Contact Element Evaluation Using Probe Mark Image Analysis

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Solution Overview

Problem

Existing methods for evaluating contact elements in electrical circuits, such as bond-pads or bumps, often result in deformation and incorrect identification of probe marks, leading to costly misclassification of functional dice as non-functional due to deformation and resemblance of artifacts to probe marks.

Innovation Solution

A method and system that acquire and compare images of contact elements to evaluate characteristics by comparing the number and presence of potential probe marks, ignoring artifacts and determining defects or obstacles, using image acquisition and processing to differentiate between actual probe marks and artifacts, and measuring probe mark depth and spatial relationships.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a probe contacts a bond pad or bump during electrical testing, then electrical functionality can be tested, but the contact element may be deformed creating probe marks that can render the wafer inoperative

Engineering Contradiction:

Improveelectrical testing efficiencyVSAvoidcontact element integrity

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The system performs preliminary optical inspection to identify contact elements that have been contacted by probes before functional testing. By pre-identifying contacted elements, the system can adjust test parameters or interpret results knowing which elements have already been mechanically engaged, thus preventing false failures and improving reliability of the testing process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses optical inspection feedback to identify probe marks and correlates this information with electrical test results. This feedback loop allows the system to distinguish between functional failures and mechanical damage, enabling more accurate reliability assessment of the contact elements after testing

Inventive Principle:

Principle #23Feedback

2Extent of automation

If automatic inspection systems identify artifacts as probe marks, then inspection coverage is increased, but functional dice are incorrectly classified as non-functional

Engineering Contradiction:

Improveinspection automationVSAvoidprobe mark identification accuracy

Core Design Contradiction:

Extent of automationVSMeasurement precision

Solution Approach 1:

The system introduces an intermediary analysis layer that uses multiple image capture conditions (different angles, lighting, or magnifications) to verify potential probe marks. This intermediary step acts as a filter between automated detection and final classification, allowing the system to maintain high automation while improving identification accuracy by cross-validating artifacts against multiple imaging perspectives

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes imaging parameters (such as angle, illumination, or focus) to capture the same contact elements under different conditions. By analyzing how potential probe marks appear across multiple parameter sets, the system can distinguish true probe marks from artifacts, thereby improving measurement precision while maintaining automation

Inventive Principle:

Principle #35Parameter changes

3Ease of operation

If probes are made very tough with very small tips for precise contact, then testing capability is improved, but the risk of deforming larger, less durable contact elements increases

Engineering Contradiction:

Improvetesting capabilityVSAvoidcontact element deformation

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The system performs preliminary optical inspection to identify and characterize contact elements before testing. By knowing the location, size, and initial condition of each contact element, the system can optimize probe contact parameters or alert operators to potential deformation risks, thus maintaining testing capability while reducing harmful effects

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system replaces purely mechanical contact-based assessment with optical inspection and image analysis to evaluate contact element condition. This substitution allows non-contact verification of contact element integrity, enabling the use of tough, small-tip probes for testing while using optical methods to detect and assess any deformation without requiring mechanical measurement

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS8577123B2Method and system for evaluating contact elements

Publication Date: 2013.11.05 CAMTEK LTD

AI summary

A method, system and a computer program product for evaluating contact elements, the method includes: acquiring images of multiple groups of contact elements, wherein each group of contact element was expected to be contacted during a test by the same group of probes so as to form multiple probe marks; and evaluating at least one characteristic of a first contact element in response to a comparison between a number of potential probe marks that appear in the image of a first contact element and a number of potential probe marks that appear in an image of a second contact element.