MEMS Die Warpage During Curing of Die Attach Material

2015 ◽  
Author(s):  
Hohyung Lee ◽  
Ruiyang Liu ◽  
Seungbae Park ◽  
Xiaojie Xue
Keyword(s):  
Material Properties ◽  
Residual Strain ◽  
Critical Role ◽  
Measurement Data ◽  
Curing Process ◽  
Assembly Process ◽  
Structural Elements ◽  
Mems Sensor ◽  
Fea Model ◽  
Die Attach

Microelectromechanical system (MEMS) packages are vulnerable to stresses due to its functional structure. During the assembly process of the package, stresses stemming out of CTE mismatches of the structural elements and curing of the die attach material can cause warpage of the MEMS die [1]. Even though die attach material takes relatively small volumetric portion of the package, it plays a critical role in warpage of the die due to its location and sensitivity of a MEMS sensor. Most of virgin die attach adhesives are in a state of viscous liquid and, as it is cured the material properties such as modulus and CTE change. Accordingly, residual strain is cumulated on MEMS die after curing process and signal trim process is required. Therefore, the material properties changes depending on the curing profile is valuable information for assembly process of the MEMS package. To monitor the material properties changes and shrinkage during curing process, strain and modulus of a die attach material are measured in each curing step. Also, to investigate the material property change depending on the curing profile, two different curing profiles are used. Experimental data show that die attach materials are gradually cured after each thermal cycling, which cause the increment of the modulus and glass transition temperature (Tg) with shrinkage at elevated temperature. Using the measurement data, FEA model is built to predict the warpage of the MEMS die. In the FEA model, residual strain on MEMS die is calculated by inputting material properties of die attach in each curing step. Also, die warpage of the package during the curing process is monitored using an optical profiler for the validation of the simulation results.

Investigation of Transfer Mold Process Effects on Semiconductor Package Warpage

2009 ◽  
Author(s):  
Jason M. Brand ◽  
Myung J. Yim ◽  
Ravi Kumar
Keyword(s):  
Solder Joint ◽  
Material Property ◽  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Filler Concentration ◽  
Packaging System ◽  
Property Variation ◽  
Molding Compound ◽  
Fea Model ◽  
Die Attach

In recent years, Package on Package (PoP) is increasingly used for high density package solutions. Generally the top package is a stacked memory packaging system connected to a bottom logic packaging system via solder joint: this is representative of PoP configurations. To guarantee the assembly yield and reliability of the solder joint between the top package and bottom package, mechanical compliance between these two packages is crucial during package stacking. Henceforth package warpage needs to be understood and controlled to meet the assembly yield targets. The complexity of the package configuration increases by thinner package thickness, higher number of stacking dies and large package size. Controlling the warpage within the target requirement is very challenging, especially when the material behaviors of substrate, die, molding compound and die attach film are different and also changing as a function of temperature. Certainly, the material properties of key components in top PoP package plays a crucial role in warpage performance. Among various material properties, the chemical cure shrinkage, coefficient of thermal expansion and storage modulus for the molding compounds are determining factors on the temperature dependant warpage control of top PoP package. Warpage variation still exists within parts processed at the same time mainly due to slight material property variation. In this paper, the cause of the warpage variation is investigated. The main cause was found to be filler migration effect in narrow gaps with in the stacked die package during the mold process, which resulted in different filler concentration and distribution, and finally different local molding compound material property among the package unit location in the substrate strip. The findings indicate that mold pressure is not a major modulator of warpage, while filler distribution can dramatically alter the warpage behavior. FEA model results and warpage data are presented to validate the filler migration phenomena and warpage behavior impact. The findings and results provide some clues and design/process guideline for warpage control in Top PoP package, which influence the PoP assembly yield and reliability.

Experimental Measurement and Analysis of Microelectronics Application Polymer Materials Properties

1992 ◽  
Vol 264 ◽  
Author(s):  
Y.H. Jeng ◽  
Mirng-Ji Lii
Keyword(s):  
Thin Film ◽  
Material Properties ◽  
Silicon Substrate ◽  
Coupling Effect ◽  
Measurement Techniques ◽  
Epoxy Adhesive ◽  
Polymer Materials ◽  
Fea Model ◽  
Curvature Measurement ◽  
Substrate Curvature

AbstractA laser based surface scanning technique was utilized to measure the polyimide coated silicon wafer curvature resulting from thermal cycling and mismatch, Meanwhile, mechanical properties of polyimide thin film were characterized by DMA, TMA and tensile test. Based on the obtained material properties, A FEA model was developed to analyze the experimental results -reasonable correlation was obtained.Similar approaches were taken one step further in the MCM silicon substrate curvature measurement. In a MCM package with silicon substrate, epoxy adhesive, and ceramic package, substrate warpage was developed in a thermal cycle due to thermal mismatch between the substrate and the package and coupling effect linked by epoxy adhesive. Three different substrate curvature measurement techniques were applied to identify the substrate curvature and epoxy thin film properties were also well characterized. A 3D FEA model incorporating with the epoxy material properties was developed to analyze the substrate warpage and investigate an optimal package design.

