Interactions Between Flip Chip Underfill and Solder Alloy

2010 ◽  
Vol 132 (3) ◽  
Author(s):  
D. Blass ◽  
P. Borgesen
Keyword(s):  
Solder Alloy ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Moisture Sensitivity ◽  
Complex Issue ◽  
Shock Testing ◽  
Out Of Plane ◽  
Level 3 ◽  
Mechanical Optimization

The effects of underfill selection on flip chip reliability were always a complex issue. Mechanical optimization of the underfill performance, achieved by the addition of appropriate fillers, is invariably a tradeoff between the adhesion and the coefficient of thermal expansion (CTE) and, thus, also between in-plane and out-of-plane stresses. Another critical concern is the degradation of the underfill in processing and/or long term exposure to operating temperatures and ambient humidity. This is strongly affected by the chemical compatibility with combinations of solder mask, chip passivation, and flux residues. The latter is believed to be responsible for our observation of interactions with the solder alloy, too. As for the effects of glass transition temperatures and CTE, we find materials that were close to optimum for eutectic SnPb to be very far from the best options for lead free joints. We report on two sets of systematic experiments. The first addressed the performance of combinations of underfills, no-clean fluxes, and solder alloys in a JEDEC level 3 moisture sensitivity test. The second one involved thermal shock testing of flip chip assemblies underfilled with one of five different materials after soldering with SnCu, SAC305, and SnPb.

Process Characterization and the Effect of Process Defects on Flip Chip Reliability

1999 ◽  
Author(s):  
Brian J. Lewis ◽  
Hilary Sasso
Keyword(s):  
Process Parameters ◽  
Flip Chip ◽  
Failure Modes ◽  
Shock Testing ◽  
Fine Pitch ◽  
Process Characterization ◽  
Solder Bumps ◽  
Optimum Height ◽  
High Yields

Abstract Processing fine pitch flip chip devices continues to pose problems for packaging and manufacturing engineers. Optimizing process parameters such that defects are limited and long-term reliability of the assembly is increased can be a very tedious task. Parameters that effect the robustness of the process include the flux type and placement parameters. Ultimately, these process parameters can effect the long-term reliability of the flip chip assembly by either inhibiting or inducing process defects. Therefore, care is taken to develop a process that is robust enough to supply high yields and long term reliability, but still remains compatible with a standard surface mount technology process. This is where process optimization becomes most critical and difficult. What is the optimum height of the flux thin film used for a dip process? What force is required to insure that the solder bumps make contact with the pads? What are the limiting boundaries in which high yields and high reliabilities are achieved, while maintaining a streamlined, proven process? The following study evaluates a set of process parameters and their impact on process defects and reliability. The study evaluates process parameters including, flux type, flux application parameters, placement force and placement accuracy to determine their impact. Solder voiding, inadequate solder wetting, and crack propagation and delamination in the underfill layer are defects examined in the study. Assemblies will be subjected to liquid-to-liquid thermal shock testing (−55° C to 125°C) to determine failure modes due to the aforementioned defects. The results will show how changes in process parameters effect yield and reliability.

Reliability Analysis of Flip Chip Designs Via Computer Simulation

2000 ◽  
Vol 122 (3) ◽  
pp. 214-219 ◽  
Author(s):  
Hua Lu ◽  
C. Bailey ◽  
M. Cross
Keyword(s):  
Material Properties ◽  
Flip Chip ◽  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Empirical Relationship ◽  
Life Time ◽  
Fatigue Reliability ◽  
Chip Design ◽  
Flip Chips ◽  
Out Of Plane

