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Detailed selection of military electronic components

by AOMag | post a comment

Electronic components are the basic components of an electronic system, and are basic units of circuits that can perform 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 performance, reliability, life cycle and other technical indicators of the entire military electronic products. Therefore, the correct and effective selection and use of electronic components is an important task to improve the reliability level of military products. At present, the world is undergoing a new military revolution. Informatization is the essence and core of this new military revolution. The necessary conditions for realizing the informatization of military equipment are high-level and highly reliable military electronic components. Electronic components, especially microelectronic devices, are increasingly used in military equipment, and the selection and application of electronic components is increasingly important.

This article focuses on the procurement, screening, destructive physical analysis and failure analysis in the selection and use of military electronic components, and lists the selection and use criteria of components and the whole process flow chart. Electronic components are the basic components of an electronic system, and are basic units of circuits that can perform 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 performance, reliability, life cycle and other technical indicators of the entire military electronic products. 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 reliability. The inherent reliability is mainly guaranteed by design and manufacturing work. This is the task of component manufacturers. However, the failure analysis data at home and abroad shows that nearly half of the component failures are not due to the inherent reliability of the components, but to the user's improper selection or incorrect use of components.

Therefore, in order to ensure the reliability of military electronic products, it is necessary to strictly control the selection and application of electronic components. 1, the classification of electronic components As the name suggests, components can be divided into two major categories of components and devices. There are resistors, capacitors, inductors, relays and switches in the components; devices can be divided into semiconductor discrete devices, integrated circuits and electric vacuum devices. Table 1 is the component classification table.
2, the quality level of electronic components The quality level of components refers to the quality control level of the manufacturing, inspection and screening process according to the product implementation standards or the technical agreement between the supplier and the buyer before the component is installed. The higher the quality level, the higher the reliability level. In order to ensure the quality of military components, China has established a series of component standards. In the early 1980s, the "seven specialties" 8406 technical conditions (hereinafter collectively referred to as "seven specialties"), the "seven specialties" technical conditions were established. The basis of China's military component standards, the components currently controlled according to the "seven specialties" or its tightening conditions are still the main varieties used by aerospace and other departments. (Note: "Seven specialties" refers to special personnel, special planes, special materials, special approval, special inspection, special skills, special cards). According to the development trend, the "seven special" conditions will gradually transition to the national military standard (GJB) of components. The military standardization organization of China has established the national military standard GJB system with reference to the US military standard (MIL) system.

3, the choice of electronic components Improper selection of components will cause the reliability level of the purchased components does not meet the requirements, thus affecting the reliability of the system, so the selection of components must be controlled. 3.1 Principles of component selection

(1) The technical performance of components should meet the product requirements. Environmental adaptability should meet the requirements of military products, generally a 55~C~125~C. (2) The quality level of components should meet the requirements of the product.
(3) Consider the requirements for derating.
(4) It is preferred to use mature, stable, reliable, promising and continuously available standard components.
(5) The domestically produced components are preferred, especially the components on the military qualified product catalogue and the components produced by the IS09001 certified component manufacturers.

3.2 Selection order of domestic components

(1) Selecting components that have been certified and certified to conform to the national military standard;
(2) Selecting components that have been tested and meet the requirements and can be stably supplied by the “seven special” fixed-point manufacturers.

3.3 The selection order of imported components When selecting imported devices (especially those imported from the United States), it should be cautious and prudent for political reasons. Foreign embargoed components sometimes occur; second, foreign markets have changed greatly, especially US military products. The gear shift has had an impact on the production and maintenance of many products in China. The order of selection is:

(1) Selecting components in the QPL/PPL of foreign authorities;
(2) Select high-reliability components that have undergone strict aging screening in the production process (such as integrated circuit 883 and above, semiconductor discrete devices are JAN FX and above);
(3) Select industrial-grade devices that have undergone secondary screening and are DPA-compliant and meet the military temperature range (a 55cc to l25cc);
(4) Avoid using the “broken” military products that have stopped production in foreign countries. The US military microelectronics device is broken, which means that a large number of US military microelectronic devices are no longer produced or will no longer be produced. The United States gives a special definition: "Diminishing Manufacturing Sources and Material Shortages", referred to as For DMSMS.

3.4 Prepare the component preferred catalogue as the overall unit of the model. The component catalogue should be developed, and the component types and specifications selected for the model should be compressed according to the preferred catalog. The quality grade of the components should be controlled to better ensure the components. The quality of supply is more conducive to integrated logistics support.

3.4.1 Preparation process

(1) Establish a compilation group;
(2) Research and collection of component usage requirements. The quality of domestic component manufacturers and the status of foreign components;
(3) Understand the latest “disconnected” military products of foreign components;
(4) Prepare a draft for comments;
(5) A summary analysis of various opinions;
(6) After review, it is released by the general unit.

3.4.2 Dynamic management is based on the change of the components used in the product development and production stage, the changes of the components manufacturer's products and their quality status, and the information feedback during the use of the components. , the revision of the preferred directory should be carried out.

