Iec 60300 3 7 1999

Microsoft Word 300 3 7f doc NORME INTERNATIONALE CEI IEC INTERNATIONAL STANDARD 60300 3 7 Première édition First edition 1999 05 Gestion de la sûreté de fonctionnement – Partie 3 7 Guide d’application[.]

Domaine d'application

Généralités

When the analysis results outlined in Article 7 indicate the need for a decontamination process, a decontamination plan becomes essential Due to the variety of electronic equipment and their potential applications, specific details of the planning process, such as the level of decontamination application, types of processes, and constraints, cannot be standardized However, a general planning procedure is provided below, along with guidance for selecting specific parameters.

Etape 1 – Identification des objectifs et des buts

Cette étape est primordiale dans le processus de planification L'efficacité du processus de déverminage ne peut pas être garantie sans une identification des objectifs à atteindre.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU. c) Inadequate design

RSS is mainly intended to detect inherent flaws or induced flaws Inadequate design should preferably be addressed by other tests, such as well structured design acceptance tests.

Flaws caused by inadequate design can be found in both components and assemblies.

Certain design flaws, such as tolerance interference, drifts, and propagation delay issues, often go undetected by standard evaluation methods like worst case analysis or reliability tests These flaws typically manifest as failures only when subjected to specific types of stress.

A pre-production screening process test is essential for evaluating flaws and their densities, as well as for assessing the effectiveness of various screens used in flaw precipitation The data obtained from this process is crucial for optimizing and stabilizing the production screening process However, caution is necessary to prevent misinterpretation of the data, which can often be misleading in certain situations.

– pre-production hardware configuration may be different from production configuration;

– the quality of components/materials used in pre-production hardware may be different from that of production hardware;

– lack of adequate quality control during pre-production phase;

– immature manufacturing processes during pre-production phase.

These factors have to be considered when using pre-production screening process data to select the production screening process and deciding on its parameters.

15 Planning, performing and eliminating a reliability stress screening process

When the analysis in clause 7 indicates the necessity for an RSS process, a screening plan must be developed Given the variety of electronic hardware and their diverse applications, the specifics of the planning process—including the application level, types of screening processes, and stress levels—cannot be standardized Nonetheless, a general planning procedure is outlined below, providing guidance on selecting the appropriate parameters.

15.2 Step 1 – Identification of objectives and goals

This step is essential in the planning process Effectiveness of the screening process cannot be ensured without clear identification of objectives and goals to be achieved.

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU.

A debugging process is typically implemented with at least one of the following objectives in mind: a) to achieve a required level of reliability This is necessary when reliability predictions, operational data, or test data indicate a reliability level that falls below the required or expected standard.

It is crucial to understand that a lower reliability level is primarily due to defects, rather than other types of failures that cannot be eliminated through the debugging process or can be addressed more effectively by alternative methods Achieving an acceptable or higher specified maximum defect density is essential, especially when a contract outlines such a requirement or when operational warranty data and cost analysis indicate the need to reduce defect density to meet customer expectations and financial goals Additionally, maximizing the number of defects addressed within a fixed budget is necessary when a constrained debugging program is implemented.

To ensure the effectiveness of the pest control program, it is essential to measure the results of the pest removal process against predefined quantitative goals It is important to assess the adequacy of the pest control level, the testing regime, and the number of anticipated or observed failures.

When aiming to achieve a specific defect density, it is essential to consider several factors Firstly, the complexity of the studied material plays a crucial role, which is assessed based on the number and variety of components and subcomponents, the materials used, and the types of connections and interconnections involved in its construction.

The complexity of a system directly correlates with the expected density of defects; established techniques are less likely to have defects compared to those that are not fully matured New or complex manufacturing processes, along with inadequate quality control measures, contribute to a higher defect density, while proven and well-controlled processes minimize the likelihood of defects in electronic materials Additionally, whether materials, components, or modules have undergone prior debugging by the vendor or subcontractor affects the defect density It is crucial to assess the type and level of stress the materials will face in real-world applications, as certain defects may lead to failures under high-stress conditions but may remain undetected in less demanding environments This evaluation requires a deep understanding of the characteristics and time-dependent factors associated with the types of defects considered.

