Low transmission loss halogen-free MLB material targets wireless base stations

Low transmission loss halogen-free MLB material targets wireless base stations

Technology News |
By Jean-Pierre Joosting

Claiming to be the industry’s first halogen-free multi-layer board material for RF power amplifiers, it is designed to contribute to compact-sizing and stable operation of wireless base stations.

In the fifth-generation mobile communication system (“5G”), currently being developed for implementation in 2020, data communication by a variety of equipment such as smartphones is predicted to require a much greater capacity and higher transmission rates. For 5G communication, demand for “small cells “, small base stations that can cover hot spots with high user demand, is expected to expand substantially. RF power amplifier boards used in compact-sized small cells will require a multi-layer structure to achieve further space saving in place of the current mainstream double-sided boards. The industry also requires multi-layer boards that can carry out high-speed communication in high frequency domains while providing low transmission losses as well as low heat generation. Panasonic’s proprietary resin design technology has enabled the industry’s first commercial production of multi-layer circuit board material for RF power amplifiers by providing halogen-free, low transmission loss and high thermal conductivity features that, up to this point, have represented a major technical barrier.
The material exhibits -20 dB/m transmission loss at 20 GHz. Thermal conductivity is  0.6 W/(m·K) – 1.5 times that of the Panasonic’s conventional product – enabling effective dissipation of heat from hot components used on the power amplifier to provide reliable operation.

The material protects against deterioration of transmission characteristics in high-temperature environments, thereby contributing to the long-term durability of the base stations.Dielectric constant change rate is 1.0%, while dissipation factor change rate is 3.5% (1000 hours at 125°C). This is in contrast to dielectric constant change rate of current products of 3.0%, and issipation factor change rate of current products of 80% (1000 hours at 125°C).

Low transmission loss

Previous circuit board materials for RF power amplifiers were produced primarily with a double-sided structure and they were not designed with a multi-layer structure in mind. With communication systems becoming ever more compact, the adoption of small cells and smaller board areas is necessary, so multi-layer designs are increasingly being adopted. From an environmental viewpoint, halogen-free materials are ideal – however, alternative non-halogen flame retardant component structures tend to show considerable transmission loss in the high frequency range. Panasonic, by applying its proprietary resin design technology, has commercialized the industry’s first halogen-free multi-layer board material for RF power amplifiers that is flame retardant and has low transmission loss in the high frequency range, which were difficult in the past. By achieving a multi-layer structure of 10 layers or so, usable for high-speed communication in the milliwave band of 20 to 80 GHz, it is expected to contribute to compact-sizing of wireless base stations and the achievement of 5G mobile communication systems.

Transmission loss versus frequency.

High thermal conductivity for reliable operation.

Small cells consist of high heat generating components mounted on a relatively small electronic circuit board. Use of conventional board materials would cause the heat-generating components to become extremely hot, increasing the risk of operational instability and failure. Because R-5575 employs a highly thermally conductive resin design that disperses and dissipates the heat generated by components, temperatures can be kept low, therefore achieving stable operation of communication base stations.

Low deterioration of transmission characteristics ensure longevity

Board materials for RF power amplifiers used to be subject to the problem of deteriorating transmission characteristics when used for many hours in a high-temperature environment because they are made from resin. Panasonic’s proprietary resin technology that is used in R-5575 successfully minimizes any deterioration in dielectric constant and dissipation factor even during extended use at high temperatures. This feature is expected to preserve stable transmission characteristics and contribute to the long-term stable operation of communication base stations.

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