NXP Semiconductors has claimed the industry’s first top-side cooling solution for RF power, which reduces the thickness and weight of 5G radios by more than 20 percent. The new family of top-side cooled RF amplifier modules offer high power capabilities and advanced thermal performance to enable smaller, thinner and lighter radios for 5G base stations.
A big driver behind the development is the need for further integration, said Gavin Smith, RF product launch and global distribution manager at NXP. “The main thing is bringing more integration within the package, which enables smaller and, in some cases, lighter radios.”
Smith said the new package is not common for the RF space, although it is used on the digital side.
In addition to helping radio designers create thinner and lighter 5G radio units, the GaN multi-chip module series also reduces the carbon footprint for the manufacture and deployment of 5G base stations. The smaller base stations also blend more easily into the environment and make installation easier and more cost effective.
Deployment cost is a major factor for some of the heavier equipment, requiring cranes to bring the base stations on top of the building or other infrastructure and that costs money, said Smith. Now with base stations weighing below 23 kg, people can carry one by hand, he added.
In addition, top-side cooling enables less material used in the radio and a smaller wind profile, which requires fewer accessories to support the radio, Smith said.
Top-side cooled RF power module (Source: NXP Semiconductors)
The first products in the new family combine NXP’s LDMOS and GaN technologies and top-side cooling packaging in multi-chip modules. NXP introduced its multi-technology (LDMOS, GaN and SiGe) multi-chip modules in 2018 and opened its RF GaN fab in 2020 to help meet growing demand for higher frequency and greater bandwidth requirements.
The top-side cooled RF power module series is designed for 32T32R, 200-W radios covering 3.3 GHz to 3.8 GHz. By combining NXP’s in-house LDMOS and GaN semiconductor technologies, the devices achieve high gain and efficiency with wideband performance, delivering 31-dB gain and 46 percent efficiency over 400 MHz of instantaneous bandwidth.
Design benefits
The key advantage of the top-side cooling, along with the multi-chip package, is the streamlined 5G radio design. These include enabling the power amplifier (PA) to be mounted on the side of the heat sink, removing the separate RF shield, and eliminating the need for the copper coin in the printed circuit board (PCB) and embedding it in the module for a simplified thermal path as well as reducing the size of the filter and the number and length of the connectors. It also enables all of the components to be mounted on the same side of the PCB and cooled directly with the heat sink, which also acts as the RF shield.
The main difference between a [bottom cooled] conventional radio and [top cooled] thin MIMO is the total quantity of layers associated with the two different types, said Nathan Glaza, integrated power solutions portfolio manager at NXP. “The thin MIMO gives end customers the ability to minimize the design and layers to help make them thinner and lighter.”
This is accomplished “by creating the topside-cooled power amplifier module, which gives us the ability to flip the module and put it on the other side of the PCB, so it’s now on the digital side, which means the thermal interface itself is pointing in one direction,” said Glaza. “By doing that it enables the ability to remove the coin from the PCB, which helps reduce some of the weight and cost for the end customer. But we’ve also embedded that coin in the PA module so we can shrink the overall size of the main heat sink by 20 percent.”
In addition, the filter, which is a dielectric instead of a cavity filter, along with the circulator, can be moved to the other side of the PCB, and now all of the components are on the same side of the PCB, said Glaza. The design also eliminates the above shield, which was required in a bottom-cooled conventional radio to help with the performance of the PA and other RF components, and embeds the shield in the heat sink, he added.
“By removing a lot of those layers and the bigger filter, it gives us the ability to shrink the overall radio and reach that 20 percent or more reduction in radio thickness and in weight,” Glaza said.
Bottom-cooled conventional radio versus top-side cooled thin MIMO (Source: NXP Semiconductors)
The design also delivers cost savings, Smith said. He attributes some of those savings to fewer and shorter connectors, which also reduce RF losses; the removal of the top shield, and the elimination of the copper coin, which simplifies the thermal path for better thermal performance.
“The clean separation of thermal paths and better thermal performance are the main messages,” Smith added.
The A5M34TG140-TC, A5M35TG140-TC and A5M36TG140-TC modules are available today. An evaluation board is available for the A5M36TG140-TC as part of the company’s RapidRF reference board series.
Top-side cooling evaluation board (Source: NXP Semiconductors)
Advertisement
Learn more about NXP Semiconductors
