associated with optimizing bonding parameters, provides a more accurate evaluation of bond pad robustness, and helps identify the cause of bondability issues, enabling faster process optimization and minimizing defects like underpad damage and ball lift.
Implementation Method 1
measuring a depth-force profile comprising a relationship between each predetermined force that is applied and a resultant depth of the indentation
Implementation Method 2
making one or more indentations onto at least one bond pad of the substrate with the indentation tool by applying a series of predetermined forces
Data Source
AI summary
For selecting suitable bonding parameters for forming wire bonds onto bond pads of a substrate, one or more indentations are made onto at least one bond pad of the substrate with an indentation tool by applying a series of predetermined forces onto the at least one bond pad with the indentation tool. A depth-force profile of the substrate is measured comprising a relationship between each predetermined force that is applied and a resultant depth of the indentation made by the indentation tool. An appropriate set of bonding parameters suitable for forming wire bonds on the substrate is determined based on the measured depth-force profile.