It is crucial to emphasize that environmental and operational profiles are entirely unrelated to the selected types of decontamination, due to the distinct differences between environmental qualification testing and the decontamination process The nature and maturity of the manufacturing processes used to produce the equipment lead to variations in defects, both in intensity and density High-intensity defects can almost certainly cause failures due to their degradation mechanisms, resulting in failures during the equipment's lifespan Additionally, it may be necessary to have stringent environments for low-intensity defects to cause failures, which might not occur in less severe conditions.

An RSS process is typically implemented to meet specific objectives, primarily to attain a desired level of reliability This is particularly relevant when reliability predictions, field data, or test results reveal that the current reliability falls short of the required or anticipated standards.

It is crucial to understand that the lower reliability level is attributed to flaws rather than other failures that cannot be addressed by RSS or are better managed through alternative methods Achieving a specified maximum allowable flaw density is essential, especially when a contract outlines this requirement or when warranty data and cost analyses indicate the necessity to lower flaw density to meet customer expectations and cost objectives Additionally, it is important to maximize the number of flaws within a predetermined budget, particularly when a reliability stress screening program is implemented with a fixed financial allocation.

To ensure the effectiveness of a screening program, measurable pre-set quantitative goals are essential Key factors influencing flaw density include the complexity of the hardware, which is determined by the variety of components and connections; the maturity of the technology, where established technologies exhibit fewer flaws; the manufacturing processes, where new or poorly controlled methods increase flaw density; the history of previous screening processes for materials and components; and the application environments, which dictate the stress levels the hardware will face Understanding these factors is crucial for setting appropriate goals and evaluating the expected flaw density in electronic hardware.

It is crucial to note that the environmental and operational profiles are unrelated to the selected screen types, as there is a significant distinction between environmental qualification tests and the RSS process The intensity and density of flaws in hardware depend on the manufacturing processes used, with high-intensity flaws posing a risk of failure due to their degradation mechanisms during the hardware's useful life Conversely, low-intensity flaws may only lead to failures in harsh environments and might not fail at all in benign conditions.

By taking into account all the aforementioned factors and comparing them to similar materials with equivalent complexity and manufacturing processes, it is feasible to determine a maximum defect density This can be expressed as the maximum allowable percentage of fragile entities in the market, as outlined in IEC 61163-1.

Etape 2 – Conception et application du processus de déverminage

The selection of deworming types, their parameters, intensity, and appropriate application levels is the most crucial step in the overall process An ideal deworming approach aims to convert defects into production failures without damaging or degrading components or materials of satisfactory quality.

A thorough understanding of the key points outlined below is essential for the proper design and implementation of decontamination processes Decontamination sequences are detailed in IECQ documents, such as IEC 60747 and IEC 60748 This includes various types of decontamination processes.

Les différents types de processus de déverminage, leurs caractéristiques et leurs capacités à accélérer les mécanismes de dégradation.

Ci-après figurent des exemples de différents types de processus électriques, mécaniques et autres processus de sélection représentant des candidats éventuels pour le processus de déverminage:

– cycles de température (vitesse de variation de la température);

– contrainte électrique, y compris transitoires et autres perturbations électromagnétiques;

– combinaison de température élevée et vibration;

– combinaison de cycles de température et de vibration aléatoire;

– combinaison de cycles de température, de vibration aléatoire et de cycles de puissance;

– combinaison de cycles de température, de vibration aléatoire et d'altitude;

– combinaison de cycles de température et vibration sinusọdale;

– cycles de puissance. b) Processus de déverminage courant

Divers exemples de processus de déverminage couramment utilisés (et leurs caractéris- tiques) sont proposés ci-dessous.

1) Température élevée: processus de déverminage efficace qui peut être appliqué à tout niveau Le composant ayant la température assignée la plus faible détermine la tempé- rature maximale pouvant être utilisée Par conséquent, une valeur de température supérieure peut être tolérée pour des composants et des niveaux d'ensemble inférieurs Comparé à d'autres déverminages, il est considéré comme le moins cỏteux.

