Circuits Assembly - April 2008 - (Page 27)

Component Packaging Figure 10. Comparison of measured eye-diagrams for wire bond vs. flip-chip at 3.3 Gb/s data rate. Figure 11. Comparison of measured eye-diagrams for wire bond vs. flip-chip at 3.3 Gbps data rate. memory interconnect topology was built. PRBS signals from the signal generator were connected to the bond wire side of the DRAM package, and the eye diagram was measured at the memory controller package. The test results were then compared to simulation results to validate the simulation platform (Figure 9a and Figure 9b). Except for the somewhat more pronounced overshoot/ undershoot in the simulation results, most likely caused by an underestimate of system loss factor, the measurements and simulation agree well. For practical DRAM packaging, a key question was whether wire bond would work in higher speed DDR2/DDR3 and even DDR4 applications, or if a more costly flip-chip package is necessary. Our DIMM design proved wire bond is sufficient for DDR2 800MHz. Using the test platform, we studied wire bond vs. flipchip packages at much higher speeds in the DDR3/DDR4 range. Figure 10 compares measured eye diagrams for wire bond vs. flip-chip at a 3.3Gbps data rate with 4pF load capacitance, while Figure 11 compares them at 6.0 Gbps with 2pF load capacitance. The impact on signal quality due to wire bonding can be seen at around 6.0 Gbps, which is much higher than the speed range of concern. Also noteworthy is the I/O load capacitances have a much greater effect on signal deterioration. Future work will focus on generating and analyzing more detailed power and ground distribution system models, and simulation of SSO and interconnect using actual DDR3 and DDR4 device information. ■ Frank Y. Yuan, Ph.D., is a principal engineer and Richard Crisp is director of high-performance packaging and applications at Tessera Inc. (tessera.com); fyuan@ tessera.com. Get right down to it! 24 Cr 35 Br 48 80 82 Cd Hg Pb Cut Y our Lab Costs Down to Size Why Test 500 Components, When You Only Need to Test Five? Let the Innov-X RoHS Engine drive your compliance • • • Straightforward RoHS Screening Solutions Call: [781] 938 - 5005 [866] 4 - innov - X Email:sales@innovxsys.com Watch our Video Demos: www.innovxsys.com/ rohs-demo Book an on-line or on-site demo: www.innovxsys.com/rohs Focus laboratory testing costs Screen non-destructively without disassembly Detect PPM levels of Pb, Hg, Cd, Cr and Br in seconds Automatically classify mixed or homogenous – alloy or polymer Confirm supplier MTR’s Don’t slow production RoHS XRF screening can pay for itself Risk Cost • • • • XRF Screening Require Certs. Do Nothing Cost/Risk Analysis Innov-X Systems, Inc., Worldwide Headquarters, Woburn, MA USA. Innov-X Systems and the Innov-X Systems logo are trademarks of Innov-X Systems, Inc. in the United States and all other countries. All other marks are properties of their respective owners. ©2007 Innov-X Systems, Inc. All rights reserved. Disclosure TM circuitsassembly.com Circuits Assembly APRIL 2008 27 http://www.innovxsys.com/rohs-demo http://www.innovxsys.com/rohs http://www.innovxsys.com/rohs http://tessera.com http://circuitsassembly.com

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Circuits Assembly - April 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing Design and Modeling of High-Speed, High-Density 3-D CSPs and Memory Modules The ‘Big Brush Off’ Revisited Impact of Soldering Atmosphere on Solder Joint Formation Beyond Moore’s Law ESD Control For Class 0 ESDS Devices Growing Your Brand This Year’s Model Tech Tips Reflow Soldering Process Doctor Pb-Free Lessons Learned Getting Lean Equipment Advances Apex Product Preview Ad Index Assembly Insider Technical Abstracts

Circuits Assembly - April 2008

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