Microstructural Evolution of Viscoelastic Properties of Underfills Under Sustained High Temperature Operation

2021 ◽  
Author(s):  
Pradeep Lall ◽  
Madhu Kasturi ◽  
Haotian Wu ◽  
Jeffrey C. Suhling ◽  
Edward Davis
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Optical Microscope ◽  
Dynamic Mechanical Properties ◽  
Isothermal Exposure ◽  
Dynamic Mechanical ◽  
Fine Pitch ◽  
Long Time

Abstract Automotive underhood electronics are subjected to high operating temperatures in the neighborhood of 150 to 200? for prolonged periods in the neighborhood of 10-years. Consumer grade off-the shelf electronics are designed to operate at 55 to 85? with a lower use-life of 3 to 5 years. Underfill materials are used to provide supplemental restraint to fine-pitch area array electronics and meet the reliability requirements. In this paper, a number of different underfill materials are subjected to automotive underhood temperatures to study the effect of long time isothermal exposure on microstructure and dynamic-mechanical properties. It has been shown that isothermal aging oxidizes the underfill, which can change the mechanical properties of the material significantly. The oxidation of underfill was studied experimentally by measuring oxidation layer thickness using polarized optical microscope. The effect on the mechanical properties was studied using the dynamic mechanical properties of underfill with DMA (Dynamic Mechanical Analyzer). Two different underfill materials were subjected to three different isothermal exposure, which are below, near and above the glass transition temperature of the underfills. The dynamic mechanical viscoelastic properties like storage modulus, loss modulus, tan delta and their respective glass transition temperatures were investigated. Three point bending mode was used in the DMA with a frequency of 1 Hz operating at 3?/min.

Correlation of Microstructural Evolution With the Dynamic-Mechanical Viscoelastic Properties of Underfill Under Sustained High Temperature Operation

2020 ◽  
Author(s):  
Pradeep Lall ◽  
Madhu Kasturi ◽  
Haotian Wu ◽  
Ed Davis ◽  
Jeff Suhling
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Optical Microscope ◽  
Dynamic Mechanical Properties ◽  
Isothermal Exposure ◽  
Dynamic Mechanical ◽  
Fine Pitch ◽  
Long Time

Abstract Automotive underhood electronics are subjected to high operating temperatures in the neighborhood of 150 to 200°C for prolonged periods in the neighborhood of 10-years. Consumer grade off-the shelf electronics are designed to operate at 55 to 85 °C with a lower use-life of 3 to 5 years. Underfill materials are used to provide supplemental restraint to fine-pitch area array electronics and meet the reliability requirements. In this paper, a number of different underfill materials are subjected to automotive underhood temperatures to study the effect of long time isothermal exposure on microstructure and dynamic-mechanical properties. It has been shown that isothermal aging oxidizes the underfill, which can change the mechanical properties of the material significantly. The oxidation of underfill was studied experimentally by measuring oxidation layer thickness using polarized optical microscope. The effect on the mechanical properties was studied using the dynamic mechanical properties of underfill with DMA (Dynamic Mechanical Analyzer). Two different underfill materials were subjected to three different isothermal exposure, which are below, near and above the glass transition temperature of the underfills. The dynamic mechanical viscoelastic properties like storage modulus, loss modulus, tan delta and their respective glass transition temperatures were investigated. Three point bending mode was used in the DMA with a frequency of 1 Hz operating at 3 °C/min.

A Comparative Study on Dynamic Mechanical Properties of Radial and Chordwise Direction of Bamboo

2013 ◽  
Vol 838-841 ◽  
pp. 2227-2230
Author(s):  
Chun Gui Du ◽  
Ren Li ◽  
Zhe Wang ◽  
Hong Wei Yu ◽  
Chun De Jin
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Transition Temperature ◽  
Dynamic Mechanical Analysis ◽  
Radial Direction ◽  
Loss Modulus ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Dynamic Mechanical ◽  
Environment Temperature

