精密PCB製造、高頻PCB、高速PCB、標準PCB、多層PCB和PCB組裝。
在解釋檢查工作之前 PCB電路板 接線完成, 我將介紹這3種PCB的特殊佈線技巧. PCB佈局的佈線將從3個方面進行說明：直角佈線, 差分路由, and serpentine routing:
1. Right-angle wiring (three aspects)
The influence of right-angle wiring on the signal is mainly reflected in three aspects: first, 轉角可以等效於輸電線路上的電容性負載, 减慢上升時間； 第二, 阻抗不連續會引起訊號反射； 第3, 直角由電磁干擾產生, 至10GHz以上射頻設計領域, 這些小直角可能成為高速問題的焦點.
2. Differential traces ("equal length, 等距離, reference plane")
What is a differential signal (Differential Signal) 用外行的話來說, 驅動端發送兩個相等且相位相反的訊號, 接收端通過比較兩個電壓之間的差异來判斷邏輯狀態“0”或“1”. 攜帶差分訊號的一對記錄道稱為差分記錄道. 與普通單端訊號道相比, differential signals have obvious advantages in the following three
Aspect:
1. 抗干擾能力强, 因為兩個差分記錄道之間的耦合非常好. 當外界有譟音干擾時, 它們幾乎同時耦合到兩條線路上, 接收端只關心兩個訊號之間的差异. 因此, 外部共模雜訊可以完全消除.
2. 它可以有效抑制電磁干擾. 以同樣的管道, 因為兩個訊號的極性是相反的, 它們輻射的電磁場可以相互抵消. 聯軸器越緊, 釋放到外部世界的電磁能量越少.
3. 定時定位, 因為差分訊號的切換變化位於兩個訊號的交點處, 與依賴於兩個閾值電壓的普通單端訊號不同, 高和低, 囙此，受工藝和溫度的影響較小, 並且可以减少定時誤差. 它也更適用於具有低幅度訊號的電路. The current popular LVDS (low voltage differential signaling) refers to this small-amplitude differential signaling technology.
3. Serpentine line (adjustment delay)
Serpentine line is a type of routing method often used in Layout. 其主要目的是調整延遲以滿足系統定時設計要求. The two key parameters are the parallel coupling length (Lp) and the coupling distance (S). 明顯地, 當訊號在蛇形軌跡上傳輸時, 平行線段之間會發生耦合, 以差模形式. 小的, Lp越大, 耦合度越大. 由於串擾，它可能導致傳輸延遲的减少，並大大降低訊號質量. 該機制可參攷共模和差模串擾的分析. Here are a few tips for Layout engineers when dealing with snakes:
1) Try to increase the distance (S) of parallel line segments, 至少大於3H, H是指訊號軌跡到基準面的距離. In layman's terms, 它是繞著一個大彎走的. 只要S足够大, 幾乎可以完全避免互耦效應.
2) Reduce the coupling length Lp. 當雙Lp延遲接近或超過訊號上升時間時, 產生的串擾將達到飽和.
3) The signal transmission delay caused by the serpentine line of the strip line or the buried microstrip line is smaller than that of the microstrip line. 理論上, 帶狀線不會因差模串擾而影響傳輸速率.
4) For high-speed and signal lines with strict timing requirements, 儘量不要走彎彎曲曲的路線, 尤其是不要在小範圍內蜿蜒.
5) Serpentine traces with any angle can often be used, 這可以有效地减少它們之間的耦合.
6) In high-speed PCB設計, 蛇形線路沒有所謂的濾波或抗干擾能力, 它只能降低訊號質量, 囙此，它僅用於定時匹配，沒有其他用途.
7) Sometimes the spiral routing can be considered for winding. 模擬結果表明，該方法優於常規的蛇形路由.
全體的 PCB設計 drawing inspection items
1) No circuit analysis; no circuit is divided into basic units in order to smooth the signal;
2) Does the circuit allow the use of short or isolated critical leads;
3) Where must be shielded, is it effectively shielded;
4) Make full use of the basic grid graphics without;
5) Whether the size of the printed circuit board is the size;
6) Whether to use the selected wire width and spacing as much as possible;
7) Whether the preferred pad size and hole size are used;
8) Whether the photographic plate and sketch are suitable;
9) Is there less jumper wire used; does the jumper wire pass through components and accessories;
10) Are the letters visible after assembly; are their sizes and models correct;
11) In order to prevent blistering, 大面積銅箔是否已打開?
12) Are there tool positioning holes?