Taking into account the various factors alongside comparable hardware with similar complexity and manufacturing processes, it is possible to determine a maximum flaw density, which can be quantified as the highest permissible percentage of defective items available in the market.

15.3 Step 2 – Screening process design and application

Choosing the right screen types, along with their specifications and strength, is crucial in the overall process The optimal screen effectively identifies defects, leading to factory failures, while preserving the integrity of quality components and materials.

A thorough understanding of the topics listed below is essential for proper screen design and application Some screening sequences can be found in IECQ documents, for example, the

IEC 60747 and IEC 60748 series. a) Screening process types

The different types of screening processes, their characteristics and their capabilities in accelerating the degradation mechanisms.

The following are examples of different types of electrical, mechanical and other screening processes which constitute potential candidates for the stress screening process:

– electrical stress, including transients and other electromagnetic disturbances;

– combined elevated temperature and vibration;

– combined temperature cycling and random vibration;

– combined temperature cycling, random vibration and power cycling;

– combined temperature cycling, random vibration and altitude;

– combined temperature cycling and sine vibration;

– power cycling. b) Common screening processes

Examples of commonly used screening processes (and their characteristics) include the following.

1) Elevated temperature: an effective screening process which can be applied at any level.

The maximum allowable temperature is dictated by the component with the lowest temperature rating, allowing for higher tolerances in other components and lower assembly levels Additionally, this screen is recognized as the most cost-effective option compared to others.

Défectuosités typiques détectées: dérives, défauts de connexion, contamination et problèmes chimiques.

When monitoring the decontamination process under high-temperature conditions, it is crucial to track the temperature at the component level or nearby, rather than relying on the average oven temperature Additionally, the temperature monitoring system should operate independently from the temperature control system.

2) Cycles de température: processus de déverminage très efficace pouvant être appliqué à tous les niveaux Son efficacité est due à sa forte capacité potentielle à révéler une large gamme de défectuosités intrinsèques, induites par le processus et induites par l’exécution du travail.

– valeurs haute et basse des températures;

Défectuosités typiques détectées: tolérances incorrectes, dérives, défaillances d'étanchéité, connexions défectueuses, contacts de relais défectueux, contamination, problèmes chimiques et cartes imprimées défectueuses.

During the temperature cycling process for decontamination, it is crucial to monitor the temperature at the component level rather than relying on the average oven temperature The temperature monitoring system should operate independently from the temperature control system The rate of temperature change is significantly affected by the thermal capacity within the test chamber, including decontaminated entities, connectors, cables, and control equipment If the decontaminated entities are powered off at the start of the cooling cycle and powered on at the beginning of the heating cycle, a maximum thermal stress can be anticipated immediately after powering on the entities.

3) Vibration: processus de déverminage efficace, particulièrement quand il est appliqué à des niveaux d'ensemble plus élevés La vibration est par exemple un processus de déverminage utile pour certaines pièces électromécaniques.

– type de vibration, (sinusọdale et aléatoire);

– niveau de vibration, fréquence et amplitude;

– nombre d'axes (parmi six degrés de liberté);

Défectuosités typiques détectées: matériel détaché, connexions défectueuses, fils cassés, problèmes structurels et contamination d'éléments L'essai par vibration acoustique

(PIND) constitue un processus spécial de déverminage par vibration (Voir les documents MIL STD 750, 2052 et MIL STD 883, 2020.)

Due to resonance effects, a portion of the decontaminated entity may experience acceleration levels up to approximately 25 times that of the entity itself It is essential for the monitoring circuit to be independent of the control circuit concerning vibration hardware Vibration can be applied along one, two, or three axes, or in an oblique vector that applies vibration across all three axes simultaneously When selecting the direction(s) of vibration, it is crucial to consider the resonance frequencies of subsystems and components, as well as their durability.

A fixed-frequency sinusoidal vibration primarily excites components and subsystems with a resonance frequency close to that frequency When a sinusoidal sweep is applied, it excites one resonance frequency at a time In contrast, random vibration stimulates all resonances simultaneously, leading to increased stress levels and a higher likelihood of component collisions.