The dynamic mechanical properties of radial and chordwise bamboo pieces were tested by dynamic mechanical analysis (DMA). The results show that the storage modulus and loss modulus and tangent delta of chordwise direction were all larger than the radial direction of bamboo; the peak of glass transition temperature of chordwise direction is high than the radial direction, and their sizes are very close; dynamic mechanical analysis can provide a reference for the optimization applicable environment temperature of curtain plybamboo.

scholarly journals Comparative dynamic mechanical properties of non-superheated and superheated A357 alloys

2017 ◽  
Author(s):  
Mazlee Mohd Noor
Keyword(s):  
Mechanical Properties ◽  
Storage Modulus ◽  
Elevated Temperatures ◽  
Loss Modulus ◽  
Optical Microscope ◽  
Dynamic Mechanical Properties ◽  
Damping Capacity ◽  
A357 Alloy ◽  
Dynamic Mechanical ◽  
Eutectic Si

The influence of superheat treatment on the microstructure and dynamic mechanical properties of A357 alloys has been investigated. The study of microstructure was performed by the optical microscope. Dynamic mechanical properties (storage modulus, loss modulus, and damping capacity) were measured by the dynamic mechanical analyzer (DMA). Microstructure showed coarser and angular eutectic Si particles with larger α-Al dendrites in the non-superheated A357 alloy. In contrast, finer and rounded eutectic Si particles together with smaller and preferred oriented α-Al dendrites have been observed in the superheated A357 alloy. Dynamic mechanical properties showed an increasing trend of loss modulus and damping capacity meanwhile a decreasing trend of storage modulus at elevated temperatures for superheated and non-superheated A357 alloys. The high damping capacity of superheated A357 has been ascribed to the grain boundary damping at elevated temperatures.

scholarly journals Dynamic Mechanical Properties of Hybrid Layered Silicates/Kaolin Geopolymer Filler in Epoxy Composites

2017 ◽  
Vol 54 (3) ◽  
pp. 543-545 ◽  
Author(s):  
Yusrina Mat Daud ◽  
Kamarudin Hussin ◽  
Azlin Fazlina Osman ◽  
Che Mohd Ruzaidi Ghazali ◽  
Mohd Mustafa Al Bakri Abdullah ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
High Speed ◽  
Hybrid Composites ◽  
Loss Modulus ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Layered Silicates ◽  
Epoxy Composites ◽  
Damping Factor ◽  
Dynamic Mechanical

Preparation epoxy based hybrid composites were involved kaolin geopolymer filler, organo-montmorillonite at 3phr by using high speed mechanical stirrer. A mechanical behaviour of neat epoxy, epoxy/organo-montmorillonite and its hybrid composites containing 1-8phr kaolin geopolymer filler was studied upon cyclic deformation (three-point flexion mode) as the temperature is varies. The analysis was determined by dynamic mechanical analysis (DMA) at frequency of 1.0Hz. The results then expressed in storage modulus (E�), loss modulus (E�) and damping factor (tan d) as function of temperature from 40 oC to 130oC. Overall results indicated that E�, E�� and Tg increased considerably by incorporating optimum 1phr kaolin geopolymer in epoxy organo-montmorillonite hybrid composites.

Dynamic Mechanical Properties of Grafted Polypropylene Composites Reinforced with Acetylated Wheat Straw Fibers

2015 ◽  
Vol 1767 ◽  
pp. 139-143
Author(s):  
Ramón Sánchez ◽  
Jacobo Aguilar ◽  
Silvia Y. Martínez ◽  
Reyes J. Sanjuan ◽  
Gerardo A. Mejía ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Wheat Straw ◽  
Coupling Agent ◽  
Optical Microscope ◽  
Dynamic Mechanical Properties ◽  
Particle Sizes ◽  
Polypropylene Composites ◽  
Dynamic Mechanical ◽  
Twin Screw ◽  
Composite Pellets

