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First, the generation of electronic equipment reliability problems
Modern electronic equipment, especially military electronic equipment, is becoming more and more oriented towards light, thin, short, small, high density, high automation and high precision. The main technical contradiction of its development lies in: if no special measures are taken to improve its reliability Sex, then the more complex and accurate the device, the lower its reliability. For example, a modern electronic equipment system consists of several components and various manufacturing processes (processes), which are interdependent and complex systems. If one of the components is damaged or a manufacturing process is not perfect, the entire system will fail. It can be seen that the reliability of a modern electronic equipment system does not exceed the reliability of the components that constitute the least reliable in the system and the process reliability of each manufacturing process. At the end of the Second World War (1944 - 1945), especially during the Korean War (1950 - 1952), according to relevant US sources, radio communication equipment had 14% of the time, and underwater acoustic equipment had 48% of the time. About 84% of radar equipment is in non-working state; in 1949 alone, about 70% of marine radio electronic equipment is in non-working state... Therefore, to identify the cause of unreliability, improve The reliability of radio electronic equipment has become a national imperative in the United States. Dozens of military departments of the US Army and Navy conducted large-scale investigations of equipment. That is, from this point on, the statistical research method of reliability has been recognized.
Second, the definition and mathematical description of the reliability of electronic equipment
1. Definition of reliability According to the national standard GB 6583-1994, the reliability of a product refers to the ability of a product to perform a specified function within a specified time under specified conditions. The reliability of the actual use of an electronic device or system is called operational reliability. The reliability of work can be divided into inherent reliability and reliability of use. Intrinsic reliability is the reliability that product design and manufacturers must establish, that is, reliability based on reliability planning, from the selection of raw materials and components, through design, manufacturing, testing, to the various stages of equipment or system production. Use reliability refers to the reliability of products that have been produced, affected by factors such as packaging, transportation, storage, installation, use, and maintenance. From a modern point of view, with the continuous introduction of micro-assembly technology, reliability includes four elements of durability, maintainability, design reliability and process reliability.
● Durability: The product is trouble-free or has a long service life. For example, when a space-detecting satellite is launched, it is expected that it will work without problems for a long time, but from a certain point of view, it is impossible for any product to fail 100%.
● Maintainability: When the product fails, it can be quickly and easily removed through maintenance, which is maintainability. For example, airplanes and cars are expensive and highly concerned with safety and reliability. This is generally extended by daily maintenance and maintenance, which is preventive maintenance.
●Design reliability: This is the key to determining the quality of the product. Due to the complexity of the human-machine system and the possible errors in the operation and the various factors affecting the operating environment, the possibility of error still exists, so the design When considering the ease of use and ease of operation of the product, this is the design reliability.
● Process reliability: High density, micro-components, and micro-welding technologies are becoming more and more popular in modern electronic manufacturing. The United States is the second country in the world to launch satellites. It is such a major event that raises the prestige of the country. It has also suffered setbacks because of a small problem involving welding. About 80% of the failures caused by manufacturing factors in today's domestic and foreign electronic products are caused by welding quality problems. In the failure of solder joints, the failure of solder joints of surface array package devices (such as BGA, CSP, FCOB, etc.) accounts for about 80% of the total solder defects. Obviously, solving the solder joint failure problem of surface array package devices (such as BGA, CSP, FCOB, etc.) is the most important to improve the quality and reliability of modern electronic products manufacturing, which is the challenge of process reliability.
