Circuits Assembly - August 2008 - (Page 48)

Technical Abstracts In Case You Missed It Component Reliability “Package-on-Package Warpage – Impact on Surface Mount Yields and Board Level Reliability” Authors: Niranjan Vijayaragavan, Flynn Carson and Addi Mistry; niranjan.vijayaragavan@spansion.com. Abstract: This paper presents a systematic study performed to modulate the warpage of the top and bottom PoP, and to study the effect of the relative warpage of the top and bottom PoP on surface mount yields during PoP assembly. A 15 x 15 mm PoP module was selected as it magnifies the warpage effects. Shadow moiré was used for high temperature warpage measurement while subjecting the test samples to a simulated reflow profile. (Electronic Components & Technology Conference, May 2008) PWB Reliability “A Comprehensive Parallel Study on the Board Level Reliability of SAC, SACX and SCN Solders” Authors: Fubin Song, Jeffery C. C. Lo, Jimmy K. S. Lam, Tong Jiang, S. W. Ricky Lee Abstract: Although a large number of research studies have been performed and are currently under way in the Pb-free soldering area, especially on the reliability of SAC solder joints, data on comparison of SAC solders with other Pbfree solders (such as SCN) remain scarce. This paper presents a systematic reliability study of Pb-free solder joints with different solder alloys. The assemblies include two kinds of components (QFN and PBGA) with different terminal metallurgies, and five kinds of Pb-free solder pastes (SAC 305, SAC 387, SACC, SACS and SCN). The results and analysis of different reliability tests (accelerated thermal cycling, package shear/pull, bending and drop tests) with the five kinds of solders are discussed. (Electronic Components & Technology Conference, May 2008) at the joint interfaces and those dispersed in the bulk solder. NiAu pad metallization resulted in more creep-resistant joints than did copper. These effects were more pronounced at lower test temperatures. Solder joint creep resistance increased with joint size. Larger joints also were more prone to brittle interface failure than smaller joints. This was true in package- and board-level tests. Finite element analysis indicated the test vehicle used to generate data for constitutive constants significantly can affect the predicted fatigue life in cyclic drop or temperature cycle testing. More creep-resistant behavior resulted in lower strain and work for both temperature cycle and drop test conditions. When comparing strain vs. work as a damage indicator, it is seen that work is less sensitive to variations in the constitutive constants. (Electronic Components & Technology Conference, May 2008) “Effects of Warpage on Fatigue Reliability of Solder Bumps: Experimental and Analytical Studies” Authors: Wei Tan, I. Charles Ume, Ying Hung and C. F. Jeff Wu; charles.ume@me.gatech.edu. Abstract: PWB and component warpage results principally from CTE mismatch among the materials that make up the assembly. Warpage occurring during surface-mount reflow processes and normal operations may lead to severe solder bump reliability problems. This research studied the effect of initial PWB warpage on the low cycle thermal fatigue reliability of solder bumps in plastic PBGA packages, using experimental and analytical methods. A real-time projection moiré warpage measurement system was used to measure the surface topology of assembly samples at different temperatures. The thermal fatigue reliability of solder bumps was evaluated from experimental thermal cycling tests and finite element simulation results. 3-D models of PCBs with varying board warpage were used to estimate solder bump fatigue life for different types of PBGAs mounted on PWBs. To improve the accuracy of FE results, the projection moiré method was used to measure the initial warpage of PWBs, and this warpage was used as a geometric input to the FEM. The simulation results were validated and correlated with the experimental results obtained using the projection moiré technique and accelerated thermal cycling tests. An advanced prediction model was generated to predict board level solder bump fatigue life based on the initial PWB warpage, package dimensions and locations, and solder bump materials. (Electronic Components & Technology Conference, May 2008) circuitsassembly.com CirCuits Assembly provides abstracts of papers from recent industry conferences and company white papers. With the amount of information increasing, our goal is to provide an added opportunity for readers to keep abreast of technology and business trends. Solder Joint Reliability “Effect of Joint Size and Pad Metallization on Solder Mechanical Properties” Authors: Robert Darveaux, Corey Reichman, C.J. Berry, Wen-Sung Hsu, Ahmer Syed, Chang Woo Kim, Jung Hun Ri, Tae Seong Kim; rdarv@amkor. com. Abstract: Metallurgical analysis, mechanical testing and finite element analysis were conducted to understand the effect of joint size and pad metallization on solder behavior. A range of design and material variables was evaluated. The pad metallization affected both the intermetallic compounds Circuits Assembly AUGUST 2008 48 http://circuitsassembly.com

Table of Contents Feed for the Digital Edition of Circuits Assembly - August 2008

Circuits Assembly - August 2008 Contents Caveat Lector Industry News Market Watch Talking Heads Screen Printing Better Manufacturing Auditing a Fabricatior Cutting Machine Programming Time Simultaneous Acoustic Imaging and Surface Mapping Tech Tips Soldering Test and Inspection Process Doctor Pb-Free Lessons Learned Getting Lean Component Advances Product Spotlight Ad Index Assembly Insider Techincal Abstracts

Circuits Assembly - August 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.