How do mobile phones choose electronic components?

For machine manufacturers, especially large terminal product manufacturers (such as Huawei), there are corresponding "selection criteria" for the selection of electronic components. The reason is very simple. Taking a mobile phone as an example, a mobile phone requires thousands of parts If a material problem affects the entire production line, specifications are indispensable, but for Huawei’s “selection criteria”, someone said: When I entered Huawei, the entire company was in the “standardization” movement, everyone Writing specifications, work, performance and technical level are all based on specifications (large companies guided by kpi are easy to make "changes"). At that time, many people wrote various equipment selection specifications according to the type of equipment, so When you look back at the schematic diagram, the most common thing you hear is "the specification is written this way". The possible problems with the "selection specification" First, is the person who writes the specification skilled? Is it detailed? If there is an error, it is even more harmful.

Secondly, the specification sometimes inhibits the developer’s thinking. Everything is carried out according to the specification, which may not be suitable for the actual design scenario. For example, I need low-cost design, but the specification emphasizes high quality, which may not be applicable. Some developers do not believe that, for example, crystal oscillators require pf-class capacitors above 50mhz as power filters, but not capacitors below 50mhz. Everyone does not want to know or why, such as network transformer protection, indoor and outdoor, according to The design requirements of various electromagnetic compatibility standards, direct drawing is possible, but few people think why, do not know what the test results are, when they actually encountered difficulties, the specifications sometimes can indeed improve work efficiency and product quality, but the tool The more developed, the easier it is for people to fall.

Finally, due to the rapid development, some device selections are not suitable for writing specifications. Because of the strong lag, although there are shortcomings, it is undeniable that the specification is a very useful means. It is the essence of a large amount of theoretical analysis + experience accumulation + practical data. This is based on A large number of tests and practical cases have summarized things. For example, when selecting aluminum electrolytic capacitors, it should be considered that the steady-state operating voltage is less than 90% of the rated withstand voltage; tantalum capacitors require a steady-state reduction of 50%; ceramic capacitors require a steady-state reduction of 85% because The actual mode of some devices and the worst environment (high temperature, low temperature, maximum power consumption), the difference between steady-state power and transient power are considered here.

Factors to be considered in device selection In Huawei's pdm system, devices are divided into "preferred", "non-preferred", "disabled", "dedicated terminal" and other categories, engineers can intuitively judge whether the device is based on this preference level It is the preferred device. So, what factors are considered in the best choice of equipment? The availability, especially Huawei, as a manufacturer, has already delivered a large number of products, carefully selecting equipment with a reduced life cycle, and prohibiting the selection of equipment that is no longer in use. I designed a circuit in 2005. When I designed it, I copied someone else’s circuit. When I dealt with it, I found that this device could not be bought at all, because this device has been discontinued. I can only work in electronics Market to buy refurbished equipment.