A flip chip component is a silicon chip mounted to a substrate with the active area facing the substrate. This paper presents the results of an investigation into the relationship between a number of important material properties and geometric parameters on the thermal-mechanical fatigue reliability of a standard flip chip design and a flip chip design with the use of microvias. Computer modeling has been used to analyze the mechanical conditions of flip chips under cyclic thermal loading where the Coffin-Manson empirical relationship has been used to predict the life time of the solder interconnects. The material properties and geometry parameters that have been investigated are the Young’s modulus, the coefficient of thermal expansion (CTE) of the underfill, the out-of-plane CTE CTEz of the substrate, the thickness of the substrate, and the standoff height. When these parameters vary, the predicted life-times are calculated and some of the features of the results are explained. By comparing the predicted lifetimes of the two designs and the strain conditions under thermal loading, the local CTE mismatch has been found to be one of most important factors in defining the reliability of flip chips with microvias. [S1043-7398(00)01203-2]

scholarly journals Tooth loss in complying and non-complying periodontitis patients with different periodontal risk levels during supportive periodontal care

2021 ◽  
Author(s):  
Roberto Farina ◽  
Anna Simonelli ◽  
Andrea Baraldi ◽  
Mattia Pramstraller ◽  
Luigi Minenna ◽  
...  
Keyword(s):  
Active Treatment ◽  
Clinical Relevance ◽  
Tooth Loss ◽  
Loss Rate ◽  
Risk Levels ◽  
Recall Interval ◽  
Level 3 ◽  
The Difference ◽  
Periodontal Risk

Abstract Objectives To evaluate yearly tooth loss rate (TLR) in periodontitis patients with different periodontal risk levels who had complied or not complied with supportive periodontal care (SPC). Materials and methods Data from 168 periodontitis patients enrolled in a SPC program based on a 3-month suggested recall interval for at least 3.5 years were analyzed. For patients with a mean recall interval within 2–4 months (“compliers”) or > 4 months (“non-compliers”) with different PerioRisk levels (Trombelli et al. 2009), TLR (irrespective of the cause for tooth loss) was calculated. TLR values were considered in relation to meaningful TLR benchmarks from the literature for periodontitis patients either under SPC (0.15 teeth/year; positive benchmark) or irregularly complying with SPC (0.36 teeth/year; negative benchmark). Results In both compliers and non-compliers, TLR was significantly below or similar to the positive benchmark in PerioRisk level 3 (0.08 and 0.03 teeth/year, respectively) and PerioRisk level 4 (0.12 and 0.18 teeth/year, respectively). Although marked and clinically relevant in non-compliers, the difference between TLR of compliers (0.32 teeth/year) and non-compliers (0.52 teeth/year) with PerioRisk level 5 and the negative benchmark was not significant. Conclusion A SPC protocol based on a 3- to 6-month recall interval may effectively limit long-term tooth loss in periodontitis patients with PerioRisk levels 3 and 4. A fully complied 3-month SPC protocol seems ineffective when applied to PerioRisk level 5 patients. Clinical relevance PerioRisk seems to represent a valid tool to inform the SPC recall interval as well as the intensity of active treatment prior to SPC enrollment.

Analysis of Long-Term and Thermal Cycling Tests for a Commercial Solid Oxide Fuel Cell

2017 ◽  
Vol 14 (4) ◽  
Author(s):  
Dustin Lee ◽  
Jing-Kai Lin ◽  
Chun-Huang Tsai ◽  
Szu-Han Wu ◽  
Yung-Neng Cheng ◽  
...  
Keyword(s):  
Fuel Cell ◽  
Thermal Cycling ◽  
Solid Oxide Fuel Cell ◽  
Coefficient Of Thermal Expansion ◽  
Solid Oxide ◽  
Oxide Fuel ◽  
Flow Rates ◽  
Degradation Rates ◽  
Two Stages

