Lidar Sensor Bond Resistance Testing via Trace Comparison
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Solution Overview
Problem
The bonding properties of connection bumps in lidar sensor assemblies degrade over time, especially in harsh environments, which can affect the reliability of flash lidar sensors used in autonomous driving applications.
Innovation Solution
A method and system for testing the bonding of a sensor assembly by measuring reference and test resistances along conductive traces and connection bumps, using a processor to calculate bond resistance and compare it to a predetermined value, with a resistance measuring device and a human-machine interface for alerting when degradation is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connection bumps are used to bond detector array to integrated circuit, then electrical and mechanical connection is achieved, but bonding properties degrade over time in harsh environments
Solution Approach 1:
The patent performs preliminary bonding strength testing during the manufacturing process by measuring resistance through the connection bumps. This allows detection of bonding defects before the sensor assembly is deployed, preventing unreliable bonds from entering service and enabling early identification of bonds that may degrade quickly in harsh environments.
Solution Approach 2:
The patent implements a feedback mechanism where resistance measurements are continuously monitored and compared against reference values. When resistance changes indicate bonding degradation, the system can trigger alerts or corrective actions, allowing proactive maintenance before complete bonding failure occurs in harsh environmental conditions.
2Measurement precision
If resistance measurement testing is implemented to monitor bond resistance, then bonding degradation can be detected, but device complexity increases
Solution Approach 1:
The patent enables the sensor assembly to perform self-testing by incorporating test traces and measurement circuits within the assembly itself. The resistance measurement system uses existing conductive paths and integrated circuits to monitor bond resistance without requiring external specialized equipment, allowing the device to monitor its own bonding health.
Solution Approach 2:
The patent designs the resistance measurement system to serve multiple functions: it measures bond resistance, provides reference comparisons, triggers alerts, and can potentially guide maintenance decisions. This multi-functional approach consolidates what could be separate complex systems into a unified monitoring solution that adds measurement capability without proportionally increasing overall device complexity.
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 allows for continuous monitoring of bond resistance, predicting potential failures and ensuring reliable sensor performance by identifying when the bonding properties reach unacceptable levels, thus maintaining consistent operation in harsh conditions.
Implementation Method 1
measuring a reference resistance along a reference trace defined by conductive material on at least one of an integrated circuit and a detector array... measuring a test resistance along a test trace defined by conductive material on the detector array, at least two of the connection bumps, and conductive material on the integrated circuit
Data Source
AI summary
A lidar sensor assembly includes a detector array having a plurality of photodetectors. An integrated circuit is bonded to the detector array via a plurality of connection bumps. A reference trace is defined by conductive material on at least one of the integrated circuit and the detector array. A test trace is defined by conductive material on the detector array, at least two of the connection bumps, and conductive material on the integrated circuit. A resistance measuring device is configured to independently measure a reference resistance along the reference trace and a test resistance along the test trace. The assembly also includes a processor in communication with the resistance measuring device. The processor is configured to receive the reference resistance and the test resistance, subtract the reference resistance from the test resistance to produce a bond resistance, and compare the bond resistance to a predetermined resistance value.