Effects of Moisture Exposure on the Mechanical Behavior of Polymer Encapsulants in Microelectronic Packaging

2013 ◽  
Author(s):  
Nusrat J. Chhanda ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Testing Machine ◽  
Adsorbed Water ◽  
Ultimate Tensile Stress ◽  
Stress Strain ◽  
Uniaxial Test ◽  
Organic Structure ◽  
Strain Behavior ◽  
Humidity Chamber

Polymer encapsulants exhibit evolving properties that change significantly with environmental exposures such as moisture uptake, isothermal aging and thermal cycling. In this study, the effects of moisture adsorption on the stress-strain behavior of a polymer encapsulant were evaluated experimentally. The uniaxial test specimens were exposed in an adjustable thermal and humidity chamber to combined hygrothermal exposures at 85 °C/85% RH for various durations. After moisture preconditioning, a microscale tension-torsion testing machine was used to evaluate the complete stress-strain behavior of the material at several temperatures. It was found that moisture exposure caused plasticization and strongly reduced the mechanical properties of the encapsulant including the initial elastic modulus and ultimate tensile stress. Reversibility tests were also conducted to evaluate whether the degradations in the mechanical properties were recoverable. Upon fully redrying, the polymer was found to recover most but not all of its original mechanical properties. As revealed by FTIR, some of the adsorbed water had been hydrolyzed in the organic structure of the epoxy-based adhesive, causing permanent changes to the mechanical behavior.

Mechanics of Wavy Network With Diamond-Shaped Inclusions

2017 ◽  
Author(s):  
Mona Monsef Khoshhesab ◽  
Yaning Li
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Mechanical Behavior ◽  
Geometric Constraints ◽  
Cellular Solids ◽  
Biomedical Devices ◽  
Stress Strain ◽  
Engineering Applications ◽  
Smart Composites ◽  
Strain Behavior

In this investigation, mechanical behavior of periodic cellular solids with diamond-shaped inclusions connected via wavy network were explored. Two families of cellular solids within this category were designed based on two different geometric constraints. Auxetic effects and snap-through instability were observed for each family, respectively. The mechanical properties, including the stress-strain behavior, stiffness and Poisson’s ratio, were systematically quantified via finite element (FE) simulations. The parametric space for auxetic effects and snap-through instability was numerically identified. This study demonstrates the connection and transition between mechanical auxeticity and snap-through instability. The materials designed have potential engineering applications, such as lightweight supporting and protective foams, biomedical devices, smart composites or fabrics with switchable properties responsive to external environments.

Experimental Characterization of Underfill Materials Exposed to Moisture Including Preconditioning

2015 ◽  
Author(s):  
Promod R. Chowdhury ◽  
Nusrat J. Chhanda ◽  
Jeffrey C. Suhling ◽  
Pradeep Lall
Keyword(s):  
Room Temperature ◽  
Flip Chip ◽  
Mechanical Response ◽  
Testing Machine ◽  
Ultimate Tensile Stress ◽  
Production Equipment ◽  
Material Behavior ◽  
Tensile Creep ◽  
Uniaxial Test ◽  
Humidity Chamber

Microelectronic encapsulants exhibit evolving properties that change significantly with environmental exposures such as isothermal aging and high humidity conditions. In this work, the material behavior changes occurring in underfill materials subjected to moisture exposures in an humidity chamber have been characterized using 60 × 3 × 0.5 mm uniaxial test specimens which were cured with production equipment using the same conditions as those used in actual flip chip assembly. After curing, the samples were divided into two groups and subjected to different preconditioning: (1) no preconditioning, (2) prebaking at 85 C for 24 hours. The fabricated and preconditioned uniaxial test specimens were then exposed in an adjustable thermal and humidity chamber to combined hygrothermal exposures at 85 C and 85% RH for various durations (0, 1, 3, 10, 30, 60 days). After the moisture exposures, a microscale tension-torsion testing machine was used to evaluate the complete stress-strain behavior of the material at room temperature (25 C). In addition, the viscoelastic mechanical response of the underfill encapsulant has also been characterized via creep testing at room temperature for several applied stress levels after the moisture exposures. From the recorded results, it was found that the moisture exposures strongly degrade the mechanical properties of the tested underfill including the initial elastic modulus, ultimate tensile stress, and tensile creep rate. Prebaking was found to increase the initial material properties, but the degradations due to subsequent moisture exposures occurred in a similar manner.

