Gold Stud Bump on Sn Based Solders

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 001870-001894
Author(s):  
Terence Q. Collier
Keyword(s):  
Solder Joint ◽  
Cross Sections ◽  
Flip Chip ◽  
Void Formation ◽  
Sac305 Solder ◽  
Thick Gold ◽  
Flip Chip Assembly

When thick gold and tin come into contact the intermetallic formed is not one for long term reliability. AuSn intermetallics can lead to void formation, increased resistance and a very brittle joint that will fail in time. Such intermetallic formations occur when gold stud bumps are brought into contact with Sn based allows. Fine pitched devices, such as optical, typically use gold studs due to the tight pitch and small pad sizes. By transforming the gold to a less benign state the gold stud bumps allow assembly using standard Sn based solders. Such a process is beneficial when cheapers solders can be used as well as standard flip chip assembly equipment. This paper will provide cross sections of gold stud bumps with SAC305 solder after 3X reflow. The 3X reflow is required to demonstrate the capability and reliability of the modified solder joint. Rozalia/Ron ok move from 2.5/3D to FC/WLP 12-21-11.

Electromigration Performance of Flip-Chips with Lead-Free Solder Bumps between 30 μm and 60 μm Diameter

2012 ◽  
Vol 2012 (1) ◽  
pp. 000891-000905 ◽  
Author(s):  
Rainer Dohle ◽  
Stefan Härter ◽  
Andreas Wirth ◽  
Jörg Goßler ◽  
Marek Gorywoda ◽  
...  
Keyword(s):  
Flip Chip ◽  
Failure Modes ◽  
Solder Bump ◽  
Void Formation ◽  
Lead Free ◽  
Large Temperature ◽  
Flip Chips ◽  
Solder Bumps ◽  
Current Densities

As the solder bump sizes continuously decrease with scaling of the geometries, current densities within individual solder bumps will increase along with higher operation temperatures of the dies. Since electromigration of flip-chip interconnects is highly affected by these factors and therefore an increasing reliability concern, long-term characterization of new interconnect developments needs to be done regarding the electromigration performance using accelerated life tests. Furthermore, a large temperature gradient exists across the solder interconnects, leading to thermomigration. In this study, a comprehensive overlook of the long-term reliability and analysis of the achieved electromigration performance of flip-chip test specimen will be given, supplemented by an in-depth material science analysis. In addition, the challenges to a better understanding of electromigration and thermomigration in ultra fine-pitch flip-chip solder joints are discussed. For all experiments, specially designed flip-chips with a pitch of 100 μm and solder bump diameters of 30–60 μm have been used [1]. Solder spheres can be made of every lead-free alloy (in our case SAC305) and are placed on a UBM which has been realized for our test chips in an electroless nickel process [2]. For the electromigration tests within this study, multiple combinations of individual current densities and temperatures were adapted to the respective solder sphere diameters. Online measurements over a time period up to 10,000 hours with separate daisy chain connections of each test coupon provide exact lifetime data during the electromigration tests. As failure modes have been identified: UBM consumption at the chip side or depletion of the Nickel layer at the substrate side, interfacial void formation at the cathode contact interface, and - to a much lesser degree - Kirkendall-like void formation at the anode side. A comparison between calculated life time data using Weibull distribution and lognormal distribution will be given.

Electro-migration behavior of Pb-free Flip Chip Bumps

2006 ◽  
Vol 3 (1) ◽  
pp. 32-36 ◽  
Author(s):  
Riet Labie ◽  
Tomas Webers ◽  
Bart Swinnen ◽  
Eric Beyne
Keyword(s):  
Solder Joint ◽  
Flip Chip ◽  
Void Formation ◽  
Test Structure ◽  
Strong Impact ◽  
Migration Behavior ◽  
Resistance Change ◽  
Solder Material ◽  
Free Solder ◽  
The Stability

Most reliability studies, carried out for characterising new Pb-free solder material, put main focus on the thermal-mechanical behaviour of the solder joints. However, it is seen that electro-migration has a big impact on the intermetallic formation between the pad finish (UBM) and the solder material. Electro-migration therefore has a strong impact on the stability and reliability of the joint. A special test structure for flip chip electro-migration has been developed and applied to a CuNiAu – Sn – CuNiAu solder joint. This novel test structure not only monitors the resistance change of the whole bump stack but also allows separating resistance changes at each side (anodic and cathodic) of the bump. It is noticed that at the cathodic UBM, which is the UBM where the electrons enter the solder joint, the UBM consumption is significantly faster than at the anodic side or at a thermal reference bump. It also results in void formation at the cathode which leads to an accelerated failure.

