Here is the abstract you requested from the IMAPS_2010 technical program page. This is the original abstract submitted by the author. Any changes to the technical content of the final manuscript published by IMAPS or the presentation that is given during the event is done by the author, not IMAPS.
|Next Generation High Dk, Low Df Organic Laminate for RF Modules and High Frequency Applications|
|Keywords: Low Loss , RF, High Frequency|
|We present a novel ultra-high density high performance thin organic substrate for RF and high frequency applications by using new generation halogen free high Dk and low Df material (X-R series) and compatible low cost conventional PCB facilities and processes. In RF and high frequency applications, the dielectric loss dominates the overall signal loss. The conventional PCB materials, such as FR-4 and epoxy based materials are not suitable because they cause excessive losses and distortion. The advantages of ceramic materials are very low loss at high frequencies. However, they are thick, heavy and expensive. The X-R is a new organic laminate designed for high-density interconnect multilayer RF substrate uses. Its dielectric loss tangent is 0.003 measured at 1GHz, equivalent to that of typical ceramic, LCP and PTFE. Its dielectric constant is 7.0, similar to a typical ceramic material. The thickness of X-R laminate used here is 50um, much lesser than typical ceramic substrate. Profile-free 12 um thick copper foils are clad on both sides. Unlike ceramic and LCP/PTFE substrate, the fabrication processes of multilayer X-R substrate are totally compatible with conventional FR-4 material. It is a thermal setting glass fiber reinforced hydrocarbon polymer which is dimensional stable. Ultra-fine trace circuits can be formed in multilayer structure. Process characterization test vehicles were designed and fabricated for evaluating this new material. 40um through holes were drilled by CO2 laser and 20um copper lines and spaces were fabricated by using chemical etching method, primarily due to the smooth copper foil. Furthermore, to demonstrate RF integration, 2 to 4-metal layer structure test vehicles were designed, fabricated and tested. The test vehicle included RF characterization structures such as transmission lines, inductors and capacitors and bandpass filters. Due to the ultra thin X-R substrate with high Dk, low Df, and profile-free copper, about 40% size reduction was seen on the bandpass filters with low insertion loss and good return loss. Associated with profile-free copper surface the low loss X-R substrate shows lower transmission loss, compared to LTCC. The new X-R laminate provides a thin, light, high performance and low cost RF organic platform with high functionality and flexibility.|
|Fuhan Liu, Research Engineer
Georgia Institute of Technology