4) Cycles de température et de vibrations: processus de déverminage très efficace, particulièrement quand il est appliqué à des niveaux d'ensemble plus élevés, car il possède une forte capacité à révéler à la fois les défectuosités de composant et celles qui relèvent du processus de fabrication.

Typical flaws detected: drifts, poor connections, contamination and chemical problems.

When managing the elevated temperature stress screening process, it is crucial to monitor the temperature directly at or near the component rather than relying on the average oven temperature Additionally, the temperature monitoring system must operate independently from the temperature control system.

2) Temperature cycling: a very effective screening process that can be applied at all levels Its effectiveness is due to its high potential capability to reveal a wide variety of inherent, process induced and workmanship induced flaws.

– high and low temperature values;

Typical flaws detected: incorrect tolerances, drifts, hermetic seal failures, poor connections, bad relay contacts, contamination, chemical problems, and PCB flaws.

When managing the temperature cycling stress screening process, it is crucial to monitor the temperature close to the component rather than relying on the oven's average temperature The temperature monitoring system must operate independently from the temperature control system Additionally, the thermal mass within the test chamber, including the screened items, connectors, cables, and control equipment, significantly affects the rate of temperature change Notably, maximum thermal stress is likely to occur immediately after the items are powered on at the beginning of the heating cycle, following their shutdown during the cooling cycle.

3) Vibration: an effective screening process, especially when applied at higher assembly levels Vibration is for example a useful screening process for some electromechanical parts.

– type of vibration (sine or random);

– vibration level, frequency and amplitude;

– number of axes (of possible six degrees of freedom);

Typical flaws detected: loose hardware, poor connections, broken wires, structural problems and particle contamination A special vibration screening process is the

Particle Impact Noise Detection (PIND) (See MIL STD 750, 2052 and MIL STD 883,

Etape 3 – Analyse cỏts/bénéfices

The goal of the debugging process is primarily cost-driven, whether it aims to meet specified reliability requirements or reduce warranty costs Therefore, conducting a cost-benefit analysis is essential to evaluate the debugging process To achieve savings through debugging, the total cost of the debugging process must be lower than the combined costs of failure detection and repair during manufacturing or operation, warranty expenses, and losses stemming from the company's damaged reputation.

15.4.2 Facteurs à prendre en considération pour évaluer le cỏt du processus de déverminage:

Il convient de prendre en compte les facteurs suivants pour évaluer le cỏt du processus de déverminage:

– niveau d'application, (composant, ensemble, sous-système ou système);

– quantité de matériel à déverminer (nombre par semaine et volume);

LICENSED TO MECON Limited - RANCHI/BANGALORE FOR INTERNAL USE AT THIS LOCATION ONLY, SUPPLIED BY BOOK SUPPLY BUREAU. f) Adequacy of the functional test in detecting failures caused by flaws

Testing items before and after the reliability stress screening (RSS) process using the same test equipment and program is highly advisable This practice enhances confidence in estimating the number of failures that occur during the RSS process.

To effectively identify intermittent failures and accurately time each occurrence, it is advisable to monitor specific functional parameters of the items throughout the RSS process.

When designing screening processes for targeted flaws, it is crucial to consider the availability and capability of test equipment to detect various failure modes For instance, intermittent failures necessitate prolonged functional tests under stress, while dynamic failures, such as those caused by drifts and propagation delays, require careful monitoring of input/output signals Evaluating the ability to exercise and monitor these modes is essential for effective screening process objectives and goals.

The design of the screening process must align with the specific objectives and goals of the screening program It is essential to establish a consensus on the anticipated flaw density before the screening and the desired flaw density following the screening Additionally, considerations regarding the costs of alternative screening methods and their application levels are crucial.

When designing screening processes, it is essential to assess the costs of equipment, functional test instruments, and labor against the effectiveness of the screening methods in identifying flaws Detailed cost analyses are provided in section 15.4 To optimize economic efficiency, it is advisable to utilize standard stress equipment, such as climatic chambers and vibration tables, and to select stress severities from the IEC 60068-2 series whenever feasible.

