Ten misunderstandings in the reliability of electronic products

Date：2022-01-20 13:31:00Views：932

Common reliability design principles and methods include component selection and control, thermal design, simplified design, derating design, redundancy and fault tolerance design, environmental protection design, robust design and human factor design. Except that component selection and control and thermal design are mainly used for reliability design of electronic products, other design principles and methods are applicable to reliability design of electronic products and mechanical products.

During the design of electronic products, technical activities are taken to eliminate potential defects and weak links of products, prevent faults, and ensure that the specified inherent reliability requirements are met. Reliability design is an important part of reliability engineering and the most critical link to realize the inherent reliability requirements of products. It is realized by formulating and implementing reliability design criteria on the basis of reliability analysis.

Misunderstanding 1. Product failure = unreliable product

There may be other reasons for the problems of the product, in addition to considering the problems of R & D and design. Product reliability is "the ability to complete specified functions within specified time and under specified conditions". The conditions of the use site often exceed the specified conditions, which may be implied.

Misunderstanding 2. Transition process = steady state process

The introduction of "a curve affecting product reliability and social harmony" can well explain the content of this figure.

Misunderstanding 3. Take the reduction lightly

Everyone can reduce the amount, such as painting, but not everyone can survive by painting.

1. The derating coefficients of devices with the same function but different processes are different.

2. The derating coefficients of adjustable devices and fixed value devices are different.

3. The derating coefficient is different with different loads.

4. The derating coefficient of conductors of the same specification is different in multi turn and single turn applications.

5. Some parameters cannot be derated.

6. The junction temperature derating shall not be omitted.

Misunderstanding 4. The device can be used safely

Why is device damage often called "burn"? The reason is that most device failures are thermal failures. In addition, the device ambient temperature ≠ the overall ambient temperature. The device environment is affected by the heat dissipation of other devices in the chassis. Generally, the device ambient temperature is higher than the overall ambient temperature.

Myth 5. Electronic reliability has nothing to do with machinery and software

The treatment of installation, wiring, layout and spraying will affect the electrical performance; Electromagnetic compatibility, faulty welding, heat dissipation, vibration and noise, corrosion and grounding are all related to the structure; The error prevention, error judgment, error correction and fault tolerance measures of software can avoid mechanical and electronic defects.

Myth 6. The device is very simple. It doesn't matter whether the datasheet is available or not

When doing the design, you must get the datasheet of all devices, then read all graphs, charts and parameters on it, and finally establish a connection with these curves in the design. The design needs to carefully confirm the static working point of the device in our circuit.

Myth 7. Maintainability has nothing to do with me

What is the purpose of electronic product reliability work? It's making money. What makes money? It's hard to open source and save money. It's easy to save money. Don't always think about saving material costs, saving material costs and high maintenance costs. Change from early death to late death, sooner or later. The best way is to pay attention to maintainability and save this part of the cost. This is a real profit.

Misunderstanding 8. Poor process control is the lack of good technicians

Poor process control is not only the problem of technicians, but also the construction process of a value chain. The requirements of the design engineer for the components, the manufacturer selection of the procurement engineer, and the control content of the inspection link should be designed for the key indicators of the components. The failure mechanism and damage of the components should not be introduced into the detection method, and the damage should not be introduced into the assembly link (wave soldering furnace temperature control, anti-static treatment of manual welding table, etc.) In the delivery inspection link, it is necessary to check some contents that may lead to product failure due to device parameter drift, and the failure shall not be introduced in the maintenance link.

It can be seen from the above that only two process engineers can guarantee the problem. Therefore, it is concluded that the specific approach is to establish consistency. The premise of consistency is that designers provide sufficient and primary and secondary technical information. The process is only based on design drawings and design documents to ensure manufacturing reliability, which is infinitely close to design reliability.

Myth 9. Relationship between MTBF value and failure rate of a single specific machine

MTBF is a macro and statistical concept, and single machine fault is a micro and specific concept.

Myth 10. Strengthening the test can solve the reliability problem

Since this problem can be listed as one of the ten misunderstandings, its definition is naturally wrong.

Summary:

1. Some problems can't be measured by simulation test.

2. Test means = engineering calculation + specification review + simulation test + electronic simulation.

3. According to the results of temperature enhancement test, the corresponding low-temperature working time can not be calculated.

After the electronic product is designed and formed, the product reliability test must also be carried out. The product reliability test is a necessary step to stimulate the potential failure mode, put forward improvement measures, and determine whether the project or system meets the predetermined reliability requirements.