Abstract
This paper shows that an intermittent AC coupling defect occurring in a DDR4 data channel will cause more intermittent errors in DDR4, compared to such defect in DDR3. The intermittent AC coupling defect occurs due to intermittent fracture in DDR4 package solder ball. The defect causes DC offset in DDR4, which shifts the data signal or data eye and results in DDR4 data channel failure. The DC offset occurs due to the asymmetric nature of pseudo open drain termination scheme. DDR4 data channel response is compared with DDR3 channel. It is shown that pseudo random binary sequence (PRBS) pattern will always cause failure for DDR4, but PRBS will only cause failure in DDR3 if the sequence of consecutive 0’s or 1’s in PRBS pattern is long enough to cause threshold violation. As a result there will be more intermittent errors in DDR4 compared to DDR3. The defect due to fracture in solder ball is modelled by an AC coupling capacitor. A 1nF AC coupling capacitor corresponding to a solder ball fracture of height about 1nm is used to show the difference between DDR4 and DDR3 response.
Highlights
DDR4 introduced a major change in architecture of DDR SDRAM memory by adopting pseudo open drain (POD) I/O standard for data lines [1]
SIMULATION SETUP The intermittent fracture occurs in the solder ball of the DDR4 fine pitch ball grid array (FBGA) package and it changes the behaviour of DDR4 data channel
Intermittent fractures in solder balls will always result in data channel failure for DDR4
Summary
DDR4 introduced a major change in architecture of DDR SDRAM memory by adopting pseudo open drain (POD) I/O standard for data lines [1]. M. Waqar et al.: DDR4 Data Channel Failure Due to DC Offset Caused by Intermittent Solder Ball Fracture. M. Waqar et al.: DDR4 Data Channel Failure Due to DC Offset Caused by Intermittent Solder Ball Fracture TABLE 3. M. Waqar et al.: DDR4 Data Channel Failure Due to DC Offset Caused by Intermittent Solder Ball Fracture FIGURE 3. The intact solder ball (no fracture) case S21 parameter shows that the transmitted signal has maximum value at lower frequencies and the signal value decreases as the frequency increases. At high frequencies both the intact solder ball (no fracture) case and the fractured solder ball case have same S21 parameter characteristics
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call