Electronic Design - What are the mistakes often made in the PCB design process

In terms of the current development status and trends of international electronic circuits, the development prospects of PCBs are very broad, but we will inevitably encounter some errors in the PCB design process. This article will take you to see the development prospects of PCBs and the common ones. Kind of mistakes, do you make these mistakes? Knowing them before they affect the overall function of the circuit board is a good way to avoid costly production delays.

First look at the development prospects and trends of PCB:

1. Chip-scale packaging CSP will gradually replace TSOP and ordinary BGA

CSP is a chip-scale package, it is not a separate form of packaging, but a chip-scale package called when the chip area is comparable to the package area. CSP package allows the ratio of chip area to package area to exceed 1: which is quite close to the ideal situation of 1:1, which is about 1/3 of the ordinary BGA; the center pin form of the CSP package chip effectively shortens the signal conduction The distance, the attenuation of the chip is reduced, and the anti-interference and anti-noise performance of the chip can also be greatly improved. In the CSP packaging method, the chip particles are soldered on the PCB board through a solder ball, because the solder joints and the PCB board The contact area is large, so the heat generated by the chip in operation can be easily conducted to the PCB board and dissipated.

Development prospects: Chip-scale packaging developed in response to the light, thin, short, and small electronic products is a new generation of packaging methods. According to the development trend of electronic products, chip-scale packaging will continue to develop rapidly and gradually replace TSOP (ThinSmallOutlinePackage) packaging and Ordinary BGA package.

2. The output value of photovoltaic panels will increase by 14% annually by 2010

The photoelectric board is the photoelectric backplane, which is a special printed circuit board with built-in light path, and it is also a kind of backplane, which is mainly used in the communication field. The main advantages of the photoelectric backplane: low signal distortion; avoid noise; very low crosstalk; loss is independent of frequency; dense wavelength multiplexing technology; 12-6 channel multi-channel connector; waveguide multi-channel connector; improved dispersion The reliability of the cable; the number of layers of the photoelectric board can reach 20, the circuit is more than 20,000, and the connector is 1000 pins; the traditional backplane adopts copper wires, and its bandwidth is limited to a certain extent.

Development prospects: Due to the increase in bandwidth and distance, copper transmission lines will reach the limits of bandwidth and distance, while optical transmission can meet the needs of increased bandwidth and distance. The photoelectric backplane is mainly used for communication exchange and data exchange, and future development will be applied to workstations and servers. According to forecasts, by 2010, the global output value of optoelectronic backplanes will reach 200 million US dollars, an annual increase of about 14%.

Third, the development prospects of rigid-flex board are very promising

Flexible board FPC used to be called chaotically. It was first called soft board, and later it was also called flexible board, flexible printed circuit board and so on.

Rigid-flex printed board refers to a printed board that contains one or more rigid areas and one or more flexible areas, which is composed of rigid boards and flexible boards laminated together in an orderly manner, and formed by metalized holes Electrical connections. Rigid-flex printed boards can not only provide the supporting function of rigid printed boards, but also have the flexibility of flexible boards, which can meet the requirements of three-dimensional assembly. In recent years, the demand has increased. The traditional rigid-flex board design idea is to save space, facilitate assembly and improve reliability; a new type of rigid-flex board that integrates traditional rigid-flex board design and micro-blind via technology provides a new solution for the interconnection field. Its advantages are: suitable for folding mechanisms, such as flip phones, cameras, and laptops; improve product reliability; use traditional assembly methods, but can simplify assembly and be suitable for 3D assembly; combine with micro-via technology to provide better Design convenience and use of smaller components; use lighter materials instead of traditional FR-4.

Rigid-flex boards used in mobile phones are generally formed by connecting two layers of flexible boards and rigid boards.

Development prospects: Rigid-flex board is a type of PCB that has grown very rapidly in recent years. It is widely used in computers, aerospace, military electronic equipment, mobile phones, digital (camera) cameras, communication equipment, analytical instruments, etc. According to forecasts, the average annual growth rate from 2005 to 2010 is more than 20% based on output value, and the average annual growth rate based on area is more than 37%, which greatly exceeds the growth rate of ordinary PCBs. So far, there are few manufacturers that can produce rigid-flex boards, and almost no manufacturers have experience in mass production, so its development prospects are very promising.

