The emergence of 5G technology challenges HDI PCB

If 4G has changed your life, then 5G may change the entire society.

5G can achieve transmission speeds of several gigabits per second without the use of optical fibers. It will completely change our perception of fast-moving Internet and have all the prerequisites for creating new applications, such as in entertainment, AR (augmented reality), VR (virtual reality), distance learning, and medical fields.
The 5G era has arrived, and more and more mobile wireless communication systems are undergoing upgrades and conversions to adopt 5G technology to better connect to the Internet of Things (IoT). The surprising speed of 5G will open up new market opportunities for all industries that use, design, and manufacture system components and applications.
What does this mean for the HDI PCB industry?
First of all, we must prioritize material issues when designing and constructing PCB stacks. 5G PCBs must meet all specifications when carrying and receiving signal transmission, providing electrical connections, and providing control for specific functions. At the same time, it is also necessary to solve the challenges of PCB design, such as maintaining signal integrity at a higher speed, heat dissipation management, and how to prevent electromagnetic interference (EMI) between the data and the board.
Mixed signal receiving circuit board design
Today, most systems are dealing with 4G and 3G PCBs. This means that the component's transmit and receive frequency range is 600 MHz to 5.925 GHz, and the bandwidth channel is 20 MHz, or 200 kHz for IoT systems. When designing PCBs for 5G network systems, depending on the application, these components will require millimeter wave frequencies of 28GHz, 30GHz or even 77GHz. For bandwidth channels, the 5G system will process 100MHz below 6GHz and 400MHz above 6GHz.
Higher speeds and frequencies will require the use of suitable materials in the PCB to simultaneously capture and transmit lower and higher signals without signal loss and EMI. At the same time, the equipment will become lighter, more portable, and smaller. Due to strict weight, size and space constraints, PCB materials must be flexible and lightweight to accommodate all microelectronic devices on the circuit board.

For PCB copper traces, thinner traces and stricter impedance control must be followed.
The material base is also being redesigned. Printed circuit board companies are studying materials with a dielectric constant as low as 3, because standard materials for low-speed PCBs are usually 3.5 to 5.5. Tighter glass fiber weave, lower loss factor loss material and low profile copper will also become the choice for high-speed PCBs for digital signals, thereby preventing signal loss and improving signal integrity.
EMI shielding problem
EMI, crosstalk and parasitic capacitance are the main problems of circuit boards. In order to cope with the crosstalk and EMI generated by the analog and digital frequencies on the board, it is recommended to separate the wiring. The use of multilayer boards will provide better versatility to determine how to place high-speed traces so that the paths of the analog and digital return signals are kept away from each other, while keeping the AC and DC circuits separate. Adding shielding and filtering when placing components should also reduce the amount of natural EMI on the PCB.
In order to ensure that there are no defects and serious short circuits or open circuits on the copper surface, advanced automatic optical inspection systems (AOI) with higher functions and 2D metrology are used to check the traces of the conductors and measure them. These technologies will help PCB manufacturers look for possible signal degradation risks.
Cooling challenge
A higher signal speed will cause the current through the PCB to generate more heat. PCB materials used for dielectric materials and core substrate layers will need to adequately handle the high speeds required by 5G technology. If the material is insufficient, it may cause copper traces, peeling, shrinkage and warping, because these problems will cause the deterioration of the PCB.
In order to cope with these higher temperatures, manufacturers will need to focus on the choice of materials that solve the thermal conductivity and thermal coefficient issues. Materials with higher thermal conductivity, excellent heat transfer, and consistent dielectric constant must be used to make a good PCB to provide all the 5G features required for this application.