1, the concept of "Layer (Layer)"
With word processing or many other software for the realization of the image, text, color and other nested and synthesis and introducing the concept of "layer" with somewhat, Protel "layer" is not virtual, truly, truly, but the printing plate material itself of the copper foil layer. Nowadays, because of the electronic circuit element intensive installation. Anti interference and wiring and other special requirements, some of the newer electronic products used in the printing plate have upside down for walk the line, not only in the middle of the plate can be also has special processing mezzanine copper foil, for example, now computer motherboard used much in more than 4 layer board materials.Most of these layer due to the machining is relatively difficult to walk line relatively simple Power wiring layer (such as Ground in software Dever and Power Dever), and the commonly used large filling way to wiring (such as in software ExternaI P1a11e and the Fill). And the location of the surface layer and the place of intermediate layers need to be connected with the software mentioned in the so-called "hole (Via)" to communicate. With the above explanation, it is not hard to understand "multi-layer welding plate" and "wiring layer Settings" on the concept. A simple example, many people wiring is complete, to print it out when they found a lot of connection terminal bonding pad, it is his own add components library ignores the concept of "Layer", did not draw his encapsulation of bonding pad feature is defined as "multi-layer (Mulii Layer). To remind is, once selected the Layer number of the board is used, be sure to shut down those unused layers, avoiding detours.
2, Via (Via)
For connecting line between each layer, each layer needs to be connected the wires wenhui place a public hole drilling, this is a hole. Process in a hole on the wall of hole on cylinder with a layer of metal plating, chemical deposition method is used to connect the copper foil of intermediate layers need to be connected, and via both sides make ordinary welding plate shape, can be directly with upper and lower sides of the line, also is not even. In general, when designing circuit right hole processing has the following principles:
(1) Holes use less as far as possible, if chose a hole, it is important to deal with it and the surrounding each entity's clearance, especially easy to ignore in the middle of each layer and a hole is not connected to the line and hole clearance, if it is a automatic wiring, can be in "number Via minimization" (Via Minimiz8tion) in the sub menu select "on" to automatically resolve.
(2) the carrying capacity, the greater the need for a hole size is larger, such as power supply layer and layer formation with other join the hole will be larger.
3、Overlay（Overlay）
For the convenience of installation and maintenance of the circuit, etc., in the printing plate need logo on the upper and lower surface of the printing design and writing code and so on, such as component label and nominal value, components outside the profile shape and the signs of the manufacturer, production date, etc. Many beginners the contents of the silk screen layer, only pay attention to the text symbols placed in neatly beautiful, ignoring the actual effect of PCB making. They design on the board of character is not is blocked by element is invaded help welding area has been put on credit, and the components of label on the adjacent components, so the design will bring great inconvenience to assembly and maintenance. Correct printing layer character layout principle is: "don't ambiguity, and the beauty is generous."
4, the particularity of SMD
There are a lot of SMD encapsulation, Protel encapsulation of the rolls surface welding device. The biggest characteristic of this kind of device in addition to small size is single distribution yuan pin hole. Therefore, choose this kind of device to define a good device in the face, in order to avoid "Missing pin (Missing Plns)". In addition, this kind of components related to text annotation can only with the component's presence.
5, grid filling area (External Plane) and populate the area (Fill)
Network as their name suggests, the fill area is the copper foil processing into a network of large area, populated area is only intact copper foil. On the computer in the process of beginners tend to see the difference between the two, in essence, as long as you to enlarge drawings after the be clear at a glance. It is usually not easy to tell the difference, so when using less attention to the distinction between the two, want to stress is that the former has the strong according to the characteristic of the circuit to inhibit the action of the high frequency interference, is suitable for large area filling should be done in place, especially in the areas as shielding area, divided area or high current is particularly appropriate when the power cord. The latter is more used for general wire ends or turning area need to fill small area, etc.
6, welding plate (Pad)
Welding plate is PCB design "> most often contacts in the PCB design is also the most important concept, but beginners tend to ignore it and correction, the choice of using circular pad in the design of the same. Select element type of bonding pad to comprehensively consider the elements of shape, size, layout, vibration and heat conditions, factors such as stress direction. Protel in encapsulation repository is given a series of different size and shape of the solder, such as round, square, octagon, round square and positioning with solder, etc., but sometimes it is not enough to use, the need to edit. For example, the fever and stress is larger, the current large welding plate, can be designed into tears" shape ", in the familiar PCB line output transformer of TV in the design of the pin pad, many manufacturers is adopted in this form. In general, when editorial solder in addition to the above said, consider the following principles:
(1) shape length doesn't conform to consider connection width and the size of the weld length of side plate of a particular difference too much;
(2) need to choose when walk line length between components lead Angle asymmetry of bonding pad often get twice the result with half the effort;
(3) all the components according to the size of the welding plate hole components pin thickness editor determined respectively, the principle is the size of the hole is bigger than the pin diameter 0.2 0.4 mm.
7, all kinds of membrane (Mask)
The membranes not only is necessary, in the process of PcB production process and components necessary for welding. According to the position of "membrane" and its role, "membrane" can be divided into components or welding surface run-off membrane (TOp or Bottom and the surface of the element (or welding surface) resistance welding membrane (TOp or BottomPaste Mask) two kinds. As the name implies, run-off film is coated on the bonding pad, to improve the performance of weldable a membrane, which is in the green board is slightly superior to pad the light round spot. Resistance welding film is just the opposite, in order to adapt the board made of wave soldering welding such as form, requirements on board, a plate of copper foil can't stick tin, so outside welding plate parts are coated with a layer of paint, used to prevent these parts on the tin. Visible, these two kinds of membrane is a complementary relationship. This discussion, it is not hard to determine the menu similar to the solder Mask En1argement "projects such as set up.
8, Line fly, fly line has a double meaning:
Automatic wiring like a rubber band for observation network connection, in the table to components through the network and makes a preliminary layout, with the "Show commands can see the layout of the network connection cross condition, position of constantly adjust components make the cross at least, to achieve maximum automatic wiring completion rate. This step is very important, can be said to be a knife and cutting wood work, spend more time and value. In addition, the automatic wiring end, what the network has not yet been cloth, also can through the function to find the. Find out cloth after pass network, manual compensation are available, and can't compensate the will use the second meaning of" fly line ", is in the future with wire connected on the board of the network. To hand over to treat, if the circuit board is large quantities of automatic line production, the fly line can be regarded as zero resistance, a unified welding plate spacing of the resistance element for design.
