Temporal and frequency characteristic analysis of margin-related failures caused by an intermittent nano-scale fracture of the solder ball in a BGA package device

Abstract

This paper analyzes the solder ball fracture that could be a source of intermittent errors. The electrical characteristics of a momentary fracture (open), which may appear at the very beginning of a progressive solder ball failure, are extensively studied. The alternating current (AC)-coupling capacitor is defectively formed because of the fractured solder ball, and it can block low-frequency components of the bit data stream. The distorted signal reduces signal integrity under the fracture and results in increased jitter and reduced eye window. This fracture causes the dropping of the signal voltage level, and this dropping erroneously affects the system when multiple failing conditions are simultaneously satisfied. The major failing condition is the fracture height size, which determines the defective AC-coupling capacitor and changes the channel transmission characteristic. The other major condition is the bit pattern, which includes the frequencies affected by the defective channel. SPICE simulation is conducted to demonstrate the effects of a momentary fracture using the DDR3 memory tester system. In the case of a 10nm fractured solder ball with a pseudo-random binary sequence (PRBS) pattern, the eye height is reduced from 597mV to 349mV, and the jitter is increased from 38ps to 132ps. The bits that violate the eye-mask window begin to appear with a heavy bit stream and cause intermittent bit errors.