Reliability is a cornerstone of engineering, ensuring that devices perform consistently and effectively across a wide range of applications. In industries such as telecommunications, automotive systems, and industrial sensing, reliability testing is vital not only for safety but also for reducing maintenance costs, maintaining operational performance, and meeting customer expectations.
Photonic Integrated Circuits (PICs) are no exception to the demand for reliability. PICs are integral to key applications such as communications, LiDAR, and sensing. For example, an unreliable PIC could lead to costly telecom infrastructure repairs, incorrect object detection by autonomous vehicles, or failures in sensing hazardous gases in chemical plants, each with potentially severe consequences.
Reliability testing ensures PICs meet industry standards and perform consistently in real-world conditions. Devices often experience early-life failures, commonly referred to as “infant mortality,” within the first 6 to 12 months due to manufacturing yield issues. Identifying these failures through burn-in testing at full capacity is crucial. Environmental stressors such as electromigration, corrosion, thermal shock, and mechanical fatigue also pose significant risks, which can be mitigated by using statistical models to predict performance under extreme conditions. By rigorously testing devices until failure, manufacturers gain insights into long-term performance, ensuring the durability and functionality of PICs.
The Testing Workflow
To validate the reliability of a system, standardized protocols from industry agencies and consultancy groups are followed. In PIC reliability testing, it is important to distinguish between two key approaches:
- ● Certification Testing: Focused on meeting strict thresholds to ensure the robustness of the final product. By categorizing devices based on their reliability, manufacturers can tailor offerings for different market segments, ranging from premium-grade devices to cost-optimized options.
- ● Component-Level Testing: Aimed at understanding the independent performance limits of individual PIC subcomponents. These tests provide critical insights into failure mechanisms and help improve packaging and overall system robustness, even if they do not directly apply to complete systems.
A typical testing workflow includes the following stages:
- ► Potential Risk Analysis
To evaluate the system’s specifications, a Failure Mode and Effect Analysis (FMEA) is conducted. This involves identifying potential failure modes, analyzing their origins, consequences, and primary or secondary root causes. Key contributors include fabrication quality variability (e.g., layer thicknesses, doping concentrations), limitations in tolerance simulations (e.g., thermal expansion, material fatigue), and environmental factors like moisture or humidity. - ► Testing Plan Development
A comprehensive testing plan defines the conditions under which the system will be assessed, and tailored to the specific application and market requirements. This includes defining the device types, parameters to be tested, and industry standards to follow. Key elements of the plan include specifying test types (e.g., burn-in, HALT, HAST), environmental conditions (e.g., temperature, humidity, gas atmosphere), and whether tests will be destructive or non-destructive. Performance metrics such as time to failure, degradation rates, and lifetime are also outlined. This plan enables a systematic approach to identify failure modes, refine reliability predictions, and implement design improvements. - ► Performing the Test Campaign
- The planned tests are executed in a controlled environment using calibrated equipment. Common reliability tests include:
- 🞄 Thermal Cycling/Shock: Exposing the system to rapid temperature changes to evaluate thermo-mechanical fatigue and stress resistance.
- 🞄 Burn-in Testing: Operating the device continuously under extreme conditions to detect early failures and assess long-term durability.
- 🞄 Humidity and Temperature Testing: Subjecting the system to 85% relative humidity at 85ºC to evaluate corrosion and material degradation.
- 🞄 Accelerated Aging: Using statistical methods to simulate long-term performance under demanding conditions in a shorter timeframe.
- Specialized techniques, such as optical testing before and after reliability campaigns, are also employed to assess changes in output power, wavelength stability, or insertion loss. Pre- and post-test evaluations are crucial for identifying degradation levels, deciding whether devices should be reused or isolated for further testing phases, and ensuring compliance with customer-defined conditions.
- ► Data Processing and Conclusions
Data processing combines test results with fabrication quality reports and multiphysics simulations. Statistical models are applied to analyze system durability, identify failure points, and evaluate performance across various conditions. The insights gained help implement protective measures, such as encapsulation and thermal management, to enhance reliability. By addressing these findings, manufacturers can optimize designs to meet industry standards and ensure that devices remain reliable under real-world challenges.
PICs are a niche
Unlike microelectronics, which adhere to well-established standards like JEDEC, or bulky optical systems guided by Telcordia GR 468, the photonics industry lacks a universal framework for PIC reliability testing. This gap makes it difficult for companies to compare PIC performance using standardized criteria. Moreover, unexpected failure modes can emerge when fabrication variability and operational stresses are not adequately accounted for.
PICs that leverage CMOS fabrication processes benefit from existing microelectronics standards, such as MIL-STD-883, though additional considerations may be necessary. This adaptability is especially relevant for Electronic Photonic Integrated Circuits (EPICs), where photonic and electronic components are tested simultaneously. Combining these tests ensures the reliability of both domains, offering a comprehensive evaluation.
As the photonics industry transitions from research-focused innovation to commercialization, there is a growing emphasis on adopting Design for Reliability (DfR) practices. Early-stage reliability assessments help identify potential issues, preventing costly corrections during production scaling. Incorporating DfR techniques is vital for applications demanding high reliability, such as telecommunications, aerospace, and medical technologies. Until the industry requirements are standardized, the responsibility of reliability and qualification falls on the end user instead of the foundries.
Reliability testing at VLC Photonics
At VLC Photonics, we are expanding our reliability testing capabilities to meet the evolving demands of PICs. Our facilities are equipped with advanced thermal and humidity testing tools, and we adhere to rigorous ISO 9001 standards. By offering tailored reliability tests, we address the climatic, mechanical, and electrical challenges faced by our customers’ products.
Our testing services align with recognized standards such as JEDEC, MIL-STD-883, and IEC, covering conditions like thermal cycling, moisture resistance, and thermal shocks. We are also extending our portfolio to include tests for electrical discharges (ESD) and low-pressure environments, ensuring comprehensive coverage for a variety of use cases.
We aim to provide precise, reliable testing that meets industry requirements and helps our customers optimize their products for real-world conditions. By leveraging our expertise and state-of-the-art facilities, we help ensure that your PICs meet the highest quality and durability standards.
