In Situ Evaluation of Residual Stresses in an Organic Die-Attach Adhesive

1998 ◽  
Vol 120 (3) ◽  
pp. 314-318 ◽  
Author(s):  
A. S. Voloshin ◽  
P.-H. Tsao ◽  
R. A. Pearson
Keyword(s):  
Residual Stresses ◽  
Digital Image Analysis ◽  
Moisture Absorption ◽  
Coefficient Of Thermal Expansion ◽  
Back Side ◽  
Curing Process ◽  
Die Attach ◽  
Topology Changes ◽  
Stress Buildup

Development of the residual stresses in an organic adhesive, alumina filled epoxy (EPO-TEK H65-175MP) during curing process has been studied in-situ. The effect of the adhesive’s thickness was evaluated by preparing samples and analyzing residual stresses. Samples were prepared by applying a layer of the epoxy in various thicknesses on the back side of the silicon die. The topology changes of the die’s surface during curing process and cooling of the epoxy were monitored by digital image analysis enhanced moire´ interferometry (DIAEMI). Residual stresses were calculated from the curvature changes of the surface of the die. The results show that the stress buildup is mainly caused by the mismatch in coefficient of thermal expansion between the adhesive and the die. Relaxation of the residual stress was found while the samples were kept in an open environment at room temperature. Such reduction in stress may be attributed to moisture absorption by the epoxy that results in expansion of the epoxy.

Transient and Residual Stresses and Displacements in Self-Curing Bone Cement—Part I: Characterization of Relevant Volumetric Behavior of Bone Cement

1982 ◽  
Vol 104 (1) ◽  
pp. 21-27 ◽  
Author(s):  
A. M. Ahmed ◽  
W. Pak ◽  
D. L. Burke ◽  
J. Miller
Keyword(s):  
Thermal Expansion ◽  
Residual Stresses ◽  
Bone Cement ◽  
Coefficient Of Thermal Expansion ◽  
Stress Generation ◽  
Curing Process ◽  
Cooling Phase ◽  
Volumetric Behavior ◽  
Fixation System

In this first part of a two-part report, some aspects of the volumetric behavior of bone cement during its curing process are examined as a prelude to an analysis for the transient and residual stresses and displacements in stem fixation systems. Experiments show that stress generation in the cement is associated with its temperature while curing and that during the cooling phase, the stresses are mainly due to thermal as opposed to bulk shrinkage. The appropriate coefficient of thermal expansion of bone cement has been evaluated from measurements in a simulated fixation system in conjunction with a thermoelastic analysis.

An Optimization of Two-Steps Curing Profile to Eliminate Voids Formation in Underfill Epoxy for Hi-CTE Flip Chip Packaging

2010 ◽  
Vol 97-101 ◽  
pp. 23-27 ◽  
Author(s):  
Zainudin Kornain ◽  
Azman Jalar ◽  
Rozaidi Rashid ◽  
Shahrum Abdullah
Keyword(s):  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Ball Grid Array ◽  
Statistic Analysis ◽  
Curing Process ◽  
Ceramic Ball ◽  
Die Attach ◽  
Ball Grid Array Package ◽  
Flip Chip Packaging ◽  
The Impact

Underfilling is the preferred process to reduce the impact of the thermal stress that results from the mismatch in the coefficient of thermal expansion (CTE) between the silicon chip and the substrate in Flip Chip Packaging. Voids formation in underfill is considered as failure in flip chip manufacturing process. Voids formation possibly caused by several factors such as poor soldering and flux residue during die attach process, voids entrapment due moisture contamination, dispense pattern process and setting up the curing process. This paper presents the optimization of two steps curing profile in order to reduce voids formation in underfill for Hi-CTE Flip Chip Ceramic Ball Grid Array Package (FC-CBGA). A C-Mode Scanning Aqoustic Microscopy (C-SAM) was used to scan the total count of voids after curing process. Statistic analysis was conducted to analyze the suitable curing profile in order to minimize or eliminate the voids formation. It was shown that the two steps curing profile provided solution for void elimination.

