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August 2014 • The PCB Design Magazine 25 feature RF CAPACIToR MATERIAL FoR USE IN PCBS continues fillers are randomly oriented) [8,9] . The product is the copper clad laminate (CCL) with a standard panel, 18 x 24 inches. It was composed of two sheets of copper foils on both ends with organic based composite dielectrics having fillers dis- persed into polymer in between. Copper foils are available in various thicknesses, 0.5 ounce and 1 ounce being the dominant thickness, but thinner copper foil would help to minimize the variation in capacitance during etching pro- cess in PCB manufacturing. The typical Dk and DF of the RF capacitor laminate at 1GHz were measured, 7.8 and 0.0022, respectively. We are expanding the product's capacitance density range up to 670 pF/cm 2 thinning dielectrics and process optimization. The standard reliability tests including solder shock, solder float, time to delamination and THB (temperature, humid- ity and bias) testing were performed and all these tests passed. C. Uniformity of Capacitance Capacitance tolerance for the organic-based RF capacitor laminate is critical for the appli- cation of forming discrete type embedded ca- pacitors inside the organic packaging substrate. In this case, capacitance tolerance can be ex- pressed as 3 sigma in the form of (mean of ca- pacitance) ± (3 sigma) for the footprint size of the capacitor. Smaller tolerance in capacitance is desirable to achieve better yield performance of the RF device in manufacturing [2] . However, when forming discrete embedded capacitors inside the organic substrate for RF module, the materials and processes don't currently allow for the tight tolerances due to the material and the process variation. The dispersion techniques for the ceramic fillers in polymer and the right Figure 5: Frequency dependence of Dk and DF of the developed RF capacitor laminate. Figure 4: seM images (on the coating surface) of samples with (a) dispersion condition A and (b) dispersion condition B.