Signal integrity or SI is a measure of the quality of an electrical signal. In igital electronics, a stream of binary values is represented by a voltage (or current) waveform. Over short distances and at low bit rates, a simple conductor can transmit this with sufficient fidelity. However, at high bit rates and over longer distances, various effects can degrade the electrical signal to the point where errors occur, and the device fails. Signal integrity engineering is the task of analyzing and mitigating these impairments. Signal integrity engineering is an important activity at all levels of electronics packaging, from internal connections of an integrated circuit (IC) , through the package, the printed circuit board (PCB), the backplane, and inter-system connections. While there are some common themes at these various levels, there are also practical considerations, in particular the interconnect flight time versus the bit period, that cause substantial differences in the approach to signal integrity for on-chip connections versus chip-to-chip connections.