The effects of isothermally long-term and thermal cycling tests on the performance of an ASC type commercial solid oxide fuel cell (SOFC) have been investigated. For the long-term test, the cells were tested over 5000 h in two stages, the first 3000 h and the followed 2000 h, under the different flow rates of hydrogen and air. Regarding the thermal cycling test, 60 cycles in total were also divided into two sections, the temperature ranges of 700 °C to 250 °C and 700 °C to 50 °C were applied for the every single cycle of first 30 cycles and the later 30 cycles, respectively. The results of long-term test show that the average degradation rates for the cell in the first 3000 h and the followed 2000 h under different flow rates of fuel and air are 1.16 and 2.64%/kh, respectively. However, there is only a degradation of 6.6% in voltage for the cell after 60 thermal cycling tests. In addition, it is found that many pores formed in the anode of the cell which caused by the agglomeration of Ni after long-term test. In contrast, the vertical cracks penetrating through the cathode of the cell and the in-plane cracks between the cathode and barrier layer of the cell formed due to the coefficient of thermal expansion (CTE) mismatch after 60 thermal cycling tests.

Application of an Epoxy Cap in a Flip-Chip Package Design

1989 ◽  
Vol 111 (1) ◽  
pp. 16-20 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Thermal Expansion ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Preliminary Test ◽  
Elastic Stability ◽  
Thermally Induced ◽  
Package Design ◽  
Silicone Gels ◽  
Low Modulus ◽  
Supporting Frame

In order to combine the merits of epoxies, which provide good environmental and mechanical protection, and the merits of silicone gels, resulting in low stresses, one can use an encapsulation version, where a low modulus gel is utilized as a major encapsulant, while epoxy is applied as a protecting cap. Such an encapsulation version is currently under consideration, parallel with a metal cap version, for the Advanced VLSI package design which is being developed at AT&T Bell Laboratories. We recommend that the coefficient of thermal expansion for the epoxy be somewhat smaller than the coefficient of thermal expansion for the supporting frame. In this case the thermally induced displacements would result in a desirable tightness in the cap/frame interface. This paper is aimed at the assessment of stresses, which could arise in the supporting frame and in the epoxy cap at low temperatures. Also, the elastic stability of the cap, subjected to compression, is evaluated. The calculations were executed for the Advanced VLSI package design and for a Solder Test Vehicle (STV), which is currently used to obtain preliminary information regarding the performance of the candidate encapsulants. It is concluded that in order to avoid buckling of the cap, the latter should not be thinner than 15 mils (0.40 mm) in the case of VLSI package design and than 17.5 mils (0.45 mm) in the case of STV. At the same time, the thickness of the cap should not be greater than necessary, both for smaller stresses in the cap and for sufficient undercap space, required for wirebond encapsulation. The obtained formulas enable one to evaluate the actual and the buckling stresses. Preliminary test data, obtained by using STV samples, confirmed the feasibility of the application of an epoxy cap in a flip-chip package design.

scholarly journals Tackling Complexity of the Just Transition in the EU: Evidence from Romania

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1509
Author(s):  
Roxana Voicu-Dorobanțu ◽  
Clara Volintiru ◽  
Maria-Floriana Popescu ◽  
Vlad Nerău ◽  
George Ștefan
Keyword(s):  
Environmental Sustainability ◽  
Power Plants ◽  
Point Of View ◽  
Major Power ◽  
Complex Issue ◽  
Energy Mix ◽  
Carbon Neutrality ◽  
Vulnerable Consumers ◽  
The Eu

The process of reaching carbon neutrality by 2050 and cutting CO2 emissions by 2030 by 55% compared to 1990 as per the EU Green Deal is highly complex. The energy mix must be changed to ensure long-term environmental sustainability, mainly by closing down coal sites, while preserving the energy-intensive short-term economic growth, ensuring social equity, and opening opportunities for regions diminishing in population and potential. Romania is currently in the position of deciding the optimal way forward in this challenging societal shift while morphing to evidence-based policy-making and anticipatory governance, mainly in its two coal-mining regions. This article provides possible future scenarios for tackling this complex issue in Romania through a three-pronged, staggered, methodology: (1) clustering Romania with other similar countries from the point of view of the Just Transition efforts (i.e., the energy mix and the socio-economic parameters), (2) analyzing Romania’s potential evolution of the energy mix from the point of the thermal efficiency of two major power plants (CEH and CEO) and the systemic energy losses, and (3) providing insights on the socio-economic context (economic development and labor market transformations, including the component on the effects on vulnerable consumers) of the central coal regions in Romania.