ABSTRACTDynamic mechanical properties of polypropylene (PP) and grafted polypropylene (PP-g-MA) composites reinforced with acetylated wheat straw fibers (WSF) is reported in this work. The materials were prepared with different fiber particle sizes (40, 80 and 140 U.S. mesh) and at different fiber contents (5, 10 and 15 wt.%). The PP and PP-g-MA composites, where anhydride maleic (MA) was used as coupling agent, were obtained using a twin-screw extruder; whereas an injection-molding machine molded the composite pellets into testing specimens. To observe the morphology of the composites, micrographs were taken with an optical microscope. The Dynamic mechanical properties were analyzed using a torsional rheometer. The morphological analysis showed a high porous structure somehow similar to foamed materials. The storage modulus (G′) increased by increasing the fiber content, and decreased with fiber particle sizes for the PP composites. Meanwhile, the use of the coupling agent additive promoted a modulus increase due to higher fiber-polymer interaction, from better adhesion and chemical bonds formation between the fibers-coupling agent-PP.

scholarly journals Influence of Thermally-Accelerated Aging on the Dynamic Mechanical Properties of HTPB Coating and Crosslinking Density-Modified Model for the Payne Effect

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 403 ◽  
Author(s):  
Yongqiang Du ◽  
Jian Zheng ◽  
Guibo Yu
Keyword(s):  
Mechanical Properties ◽  
Aging Time ◽  
Loss Modulus ◽  
Accelerated Aging ◽  
Crosslinking Density ◽  
Dynamic Mechanical Properties ◽  
Maximum Elongation ◽  
Solid Rocket Motor ◽  
Payne Effect ◽  
Dynamic Mechanical

Hydroxyl terminated polybutadiene (HTPB) coating is widely used in a solid rocket motor, but an aging phenomenon exists during long-term storage, which causes irreversible damage to the performance of this HTPB coating. In order to study the effect of aging on the dynamic mechanical properties of the HTPB coating, the thermally-accelerated aging test was carried out. The variation of maximum elongation and crosslinking density with aging time was obtained, and a good linear relationship between maximum elongation and crosslinking density was found by correlation analysis. The changing regularity of dynamic mechanical properties with aging time was analyzed. It was found that with the increase of aging time, Tg of HTPB coating increased, Tα, tan β and tan α decreased, and the functional relationships between the loss factor parameters and crosslinking density were constructed. The storage modulus and loss modulus of HTPB coating increased with the increase of aging time, and decreased with the increase of pre-strain. The aging enhanced the Payne effect of HTPB coating, while the pre-strain had a weakening effect. In view of the Payne effect of HTPB coating, the crosslinking density was introduced into Kraus model as aging evaluation parameter, and the crosslinking density modified models with and without pre-strain were established. The proposed models can effectively solve the problem that the Kraus model has a poor fitting effect under the condition of small strain (generally less than 1%) and on the loss modulus, which have improved the correlations between the fitting results and the test results.

Thermal stability and dynamic mechanical behavior of functional multiphase boride ceramics/epoxy composites

2019 ◽  
Vol 39 (6) ◽  
pp. 508-514
Author(s):  
Yannan He ◽  
Zhiqiang Yu
Keyword(s):  
Mechanical Properties ◽  
Thermal Stability ◽  
Loss Modulus ◽  
Dynamic Mechanical Properties ◽  
Mechanical Analysis ◽  
Epoxy Composites ◽  
Scanning Calorimetry ◽  
Element Analysis ◽  
Reaction Heat ◽  
Dynamic Mechanical

Abstract The thermal and dynamic mechanical properties of epoxy composites filled with zirconium diboride/nano-alumina (ZrB2/Al2O3) multiphase particles were investigated by means of differential scanning calorimetry, dynamic thermo-mechanical analysis, and numerical simulation. ZrB2/Al2O3 particles were surface organic functional modified by γ-glycidoxypropyltrimethoxysilane for the improvement of their dispersity in epoxy matrix. The results indicated that the curing exotherm of epoxy resin decreased significantly due to the addition of ZrB2/Al2O3 multiphase particles. In comparison to the composites filled with unmodified particles, the modified multiphase particles made the corresponding filling composites exhibit lower curing reaction heat, lower loss modulus, and higher storage modulus. Generally speaking, the composites filled with 5 wt% modified multiphase particles presented the best thermal stability and thermo-mechanical properties due to the better filler-matrix interfacial compatibility and the uniform dispersity of modified particles. Finite element analysis also suggested that the introduction of modified ZrB2/Al2O3 multiphase particles increased the stiffness of the corresponding composites.

