Electronic components (hereinafter referred to as components) are an important part of electronic products and the most basic unit of electronic products. The reliability of components is directly related to the reliability of the entire system. Therefore, the reliability of components is one of the important links to ensure product reliability in the model development process, and it is also of great significance to speed up the model development progress, ensure the development quality, save development costs, reduce comprehensive security costs and life cycle costs. .
Secondary screening of components
The screening of components is divided into two categories: "primary screening" and "secondary screening". The screening of components according to the product specifications (general specifications, detailed specifications) of components before they are delivered to users is called "primary screening". The re-screening performed by the user according to the usage requirements after purchase is called "secondary screening".
At present, there are some differences between the production level of domestic components and the use requirements of the developed products in general, and the screening items and stress requirements of a screening conducted by manufacturers may not necessarily meet the needs of product development.
There are not many real "military standard" products in imported components, most of which are low-end products, and there may be many fake and inferior products.
However, the developed products are often highly targeted, and components with a certain failure mode must be strictly eliminated, otherwise the product cannot be guaranteed to work reliably. These all 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.
There are several issues that should be paid attention to in the secondary screening:
1. 100% secondary screening should be implemented for the components used in the model development, so as to maximize the elimination of components with a certain failure mode.
2. Selective screening for the use of the product. For example, the assessment of the ability to resist radiation exposure is a special case. It must be considered for aerospace electronic equipment, and basically can not be considered for terrestrial electronic equipment.
3. For components that cannot be screened due to means problems, other control methods must be adopted to ensure their quality. For example, some tests have been carried out on the circuit used or other units have been commissioned to carry out tests and so on.
4. Considering the limitations of secondary screening, its batch allowable failure percentage (PDA) must be strictly controlled.
Common items for secondary screening:
Temperature Cycling: Checking for Structural Defects
Constant Temperature Acceleration: Check Inner Leads
Particle collision noise detection: check for impurities
Electro-Aging: Checking for Early Failure
High and low temperature test: check parameter drift
Normal temperature initial test and final test: check whether the product is qualified
Leak detection: Check for leaks
Destructive Physical Analysis (DPA) of Components
Destructive physical analysis (DPA) technology is developed in response to engineering needs and to ensure the high reliability of components. It can reflect some defects that are impossible to find in the secondary screening process of components.
A large number of statistics show that the proportion of non-conforming items that can be eliminated through screening, such as external visual inspection, PIND and leak detection, accounts for 36.9%, while the defects that cannot be eliminated through screening are included in internal visual inspection, shear force, bonding force. The equal proportion reaches 63.1%, which shows that the number of proposals that cannot pass the screening is too large.
General principles for carrying out DPA:
1. The components selected for important types or general types of important electronic products need to be DPA;
2. The grade of the device is lower than the component required by the model;
3. Failure to retrograde components that can be supplemented according to the model requirements;
4. Components of the same batch that have failed in the test;
5. For components that have exceeded the storage period, the DPA test should be reasonably selected and the DPA laboratory certified by the relevant department should be selected.
Storage and custody of components
The storage and storage of components must comply with the specified storage and storage conditions, especially for electronic components that require moisture-proof, anti-corrosion, anti-aging, anti-static and other electronic components, and should be properly stored in the warehouse where components are stored. For sub-category storage, the warehouse should be clearly marked, arranged in an orderly manner, safe and secure, reasonably stored, clean and tidy, with records of temperature and humidity. In the process of stockpiling, regular quality inspections are carried out on electronic components that require regular testing, and unqualified products are found to be isolated and shipped out of the warehouse in time, and recorded.
Electrical installation and debugging of components
When the inherent reliability and use reliability of the components are a certain value, the reliability of the electrical installation process determines the reliability of electronic products. Therefore, we must pay attention to the electrical reliability of electronic components to ensure the reliability of electronic components.
Components enter the production workshop, and electric welding is carried out according to the drawings and process requirements. The soldering time, soldering temperature and anti-static requirements of various components should be clearly given in the electrical process.
If the welding time of a CMOS integrated circuit is less than 4s and the welding temperature is less than 240℃, it should be welded in the electrostatic protection area. For some integrated circuits that are easy to replace or not suitable for direct welding, the integrated circuit socket should be welded first. For those with heat dissipation requirements, the welding height should be specified.
The electrical installation workers in the production workshop should be trained to be able to complete the unfinished matters in the sampling inspection of components, such as whether the components are mixed, whether the identification is correct, whether the welding feet or pins are deformed, and whether the appearance is damaged.
Before power-on debugging of the printed board, mainly check the direction of the components, and whether the printed board is soldered for short-circuit, virtual welding, etc. Whether the debugging process is live or not, special attention should be paid to electrostatic protection and debugging tools. Whether the debugging tool meets the anti-static requirements directly affects the smoothness of the electrostatic discharge path of the electrostatic sensitive device during the debugging process. When debugging and replacing components or discovering problems, detailed records should be recorded, and designers should be notified to find out the reasons.
For example: the meter uses a potentiometer with a deviation of 500Ω and a deviation of no more than 10%, and the batch quality is critical to 461Ω, which is qualified. Denso debugging found that the predetermined function is difficult to adjust. The designer analyzes the circuit according to the debugging record, and determines which component parameters are not suitable. Then replace it to improve the reliability of the components.
Component Failure Analysis
Failure analysis is an important way to find and solve problems. When component failure is found in the process of product testing, system joint debugging, etc., for components with typical failure or batch quality problems, the component quality control department should organize relevant technical personnel. Conduct failure analysis together with quality control personnel to clarify the failure mechanism and find out the cause of failure;
The failure of critical and important components, the repeated failure of components with unknown reasons, and the selected components of unknown or low quality level should be regarded as the key points, which can be carried out by professional failure analysis laboratories. Through the test marketing analysis, the design can be improved, the management of key processes can be strengthened, and the reliability of the product can be continuously improved;
At the same time, the technical level of design, manufacture and related personnel has also been improved. If it is confirmed that it is a batch quality problem after the failure analysis, a notification and warning should be issued at least within the scope of the developed model to avoid the recurrence of similar situations.
Build component quality database
The establishment of a component quality database can comprehensively reflect the quality status of components, from which we can see the production level and technological level of the manufacturer, and can provide corresponding quality data for the components selected for model development, providing a basis for some decision-making.
According to this, suppliers can also be adjusted, and specific manufacturers can be selectively entrusted to carry out research and development of new components and put forward suggestions for funding technical transformation, so as to further ensure the quality and reliability of components. The model development unit should establish the information storage information database from the whole process of component selection, ordering, supervision and acceptance, secondary screening, DPA, storage and failure analysis, and establish a searchable component destination including information on installed components and failed components. information base.
The database should be established by the quality inspection department, with the cooperation of procurement, testing and development departments, and provide corresponding data. The quality department uses the computer to carry out statistics and analysis on the database, and then feed back the results to the procurement, testing and development departments, and adjust the procurement, testing and adoption of components accordingly to improve the reliability of components.
In order to improve the reliability of electronic components, we must do a good job in the design, selection, inspection, testing, screening, storage, and electrical installation of components; it will provide a solid foundation for improving the reliability of electronic products. According to the above discussion and the experience of some model development, it can be seen that:
1. The preparation of the model component selection catalog is the cornerstone of component work, which must be given full attention.
2. Secondary screening is a must for installed components, and key models require 100% secondary screening.
3. Failure analysis and DPA are important means of discovering quality problems of components. In the long run, they greatly reduce the life cycle cost of equipment.