scholarly journals FCCSP IMC growth under reliability stress follows automotive criteria

2019 ◽  
Vol 3 (1) ◽  
pp. 70-83
Author(s):  
Wei Wei Liu ◽  
Berdy Weng ◽  
Scott Chen
Keyword(s):  
High Temperature ◽  
Flip Chip ◽  
Stress Test ◽  
Temperature Cycling ◽  
Content Type ◽  
Initial Stage ◽  
High Temperature Storage ◽  
Temperature Cycling Test ◽  
Temperature Storage

Purpose The Kirkendall void had been a well-known issue for long-term reliability of semiconductor interconnects; while even the KVs exist at the interfaces of Cu and Sn, it may still be able to pass the condition of unbias long-term reliability testing, especially for 2,000 cycles of temperature cycling test and 2,000 h of high temperature storage. A large number of KVs were observed after 200 cycles of temperature cycling test at the intermetallic Cu3Sn layer which locate between the intermetallic Cu6Sn5 and Cu layers. These kinds of voids will grow proportional with the aging time at the initial stage. This paper aims to compare various IMC thickness as a function of stress test, the Cu3Sn and Cu6Sn5 do affected seriously by heat, but Ni3Sn4 is not affected by heat or moisture. Design/methodology/approach The package is the design in the flip chip-chip scale package with bumping process and assembly. The package was put in reliability stress test that followed AEC-Q100 automotive criteria and recorded the IMC growing morphology. Findings The Cu6Sn5 intermetallic compound is the most sensitive to continuous heat which grows from 3 to 10 µm at high temperature storage 2,000 h testing, and the second is Cu3Sn IMC. Cu6Sn5 IMC will convert to Cu3Sn IMC at initial stage, and then Kirkendall void will be found at the interface of Cu and Cu3Sn IMC, which has quality concerning issue if the void’s density grows up. The first phase to form and grow into observable thickness for Ni and lead-free interface is Ni3Sn4 IMC, and the thickness has little relationship to the environmental stress, as no IMC thickness variation between TCT, uHAST and HTSL stress test. The more the Sn exists, the thicker Ni3Sn4 IMC will be derived from this experimental finding compare the Cu/Ni/SnAg cell and Ni/SnAg cell. Research limitations/implications The research found that FCCSP can pass automotive criteria that follow AEC-Q100, which give the confidence for upgrading the package type with higher efficiency and complexities of the pin design. Practical implications This result will impact to the future automotive package, how to choose the best package methodology and what is the way to do the package. The authors can understand the tolerance for the kind of flip chip package, and the bump structure is then applied for high-end technology. Originality/value The overall three kinds of bump structures, Cu/Ni/SnAg, Cu/SnAg and Ni/SnAg, were taken into consideration, and the IMC growing morphology had been recorded. Also, the IMC had changed during the environmental stress, and KV formation was reserved.

scholarly journals Towards a long-term dataset of ELBARA-II measurements assisting SMOS level-3 land product and algorithm validation at the Valencia Anchor Station

2015 ◽  
pp. 55
Author(s):  
R. Fernandez Moran ◽  
J. P. Wigneron ◽  
E. Lopez-Baeza ◽  
M. Miernecki ◽  
P. Salgado-Hernanz ◽  
...  
Keyword(s):  
Soil Moisture ◽  
Anchor Station ◽  
Ocean Salinity ◽  
Algorithm Validation ◽  
Level 3

