In the PCB board design, the engineer is concerned, the circuit design is the most basic. But many engineers tend to be careful in the design of complex and difficult PCB boards, while ignoring some of the attention in the design of the PCB board, which leads to errors. It is possible to make a very perfect circuit when the problem is converted into a PCB board or completely broken down. Therefore, in order to help engineers to reduce design changes in the PCB board design, improve work efficiency, in this paper several aspects of the design process in the PCB board to pay attention to.

1, PCB board design of the cooling system design
In the PCB board design, the design of the cooling system includes the cooling method and the selection of the cooling components, as well as the consideration of the coefficient of thermal expansion. Now PCB board is commonly used in the way of heat: through the PCB board itself, heat, to the PCB board and the heat transfer plate and so on.
In the traditional PCB board design, due to the plate the copper clad / epoxy glass cloth base or phenolic resin glass cloth base, there are a small number of the use of paper-based cover copper board. These materials and electrical properties and processing performance good, but thermal conductivity is poor. Because now the PCB design of QFP and BGA surface mounted components widely used, the heat generating components a pass to the PCB board. Therefore, to solve the heat radiation is the most effective way is to enhance the heat dissipation capability of direct contact with the heating element of the PCB board itself, through the PCB board transfer is derived to or send out.
When the PCB board has a large number of devices with a large amount of heat, the heating device of the PCB board is equipped with a heat sink or a heat conducting pipe; when the temperature can not be reduced, the heat radiator with fan can be adopted. When the PCB board is heated, the heat radiating cover is adopted, and the radiating cover is integrally buckle on the component surface, so that the heat radiating cover is contacted with each component on the PCB board. For video and animation production of professional computer, and even the need to use a cool way to cool.

2, PCB board design components selection and layout
In the PCB board design, no doubt to face the choice of components. Characteristics of each component is not the same size, even if the components characteristics of the same products from different manufacturers may also is not the same, so in the PCB design for the selection of the components must to know and communicate with supplier components and understand these characteristics of PCB design of influence.
At present, the choice of appropriate memory for PCB design is also very important, because of the DRAM and flash memory will continue to update, the PCB designer to think the new design is not affected by the impact of memory market is a big challenge. So PCB board designers have to aim at the memory market and keep in close contact with the manufacturers.
In addition to a large amount of heat some components must carry out the necessary calculations and their layout also need special consideration, a large number of components together can produce more heat, causing the solder layer deformation separation and even ignite the PCB board. Therefore, PCB board design and layout engineers must work together to ensure that the components are suitable for the layout.
Layout should first consider the size of the PCB board size. PCB board size is too large, the printed line length, the impedance increases, anti noise capacity decreased, the cost is also increased; PCB board over an hour, the heat is not good, and the adjacent lines are vulnerable to interference. In determining the size of the PCB board, and then determine the location of special components. Finally, according to the functional unit of the circuit, the layout of all the components of the circuit is carried out.

3, PCB board design in the design of testability
The key technologies of testability of PCB board include: testability measurement, design and optimization of testability mechanism, processing and fault diagnosis of test information. In fact, the testability design of PCB board is to introduce a kind of testability method which can be convenient for testing, and it can be introduced into the PCB board. Therefore, the reasonable and effective design of testability mechanism is the guarantee to improve the level of testability of PCB board successfully. To improve product quality and reliability, reduce product life cycle cost, requirements of design for test techniques to quickly and easily access to PCB test feedback information, can easily according to the feedback information to make fault diagnosis. In the PCB board design, to ensure that the probe position and access to the DFT and other probe head will not be affected.
With the miniaturization of electronic products, components of the pitch is getting smaller and smaller, the installation density will be more and more large. For testing the circuit nodes is less and less, so the printed board assembly of online test difficulty is also growing, so in the PCB board design should give full consideration to the printed circuit board can be tested electrical conditions and physical and mechanical conditions, the appropriate machinery and electronic equipment for testing.

4, PCB board design in the humidity sensitive level MSL
Sensitive Level MSL:Moisure, that is, the humidity sensitive level, in the proof of the label on the outside of the bag, is divided into: 1, 2, 2a, 3, 4, 5, 5A, eight 6 levels. On humidity has special requirements or packaging have wet sensitive element labeled components must be effective management, to provide material storage and manufacturing environment temperature and humidity control, thereby ensuring the insulation performance of moisture sensitive components reliability. In baking, BGA, QFP, MEM, BIOS and other requirements of vacuum packaging, high temperature and high temperature resistant components, respectively, at different temperatures baking, pay attention to baking time. PCB board baking requirements of the first reference to the PCB board packaging requirements or customer requirements. After baking the humidity sensitive components and PCB plate at room temperature can not be more than 12H, not to use or not to use at room temperature is not more than 12H of the humidity sensitive components or PCB plate must be sealed with vacuum or put in a dry box storage.