Method and apparatus for decoupling ball grid array devices

The present invention is directed to a method and apparatus for decoupling pins of a high density integrated circuit mounted on a circuit board and in particular to providing a method and system for providing decoupling capacitance with respect to power and/or ground pins of a ball grid array integrated circuit. A small circuit board, preferably having or providing capacitance is mounted on the surface of a main circuit board opposite the surface where a BGA or other integrated circuit is mounted, and within the footprint defined the integrated circuit package. Preferably the small circuit board is formed from multiple interleaved conductive and dielectric layers to provide inherent capacitance in the circuit board itself. Capacitance provided by the small circuit board can be configured by selecting the number and/or size and/or placement of the conductive layers. Discrete devices can be mounted on the small circuit board if desired.