Selection and Application of Military Electronic Components

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At present, the world is undergoing a new military revolution. Informatization is the essence and core of this new military revolution. The necessary condition for realizing the informatization of military equipment is high-level and highly reliable military electronic components. Electronic components, especially microelectronic components, are increasingly widely used in military equipment, and the selection and application of electronic components are becoming increasingly important. This article focuses on the procurement, screening, destructive physical analysis and failure analysis of military electronic components in the selection and use process, and lists the selection and use criteria of components and the flow chart of the whole process.

Electronic components are the basic parts of electronic systems. They are the basic circuit units that can complete the predetermined functions and cannot be divided. Due to the large number and variety of electronic components, their performance, reliability and other parameters have a great impact on the technical indicators of the entire military electronic products, such as system performance, reliability, and life cycle. Therefore, the correct and effective selection and use of electronic components is an important task to improve the reliability level of military products. The reliability of electronic components is divided into inherent reliability and use reliability. Inherent reliability is mainly guaranteed by design and manufacturing, which is the task of component manufacturers. However, domestic and foreign failure analysis data show that nearly half of the component failures are not due to the low inherent reliability of the components, but due to improper selection or incorrect use of components by users. Therefore, in order to ensure the reliability of military electronic products, the selection and application of electronic components must be strictly controlled.

1. Classification of electronic components

As the name implies, components can be divided into two categories: elements and devices. Components include resistors, capacitors, inductors, relays, switches, etc.; devices can be divided into semiconductor discrete devices, integrated circuits, and vacuum devices, etc. Table 1 is a classification table of components.

2. Quality grade of electronic components

The quality grade of components refers to the level of quality control during the manufacturing, inspection and screening process according to product implementation standards or technical agreements between supply and demand parties before the components are installed and used. The higher the quality grade, the higher the reliability level.

In order to ensure the quality of military components, my country has formulated a series of component standards. The "Seven Special" 8406 technical conditions (hereinafter referred to as the "Seven Special" conditions) formulated in the early 1980s are the basis for establishing my country's military component standards. At present, components produced under the "Seven Special" conditions or their stricter conditions are still the main varieties used by aerospace and other departments. (Note: "Seven Special" refers to special personnel, special machines, special materials, special approvals, special inspections, special technologies, and special cards). According to the development trend, the "Seven Special" conditions will gradually transition to the national military standards (GJB) for components. my country's military standardization organization has established the national military standard GJB system with reference to the US military standard (MIL) system.

3. Selection of electronic components

Improper selection of components will result in the reliability level of the purchased components not meeting the requirements, thus affecting the reliability of the system. Therefore, the selection of components must be controlled.

3.1 Principles for selecting components

(1) The technical performance of components should meet product requirements. Environmental adaptability should meet military product requirements, generally -55°C to 125°C.

(2) The quality level of components should meet the requirements of the product. (3) Consider the derating requirements.

(4) Give priority to the use of mature, stable quality, high reliability, promising development and continuously supplied standard components.

(5) Give priority to domestic components, especially those on the military qualified product catalog and those produced by component manufacturers that have passed IS09001 certification.

3.2 Selection order of domestic components

(1) Select components that have been certified and identified and meet national military standards;

(2) Select components produced by "seven-specialized" designated manufacturers that have been tested, meet the requirements, and can provide stable supply.

3.3 Selection order of imported components

When choosing imported components (especially those from the United States), you should be extremely cautious. First, due to political reasons, foreign embargoes on components are common; second, foreign markets are changing greatly, especially the shortage of US military products has affected the production and maintenance of many products in my country. The selection order is:

(1) Select components from the QPL/PPL of foreign authoritative institutions;

(2) Select high-reliability components that have undergone rigorous aging and screening during the production process (e.g., integrated circuits of level 883 or above, and semiconductor discrete devices of level JAN FX or above);

(3) Select industrial-grade devices that have undergone secondary screening, passed DPA, and meet the military temperature range (-55cc to 125cc);

(4) Avoid continuing to use "discontinued" military products that have been discontinued in foreign countries. The discontinuation of U.S. military microelectronic devices refers to the fact that a large number of U.S. military microelectronic devices are no longer produced or will soon be discontinued. The United States has given a special definition: "Diminishing Manufacturing Sources and Material Shortages", abbreviated as DMSMS.

3.4 Compile a catalog of preferred components

As the overall unit of the model, a preferred catalog of components should be formulated, and based on the preferred catalog, the varieties and specifications of components selected for the model should be compressed in the product design, the quality grade of the components should be controlled, the supply quality of the components should be better guaranteed, and it will be more conducive to comprehensive logistics support.

3.4.1 Preparation process

(1) Establish a drafting team; (2) Investigate and collect information on the use requirements of components, the quality of domestic component manufacturers, and the status of foreign components; (3) Understand the latest situation of "discontinued" military products of foreign components; (4) Prepare a draft for soliciting opinions; (5) Summarize and analyze various opinions; (6) After review, the overall unit will issue it.

3.4.2 Dynamic Management

Dynamic management should be carried out based on the changes in the types of components used during the product development and production stages, the changes in the products and quality of component manufacturers, and the information feedback during the use of components. If the above situations change significantly, the preferred catalog should be revised.

4. Selection and use of military electronic components

Whether components can be used correctly has become an important issue affecting the reliability of military electronic components, equipment, and systems, and should be taken seriously by users.