4. Selection and use of military electronic components The correct use of components has become an important issue affecting the reliability of military electronic components, equipment and systems, and should be highly valued by users.

4.1 Selection and use of components The whole process of process flow components use selection, procurement, supervision, acceptance, screening (copying machine), destructive physical analysis (DPA), storage, use, electrical assembly, power commissioning, static electricity Protection and failure analysis, etc. The whole process flow chart of component selection and use is shown in Figure 1.

4.2 Purchasing of components As shown in Figure 1, the procurement process is an important part of ensuring that components can meet the design requirements. Therefore, the units of each system, subsystem and equipment should pay attention to the following points: (1) The manufacturer shall prepare the technical standards for the purchased components and the re-inspection specifications for the incoming products, 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 of the components, the use standards and the manufacturer; the package form, installation form and use of the components Environment; packaging and shipping requirements for components.
(3) The contractor shall pay attention to the catalogue of qualified sub-contractors when purchasing components, and the corresponding approval procedures shall be carried out when more procurement is required.
(4) How to purchase the specified quality level in actual procurement is the key to ensuring high reliability of the product. The components of the actual production model (including the front and rear suffixes), the quality grade, and the package form are completely purchased directly with the components of the drawing design. For some components with changes in the front and back suffix and unclear quality grades, the production execution standards should be determined first when purchasing. In the standard of components, the quality control standards of components in the manufacturing, inspection and screening process are generally specified. Products produced and managed according to different control standards have different quality levels. Accordingly, the product production execution standard is the main basis for dividing the quality level. If the production standard meets the production standard of the specified quality level, the component is considered to have reached the specified quality level. Secondly, the quality coefficient of the component should be clarified. The failure rate of the component can be calculated by its mass coefficient. As long as the failure rate satisfies the assigned value of the component, the component is considered to have reached the specified quality level.

4.3 Secondary screening of components Secondary screening of components is an important means of ensuring quality and reliability. Generally speaking, military products require 100% of the secondary screening of components, including 883B and "seven special". In Figure 1, when the contracting unit purchases the components back into the factory, it should follow the “Secondary Screening Specification for Model Components” to perform the secondary screening of the component design and the whole process flow chart. When the component secondary screening failure rate exceeds the specified ratio, the batch components are not allowed to be installed. In the secondary screening process, for components that do not have the screening conditions (such as large-scale 1:3 integrated circuits), the copying machine can be used (that is, the components without the screening conditions are assembled into the circuit board to perform temperature stress. Or the method of electrical stress for a long time test).

4.4 Destructive physical analysis (DPA) of components After the secondary screening of components is qualified, destructive physical analysis should be carried out on the components with high quality and unstable production in the early stage (DPA——Destructive Physical Analy- Sis) test. The focus is on this work for semiconductor discrete devices and semiconductor integrated circuits with cavities. The purpose is to verify that the quality of the component meets the intended use or intended use of the specification. DPA generally extracts 1-2 samples from a batch of components for a series of tests and analysis, and draws the conclusion that 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 for an integrated circuit DPA. Table 3 General procedure for integrated circuit DPA

4.5 Failure Analysis of Components During the commissioning and component environmental stress screening process, failures of critical and important components are found or components that fail multiple times during use without finding the cause should be analyzed for failure of components. Failure analysis of components is carried out by anatomical analysis of the failed components, and physical and chemical techniques are used to find out the failure mechanism, and improvement methods are proposed to improve the reliability of the components. Failure analysis includes failure investigation, failure mode identification, failure characterization, failure mechanism verification, and proposed corrective actions. There are more than 20 failure analysis of integrated circuits, 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) Second, the triode should avoid the selection of the manifold, and choose the silicon tube;
(2) The domestic plastic package integrated circuit can not be used for military products;
(3) The resistor RJ1~Pd7 series cannot be used because of its custom magnets tube It is hollow and easy to crack under vibration conditions. It can be replaced by RJK24~RJK26 or t/J13 and RJ14.
(4) CA30 in capacitor is not available due to leakage after storage, CA35 type can be used;
(5) Relay should be used Metal package, sealed type, parallel derating is not allowed.

4.7 Component Usage Guidelines

(1) Deep people master the technical performance of the components used and strictly control the use of new devices.
(2) Deliberately reduce the working stress (electrical, thermal, mechanical stress) of the component so that the actual applied stress is lower than its specified rated stress. Derating design can refer to GJB/Z35 "Component Derating Guidelines".
(3) In order 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) In order to solve the device failure caused by static electricity, anti-static measures must be taken in the design and use of the device. If the protection network of the anti-static damage is added to the input end of the device, the operation site must take anti-static measures. (5) Pay attention to the correct use of instruments and meters during the debugging process. For example, the instrument should be grounded normally. (6) Properly store and store components. Such as maintaining appropriate temperature and humidity; preventing the presence of harmful gases.

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