The RSS process is primarily driven by cost considerations, aiming to meet reliability requirements and minimize warranty expenses To evaluate the effectiveness of the screening process, a cost-benefit analysis is essential Ultimately, for the screening process to be advantageous, its total cost must be lower than the combined expenses of troubleshooting and repairing factory and field failures, as well as the costs associated with warranty claims and potential damage to the company's reputation.

15.4.2 Factors to be considered in evaluating the screening process cost

The following factors should be considered in evaluating the screening process cost:

– application level (component, assembly, subsystem or system);

– amount of hardware to be screened (number per week and volume);

Nature Fin de la surveillance du fonctionnement?

Première partie de l'épreuve sous contraintes

Epreuve sous contraintes et surveillance permanente

Si le système de surveillance détecte une défaillance, l'entité est envoyée en réparation 1)

Deuxième partie de l'épreuve sous contraintes

1) Il est possible qu'il ne soit pas pratique de déplacer et de réparer les entités défaillantes avant la fin de la période T M

Figure 2 – Déverminage sous contraintes d'entités réparables

Second partial stress conditioning First testing

Stress conditioning and continuous monitoring

In case the monitoring system reveals a failure the item is taken out for repair 1)

1) Sometimes it may not be practical to remove and repair the failed item before the end of the period T M

Figure 2 – Reliability stress screening of repairable items

– cỏt des installations, du matériel, des appareils etc nécessaires au processus de déverminage;

– cỏt du matériel d'essai de fonctionnement nécessaire pour la détection des défaillances, le cas échéant;

– durée du processus de déverminage;

– cỏt du stock de matériel à déverminer;

The workforce management for pest control involves planning the pest removal process, overseeing and monitoring its execution, collecting and analyzing relevant data, preparing comprehensive reports, and handling administration and logistics.

– cỏts des retouches et de la mise au rebut;

– cỏt de la formation du personnel.

15.4.3 Facteurs à prendre en considération pour évaluer l'économie réalisée grâce au processus de déverminage:

Il convient de prendre en considération les facteurs suivants pour évaluer l'économie réalisée grâce au processus de déverminage.

– augmentation de la fiabilité et de la disponibilité des entités déverminées (traduite en valeur monétaire, le cas échéant);

– diminution des cỏts/du temps de dépistage et de réparation en usine (le cas échéant);

– diminution des cỏts de dépistage et de réparation en exploitation;

– diminution du matériel d'essai et des outils requis pour le dépistage et les réparations en usine/en exploitation;

– diminution du matériel, des outils et des pièces de rechange nécessaires pour la remise en état du fait de la diminution des défaillances en usine/en exploitation;

– diminution des cỏts administratifs et logistiques associés aux défaillances en usine/en exploitation;

– amélioration de la satisfaction du client, de la notoriété et de la réputation de la société

(traduite en valeur monétaire, si possible).

Etape 4 – Préparation d'un plan de déverminage

Il convient qu'un plan de déverminage comprenne au moins les éléments suivants:

– norme de déverminage choisie pour le processus de déverminage (c'est-à-dire la

– structure organisationnelle du programme de déverminage, identifiant le personnel et ses responsabilités;

– identification de tous les modes et mécanismes de défaillance applicables;

– objectifs et buts quantifiés du programme de déverminage sous contraintes;

– identification des niveaux de processus de déverminage applicables;

– identification de tous les différents types de processus de déverminage sélectionnés;

– description des raisons justifiant la sélection et les paramètres importants de chacun des processus de déverminage sélectionnés;

– description des procédures de collecte de données, d'analyse et d'action corrective prévues pour l'optimisation du processus de déverminage;

– hypothèses concernant la structure de défaillances prévue (répartitions statistiques) et approximations réalisées pour des analyses plus simples;

– cost of facilities, equipment, fixtures, etc., required for the screening process;

– cost of functional test equipment required for failure detection, if applicable;

– duration of the screening process;

– inventory cost for hardware being screened;

