There are not only a lot of techniques in circuit design, but also a lot of mistakes. This paper introduces ten errors in circuit stability design.
Myth 1: Product failure = unreliable product
Products appear problem, sometimes not r&d problems, there have been cases, geared to the needs of domestic medium above equipment developed regions, because of good, in the country with so exported to Columbia, but frequently there fault, the fault reason is that China medium above the level of the developed areas are relatively low, so a high altitude, equipment of air tightness has been challenged, The leakage rate increases when the internal and external pressure difference increases.
Project only consider the low altitude, so the design of the house is no problem, your boss is such a requirement, who has a decision with the model export Colombia, he is the main culprit, if pipe research and development, the boss of participation in decision-making and did not put forward objection, he is the greatest sinner, sales executive decision, after all, still can forgive don't understand the technology, The vice president of technology's mistake was incompetence.
Product reliability is "the specified time, the specified conditions, the ability to complete the specified function". Readers must peruse this definition to see who can define this definition to achieve more awareness. The condition of the use site often exceeds the specified condition, and this excess may well be implied.
Myth 2: Transition process = steady state process
Myth 3: Derating is easy to do, no problem
Everyone can do it, like drawing, everyone can do it, but not everyone can make a living by drawing. For details, please refer to the article "Derating Design of Electronic Products". Here is a brief summary:
1. The derating coefficients of devices with the same function but different processes are different;
2. The derating coefficients of adjustable devices and fixed devices are different;
3. Derating coefficients are different with different loads;
4. The derating coefficients of the same specification wire are different in multi-turn and single-turn applications;
5. Some parameters cannot be derated;
6, the junction temperature derating can not be omitted.
Myth 4: Ta, devices can be used safely
Why is device damage often called "burn"? Firstly, the ambient temperature of the device is not equal to the ambient temperature of the whole machine. The ambient temperature of the device is affected by the heat dissipation of other devices in the chassis. Generally, the ambient temperature of the device is higher than that of the whole machine.
Myth 5: Electronic reliability has nothing to do with mechanical or software majors
Installation, wiring, layout, spraying treatment will affect the electrical performance; Electromagnetic compatibility, virtual welding, heat dissipation, vibration and noise, corrosion, grounding are related to the structure; The error prevention, judgment, correction and tolerance of software can avoid mechanical and electronic defects.
Myth 6: The device is very simple, there is no matter
Be sure to get all the device's Datasheet when designing, and then read all the graphs, charts and parameters on it, and finally to design the curve. The following figure is the V-I characteristic curve of the diode. It is necessary to carefully confirm the static operating point of the device in our circuit during design.
Myth 7: Maintainability is not my problem
What is the purpose of electronic product reliability work? Is to make money. What makes money? Open source and throttling, open source is difficult, throttling easy, do not always want to save from the cost of materials, materials cost is saved, maintenance cost is high, from early death to late death, sooner or later or dead, why? Better to die early than to live again. The best way is to focus on maintainability and avoid this expense. This is a real profit.
Myth 8: Poor process control is no good process personnel
Poor process control is not just a problem of process personnel, it is a value chain building process. The requirements of the design engineer for the device, the selection of the manufacturer by the procurement engineer, the control content of the inspection link should be designed for the part of the key indicators of the device, the failure mechanism and damage of the component 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.), parts of device parameter drift that may lead to product failure should be checked in the factory inspection link, and failure should not be introduced in the maintenance link.
As can be seen from the above, problems are not guaranteed by only two process engineers. Therefore, the specific approach is to establish consistency, consistency is the premise of designers to provide sufficient, primary and secondary technical information, the process is only based on the design drawings and design documents to ensure that the manufacturing reliability is infinitely close to the design reliability.
Myth 9: THE relationship between MTBF value and the failure rate of a specific machine
MTBF is a macroscopic and statistical concept, while a single machine failure is a microscopic and specific concept. Customers like to ask a question: "The MTBF value of your product is 10,000 hours, so if I buy your one, is there no problem within 10,000 hours?" This is a concept of guan Gong fighting Qin Qiong who is more powerful, let me tell the conversion relationship between them, please tell me first is 1km or 1kg large?
Myth 10: More testing will solve reliability problems
Since this question can be listed as one of the top ten misunderstandings, its definition is naturally wrong. There are three conclusions:
1, some problems can not be measured by simulation test experiment;
2, test means = engineering calculation specification review simulation test electronic simulation;
3. The corresponding low temperature working time cannot be calculated through the results of temperature strengthening test.