La misión de SMOS (Soil Moisture and Ocean Salinity) se lanzó el 2 de Noviembre de 2009 con el objetivo de proporcionar datos de humedad del suelo y salinidad del mar. La principal actividad de la conocida como Valencia Anchor Station (VAS) es asistir en la validación a largo plazo de productos de suelo de SMOS. El presente estudio se centra en una validación de datos de nivel 3 de SMOS en la VAS con medidas in situ tomadas en el periodo 2010-2012. El radiómetro Elbara-II está situado dentro de los confines de la VAS, observando un campo de viñedos que se considera representativo de una gran proporción de un área de 50×50 km, suficiente para cubrir un footprint de SMOS. Las temperaturas de brillo (TB) adquiridas por ELBARA-II se compararon con las observadas por SMOS en las mismas fechas y horas. También se utilizó la inversión del modelo L-MEB con el fin de obtener humedades de suelo (SM) que, posteriormente, se compararon con datos de nivel 3 de SMOS. Se ha encontrado una buena correlación entre ambas series de TB, con mejoras año tras año, achacable fundamentalmente a la disminución de precipitaciones en el periodo objeto de estudio y a la mitigación de las interferencias por radiofrecuencia en banda L. La mayor homogeneidad del footprint del radiómetro ELBARA-II frente al de SMOS explica la mayor variabilidad de sus TB. Los periodos de precipitación más intensa (primavera y otoño) también son de mayor SM, lo que corrobora la consistencia de los resultados de SM simulados a través de las observaciones del radiómetro. Sin embargo, se debe resaltar una subestimación por parte de SMOS de los valores de SM respecto a los obtenidos por ELBARA-II, presumiblemente debido a la influencia que la pequeña fracción de suelo no destinado al cultivo de la vid tiene sobre SMOS. Las estimaciones por parte de SMOS en órbita descendente (6 p.m.) resultaron de mayor calidad (mayor correlación y menores RMSE y bias) que en órbita ascendente (6 a.m., momento de mayor humedad de suelo).

scholarly journals Long-term regulation of renal urea transporter protein expression in rat.

1998 ◽  
Vol 9 (5) ◽  
pp. 729-736 ◽  
Author(s):  
J Terris ◽  
C A Ecelbarger ◽  
J M Sands ◽  
M A Knepper
Keyword(s):  
Polyclonal Antibodies ◽  
Collecting Duct ◽  
Brattleboro Rats ◽  
Urea Transporter ◽  
Sprague Dawley ◽  
Transporter Protein ◽  
Level 3 ◽  
Term Basis

To test the hypothesis that the abundance of the apical urea transporter of the inner medullary collecting duct (IMCD) is regulated in vivo by factors associated with altered water balance, immunoblots of rat inner medullary membrane fractions were probed with rabbit polyclonal antibodies against the renal urea transporter (RUT) gene product. In inner medullas of Brattleboro rats, which manifest severe chronic water diuresis, a 117-kD band was seen, in addition to the previously described 97-kD band. These two bands were detectable by antibodies directed against two different regions of the RUT sequence. When Brattleboro rats were treated with a 5-d infusion of arginine vasopressin (AVP) by osmotic minipump, the 117-kD band was markedly diminished, whereas the 97-kD band was unchanged. Simultaneous infusion of the diuretic agent furosemide prevented the AVP-induced decrease in the 117-kD band. In AVP-infused Sprague Dawley rats, the 117-kD band was barely perceptible. However, when AVP-treated rats were infused with furosemide for 5 d, the 117-kD band was markedly accentuated, whereas the 97-kD band was unchanged. The abundance of the 117-kD RUT protein in the renal papilla was inversely correlated with dietary protein intake. Further immunoblotting studies revealed that the 117-kD protein is heavily expressed in IMCD cells and not in non-collecting duct components of the inner medulla, and is present in low-density microsome fractions from inner medulla. From this study, the following conclusions can be made: (1) The collecting duct urea transporter is present in at least two forms (97 and 117 kD) in the IMCD. (2) The expression level of the 117-kD urea transporter protein is regulated and is inversely correlated with medullary osmolality and urea concentration, but does not correlate with circulating AVP level. (3) Although AVP regulates RUT function on a short-term basis, long-term changes in AVP levels do not increase RUT abundance.

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