– labour cost: screening process planning, conducting and monitoring of screening process, collection and analysis of screening process data, report preparation, administration and logistics;

15.4.3 Factors to be considered when evaluating cost saving due to screening process

The following factors should be considered in evaluating the cost saving due to the screening process:

– increased reliability and availability of the items being screened (translated into monetary value, when applicable);

– reduction of factory troubleshooting and repair costs/time (if any);

– reduction of field troubleshooting and repair costs;

– reduction of test equipment and tools required for factory/field troubleshooting and repairs;

– reduction of equipment, tools and spares required for retrofits due to reduction of factory/field failures;

– reduction in administrative and logistics costs associated with factory/field failures;

– increased customer satisfaction, company goodwill and reputation (translated into monetary value, if possible).

15.5 Step 4 – Preparation of a screening plan

The screening plan should include at least the following elements:

– the RSS standard chosen for the RSS process (i.e IEC 61163-1 or IEC 61163-2);

– screening programme organizational structure, identifying personnel and their responsibilities;

– identification of the main applicable failure modes and mechanisms;

– stress screening programme objectives and quantitative goals;

– identification of the hardware to be screened;

– identification of applicable screening process levels;

– identification of all the different types of screening processes selected;

– description of the rationale behind the selections and the important parameters for each of the selected screening processes;

– description of the intended data collection, analysis and corrective actions procedures for screening process optimization;

– assumptions of the expected pattern of failures (statistical distributions) and approximations made for easier analysis;

– critères de fin (ou de modification de la taille d'échantillon) du processus de déverminage;

– surveillance du matériel (en temps réel);

– disponibilité du matériel d’essai et du personnel;

– critères pour réparer les entités en essai qui présentent une défaillance pendant le cycle de déverminage;

– critères pour recommencer le déverminage si l’entité qui a présenté une défaillance lors du processus de déverminage nécessite une réparation importante ou le remplacement de sous-ensembles importants.

Niveau choisi pour le processus de déverminage

RSS is mainly intended to detect inherent flaws or induced flaws Inadequate design should preferably be addressed by other tests, such as well structured design acceptance tests.

Flaws caused by inadequate design can be found in both components and assemblies.

Certain design flaws, such as tolerance interference, drifts, and propagation delay issues, often go undetected by standard evaluation methods like worst case analysis or reliability tests These flaws typically manifest as failures only when subjected to specific types of stress, highlighting the limitations of conventional qualification tests in identifying potential design inadequacies.

A pre-production screening process test is essential for evaluating flaws and their densities, as well as for assessing the effectiveness of various screens used in flaw precipitation The data obtained from this process is crucial for refining and stabilizing the production screening process However, caution is necessary to prevent misinterpretation of the data, which can often be misleading in certain situations.

– pre-production hardware configuration may be different from production configuration;

– the quality of components/materials used in pre-production hardware may be different from that of production hardware;

– lack of adequate quality control during pre-production phase;

– immature manufacturing processes during pre-production phase.

These factors have to be considered when using pre-production screening process data to select the production screening process and deciding on its parameters.

15 Planning, performing and eliminating a reliability stress screening process

When the analysis in clause 7 indicates the necessity for an RSS process, a screening plan must be developed Given the variety of electronic hardware and their diverse applications, the specifics of the planning process—including the application level, types of screening processes, and stress levels—cannot be standardized Nonetheless, a general planning procedure is outlined below, providing guidance on selecting the appropriate parameters.

15.2 Step 1 – Identification of objectives and goals

This step is essential in the planning process Effectiveness of the screening process cannot be ensured without clear identification of objectives and goals to be achieved.

A debugging process is typically implemented with at least one of the following objectives in mind: a) to achieve a required level of reliability This is necessary when reliability predictions, operational data, or test data indicate a reliability level that falls below the required or expected standard.