Mechanical Characterization of Assemblies Bonded With Pressure-Sensitive Adhesives (PSAs)

2015 ◽  
Author(s):  
Hao Huang ◽  
Abhijit Dasgupta ◽  
Ehsan Mirbagheri ◽  
Srini Boddapati
Keyword(s):  
Mechanical Behavior ◽  
Failure Modes ◽  
Mechanical Characterization ◽  
Bonding Temperature ◽  
Process Conditions ◽  
Second Phase ◽  
Loading Conditions ◽  
Stress Strain ◽  
Strain Behavior ◽  
Pressure Sensitive

The focus of this paper is on the stress-strain behavior and creep response of a pressure-sensitive adhesive (PSA) with and without carrier layers. This study consists of two phases. The first phase focuses on understanding of the effects of fabrication profiles, including bonding pressure, bonding temperature, bonding time, and aging time, on the PSA joint strength. This part of the study is used to identify an acceptable bonding and aging conditions for manufacturing a robust PSA bonded assembly. Specimens fabricated with this selected set of bonding process conditions are then used for mechanical characterization. The second phase focuses on the assembly’s mechanical behavior (stress-strain behavior and the creep curves) under different loading conditions, including loading stress, loading rate, and loading temperature. The mechanical behavior of PSA bonded assemblies is affected not only by the loading conditions, but also by the assembly architecture. The mechanical behaviors and failure modes of PSAs with and without carrier layers are compared. The reasons for these differences are also discussed.

scholarly journals Study on Dynamic Mechanical Properties and Constitutive Model Construction of TC18 Titanium Alloy

Metals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 44 ◽  
Author(s):  
Changming Zhang ◽  
Anle Mu ◽  
Yun Wang ◽  
Hui Zhang
Keyword(s):  
Mechanical Properties ◽  
Titanium Alloy ◽  
Flow Stress ◽  
Yield Strength ◽  
Constitutive Model ◽  
Testing Machine ◽  
Dynamic Mechanical Properties ◽  
Stress Strain ◽  
Dynamic Mechanical ◽  
Different Temperatures

In order to investigate the static and dynamic mechanical properties of TC18 titanium alloy, the quasi-static stress–strain curve of TC18 titanium alloy under room temperature was obtained by DNS 100 electronic universal testing machine (Changchun Institute of Mechanical Science Co., Ltd., Changchun, China). Meanwhile, the flow stress–strain curves under different temperatures and strain rates are analyzed by split Hopkinson pressure bar (SHPB) device with synchronous assembly system. On the basis of the two experimental data, the JC constitutive model under the combined action of high temperature and impact load is established using the linear least squares method. The results show the following: the yield strength and flow stress of TC18 titanium alloy increase slowly with the increase of the strain rate, and the strain value corresponding to the yield strength is reduced. With the increase of strain, the flow stress increases at first and then decreases at different temperatures. The strain value corresponding to the transition point rises with the temperature increase, and the corresponding stress value remains basically unchanged. With the increase of experimental temperature, the flow stress shows a downward trend, and the JC constitutive model can predict the plastic flow stress well.

scholarly journals Investigation of the Mechanical Properties of St. Lawrence River Ice

1971 ◽  
Vol 8 (2) ◽  
pp. 163-169 ◽  
Author(s):  
L. W. Gold ◽  
A. S. Krausz
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Yield Stress ◽  
Power Law ◽  
River Ice ◽  
Stress Strain ◽  
Strain Behavior ◽  
Brittle Transition ◽  
Ductile To Brittle Transition ◽  
St Lawrence River

Observations are reported on the stress–strain behavior at −9.5 ± 0.5 °C of four types of ice obtained from the St. Lawrence River. The ice was subject to nominal rates of strain covering the range 2.1 × 10−5 min−1 to 5.8 × 10−2 min−1. A ductile-to-brittle transition was observed for strain rate of about 10−2 min−1. In the ductile range the four types had an upper yield stress that increased with strain rate according to a power law.

scholarly journals Mechanical properties of NiTi and CuNiTi shape-memory wires used in orthodontic treatment. Part 1: stress-strain tests

2013 ◽  
Vol 18 (4) ◽  
pp. 35-42 ◽  
Author(s):  
Marco Abdo Gravina ◽  
Ione Helena Vieira Portella Brunharo ◽  
Cristiane Canavarro ◽  
Carlos Nelson Elias ◽  
Cátia Cardoso Abdo Quintão
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Shape Memory ◽  
Orthodontic Treatment ◽  
Testing Machine ◽  
The Other ◽  
Lower Percentage ◽  
Machine Model ◽  
Military Institute ◽  
The Military

