A replacement product for PTFE woven glass circuit material has been introduced that provides superior mechanical and thermal properties, uses the RO4000® resin system for ease of fabrication and is a cost competitive option for base station antenna applications (see Figure 1).
The RO4230™ high frequency laminate extends the capabilities of the successful RO4000 product series into antenna applications. The ceramic-filled, glass-reinforced hydrocarbon-based material provides the controlled dielectric constant, low loss performance and excellent passive intermodulation response required for mobile infrastructure microstrip antenna applications.
One of the main advantages of the new RO4230 laminate is that it is fully compatible with conventional FR4 processing and does not require special treatments needed on PTFE-based laminates for plated-through-hole preparation. Thus, it is an affordable alternative to PTFE antenna materials, allowing designers to optimize performance/ price benefits.
Thermal Characteristics
The resin system of the RO4230 dielectric material is designed to provide thermo-mechanical properties critical to antenna design. Its coefficient of thermal expansion (CTE) in both the X and Y directions is similar to that of copper, thus minimizing the thermal effects of environmental conditions by reducing the stresses that can lead to warpage of the printed circuit board antenna. RO4230 material’s glass transition temperature exceeds 280°C; this, coupled with low Z-axis CTE, provides excellent plated-through-hole reliability. In addition, its increased thermal conductivity over equivalent PTFE woven glass materials (0.44 W/m/K) allows for antenna designs with increased power handling capability.
Electrical Properties
To truly be an advantageous replacement for existing antenna circuit material requires that its electrical properties closely match the needs of antenna designers so existing antennas require minimal or no redesign. RO4230 laminate has a dielectric constant (Dk) of 2.98 ±0.05 and a loss tangent (Df) of 0.0020 measured at 2.5 GHz and 0.0023 at 10 GHz. These values allow antenna designers to realize desired gain while minimizing signal loss in the feed network. In addition, RO4230 material has demonstrated low PIM performance, with values better than –155 and up to –162 dBc using two 43 dBm swept tones at 1900 MHz. Figure 2 shows an insertion loss comparison with PTFE/woven glass, RO4350 laminate and a competitive thermoset material. Figure 3 shows the effect of the RO4230 material’s improved thermal conductivity.
Conclusion
The market has had a need for an improved material for use in cellular base station antennas, satellite radio applications and WiMAX antennas, as well as others. RO4230 laminate was designed to provide an enhanced price/performance benefit over Dk 3.0 PTFE/woven glass materials.
RO4230 laminate is available in standard thicknesses of 0.030", 0.040" and 0.060" with 1 oz. electrodeposited copper cladding. Standard panel sizes are 24" × 18", 24" × 36" and 48" × 36". Nonstandard panel sizes are available up to 48" × 108".
Rogers Corp.,
Chandler, AZ (480) 961-1382,
www.rogerscorporation.com.
RS No. 302
RO4000 & R04230 are licensed trademarks of Rogers Corp.
