Ten Misunderstandings of Circuit Reliability Design (1)

There are not only many skills in PCB circuit design, but also many misunderstandings. This article will introduce ten misunderstandings in circuit stability design.

Misunderstanding 1: Product failure = product is unreliable

Product problems are sometimes not a R&D problem. There have been cases where equipment in developed areas above the middle and above levels in China was exported to Colombia because it was used well in the country, but there were frequent failures. The cause of the failure was the middle level in mainland China. The altitude of the above developed areas is relatively low, so in high altitude areas, the air tightness of the equipment is challenged, and the pressure difference between the inside and outside of the equipment increases and the leakage rate increases.

When the project was established, only low altitude was considered, so the design of others is okay. Whoever decides to export this model to Colombia is the culprit. He is simply the biggest culprit when he raises objections. After all, the sales executives’ decision-making ignorance of technology can be forgiven, and the mistake of the vice president of technology is incompetent.

Product reliability is “the ability to complete a specified function in a specified time and under a specified condition”. Readers must savour this definition carefully, study things for knowledge, and see who can achieve more knowledge when this definition is qualified. The conditions of the use site often exceed the prescribed conditions, and this exceeding is likely to be implicit.

Misunderstanding 2: Transition process = steady state process

Misunderstanding 3: Derating is easy to do without problem

Anyone who derates can be good at painting, but not everyone can survive by painting. For details, please refer to the article “Derating Design of Electronic Products” in this blog. Here is just a brief summary:

1. Devices with the same function but different processes have different derating factors.

2. Adjustable devices and fixed-value devices have different derating factors.

3. The derating factor is different for different loads.

4. The derating factor is different when the wires of the same specification are used in multi-turn and single-turn applications.

5. Some parameters cannot be derated.

6. The junction temperature derating should not be omitted.

Misunderstanding 4: The device can be used with confidence.

Why is device damage often referred to as “burning”? The reason is that device failures are mostly thermal failures. There are two specific points for attention. First, the device environment temperature ≠ the overall environment temperature, and the device environment is affected by the heat dissipation of other devices in the chassis. Generally, the ambient temperature of the device is higher than the ambient temperature of the whole machine. Second, you can recall the third question at the beginning of this lecture. For details, please refer to “Common Errors in Device Ambient Temperature and Load Characteristic Curve”.

Misunderstanding 5: Electronic reliability has nothing to do with mechanical and software majors.

Installation, wiring, layout, and spraying treatments will affect electrical performance. Electromagnetic compatibility, false welding, heat dissipation, vibration and noise, corrosion, and grounding are all related to the structure. Software error prevention, error judgment, error correction, and fault tolerance processing measures can avoid mechanical And electronic defects.