OBJECTIVE: This research aimed to compare, through traction tests, eight types of superelastic and heat-activated NiTi archwires, by six trade companies (GAC, TP, Ormco, Masel, Morelli and Unitek) to those with addition of copper (CuNiTi 27ºC and 35ºC, Ormco). METHODS: The tests were performed in an EMIC mechanical testing machine, model DL10000, capacity of 10 tons, at the Military Institute of Engineering (IME). RESULTS: The results showed that, generally, heat-activated NiTi archwires presented slighter deactivation loadings in relation to superelastic. Among the archwires that presented deactivation loadings biologically more adequate are the heat-activated by GAC and by Unitek. Among the superelastic NiTi, the CuNiTi 27ºC by Ormco were the ones that presented slighter deactivation loadings, being statistically (ANOVA) similar, to the ones presented by the heat-activated NiTi archwires by Unitek. When compared the CuNiTi 27ºC and 35ºC archwires, it was observed that the 27ºC presented deactivation forces of, nearly, ⅓ of the presented by the 35ºC. CONCLUSION: It was concluded that the CuNiTi 35ºC archwires presented deactivation loadings biologically less favorable in relation to the other heat-activated NiTi archwires, associated to lower percentage of deformation, on the constant baselines of deactivation, showing less adequate mechanical behavior, under traction, in relation to the other archwires.

Nonlinear Rate-Dependent Stress-Strain Behavior of Light-Weight Textile Conveyor Belt

2011 ◽  
Vol 675-677 ◽  
pp. 453-456
Author(s):  
Ze Xing Wang ◽  
Jin Hua Jiang ◽  
Nan Liang Chen
Keyword(s):  
Loading Rate ◽  
Testing Machine ◽  
Rate Sensitivity ◽  
Sensitivity Coefficient ◽  
Conveyor Belt ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Strain Behavior ◽  
Rate Dependent ◽  
Dependent Behavior

In order to investigate the effect of loading rate on the tensile performance, the uniaxial tensile experiments were conducted on universal testing machine under different loading rates (5 mm/min, 10mm/min, 50 mm/min, 100 mm/min and 150 mm/min), and a constant gage length equal to 200mm, resulting in loading strain rate of 4.17×10-4, 8.33×10-4/s, 4.17×10-3/s, 8.33×10-3/s,1.25×10-2/s, and the tensile stress-strain curves were obtained. The experimental results show that the tensile properties of the conveyor belt exhibit obvious rate-dependent behavior. In this paper, the rate sensitivity coefficient varied with loading rate, was calculated, and the nonlinear rate-dependent behavior was also investigated.

Microstructural Characteristics of Polyurea and Polyurethanexerogels for Concrete Confinement with FRP System

2013 ◽  
Vol 742 ◽  
pp. 237-242 ◽  
Author(s):  
Mostafa Fakharifar ◽  
Zhi Bin Lin ◽  
Cheng Lin Wu ◽  
Shruti Mahadik-Khanolkar ◽  
Nicholas Leventis ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Mechanical Properties ◽  
Pilot Study ◽  
Mechanical Behavior ◽  
Confined Concrete ◽  
Stress Strain ◽  
Microstructural Characteristics ◽  
Concrete Confinement ◽  
Energy Absorbing

Due to their exceptional mechanical properties,xerogels attract increasing attention forstructural applications. In this study, the mechanical behavior of two types of polymeric xerogelsis investigated. The excellent energy-absorbing capability of those xerogelsis demonstrated by their stress-strain relations with respect to their microstructure determined withscanning electron microscopy (SEM). A pilot study on the effects of xerogellayers in an FRP system for concrete confinementis conducted.Test results clearly indicatedthat the proposed multi-layer systemcan significantly increase the ductility of confined concrete.

Mechanical Properties of Winding Conductors Affected by Cyclic Thermal Overloads

2006 ◽  
Vol 113 ◽  
pp. 541-544 ◽  
Author(s):  
N. Višniakov ◽  
J. Novickij ◽  
D. Ščekaturovienė ◽  
M. Šukšta
Keyword(s):  
Mechanical Properties ◽  
Metal Matrix ◽  
Room Temperature ◽  
Pure Copper ◽  
Testing Machine ◽  
Liquid Nitrogen Temperature ◽  
Ultimate Tensile Stress ◽  
Climatic Chamber ◽  
Fast Heating ◽  
Before And After

The influence of thermal cyclic overloads on mechanical properties of winding conductors was investigated. Copper-niobium microcomposite, soft and hard pure copper wires were conditioned at temperatures range from 77 K to 500 K. The treatment was done during 100 cycles of fast conductor cooling to liquid nitrogen temperature and further fast heating in a climatic chamber. The ultimate tensile stress limit and the elongation at failure of metal-matrix copper-niobium microcomposite, soft and hard copper wires were measured before and after thermal treatment with a testing machine at room temperature.

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