Fourth, high multilayer PCB boards bring opportunities to the Chinese industry

Multi-layer PCB board refers to a PCB board with an independent wiring layer greater than two layers. Generally, multiple double-sided boards are laminated together, and each layer is laminated to form a whole board through a layer of insulation. High multi-layer boards generally refer to multi-layer boards with more than 10 layers. They are mainly used in switches, routers, servers and large computers. Some supercomputers use more than 40 layers.

Development prospects: ordinary multi-layer boards are mature products, and the future growth will be relatively stable; but high-level multi-layer boards have high technical content, and countries such as Europe and the United States have basically abandoned the conventional level of PCB production, which brings some opportunities to the Chinese industry. It is predicted that the annual growth of high-multilayer boards (backplanes) will be about 13% in the future.

Five, 3G board improves the technical level of PCB products

It is suitable for the printed boards of the third generation mobile communication products (3G). 3G boards generally refer to 3G mobile phone boards. It is a high-end printed circuit board, which is manufactured using an advanced 2-layer build-up process. The circuit level is 3mil (75μm). The technologies involved include electroplating and filling, stacking, and rigid flexing. A series of cutting-edge technology for printed boards. 3G technology is significantly improved over existing products.

Development prospects: 3G is the next generation of mobile communication technology. Currently, developed countries such as Europe, America and Japan have begun to use it. 3G will eventually replace the existing 2G and 2.5G communications. By the end of 2005, the number of global 3G users has increased and the total number has reached In 2005, a total of 100 million 3G mobile phones of various formats were sold, and the future development will still maintain a growth rate of more than 20%. The matched printed circuit board, the 3G board, maintained the same growth rate. The 3G board is an upgrade of existing products, and it brings the overall level of the PCB industry to a higher level.

6. The HDI board will grow rapidly in the future

HDI is the abbreviation of HighDensityInterconnect. It is a (technology) for the production of printed boards. It is currently widely used in mobile phones, digital (camera) cameras, MP3, MP4, etc., generally using build-up manufacturing. The more the number of times, the higher the technical grade of the panel. Ordinary HDI boards are basically one-time build-up. High-end HDI uses two or more build-up techniques, while using advanced PCB technologies such as stacking holes, electroplating and filling holes, and laser direct drilling. High-end HDI boards are mainly used in 3G mobile phones, advanced digital cameras, IC carrier boards, etc.

Development prospects: According to the use of high-end HDI boards-3G boards or IC carrier boards, its future growth is very rapid: the world's 3G mobile phones will grow by more than 30% in the next few years, and China will soon issue 3G licenses; IC carrier board industry consulting The organization Prismark predicts that China's predicted growth rate from 2005 to 2010 is 80%, which represents the direction of PCB technology development.

The development is indeed fast, but the errors we will encounter in PCB design are as follows:

1.) Landing mode

Although most PCB design software includes General Electric component libraries, their related schematic symbols and landing patterns, some circuit boards will require designers to draw them manually. If the error is less than half a millimeter, the engineer must be very strict to ensure the proper spacing between the pads. Mistakes made during this stage of production will make welding difficult or impossible. The necessary rework will cause costly delays.

2.) Use blind/buried vias

In the market of devices that are accustomed to using IoT today, smaller and smaller products continue to exert the greatest impact. When smaller devices require smaller PCBs, many engineers choose to use blind vias and buried vias to reduce the footprint of the circuit board to connect internal and external layers. Although the through hole can effectively reduce the area of the PCB, it reduces the wiring space, and as the number of additions increases, it may become complicated, making some boards expensive and impossible to manufacture.

3.) Trace width

In order to make the board size small and compact, the engineer's goal is to make the traces as narrow as possible. Determining the PCB trace width involves many variables, which makes it difficult, so it is necessary to fully understand how many milliamps will be required. In most cases, the minimum width requirement is not sufficient. We recommend using a width calculator to determine the appropriate thickness and ensure design accuracy.