How to control the reliability of electronic components
Electronic components are an important part of electronic products and the most basic unit of electronic products. Quality inspection of components is directly effect the reliability of the entire system.
Therefore, the reliability of components is an important part of the quality control of electrical products, and it is also of great significance for accelerating the development of new products, ensuring the quality of development, saving development costs, and reducing comprehensive support costs and life cycle costs.
Secondary screening of components
The screening of components is divided into "primary screening" and "secondary screening". The screening of components according to the product specifications of the components before they are delivered to the user is called "one-time screening". The re-screening carried out by the assembly factory according to the use requirements after purchase is called "secondary screening".
At present, the production level of electronic components in China is more or less different from the use requirements of electronic products. The screening items and quality requirements of a screening conducted by manufacturers may not meet the expected life expectancy of products. need.
There are not many genuine authentic imported components, most of which are middle and low-end products, and there may also be many fake and shoddy products.
The requirements of electrical products for electronic components are often very pertinent, and components with a certain failure mode must be strictly eliminated, otherwise the product cannot be guaranteed to work reliably. All these require us to ensure the quality of components through secondary screening. The secondary screening of components is one of the important measures in the quality control of components, which is of great significance to the reliability of products.
Several issues should be paid attention to during the second screening:
1. 100% secondary screening should be carried out on the components used in electrical products, so that components with certain failure modes can be eliminated to the greatest extent.
2. Carry out selective screening for the purpose of the product. For example: the assessment of radiation resistance is a special case. It must be considered for aerospace electronic equipment, but basically not considered for ordinary household electronic equipment.
3. For components that cannot be directly screened due to technical problems, other control methods must be adopted to ensure their quality. For example, some tests have been carried out on the circuits used or other units are commissioned to carry out tests and so on.
4. Considering the limitations of secondary screening, it must strictly control its batch allowable failure percentage (PDA).
Common test items for secondary screening:
Temperature cycling: check for structural defects
Constant temperature acceleration: check the inner lead
Particle collision noise detection: check for impurities
High and low temperature test: check parameter drift
Initial test and final test at room temperature: check product life
Leak detection: check for leaks
Destructive physical analysis (DPA) of components
Destructive physical analysis (DPA) technology is required by engineering and developed to ensure the high reliability requirements of components. It can reflect some defects that cannot be found in the secondary screening process of components.
A large number of statistics show that the proportion of unqualified products such as appearance inspection, PIND and leak detection that can be eliminated through screening is 36.9%, and the proportion of defects that cannot be eliminated through screening such as internal visual inspection and shear force reaches 63.1%. , So it is impossible to get rid of all defects through screening.
General principles for developing DPA:
1. Important electrical products or important electronic components in ordinary electrical products need to implement DPA;
2. Electronic components whose grade is lower than product requirements;
3. Failure to replace the used components according to the model requirements;
4. Components of the same batch that have failed during the test;
5. For components that exceed the storage period, select items reasonably and choose DPA laboratories certified by relevant departments for DPA testing.
Storage of components
The storage of components must comply with its specified storage and storage conditions, especially for electronic components that need to be moisture-proof, anti-corrosion, anti-aging, anti-static and other electronic components should be properly stored. The warehouse for storing components should be classified into different varieties and different batches. , The warehouse shall be clearly marked, arranged in an orderly manner, safe and secure, reasonably stored, clean and tidy, and temperature and humidity shall be recorded. Regular quality inspections are carried out on electronic components with special requirements, and unqualified products are isolated in time and recorded.
welding assembly of components
When the inherent reliability and use reliability of the components are a certain value, the reliability of the electrical equipment process determines the reliability of the electronic product. Therefore, we must pay attention to the reliability of electric welding assembly of electronic components to ensure the reliability of electronic components.
The components enter the production workshop and are welded according to the drawings and process requirements. The welding time, welding temperature and anti-static requirements of various components of the electric welding assembly process should be clearly given.
If the welding time of a CMOS integrated circuit is less than 4s and the welding temperature is less than 240℃, the welding should be done in the static protection area. For some integrated circuits that are convenient for replacement or not suitable for direct welding, the integrated circuit socket should be welded first, and the welding height should be specified for those with heat dissipation requirements.
The welding and assembly workers in the production workshop should be trained to complete defects not found in the component sampling, such as whether the components are mixed, whether the marking is correct, whether the welding foot is deformed, whether the appearance is damaged, etc.
Component failure analysis
Failure analysis is an important way to discover and solve problems. When component failures are found during product testing, the quality control department should conduct failure analysis to clarify the cause of failure for a single failure or batch of components with quality problems.
Important component failures, components with repeated failures with unknown causes, and selected components with unknown or low quality levels should be considered as the key points and can be performed by a professional failure analysis laboratory. Through failure analysis, the design can be improved, the management of key processes can be strengthened, and the reliability of the product can be continuously improved.