Backplane Pcbs: Characteristics, And Design Considerations For High-speed Data Transmission

By Author: Ryan
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The backplane PCB is the high-speed circuit that turns concepts of computing and communication into reality. They are fixed circuit plates that are used to provide the interconnection of many more printed circuit boards or modules concerning both the physical and electrical entities. Now more than ever, Backplane PCB has to be designed taking into consideration that the data rate is constantly rising and the channels’ bandwidth is growing day by day.


What is the meaning of backplane PCB?


A backplane PCB is a type of printed circuit board that can be utilized as the connection for other PCBs or even other electronic components in the said system. The concept of backplane PCB is quite simple; it aims at creating a mechanical and electrical framework of the multilayer PCB system that interconnects circuits typically using connectors or slots. This serves as a pathway or bus, It connects different circuit boards or modules and lets them converse with other circuit boards or converse.


The backplane can typically come with several connectors with many slots and sockets for adding ...
... several modules. These modules may be in the form of Central Processing Units, memory modules, and input/output cards among other equipment.


A backplane PCB is another kind of printed circuit board that serves as the connection point or a central link of other PCBs or electronic parts in the system. The essence of backplane PCB is to provide support physical as well as electrical for the connection of many circuit boards, most probably through a socket or a bus slot. It works as a bus or as a channel of transmission of data through which the different boards or modules of the device can address other boards and/or other boards can address them. Such a module may exist as a CPU, memory module, I/O card, or any other type of device. Designing backplane PCBs has now become more crucial because of the growing rates of data transmission as well as the bandwidth demands. Concerning higher-density backplane PCBs, this article provides an understanding of the features, benefits, design, and challenges of manufacturing backplane PCBs.


The major characteristics of the backplane printed circuit board


High-density interconnection: backboards are usually located above other boards/modules viewed on more than one level and have significantly more connection points due to many conductive traces.


High-speed data transmission: The backplane circuit board is primarily a high-speed data transmission board as it is responsible for effective and efficient communication which is a pre-requisite in the processing of large amounts of data in every system.


Signal integrity and power distribution: The backplane printed circuit board ensures the signals’ integrity; thus, there are minimal chances that the signals shall be lost due to interference. They can efficiently convey energy and guarantee the optimum power deliverance of the daughterboards incorporated in them.


Backplane and motherboard: Well what do you get out of reading a computer science book and listening to its contents be read to you by a computer aloud and with a strange language?


While the backplane and the motherboard are both one of the principal circuit boards of the electronic system, the main roles and the distinctive features of their usage and design might be strikingly different. The backplane is mainly designed as a high-speed multi-connector of many removable panels or sub-carriers, it can be deemed as a centrally located communication hub. In contrast, motherboards are designed to accommodate and interconnect major devices like central processing units, memory, and expansion slots which are the main constituencies of the computer. While designing the backplane, factors such as high-speed signal integrity, power distribution, and modularity for the expansion of the hardware building block are considered and when designing the motherboard, layout, and connectivity pertain to the system design and compatibility measures of the components in the architecture.


Difficulties associated with the development of backplane PCBs


PCB thickness: As for the backplane, it is not easy to control the stack thickness; to achieve the desired matching impedance and signal integrity in those backplanes, the thickness has to be enlarged due to the requirement on the impedance transmission line, power supply layer and return path.


Number of layers: In general, the number of layers; for example, the number of layers is 20 is the characteristic of the backplane, wherein interconnected circuits. This creates issues on layer registration, through hole alignment and compression.


The complexity of drilling: Due to the thickness of the backplane with printed circuit boards, greater drilling diameter and high aspect ratio are needed; in a single through hole, multiple drilling is done and this is likely to influence the accuracy of the drilling and the overall yield.


As for high-speed data transmission, has certain demands on impedance matching, but because of the different dielectric materials for the cable and the structure of the connectors, it is difficult to achieve.


Due to the high-density signals on the backplane, high-density connectors present the following challenges; the requirement of correct connector placements as well as having to meet the signal integrity.


Designing the backplane PCB


Designing a high-performance backplane PCB requires attention to two key aspects: Areas such as electrical design and mechanical design.


Electrical design


Power delivery: Adhere to a thick power/ground plane density distribution: the distribution density should be concentrated near the connector and accompanied by adequate decoupling capacitors that can provide a stable and clean power supply.


Layer structure


Stack more than 20 layers and use multiple signal return layers, more than 2. Both pairs utilize the same dielectric material and dielectric thickness for the impedance control in this case.


Signal wiring: Concerning the target impedance, during backplane PCB, design we have to ensure that the width and spacing of the traces are optimized, and we also have to run important signals on the inner layer adjacent to the reference layer.


Component placement: So decisions as to where to place bypass capacitors or termination resistors or how close the active devices should be to the connector will impact the signal integrity.


Mechanical design


Card support: Card support means using the definite rails and slots and reinforcing bars thus ensuring that the card is correctly inserted and fixed and that the weight of the circuit board does not force it to bend.


Connector installation: When connecting connectors, particularly when it is used multi-mating Connectors, it is a must to use heavy press-fit connectors and welded connectors also the base and rigid support at the back side to avoid its bending during latching and unlatching.


Thermal management: This is done to ensure that there are adequate airflow passages, that the dielectric materials used have good thermal conductivity, and that thermal equipment is used, by thermal pads/thermal through holes.


Conclusion


From the text above we can read that using backplane PCB powerful computing systems as well as communication devices are possible and these are devices which form the basis of our contemporary lives. They can ensure high speed of communication and realize the interconnection between multiple circuit boards and modules at the same time. They also include management of space and expansion, which also makes these devices ‘real’.

High Quality PCB Co., Limited is a leading PCB(Printed Circuit Board) Manufacturer in China since 1995. Dedicated to the technologies innovation, being engaged in IC Substrates, High-Density Interconnect PCB, Multi-layer PCB, Rigid Flexible PCB, Flexible, Radiofrequency PCB.