Hygrothermal Damage in Graphite/Epoxy Laminates

1987 ◽  
Vol 109 (1) ◽  
pp. 3-11 ◽  
Author(s):  
H. T. Hahn
Keyword(s):  
Residual Stresses ◽  
Moisture Absorption ◽  
Moisture Diffusion ◽  
Moisture Diffusivity ◽  
Moisture Concentration ◽  
Bulk Diffusivity ◽  
Hygrothermal Environments ◽  
Swelling Strain

The use of micromechanics equations for moisture diffusivity shows that the in situ diffusivity is slightly lower than the bulk diffusivity for matrix resins, thereby indicating absence of any matrix damage in virgin composites. When exposed to hygrothermal environments, however, composites undergo degradation which manifests itself in anomalous moisture diffusion behavior and reduced structural performance. The hygrothermal degradation is the result of matrix plasticization, microvoid formation, and microcracking. The time dependence of plasticization as well as the tensile stress resulting from steep moisture gradient is responsible for the damage induced by thermal spiking of wet composites. Swelling of neat resins is frequently less than predicted by the volume additivity. A simple micromechanics analysis provides a good estimate of composite swelling strain from resin properties. The bilinearity and the hysteresis observed in relations between swelling and moisture content are attributed to the existence of a threshold moisture concentration below which swelling is negligible. Relaxation of residual stresses is a long-term process under nonhostile environments. However, it is accelerated considerably around and above the glass transition temperature. The fast stress relaxation can change the transverse ply stress from compressive to tensile after thermal spiking, thereby inducing ply cracking and accelerating the subsequent moisture absorption. How residual stresses can affect ply cracking and delamination is shown through a fracture mechanics analysis.

In Situ Preparation and Mechanical Properties of (ZrB2+ZrC)/Zr3[Al(Si)]4C6 Composites

2014 ◽  
Vol 602-603 ◽  
pp. 438-442
Author(s):  
Lei Yu ◽  
Jian Yang ◽  
Tai Qiu
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Bending Strength ◽  
Coefficient Of Thermal Expansion ◽  
Raw Materials ◽  
Linear Increase ◽  
Fine Grain ◽  
Fine Grain Strengthening ◽  
Uniform Microstructure

Fully dense (ZrB2+ZrC)/Zr3[Al (Si)]4C6 composites with ZrB2 content varying from 0 to 15 vol.% and fixed ZrC content of 10 vol.% were successfully prepared by in situ hot-pressing in Ar atmosphere using ZrH2, Al, Si, C and B4C as raw materials. With the increase of ZrB2 content, both the bending strength and fracture toughness of the composites increase and then decrease. The synergistic action of ZrB2 and ZrC as reinforcements shows significant strengthening and toughing effect to the Zr3[Al (Si)]4C6 matrix. The composite with 10 vol.% ZrB2 shows the optimal mechanical properties: 516 MPa for bending strength and 6.52 MPa·m1/2 for fracture toughness. With the increase of ZrB2 content, the Vickers hardness of the composites shows a near-linear increase from 15.3 GPa to 16.7 GPa. The strengthening and toughening effect can be ascribed to the unique mechanical properties of ZrB2 and ZrC reinforcements, the differences in coefficient of thermal expansion and modulus between them and Zr3[Al (Si)]4C6 matrix, fine grain strengthening and uniform microstructure derived by the in situ synthesis reaction.

INVESTIGATION OF BIAXIAL ELASTIC MODULUS AND CTE OF BaTiO3 FILMS

2009 ◽  
Vol 23 (24) ◽  
pp. 4933-4941
Author(s):  
GUI-FANG HUANG ◽  
WEI-QING HUANG ◽  
LING-LING WANG ◽  
ZHONG XIE ◽  
BING-SUO ZOU ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Thermal Cycle ◽  
Laser Scanning ◽  
Stress Measurement ◽  
Coefficient Of Thermal Expansion ◽  
Bulk Material ◽  
Good Reliability ◽  
Scanning Method ◽  
As Stress

To develop high-quality film device with good reliability, it is often essential to be able to evaluate the parameters such as stress, the biaxial elastic modulus, and coefficient of thermal expansion (CTE) of film. Based on the stress measurement in situ during the thermal cycle by laser scanning method, two techniques were used to measure the biaxial elastic modulus and CTE of BaTiO 3 films deposited on substrate. The value of the biaxial elastic modulus and CTE for BaTiO 3 films determined from two methods is close, in which the biaxial elastic modulus of BaTiO 3 films is higher than that of corresponding bulk while the CTE of BaTiO 3 films is a little smaller than that of bulk material.

