【 Weak current College 】 common circuit repair basics "six" 】

PCB design concepts
1, "" layer (Layer) the concept of "
And a word processing or other software to achieve the figure, text, color, etc. of nested and synthesis and introduced the concept of the "layer" is the same, Protel "layer" is not a virtual, rather than printing plate materials themselves real the copper layer. Nowadays, because of the intensive electronic circuit components installed. Anti-jamming and wiring, and other special requirements, some newer electronic products in the printing plates not only the upper and lower surface for the alignment, in the middle of the plate can be also equipped with a special process of dissection of copper foil, for example, the computer motherboard the plate material in 4 layers above. These layers are relatively difficult because of processing and are used to set the alignment of relatively simple power supply wiring layer (such as software GroundDever and PowerDever), and often large areas populated by wiring (such as software ExternaIP1a11e and Fill). The location of the surface layer above and middleware layers need connected place software in the so-called "through-hole (Via)" to communicate. With the above explanation, it's not hard to understand "multi layer pad" and "wiring layer settings" and related concepts.
For example, many wiring is complete, to print out just found a lot of wiring of Terminal without pads, in fact, this is your own add device library ignores the concept of the "layer", didn't put their own drawing package pad character is defined as "multilayer (Mulii a Layer). To remind that, once selected the number of layers of wrap boards, be sure to turn off those unused layers, you gave me to make detours.
2, through-hole (Via)
For connecting the lines between tiers and layers need connected wires on a drill at wenhui public hole, this is the hole. Workmanship in through-hole holes in the wall of the cylinder surface chemical deposition of metallic coated with a layer for intermediate layers need connectivity connectivity of copper foil, but the hole in the upper and lower surface made of ordinary pad shapes, directly with the upper and lower surfaces of the connected line or not. In General, design lines for through-hole processing with the following principles: (1) use the hole, the hole once the use, be sure to handle it and neighboring entities of gap, particularly neglected middle layer and the hole is not connected to the line and through-hole clearance, if this is the automatic routing, you can number in the "hole" minimized (ViaMinimiz8tion) submenu select "on" to automatically resolve. (2) the greater the need for current, the larger the size of a hole, such as power and formation and other layer joins the hole is larger.

3, silk printing layer (Overlay)
For ease of installation and maintenance of the printing plate and bottom surface printing the logo and text symbols, and so on, for example symbol symbols and the nominal value, of the exterior shape and component manufacturers logo and production dates, etc. Many beginners design screen printing layer for content, only the note text symbol placement tidy appearance, ignores the real effect of PCB. They design the plates, the character is not blocked by component is invaded help welding area is put on credit, was also playing the symbol symbols in adjacent components on the design, so these will be to assemble and repair great inconvenience. Correct screen printing layer character layout principles: "no ambiguity, they must attack first, elegant".
The particularity of 4, SMD
Protel encapsulated within a large number of SMD package, i.e. the surface welding device. This type of diodes except compact outside the biggest characteristics of single-side distribution element pin hole. Therefore, the use of such devices to define good device is located, so that the "lost pin (MissingPlns)". In addition, these components can only be related to the text callout is located with the component placement.
5. grid populated area (ExternalPlane) and padding (Fill)
As the name, network-like fill area is the large copper foil processing into mesh, fill area only as complete retention of copper foil. Starter design process on a computer, often to see the differences between them, essentially, as long as you put the surface is enlarged to see at a glance. It is usually not easy to discern the difference between the two, so use the time do not pay attention to the distinction between the two, it is emphasised that the former in circuit characteristics on strong inhibitory effect of high frequency interference, suitable for doing large populated areas, particularly in some regions as a shield, partitions or high current power cord is particularly appropriate. The latter used the General line ends or transition zones need to fill a small area.

6 pads (Pad)
PADS PCB design is most frequently contact is the most important concepts, but a beginner but easily overlooked its choice and that, in the design of the routinely use circular pad. Select the symbol pad type to be considered the symbol of shape, size, layout, vibration and heat conditions, factors such as stress direction. Protel in package library provides a range of different size and shape of pads, such as round, square, square, circle and positioning is used pad, etc., but sometimes this isn't enough, you need your own editing. For example, to generate heat and force a larger, current larger pads that can be designed into the "cry of", in the familiar TV line output transformer PCB pin pad design, many manufacturers are using this form. In General, to edit pad is in addition to the above mentioned, also consider the following principles:
(1) the length of the shape is not consistent to consider the line width and pads the size difference of a specific length is not excessive;
(2) need components cited between alignment selection length when asymmetrical pads are often more effective;
(3) the symbol pad-hole size thickness by symbol pin, principles editors determine respectively is hole dimensions than the pin diameter 0.2-0.4 mm.

7, various films (Mask)
These films are not only PcB fabrication process essential, but also is a necessary condition for welding components. Press"Membrane" position and function, "film" can be divided into components surface (or welding surface) help welded membrane (TOporBottom and component surface (or welding surface) solder mask (TOporBottomPasteMask). As the name implies, will help draw in the welded membrane is pads, improve weldability can layer of film is green Board slightly larger than the pads of the light-coloured round spot. Solder mask, on the contrary, in order to enable the Board to adapt to wave soldering, welding form, request the Board non-pads of tin foil can not be sticky, so in pads away from parts are coated with a layer of coating to be used to block these sites on the Tin. Thus, these two films is a complementary relationship. From this discussion, it is difficult to determine the menu
Similar "solderMaskEn1argement" and other projects.

8. fly line
Auto-wiring for observation of banding network cabling, network table import component and do the initial layout, use the "Show command to see the layout of the network connection status of the cross, and constantly adjust the element's position to make such cross-at least for maximum automatic wiring layout pass rate. This step is very important, it can be said that the knife not to miss the firewood, spend more time on value!, autorouting ends, what network is not the Chief Administrator, can also be accessed via the feature to find. Find out the no-pass network, available manual compensation, compensation cannot be used to "fly" in the meaning of the second layer is the future of printing plate with a wire connected to these networks. To explain that, if the Board is a high-volume automatic line production, this fly line as 0-European resistance, has consolidated the pad spacing resistance element for design.