PCB electrical characteristics inspection items:
1) Has the influence of wire resistance, inductance and 電容 been analyzed; especially the impact of the critical voltage drop to grounding;
2) Whether the spacing and shape of the wire accessories meet the insulation requirements;
3) Whether the insulation resistance value is controlled and specified at key points;
4) Whether the polarity is adequately identified;
5) Has the influence of wire spacing on leakage resistance and voltage been measured from a geometrical point of view?
6) Has the medium that changed the surface coating been identified?
PCB physical characteristics inspection items:
1) Whether all pads and their positions are suitable for final assembly;
2) Whether the assembled printed circuit board can meet the 震驚 and 振動 energy conditions;
3) What is the spacing of the specified standard components;
4) Are the components that are not firmly installed or the heavier components fixed?
5) Is the heat dissipation and cooling of the heating element correct? Or is it isolated from printed circuit boards and other thermal components;
6) Are the voltage dividers and other multi-lead components positioned correctly?
7) Is the arrangement and orientation of components easy to inspect;
8) Whether all possible interference on the printed circuit board and on the entire printed circuit board assembly has been eliminated;
9) Whether the size of the positioning hole is correct;
10) Whether the tolerance is complete and reasonable;
11) Control and sign off the physical properties of all coatings;
12) Whether the ratio of the diameter of the hole to the lead wire is within the acceptable range.
PCB mechanical design factors:
Although the printed circuit board uses mechanical methods to support components, 它不能用作整個設備的結構部分. 印版邊緣, 至少每5英寸一次，以獲得一定的支撐力. The factors that must be considered in the selection and design of printed circuit boards are as follows;
1) The structure of the printed circuit board - size and shape.
2) The type of mechanical accessories and plugs required.
3) The adaptability of the circuit to other circuits and environmental conditions.
4) Consider mounting the printed circuit board vertically or horizontally according to some factors such as heat and dust.
5) Some environmental factors that need special attention, 比如散熱, 通風, shock, vibration, 濕度. 灰塵, 鹽霧和輻射.
6) Degree of support.
7) Hold and fix.
8) Easy to take off.
PCB printed circuit board installation requirements:
It should be supported within at least 1 inch of the three edge edges of the printed circuit board. 根據實踐經驗, 厚度為0的印刷電路板的支撐點間距.031--0.062英寸應至少為4英寸； 對於厚度大於0的印刷電路板.093英寸, 支撐點的間距應至少為5英寸. 採取此措施會新增印刷電路板的剛度，並破壞印刷電路板可能的共振. 某個印刷電路板在决定其安裝科技之前通常會考慮以下因素.
1) The size and shape of the printed circuit board.
2) Number of input and output terminals.
3) Available equipment space.
4) The desired ease of loading and unloading.
5) The type of installation accessories.
6) The required heat dissipation.
7) Required shieldability.
8) The type of circuit and its relationship with other circuits.
Dial-out requirements for printed circuit boards:
1) No PCB area required to mount components.
2) The influence of plugging tools on the installation distance between two printed circuit boards.
3) The mounting holes and slots should be specially prepared in the design of the printed circuit board.
4) When the plug-in tool is to be used in the equipment, 尤其是它的尺寸應該考慮在內.
5) A plug-in device is required, 通常用鉚釘固定在印刷電路板組件上.
6) In the mounting frame of printed circuit boards, 需要特殊設計，如承重法蘭.
7) The adaptability of the plugging tools used to the size, 印刷電路板的形狀和厚度.
8) The cost involved in the use of plugging and unplugging tools includes both the price of the tool and the increased expenditure.
9) In order to tighten and use plug-in tools, 要求在一定程度上能够進入設備內部.
PCB Mechanical Considerations:
Substrate properties that have a significant impact on printed circuit assemblies are: water absorption, 熱膨脹係數, 熱效能, 彎曲強度, 衝擊強度, 抗拉强度, 剪切强度和硬度. 所有這些特性都會影響印刷電路板結構的功能性和印刷電路板結構的生產率. 對於大多數應用程序, the printed circuit board's dielectric backing is one of the following:
1) Phenolic impregnated paper.
2) Acrylic-polyester impregnated glass mat with random arrangement.
3) Epoxy impregnated paper.
4) Epoxy impregnated glass cloth.
每個基材可以是阻燃的或可燃的. 以上1, 2和3可以沖孔. 金屬化孔印製電路板常用的資料是環氧玻璃布. 其尺寸穩定性適用於高密度電路, 並且可以减少金屬化孔中裂紋的發生. 環氧玻璃布層壓板的一個缺點是難以在印刷電路板的通常厚度範圍內衝壓, 囙此，通常鑽所有孔，並使用複製銑削操作來形成印刷電路板形狀.
