In this paper, the authors present the noise suppression performance using a decoupling capacitor which is embedded in an LTCC substrate. To embed high value capacitors (>20nF), a high K (over 500) material which can be co-fired with low K LTCC was developed successfully. Thin high K sheets under 10μm were co-laminated between low K sheets, which form the power and ground planes. Due to the short distance from the IC power pin to the decoupling capacitor, the ESL (Equivalent Series Inductance) is much lower than with surface mounted type capacitors, and so, SSN (Simultaneous Switching Noise) can be reduced significantly. To verify the noise suppression performance, we designed and fabricated a digital module using 100MHz CPLD (Complex Programmable Logic Device) on top of the LTCC substrate in which a 25nF decoupling capacitor was embedded. By measurement, we can see that SSN of CPLD on LTCC was reduced by 80% compared with designs that use surface mounted type 100nF capacitors. This embedded decoupling capacitor in LTCC (LEDC) can be useful for digital SiP (System In Package) to enhance noise performance and to reduce its footprint.