scholarly journals Investigation on Die Crack in a Stacked Die Package Using Finite Element Analysis

2021 ◽  
pp. 83-91
Author(s):  
Jefferson Talledo
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Coefficient Of Thermal Expansion ◽  
Crack Problem ◽  
Element Analysis ◽  
Robust Solution ◽  
Die Attach ◽  
Die Stress ◽  
Cte Mismatch ◽  
Semiconductor Packages

Die crack is one of the problems in stacked die semiconductor packages. As silicon dies become thinner in such packages due to miniaturization requirement, the tendency to have die crack increases. This study presents the investigation done on a die crack issue in a stacked die package using finite element analysis (FEA). The die stress induced during the package assembly processes from die attach to package strip reflow was analyzed and compared with the actual die crack failure in terms of the location of maximum die stress at unit level as well as strip level. Stresses in the die due to coefficient of thermal expansion (CTE) mismatch of the package component materials and mechanical bending of the package in strip format were taken into consideration. Comparison of the die stress with actual die crack pointed to strip bending as the cause of the problem and not CTE mismatch. It was found that the die crack was not due to the thermal processes involved during package assembly. This study showed that analyzing die stress using FEA could help identify the root cause of a die crack problem during the stacked die package assembly and manufacturing as crack occurs at locations of maximum stress. The die crack mechanism can also be understood through FEA simulation and such understanding is very important in coming up with robust solution.

scholarly journals TEMUAN FRAGMEN GERABAH SEBAGAI INDIKASI PERMUKIMAN KUNO DI SITUS BOROBUDUR

2013 ◽  
Vol 33 (2) ◽  
pp. 211-226
Author(s):  
Agni Sesaria Mochtar
Keyword(s):  
20Th Century ◽  
Cultural Context ◽  
The Other ◽  
Back Side ◽  
The South ◽  
South West ◽  
Pottery Sherds ◽  
Few Data ◽  
The Temple

Borobudur temple has been famously known as one of the Indonesian heritage masterpiece. Various aspects of it had been studied thoroughly since the beginning of 20th century A.D. Those studies tended to be monumental centric, giving less attention to the cultural context of the temple and its surroundings. Settlement in the nearby places is one of the topics which not have been studied much yet; leaving a big question about how the settlement supported continuity of many activities in the temple, or even the other way around; how the temple affected the settlement. There is only a few data about old settlement found in situ in Borobudur site, only abundance of pottery sherds. The analysis applied on to the potteries find during the 2012 excavation had given some information about the old settlement in Borobodur site. The old settlement predicted as resided in the south west area, in the back side of the monument.

scholarly journals Thermal Assessment and In-Situ Monitoring of Insulated Gate Bipolar Transistors in Power Electronic Modules

2019 ◽  
Author(s):  
Erick Gutierrez ◽  
Kevin Lin ◽  
Douglas DeVoto ◽  
Patrick McCluskey
Keyword(s):  
Thermal Cycling ◽  
Failure Modes ◽  
Rapid Determination ◽  
Degradation Process ◽  
In Situ Monitoring ◽  
Power Module ◽  
Insulated Gate Bipolar Transistor ◽  
Die Attach ◽  
Power Modules

Abstract Insulated gate bipolar transistor (IGBT) power modules are devices commonly used for high-power applications. Operation and environmental stresses can cause these power modules to progressively degrade over time, potentially leading to catastrophic failure of the device. This degradation process may cause some early performance symptoms related to the state of health of the power module, making it possible to detect reliability degradation of the IGBT module. Testing can be used to accelerate this process, permitting a rapid determination of whether specific declines in device reliability can be characterized. In this study, thermal cycling was conducted on multiple power modules simultaneously in order to assess the effect of thermal cycling on the degradation of the power module. In-situ monitoring of temperature was performed from inside each power module using high temperature thermocouples. Device imaging and characterization were performed along with temperature data analysis, to assess failure modes and mechanisms within the power modules. While the experiment aimed to assess the potential damage effects of thermal cycling on the die attach, results indicated that wire bond degradation was the life-limiting failure mechanism.

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