High frequency PCBs are special printed circuit boards that are used to transmit signals at frequencies between 500MHz and 2GHz.
As with any type of printed circuit board, there is much to learn about high frequency PCBs. In this article, you will learn more specifics on what a high frequency PCB is, some of the devices that us high frequency PCBs, some ways in which high frequency PCBs are designed differently than regular printed circuit boards, and how you can assure these designs are implemented correctly during the manufacturing phase.
WHAT IS A HIGH FREQUENCY PCB?
Printed circuit boards in general use a combination of electrical signals and carved pathways to help a product complete a certain function. High frequency printed circuit boards are no different.
In fact, high frequency PCBs are designed to send special signals that regular PCBs are unable to send. You will learn more about how high frequency PCBs are designed differently than PCBs later. But first, you need to know what devices high frequency PCBs can be found in.
WHAT DEVICES USE HIGH FREQUENCY PCBS?
High frequency PCBs are used in a number of everyday electronics and appliances.
To begin, you likely hold a high frequency PCB in the palm of your hand each day. Your smartphone or other mobile device contains a high frequency PCB. Smartphones have become a device that most people use almost every hour of the day. They have revolutionized communication and education thanks to the number of apps and forms of communication they are able to provide the user. Mobile devices usually have between 900 and 1,900 MHz frequencies that are used for communication through texting, video chats, the use of apps, and the calling feature.
Another device that uses high frequency PCBs are microwaves. Used to heat up our food or make a quick lunch on the go, microwaves are an integral appliance in almost every kitchen in the world. Microwave frequencies range from 300 MHz to 300 GHz.
Lastly are devices that rely on radio frequencies. These can include two-way radios and other communication devices. Radio waves allow for the dissemination of information through a specific frequency range: 20 kHz to 300 GHz.
As you can see, a number of devices that help us each and every day tend to use high frequency PCBs.
HOW MUST HIGH FREQUENCY PCBS BE MADE DIFFERENTLY FROM PCBS
Because high frequency PCBs must be able to transmit a special signal of an increased frequency, they must be designed differently from traditional printed circuit boards to avoid some issues that may arise from improper design and manufacturing.
Firstly, heat distribution must be taken into special account when designing and creating a high frequency PCB. Because electrical signals will be sent at a higher frequency, there will be more heat moving throughout the board as the signals are transmitted. This means that the board could potential heat up more quickly than a traditional printed circuit board. To address these issues, the design may need to include a fan or thermal pads that can help absorb and distribute the heat more evenly. This can help avoid issues such as overheating of the PCB.
High frequency printed circuit boards also must include either a high-frequency laminate or FR-4, an epoxy-based laminate. This is due to the high frequency of electric signals on the board. High frequency laminate is usually more expensive to make because the technician would have to maintain a thermal heat transfer during the application. While FR-4 is cheaper, it can fail if put into a high frequency board that has too high of a transmission rate. The designer would need to take several factors into consideration before choosing.
Since high frequency printed circuit boards are used to connect two objects, there should be special consideration when determining the correct pathways that need to be carved into the board during the manufacturing phase. If too much electrical signal is pushed through a small pathway, it could result in damage to the high frequency PCB. This could mean that the board overheats or even that components of the board could be burned or dislodged. Special mathematic equations can help you decide how wide and long a pathway needs to be to be able to handle the frequency.
Noise reduction also needs to be taken into account when designing and creating a high frequency PCB. As previously mentioned, since the electrical signals are being sent more often and at higher rates, the spill-over of electricity can cause noise. Noise is basically an interference into the signal. This can cause the product that the high frequency PCB is powering to experience issues that can lead to it being declared defective.
HOW TO AVOID THESE ISSUES
One of the best ways to avoid the issues mentioned above is to employ the use of a software when designing your high frequency PCB. Software has been created to help you or the high frequency PCB technician calculate the different aspects of the design of the board.
Some of these measurements include the coefficient of thermal expansion, the temperature coefficient, the dissipation factor, and the dielectric constant.
Software can also help you figure out how to best lay out your board to meet your specific needs. It can help you determine how wide and long your pathways need to be, where your PCB components should be located, and can sometimes even allow you to test these things in the software to see how your design will hold up.
Using a software and following up with a skilled PCB technician are the best way to avoid issues like the ones mentioned above. If you have poorly designed high frequency PCBs, they could impact the operation of the product you will be using them in. This could lead to customer complaints and a loss of money.
Now you have a basic knowledge of high frequency PCBs. This introductory knowledge will help you avoid mistakes in the design and manufacturing process.