Rectangular Connectors Move From Mechanical To Electrical

In the past, the selection of connectors was mainly the responsibility of mechanical engineers, because they needed to consider the layout of the entire circuit board or subsystem, and the selection of connectors was more about size and space considerations. Electrical performance usually only considers the rated current of the terminal. The design needs to decide how many terminals are used to transmit signals, the size and shape of the connector body, and the robustness of the connector, especially in military projects. In avionics or portable systems, the size of each device is critical, which is a big challenge for connector selection.

Today's connector design has completely changed. It needs to be selected by a dedicated signal integration engineer. The new connector design must also meet the electrical performance requirements, rather than measuring the electrical performance parameters after the entire connector design is completed as in the past. Especially for high-speed signals above 10GHz, electrical performance is very critical. When designing high-performance connectors, whether it is an expensive backplane connector or a common standard PC connector, the first thing to consider is the electrical performance requirements. The selection of connectors has also shifted from packaging engineers to electrical engineers who design circuits

Connector Insert
Rectangular industrial plugs increase data transmission speed
When the data transmission speed increases, the effects of capacitance and impedance become more obvious. The signal on one terminal will crosstalk to the adjacent terminal and affect its signal integrity. In addition, ground capacitance reduces the impedance of high-speed signals and attenuates the signal. The new serial PCI standard PCI Express has a maximum data transmission speed of 500MB in each direction at 2.5Gb, which greatly increases the signal speed that a single connector can transmit. In the past, high-speed signals were usually controlled by coaxial cables and coaxial connectors to control the impedance of the signal path. A similar concept is adopted in PCI Express, and each signal transmission terminal is separated from each other. Differential signal pairs can achieve this goal well because there are ground pins on one side of each differential signal pair to reduce crosstalk.

High-speed transmission is most widely used in backplane connectors, and connectors up to 10Gb/s use very sophisticated design technology. Usually the first layer is the open pin area to separate adjacent ground terminals. The next level is the ground shield installed between rows. The top layer application will include a metal ground structure around each signal terminal (or differential signal pair, as shown in Figure 1). Such a C-type metal shield achieves the best combination of data transmission speed and signal integrity, and is an ideal connector for high-speed applications.