The interconnect of 印刷電路板 系統包括芯片到電路板、PCB內部互連以及PCB與外部設備之間的互連。 In RF design, the electromagnetic characteristics at the interconnect point is one of the main problems faced by engineering design. This paper introduces various techniques of the above three types of interconnect design, including device installation methods, isolation of wiring and measures to reduce lead inductance.

There are signs that printed circuit boards are being designed with increasing frequency. As data rates continue to increase, the bandwidth required for data transmission also pushes the signal frequency ceiling to 1GHz or higher. This high frequency signal technology, although far beyond the millimeter wave technology (30GHz), does involve RF and low-end microwave technology.

RF engineering design methods must be able to handle the stronger electromagnetic field effects that are typically generated at higher frequencies. 這些電磁場會在相鄰的信號線或 PCB 線上感應出信號，導致不良串擾（干擾和總噪聲）並損害系統性能。 Backloss is mainly caused by impedance mismatch, which has the same effect on the signal as additive noise and interference.

High return loss has two negative effects: 1. The signal reflected back to the signal source will increase the noise of the system, making it more difficult for the receiver to distinguish noise from signal; 2. 2. 任何反射信號都會從本質上降低信號質量，因為輸入信號的形狀會發生變化。

Although digital systems are very fault tolerant because they only deal with 1 and 0 signals, the harmonics generated when the pulse is rising at high speed cause the signal to be weaker at higher frequencies. 雖然前向糾錯可以消除一些負面影響，但部分系統帶寬被用於傳輸冗餘數據，導致性能下降。 A better solution is to have RF effects that help rather than detract from signal integrity. It is recommended that the total return loss at the highest frequency of a digital system (usually a poor data point) be -25dB, equivalent to a VSWR of 1.1.

PCB design aims to be smaller, faster and less costly. For RFPCB, high-speed signals sometimes limit the miniaturization of PCB designs. At present, the main method to solve the crosseration problem is to carry out ground connection management, conduct spacing between wiring and reduce lead inductance. 降低迴波損耗的主要方法是阻抗匹配。 這種方法包括絕緣材料的有效管理和有源信號線和地線的隔離，特別是信號線和地之間的狀態。

由於互連是電路鏈中最薄弱的環節，在射頻設計中，互連點的電磁特性是工程設計面臨的主要問題，應研究每個互連點並解決存在的問題。 電路板互連包括芯片到電路板互連、PCB互連以及PCB與外部設備之間的信號輸入/輸出互連。

一、芯片與PCB板的互連

無論該解決方案是否有效，與會者都清楚，IC 設計技術遠遠領先於高頻應用的 PCB 設計技術。

PCB互連

高頻PCB設計的技術和方法如下：

1、傳輸線拐角應採用45°角，以減少回波損耗（圖1）；

2 insulation constant value according to the level of strictly controlled high-performance insulating circuit board. This method is beneficial for effective management of electromagnetic field between insulating material and adjacent wiring.

3. PCB design specifications for high precision etching should be improved. 考慮指定 +/-0.0007 英寸的總線寬誤差，管理佈線形狀的底切和橫截面，並指定佈線側壁電鍍條件。 Overall management of wiring (wire) geometry and coating surfaces is important to address skin effects related to microwave frequencies and to implement these specifications.

4. 凸出的引線有抽頭電感。 避免使用帶引線的組件。 對於高頻環境，最好使用表面貼裝元件。

5. For signal through holes, avoid using the PTH process on the sensitive plate, as this process can cause lead inductance at the through hole. Lead inductance can affect layers 4 to 19 if a through-hole in a 20-ply board is used to connect layers 1 to 3.

6. Provide abundant ground layers. Moulded holes are used to connect these grounding layers to prevent 3d electromagnetic fields from affecting the circuit board.

7、要選擇非電解鍍鎳或沉金電鍍工藝，不要使用HASL電鍍方法。 This electroplated surface provides a better skin effect for high-frequency currents (Figure 2). In addition, this highly weldable coating requires fewer leads, helping to reduce environmental pollution.

8. Solder resistance layer can prevent solder paste from flowing. However, due to the uncertainty of thickness and unknown insulation performance, covering the entire plate surface with solder resistance material will lead to a large change in electromagnetic energy in microstrip design. Generally, solderdam is used as welding resistance layer.

如果您不熟悉這些方法，請諮詢曾為軍用微波電路板工作過的經驗豐富的設計工程師。 You can also discuss with them what price range you can afford. For example, it is more economical to use a copper-backedCoplanar microstrip design than a stripline design, and you can discuss this with them to get better advice. 優秀的工程師可能不習慣考慮成本，但他們的建議可能會很有幫助。 培養不熟悉射頻效應、缺乏處理射頻效應經驗的年輕工程師將是一項長期的工作。

此外，還可以採用其他解決方案，例如改進計算機模型以處理射頻效應。

PCB與外部設備互連

我們現在可以假設我們已經解決了板上和分立元件互連的所有信號管理問題。 那麼如何解決從電路板到連接遠程設備的電線的信號輸入/輸出問題呢？ TrompeterElectronics, an innovator in coaxial cable technology, is working on this problem and has made some important progress (figure 3). Also, take a look at the electromagnetic field shown in Figure 4 below. 在這種情況下，我們管理從微帶線到同軸電纜的轉換。 In coaxial cables, the ground layers are interlaced in rings and evenly spaced. In microbelts, the grounding layer is below the active line. This introduces certain edge effects that need to be understood, predicted, and considered at design time. 當然，這種不匹配也會導致回損，必須盡量減少以避免噪聲和信號干擾。

The management of the internal impedance problem is not a design problem that can be ignored. The impedance starts at the surface of the circuit board, passes through a solder joint to the joint, and ends at the coaxial cable. 由於阻抗隨頻率變化，頻率越高，阻抗管理越困難。 The problem of using higher frequencies to transmit signals over broadband appears to be the main design problem.