It is crucial to understand that a lower reliability level is inherently due to defects, rather than other types of failures that cannot be eliminated through the debugging process or can be addressed more effectively by alternative methods Achieving an acceptable or higher specified maximum defect density is essential, especially when a contract outlines such a requirement or when operational warranty data and cost analysis indicate the need to reduce defect density to meet customer expectations and financial goals Additionally, it is important to maximize the number of defects addressed within a fixed budget, particularly when a constrained debugging program is necessary.

To ensure the effectiveness of the pest control program, it is essential to measure the results of the pest removal process against predefined quantitative goals It is important to assess the adequacy of the pest control level, the testing regime, and the number of anticipated or observed failures.

When aiming to achieve a specific defect density, it is essential to consider several factors Firstly, the complexity of the studied material plays a crucial role, which is assessed based on the number and variety of components and subcomponents, the materials used, and the types of connections and interconnections involved in its construction.

The complexity of a system correlates with a higher expected defect density Established techniques are less likely to exhibit defects compared to those that are still maturing New or complex manufacturing processes, along with inadequate quality control measures, contribute to increased defect density, while proven and well-controlled processes minimize defects in electronic materials Additionally, whether materials, components, or modules have undergone prior debugging by the supplier or subcontractor affects defect density Finally, assessing the type and level of stress the equipment will face in real-world applications is crucial, as certain defects may lead to failures under high-stress conditions but may remain viable in less demanding environments This evaluation requires a deep understanding of the characteristics and time-dependent factors of the defects involved.

It is crucial to emphasize that environmental and operational profiles are entirely unrelated to the selected types of decontamination, due to the distinct differences between environmental qualification testing and the decontamination process The nature and maturity of the manufacturing processes used to produce the equipment lead to variations in defects, both in intensity and density High-intensity defects can almost certainly cause failures due to their degradation mechanisms, resulting in failures during the equipment's lifespan Additionally, it may be necessary to have stringent environments for low-intensity defects to cause failures, which might not occur in less severe conditions.

An RSS process is typically implemented to meet specific objectives, primarily to attain a desired level of reliability This is particularly relevant when reliability predictions, field data, or test results reveal that the current reliability falls short of the required or anticipated standards.

It is crucial to understand that the lower reliability level is attributed to flaws rather than other failures that cannot be addressed by RSS or are better managed through alternative methods Achieving a specified maximum allowable flaw density is essential, especially when a contract outlines this requirement or when warranty data and cost analyses indicate the necessity to lower flaw density to meet customer expectations and cost objectives Additionally, it is important to maximize the number of flaws within a predetermined budget, particularly when a reliability stress screening program is implemented with a fixed cost allocation.

To ensure the effectiveness of a screening program, measurable pre-set quantitative goals are essential Key factors influencing flaw density include the complexity of the hardware, which is determined by the variety and number of components and connections; the maturity of the technology, where established technologies typically exhibit fewer flaws; the manufacturing processes, as new or poorly controlled methods can increase flaw density; the history of previous screening processes for materials and components; and the application environments, which dictate the stress levels the hardware will face Understanding these factors is crucial for accurately assessing and managing flaw density in electronic hardware.

It is crucial to note that the environmental and operational profiles are unrelated to the selected screen types, as there is a significant distinction between environmental qualification tests and the RSS process The intensity and density of flaws in hardware depend on the manufacturing processes used, with high-intensity flaws posing a risk of failure due to their degradation mechanisms during the hardware's useful life In contrast, low-intensity flaws may only lead to failures in harsh environments and might not fail at all in benign conditions.

By taking into account all the aforementioned factors and comparing them to similar materials with equivalent complexity and manufacturing processes, it is feasible to determine a maximum defect density This can be expressed as the maximum allowable percentage of fragile entities in the market, as outlined in IEC 61163-1.

15.3 Etape 2 – Conception et application du processus de déverminage

The selection of deworming types, their parameters, intensity, and appropriate application levels is the most crucial step in the overall process An ideal deworming approach aims to convert defects into production failures without damaging or degrading components or materials of satisfactory quality.

Tiêu đề	Reliability stress screening of electronic hardware
Chuyên ngành	Dependability management
Thể loại	Guidance document
Năm xuất bản	1999

Định dạng
Số trang	78
Dung lượng	488,27 KB