Circuit design skills PCB 設計過程

一般PCB基本設計流程如下：前期準備——>； PCB structure design -& GT; PCB佈局-> 接線-> 路由優化和絲網印刷——> Network and DRC inspections and structural inspections – > Plate making.

First: preparation. This includes preparing component libraries and schematics. “To do good work, must first sharpen its device”, to make a good board, in addition to the principle of good design, but also draw well. Before PCB design, the component library of schematic SCH and the component library of PCB should be prepared first. Peotel libraries can be used, but in general it is difficult to find a suitable library, it is best to make your own library according to the standard size information of the selected device. In principle, make PCB component library first, and then SCH component library. PCB元器件庫要求高，直接影響闆卡安裝； SCH的元器件庫要求相對寬鬆，只要注意引腳屬性的定義以及與PCB元器件的對應關係即可。 PS: Note the hidden pins in the standard library. 然後就是原理圖設計，準備做PCB設計。

第二：PCB結構設計。 在這一步中，根據電路板尺寸和機械定位，在PCB設計環境中繪製PCB板面，並根據定位要求放置連接器、按鈕/開關、螺絲孔、裝配孔等。 And fully consider and determine the wiring area and non-wiring area (such as how much of the screw hole around the non-wiring area).

第三：PCB佈局。 Layout is basically putting devices on a board. At this point, if all the preparatory work mentioned above is done, the network table can be generated on the schematic diagram (Design- >; CreateNetlist），然後導入PCB圖上的網絡表（design-gt; 負載網絡）。 看到整堆的設備嗡嗡聲，引腳和飛線之間提示連接。 然後您可以佈置設備。 總體佈局按以下原則進行：

（1）。 According to the electrical performance reasonable partition, generally divided into: digital circuit area (that is, afraid of interference, and interference), analog circuit area

(fear of interference), power drive area (interference source);

（2）。 Complete the same function of the circuit, should be placed as close as possible, and adjust the components to ensure the most simple connection; At the same time, adjust the relative position between the functional blocks to make the connection between the functional blocks the most concise;

（3）。 Installation position and installation intensity should be considered for components with large mass; 加熱元件應與感溫元件分開，必要時應考慮熱對流措施；

（4）。 I/O drive device as close as possible to the edge of the printing plate, close to the outlet connector;

（5）。 Clock generator (such as: crystal oscillator or clock oscillator) should be as close as possible to the device using the clock;

6. In each integrated circuit between the power input pin and the ground, need to add a decoupling capacitor (generally using high frequency good monolithic capacitor); 當電路板空間緊張時，也可以在多個集成電路周圍放置一個鉭電容器。

都是地主。 Relay coil to add discharge diode (1N4148 can be);

今天。 Layout requirements should be balanced, dense and orderly, not top-heavy or heavy

— Special attention should be paid to the actual size (area and height) of the components and the relative position of the components when placing the components to ensure the electrical performance of the circuit board and the feasibility and convenience of production and installation. At the same time, the above principles should be reflected

Under the premise, modify the placement of devices appropriately to make them neat and beautiful. For example, the same devices should be placed neatly and in the same direction, instead of being “strewn at random”. This step concerns the difficulty of board integral figure and next wiring degree, want to spend big effort to consider so. When layout, can make preliminary wiring first to not quite affirmative place, sufficient consideration.

第四：接線。 佈線是PCB設計中最重要的工序。 這將直接影響PCB板的性能。 In the process of PCB design, wiring generally has such three levels of division: the first is the distribution, which is the most basic requirement of PCB design. If the line is not cloth, get everywhere is flying line, it will be a unqualified board, can say that there is no entry. The second is the satisfaction of electrical performance. 這是衡量一塊印刷電路板是否合格的標準。 This is after the distribution, carefully adjust the wiring, so that it can achieve the best electrical performance. 然後是美學。 如果你的接線布接好了，也沒有什麼影響電器性能的地方，而是雜亂無章的過去，加上五顏六色的，鮮豔的，那就算你的電器性能有多好，在別人眼裡還是垃圾。 This brings great inconvenience to testing and maintenance. 佈線要整齊統一，不能無規則的縱橫交錯。 所有這些都應該在保證電氣性能和滿足其他個性化要求的前提下實現，否則就是捨棄本質。 接線應按以下原則進行：

（1）。 一般情況下，應先走電源線和地線，以保證電路板的電氣性能。 在條件允許的範圍內，盡量加寬電源、地線的寬度，地線最好比電源線寬，它們的關係是：地線>電源線>信號線，通常信號線寬度為：0.2～0.3mm，最薄的寬度可達0.05～0.07mm，電源線一般為1.2～2.5mm。 數字電路的PCB可用於接地導體較寬的電路，即接地網絡。 （不能以這種方式使用模擬接地。）

（2）。 In advance, wire strict requirements (such as high frequency line) for wiring, input and output side line should avoid adjacent parallel, so as not to produce reflection interference. When necessary, ground wire should be added to isolate, and the wiring of two adjacent layers should be perpendicular to each other, which is easy to produce parasitic coupling in parallel.