The Nature of Centroidal Locus in Misaligned Flip-Chip Solder Joints

1997 ◽  
Vol 119 (3) ◽  
pp. 156-162
Author(s):  
G. Subbarayan ◽  
A. Deshpande
Keyword(s):  
Solder Joint ◽  
Cross Sections ◽  
Flip Chip ◽  
Solder Joints ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Straight Line ◽  
Dimensional Models ◽  
The Cross ◽  
Three Dimensional Models

The self-alignment mechanism of molten flip-chip solder joints is being increasingly used in passive alignment of optoelectronic devices. For these applications, three-dimensional models of misaligned solder joints are necessary to understand the effect of solder joint design parameters on self alignment. To reduce the complexity of fully three-dimensional models, intuitively reasonable assumptions are often made in their theoretical development. Two such assumptions for misaligned flip-chip solder joints with circular pads are that the locus of centroids is a straight line and that the cross sections are circular in shape. In the present paper, the limits of validity of these two assumptions are explored. In general, if either the top and bottom pad radii are identical, or if there is no misalignment between the pads, then the centroidal locus is a straight line and the cross sections are circular. The extent of deviation from straight line centroidal locus or circular cross section depends on the ratio of the top and bottom pad radii and on the extent of misalignment between the pads. For a misalignment equal to 20 percent of the solder joint height and a joint with 90 percent pad diameter ratio, the deviation from straight line locus is 7 percent and the deviation from circularity is less than 1 percent. However, as the pad ratio is decreased to 50 percent, and as the misalignment is increased to 100 percent, the deviation in centroidal locus increases to 43 percent and the deviation from circularity increases to 33 percent. Thus, straight line locus and circular cross sections are reasonable assumptions for flip-chip solder joints provided the pad diameter ratio and misalignment are small.

Overview of Fatigue Failure of Pb-Free Solder Joints in CSP/BGA/Flip-Chip Applications

2009 ◽  
Vol 6 (3) ◽  
pp. 149-153 ◽  
Author(s):  
Sean M. Chinen ◽  
Matthew T. Siniawski
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Finite Element Methods ◽  
Flip Chip ◽  
Snagcu Solder ◽  
Design Considerations ◽  
Mode Of Failure ◽  
Solder Joint Fatigue ◽  
Free Solder

The purpose of this paper is to provide an overview of SnAgCu solder joint fatigue in BGA/CSP/flip-chip applications and the concern of long-term reliability. The most common mode of failure is ductile fracture due to creep strain. Several methods of predicting the overall life of the solder joint are the Coffin-Manson approach, a constitutive fatigue law, and a damage based model using FEM (finite element methods). The effects of underfill and its processes as well as design considerations that will increase reliability will also be discussed.

Preparation And elemental analysis of ancient fibers

1987 ◽  
Vol 45 ◽  
pp. 410-411
Author(s):  
Allen Angel ◽  
Kathryn A. Jakes
Keyword(s):  
Cross Sections ◽  
Physical Structure ◽  
Energy Dispersive ◽  
Archaeological Sites ◽  
X Ray ◽  
Long Term Storage ◽  
Backscattered Electron ◽  
Electron Imaging

Fabrics recovered from archaeological sites often are so badly degraded that fiber identification based on physical morphology is difficult. Although diagenetic changes may be viewed as destructive to factors necessary for the discernment of fiber information, changes occurring during any stage of a fiber's lifetime leave a record within the fiber's chemical and physical structure. These alterations may offer valuable clues to understanding the conditions of the fiber's growth, fiber preparation and fabric processing technology and conditions of burial or long term storage (1).Energy dispersive spectrometry has been reported to be suitable for determination of mordant treatment on historic fibers (2,3) and has been used to characterize metal wrapping of combination yarns (4,5). In this study, a technique is developed which provides fractured cross sections of fibers for x-ray analysis and elemental mapping. In addition, backscattered electron imaging (BSI) and energy dispersive x-ray microanalysis (EDS) are utilized to correlate elements to their distribution in fibers.

scholarly journals Seigneurial governance and the state in late medieval Guelders (14th–16th century)

2021 ◽  
Vol 36 (1) ◽  
pp. 33-59
Author(s):  
Jim van der Meulen
Keyword(s):  
State Formation ◽  
Cross Sections ◽  
Local Communities ◽  
The State ◽  
16Th Century ◽  
Modern State ◽  
Low Countries ◽  
Late Medieval ◽  
Central Argument

AbstractThis article charts the long-term development of seigneurial governance within the principality of Guelders in the Low Countries. Proceeding from four quantitative cross-sections (c. 1325, 1475, 1540, 1570) of seigneurial lordships, the conclusion is that seigneurial governance remained stable in late medieval Guelders. The central argument is that this persistence of seigneurial governance was an effect of active collaboration between princely administrations, lords, and local communities. Together, the princely government and seigneuries of Guelders formed an integrated, yet polycentric, state. The article thereby challenges the narrative of progressive state centralisation that predominates in the historiography of pre-modern state formation.

Experimental evaluation of SnAgCu solder joint reliability in 100-μm pitch flip-chip assemblies

2014 ◽  
Vol 54 (5) ◽  
pp. 939-944 ◽  
Author(s):  
Ye Tian ◽  
Xi Liu ◽  
Justin Chow ◽  
Yi Ping Wu ◽  
Suresh K. Sitaraman
Keyword(s):  
Solder Joint ◽  
Experimental Evaluation ◽  
Flip Chip ◽  
Solder Joint Reliability ◽  
Snagcu Solder ◽  
Joint Reliability
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