PCB Electrical Considerations:
In DC or low-frequency AC applications, 絕緣基板的重要電力特性為：絕緣電阻, 抗電隔離和印刷導體電阻和擊穿强度. 在高頻和微波應用中, 它是：介電常數, capacitance, 和耗散因數. 在所有應用中, 然而, 印刷導體的載流能力很重要.
佈線模式：PCB佈線路徑和定位, 在指定佈線規則的約束下, 印刷電線應在組件之間走短路線. 盡可能限制平行導線之間的耦合. 一個好的設計需要少量的佈線層, 並且還需要與所需的包裝密度相對應的寬導線和小焊盤尺寸. 應避免電線中的尖角和尖角，因為圓角和光滑的內角可能會避免可能出現的一些電力和機械問題.
PCB width and thickness:
Ampacity of etched copper conductors on rigid printed circuit boards. 對於1盎司和2盎司導線, allow for a 10% reduction of nominal value (based on load current), taking into account normal variations in etching method and copper foil thickness and temperature differences; for protected printed circuit board assembly Components (substrate thickness less than 0.032英寸, copper foil thickness more than 3 ounces) are reduced by 15%; for dip soldered printed circuit boards, 允許减少30%.
PCB導線間距：必須確定導線間距，以消除相鄰導線之間的電壓擊穿或電弧. Spacing is variable and depends primarily on the following factors: 1) The peak voltage between adjacent conductors. 2) Atmospheric pressure (working height). 3) The coating used. 4) Capacitive coupling parameters. 關鍵阻抗組件或高頻組件通常緊密放置在一起，以减少關鍵階段延遲. 變壓器和感應組件應隔離，以防止耦合； 感應訊號線應以直角正交敷設； 應隔離或牢固安裝因磁場運動產生任何電雜訊的部件，以防止過度振動.
PCB Wire Pattern Check:
1) Whether the wire is short and straight without sacrificing function;
2) Whether the limitation of wire width is complied with;
3) There is no space between wires, 導線和安裝孔之間, and between wires and pads that must be guaranteed;
4) Whether the parallel arrangement of all wires (including component leads) is relatively close is avoided;
5) Whether acute angles (90°C or less) are avoided in the wire pattern.
PCB Design Project Check Item List:
1) Check the rationality and correctness of the schematic diagram;
2) Check the correctness of the component packaging of the schematic diagram;
3) The distance of strong and weak electricity, the distance of isolation area;
4) Check the schematic diagram and PCB diagram correspondingly to prevent the loss of the network table;
5) Whether the package of the component is consistent with the actual product;
6) Whether the placement of components is appropriate:
7) Whether the components are easy to install and disassemble;
8) Check whether the temperature sensitive element is too close to the heating element;
9) Whether the distance and direction of the mutual inductance components are appropriate;
10) Whether the placement between the connectors is smooth;
11) Easy to plug and unplug;
12) Input and output;
13) Strong and weak electricity;
14) Whether digital simulation is interleaved;
15) Arrangement of windward and leeward elements;
16) Whether the directional element is wrongly flipped instead of rotated;
17) Whether the mounting holes of the component pins are suitable and whether it is easy to insert;
18) Check whether the empty foot of each component is normal and whether it is a leak;
19) Check whether there are vias in the upper and lower layers of the same network table, and the pads are connected through the holes to prevent disconnection and ensure the integrity of the line;
20) Check whether the upper and lower characters are placed correctly and reasonably, 並且不要放置組件來覆蓋字元, so as to facilitate the operation of welding or maintenance personnel;
21) The connection between the upper and lower layers of the very important line should not only be connected by the pads of the in-line components, but also by the vias;
22) The arrangement of the power supply and signal lines in the socket shall ensure the integrity and anti-interference of the signal;
23) Pay attention to the proper ratio of pads and solder holes;
24) Each plug should be placed on the edge of the PCB板 as much as possible and easy to operate;
25) Check whether the component label is consistent with the component, and the components are placed in the same direction as possible and placed neatly;
26) The power and ground wires should be as thick as possible without violating the design rules;
27) Under normal circumstances, 上層是水准的, 下層是垂直的, and the chamfer is not less than 90 degrees;
28) Whether the size and distribution of the mounting holes on the PCB are appropriate, and minimize the bending stress of the PCB;
29) Pay attention to the height distribution of components on the PCB and the shape and size of the PCB板 確保易於組裝.