（3）。 The oscillator housing should be grounded, and the clock line should be as short as possible, and not spread all over the place. Below the clock oscillation circuit, the special high-speed logic circuit should increase the area of the ground, and should not go to other signal lines, so that the surrounding electric field tends to zero;

（4）。 In order to reduce the radiation of high frequency signal, 45O broken line should be used as far as possible, instead of 90O broken line. (High requirements of the line also use double arc)

（5）。 Any signal line should not form a loop, if unavoidable, loop should be as small as possible; 通過孔的信號線應盡可能少；

6. 關鍵線要短而粗，兩邊都有保護。

都是地主。 When the sensitive signal and noise field signal are transmitted through flat cable, the method of “ground – signal – ground wire” is used.

今天。 Test points should be reserved for key signals to facilitate production and maintenance testing

Pet-name ruby. After schematic diagram wiring is completed, wiring should be optimized; At the same time, after the preliminary network check and DRC check is correct, the ground wire is filled in the area without wiring, and a large area of copper layer is used as ground wire, and the unused places are connected with the ground as ground wire on the printed board. 或者做成多層板，電源、地線各佔一層。

— PCB wiring process requirements

（1）。 線

Generally, the signal line width is 0.3mm(12mil), and the power line width is 0.77mm(30mil) or 1.27mm(50mil). 符合

The distance between lines and between lines and pads should be greater than or equal to 0.33mm(13mil). In practical application, it should be considered to increase the distance when conditions permit; When the cabling density is high, it is advisable (but not recommended) to use two cables between IC pins. The width of the cables is 0.254mm(10mil), and the distance between the cables is not less than 0.254mm(10mil).

Under special circumstances, when the pin of the device is dense and the width is narrow, the line width and line spacing can be appropriately reduced.

（2）。 PAD (PAD)

The basic requirements of PAD and transition hole (VIA) are: the diameter of PAD is greater than 0.6mm than the diameter of hole; For example, universal pin type resistors, capacitors and integrated circuits, using disk/hole size 1.6mm/0.8mm (63mil/32mil), socket, pin and diode 1N4007, using 1.8mm/1.0mm (71mil/39mil). In practical application, it should be determined according to the size of the actual components. If conditions are available, the size of the pad can be appropriately increased. The installation aperture of the components designed on the PCB board should be about 0.2 ~ 0.4mm larger than the actual size of the pins.

（3）。 Through hole (VIA)

Generally 1.27mm/0.7mm(50mil/28mil);

When the wiring density is high, the hole size can be appropriately reduced, but not too small, can consider 1.0mm/0.6mm(40mil/24mil).

（4）。 Spacing requirements for pads, wires and through-holes

PADandVIA: ≥0.3mm (12mil)

PAD和PAD：≥0.3mm (12mil)

PADandTRACK: ≥0.3mm (12mil)

TRACKandTRACK: ≥0.3mm (12mil)

當密度高時：

PADandVIA: ≥0.254mm (10mil)

PAD和PAD：≥0.254mm (10mil)

PADandTRACK: ≥0.254mm (10mil)

TRACKandTRACK: ≥0.254mm (10mil)

第五：佈線優化和絲網印刷。 “沒有最好，只有更好”！ 無論你在設計上付出多少努力，當你完成後，再看一遍，你仍然會覺得你可以改變很多。 一般的設計經驗法則是，最佳佈線所需的時間是初始佈線的兩倍。 一旦你覺得沒有什麼需要修復，你可以放置銅。 多邊形平面）。 敷銅一般敷地線（注意模擬地和數字地分開），多層板可能還需要敷電源。 對於絲網印刷，要注意不要被設備擋住或被孔和焊盤去除。 同時，設計面向元件表面，字底要鏡面處理，以免混淆水平。

第六：網絡和DRC檢查和結構檢查。 首先，在原理圖設計正確的前提下，對生成的PCB網絡文件和原理圖網絡文件進行物理連接關係NETCHECK，根據輸出文件結果及時修正設計，保證佈線連接關係的正確性； 網絡檢查正確通過後，將對PCB設計進行DRC檢查，並根據輸出文件結果及時修改設計，保證PCB佈線的電氣性能。 最後，應進一步檢查和確認PCB的機械安裝結構。

第七：製版。 It is best to have a review process before doing so.

PCB設計是對工作心智的考驗，誰的心智接近，經驗高，板子的設計好。 所以設計時要格外小心，充分考慮方方面面的因素（比如方便維護和檢查這個很多人都沒有考慮），精益求精，就能設計出好的板子。