Electrical characterization of a 500 MHz frequency EBGA package

Abstract

We developed a high-speed enhanced ball grid array (EBGA) package that can accommodate a 500 MHz ASIC with 15 W of power consumption. This package uses 32 pairs of low voltage differential signals with 400 mV full amplitude and 240 ps risetime as its highest signal speed. The differential signal pairs are designed to run all along with an isometric length including bonding wire, trace, via, and ball in order to cancel out the common mode noise. Adjacent two differential signal pairs are grouped into a channel, which is also designed to have an isometric length. This channel forms a set of parallel transmission paths. The transmission line was formed with characteristic impedance of 60 /spl Omega/ within a substrate in terms of strip line configuration. This package has a nonstub configuration using electroless nickel and gold plating. The ground pad is connected to the ground plane through the sidewall of the cavity, which is the nearest path in order to reduce ground inductance-per-pin down to 12-24 pH. Time domain waveform was simulated at the frequency of 500 MHz as the electrical characteristics of this package. The time domain waveform in an actual package was measured at risetime of 120 and 240 ps, which corresponds to 500 and 800 MHz of frequency, respectively. The simulated waveform correlates very well with the measured waveform. Signal integrity was excellent, which had small overshoot-undershoot and crosstalk noise less than 10%. Differential skew and channel skew were minimized to less than 10 ps to achieve a parallel transmission. We confirmed this at system level using our package with a 500 MHz ASIC. With our package we are able to accommodate an 800 MHz ASIC based on the time domain waveform results.