4.1 Flowchart of the whole process of component selection and use

The whole process of using components includes selection, procurement, supervision, acceptance, screening (copying), destructive physical analysis (DPA), storage, use, electrical assembly, power-on debugging, electrostatic protection and failure analysis, etc. The flow chart of the whole process of selecting and using components is shown in Figure 1.

4.2 Procurement of Components

As shown in Figure 1, the procurement process is an important step to ensure that components can meet the design requirements. Therefore, the contractors of each system, subsystem and equipment of the model should pay attention to the following points:

(1) The contractor shall prepare the technical standards and factory re-inspection specifications for purchased components, and the standards shall be consistent with the current valid drawings. (2) The contractor shall prepare a purchase list of components, including the name, model, specification, accuracy and quantity of the components; the quality grade, use standard and manufacturer of the components; the packaging form, installation form and use environment of the components; and the packaging and transportation requirements of the components.

(3) When purchasing components, the contractor should pay attention to the list of qualified sub-contractors, and should go through the corresponding approval procedures when cross-point procurement is required.

(4) How to purchase the specified quality grade in actual procurement is the key to ensure high reliability of products. Directly purchase components whose actual production model (including prefix and suffix), quality grade, and packaging form are completely consistent with the design on the drawing. For some components with different prefixes and suffixes and unclear quality grades, their production execution standards should be determined first when purchasing. In the standards of components, the quality control standards of components in the manufacturing, inspection and screening process are generally stipulated. Products organized and managed according to these different control standards have different quality grades. Based on this, the production execution standard of the product is the main basis for dividing its quality grade. If its production standard meets the production standard of the specified quality grade, it is considered that the component has reached the specified quality grade. Secondly, the quality coefficient of the component should be clarified. The failure rate of the component can be calculated through its quality coefficient. As long as the failure rate meets the value assigned to the component, it is considered that the component has reached the specified quality grade.

4.3 Secondary Screening of Components

Secondary screening of components is an important means to ensure quality and reliability.

The product requires 100% secondary screening of components, including 883B level and "seven special" level. In Figure 1, when the contracting unit purchases the components back to the factory, it should be screened in accordance with the "secondary screening specifications for components for models". When the failure rate of the secondary screening of components exceeds the specified proportion, the batch of components is not allowed to be installed and used. In the secondary screening process, for components that do not meet the screening conditions (such as large-scale 1:3 integrated circuits), the copy machine method (that is, assembling components that do not meet the screening conditions into the circuit board and conducting temperature stress or electrical stress long-term tests) can be used.

4.4 Destructive Physical Analysis (DPA) of Components

After the components are qualified after the second screening, destructive physical analysis (DPA) test should be carried out on the components with unstable quality in the early stage and the components with great improvement in production process. The focus is on semiconductor discrete devices with cavities and semiconductor integrated circuits. Its purpose is to verify whether the quality of the components meets the use or intended use of the relevant specifications. DPA generally extracts 1-2 samples from a batch of components for a series of tests and analyses, and makes a conclusion on whether the batch is qualified or not. This plays an important role in ensuring the quality and reliability of the components used. Table 3 shows the general procedure of DPA for integrated circuits.

Table 3 General procedures for integrated circuit DPA

4.5 Failure Analysis of Components

During the debugging and component environmental stress screening process, failures of key and important components or components that have failed multiple times in use without finding the cause should be analyzed for component failure. Component failure analysis is to dissect and analyze failed components, and use physical and chemical techniques to find out their failure mechanisms and propose improvement methods, thereby improving the reliability of components. Failure analysis includes failure investigation, failure mode identification, failure feature description, failure mechanism confirmation, and corrective measures. There are more than 20 types of failure analysis for integrated circuits, ranging from external analysis to internal analysis, from non-destructive analysis to destructive analysis, and then using optical, chemical, mechanical, and electronic techniques for analysis.

4.6 Component Selection Criteria

(1) Avoid choosing germanium tubes for diodes and triodes, and choose silicon tubes instead;

(2) Domestic plastic packaged integrated circuits cannot be used in military products;

(3) The resistors RJ1~Pd7 series cannot be used because their magnetic tubes are hollow and easily cracked under vibration conditions. They can be replaced by RJK24~RJK26 or t/J13, RJ14;

(4) CA30 capacitors are not suitable for use because they are prone to leakage after storage. CA35 capacitors can be used instead. (5) Relays should be metal-encapsulated and sealed. Parallel operation with derating is not allowed.

4.7 Component Usage Guidelines

(1) Have a deep understanding of the technical performance of the components used and strictly control the use of new components.

(2) Consciously reduce the working stress (electrical, thermal, and mechanical stress) of components so that the actual use stress is lower than the specified rated stress. For derating design, refer to GJB/Z35 "Component Derating Guidelines".

(3) To prevent thermal failure of electronic components, effective thermal design and environmental protection design must be adopted during the layout and installation of components.

(4) To solve the problem of device failure caused by static electricity, anti-static measures must be taken in device design and use. For example, a protection network to prevent static damage must be added to the input end of the device, and anti-static measures must be taken in the operating area.

(5) During the debugging process, attention should be paid to the correct use of instruments and meters, such as the normal grounding of instruments and meters.

(6) Store and preserve components correctly, such as maintaining appropriate temperature and humidity and preventing the presence of harmful gases.

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