Dynamic Viscoelastic Properties of Rice Kernels Studied by Dynamic Mechanical Analyzer

2007 ◽  
Vol 3 (2) ◽  
Author(s):  
Ke-cheng Chen ◽  
Dong Li ◽  
Li-jun Wang ◽  
Necati Özkan ◽  
Xiao Dong Chen ◽  
...  
Keyword(s):  
Glass Transition ◽  
Viscoelastic Properties ◽  
Loss Modulus ◽  
Brown Rice ◽  
Aluminum Foil ◽  
Moisture Loss ◽  
Dynamic Mechanical Analyzer ◽  
Rice Varieties ◽  
Razor Blade ◽  
Dynamic Mechanical

Dynamic viscoelastic properties of brown rice kernels were investigated using a dynamic mechanical analyzer (DMA). In order to meet the sample requirements for the DMA and prevent moisture loss of rice kernels during the DMA measurements, necessary precautions were taken. To prevent moisture loss of rice kernels during the DMA measurements at temperatures ranging from room temperature to 120 degrees centigrade, rice kernels were wrapped with a thin layer of sealing film. Then the wrapped rice kernels were additionally covered with an aluminum foil. Two ends of the wrapped brown rice kernels were cut with a razor blade; subsequently both ends of the cut rice kernels were filed using fine sandpaper to produce near cylindrical rice kernels with parallel ends. The storage modulus of the rice kernels decreased with increasing temperature and moisture content. The loss modulus and the tan delta (loss factor) of the rice kernels as a function of temperature showed clear peaks, which are associated with the glass transition of rice kernels. Two rice varieties had been investigated, and the results showed that the dynamic viscoelastic properties of these rice samples were not significantly different. The glass transition temperatures for the long-grain rice kernels with the moisture contents of 17.4, 13.8, and 10.9 wt.% were determined as 45, 58, and 66 degrees centigrade, respectively.

The evolution of morphology, crystallization and static and dynamic mechanical properties of long glass-fibre–reinforced polypropylene composites under thermo-oxidative ageing

2018 ◽  
Vol 32 (4) ◽  
pp. 544-557 ◽  
Author(s):  
Jing Zhang ◽  
Weidi He ◽  
Yifan Wu ◽  
Na Wang ◽  
Xiaolang Chen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Glass Transition ◽  
Glass Fibre ◽  
Ageing Time ◽  
Early Period ◽  
Dynamic Mechanical Properties ◽  
Interface Debonding ◽  
Dynamic Mechanical ◽  
Glass Fibre Reinforced ◽  
Oxidative Ageing

In this work, the static and dynamic mechanical properties, crystallization behaviours, and morphology of long glass-fibre–reinforced polypropylene (PP) composites with thermo-oxidative ageing time from 0 day to 50 days at 120°C were investigated and discussed. The static mechanical properties showed a global decrease in tensile, bending and impact strengths with increasing ageing time. From the results obtained by scanning electronic microscopic observations, interface debonding clearly occurred between the glass fibre and PP matrix in the aged samples. The crystallinity ( Xc) of the composites was analyzed by differential scanning calorimetry; annealing process played the leading role in the early period of ageing, while as ageing progressed, the degradation of PP matrix dominated the ageing process and Xc decreased. The dynamic mechanical analysis results indicated that the storage modulus and glass transition temperature of the composites also decreased with prolonging ageing time. Then, the apparent activation energy ( E) of glass transition was calculated by the Arrhenius equation with different scanning frequencies. A higher value of E was obtained for the samples in the later ageing period, which means a higher energy barrier for glass transition.

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