scholarly journals The description of friction of silicon MEMS with surface roughness: virtues and limitations of a stochastic Prandtl–Tomlinson model and the simulation of vibration-induced friction reduction

2010 ◽  
Vol 1 ◽  
pp. 163-171 ◽  
Author(s):  
W Merlijn van Spengen ◽  
Viviane Turq ◽  
Joost W M Frenken
Keyword(s):  
Surface Roughness ◽  
Critical Role ◽  
Measurement Data ◽  
Friction Model ◽  
Friction Reduction ◽  
Atomic Scale ◽  
Mems Devices ◽  
Tomlinson Model ◽  
Atomic Force ◽  
On Chip

We have replaced the periodic Prandtl–Tomlinson model with an atomic-scale friction model with a random roughness term describing the surface roughness of micro-electromechanical systems (MEMS) devices with sliding surfaces. This new model is shown to exhibit the same features as previously reported experimental MEMS friction loop data. The correlation function of the surface roughness is shown to play a critical role in the modelling. It is experimentally obtained by probing the sidewall surfaces of a MEMS device flipped upright in on-chip hinges with an AFM (atomic force microscope). The addition of a modulation term to the model allows us to also simulate the effect of vibration-induced friction reduction (normal-force modulation), as a function of both vibration amplitude and frequency. The results obtained agree very well with measurement data reported previously.

Curing and swelling kinetics of new magnetorheological elastomer based on natural rubber/waste natural rubber gloves composites

2018 ◽  
Vol 51 (7-8) ◽  
pp. 583-602
Author(s):  
Nabil Hayeemasae ◽  
Hanafi Ismail
Keyword(s):  
Natural Rubber ◽  
Material Properties ◽  
Swelling Kinetics ◽  
Curing Process ◽  
Magnetorheological Elastomer ◽  
Rubber Composites ◽  
Rubber Waste ◽  
New Type ◽  
Kinetics Of ◽  
Single Filler

This article proposes a new type of magnetorheological elastomer (MRE) based on natural rubber (NR) and waste natural rubber gloves (wNRg) blends. The material properties of the MRE samples were investigated with specific focus on the curing and swelling kinetics. Two different series were prepared; the first used carbonyl iron (CI) as the single filler in the MRE, whereas the second hybridized CI with carbon black (CB) to prepare an MRE resistant to solvents. The results show that most properties depend strongly on the nature of both fillers. The higher thermal conductivity of the CI caused a substantial decrease in both the scorch and curing times and the activation energy in the curing process. Based on the diffusion study, a higher volume of fillers in the rubber composites resulted in a greater area of blockage and restricted the penetration of the solvent tested throughout the composites, irrespective of whether CI alone or in combination with CB was used in the composites.

Multiple Fault Diagnosis Method in Multistation Assembly Processes Using Orthogonal Diagonalization Analysis

2008 ◽  
Vol 130 (1) ◽  
Author(s):  
Zhenyu Kong ◽  
Dariusz Ceglarek ◽  
Wenzhen Huang
Keyword(s):  
Fault Diagnosis ◽  
Product Information ◽  
Statistical Significance ◽  
Measurement Data ◽  
Space Representation ◽  
Assembly Process ◽  
Dimensional Control ◽  
Multiple Fault ◽  
Multiple Fault Diagnosis ◽  
Multistation Assembly

Dimensional control has a significant impact on overall product quality and performance of large and complex multistation assembly systems. To date, the identification of process-related faults that cause large variations of key product characteristics (KPCs) remains one of the most critical research topics in dimensional control. This paper proposes a new approach for multiple fault diagnosis in a multistation assembly process by integrating multivariate statistical analysis with engineering models. The proposed method is based on the following steps: (i) modeling of fault patterns obtained using state space representation of process and product information that explicitly represents the relationship between process-related error sources denoted by key control characteristics (KCCs) and KPCs, and (ii) orthogonal diagonalization of measurement data using principal component analysis (PCA) to project measurement data onto the axes of an affine space formed by the predetermined fault patterns. Orthogonal diagonalization allows estimating the statistical significance of the root cause of the identified fault. A case study of fault diagnosis for a multistation assembly process illustrates and validates the proposed methodology.

Can high-frequency data enable better parameterization of water quality models and disentangling of DO processes?

2021 ◽  
Author(s):  
Jingshui Huang ◽  
Pablo Merchan-Rivera ◽  
Gabriele Chiogna ◽  
Markus Disse ◽  
Michael Rode
Keyword(s):  
Water Quality ◽  
High Frequency ◽  
Critical Role ◽  
Measurement Data ◽  
High Frequency Data ◽  
Model Parameters ◽  
Frequency Data ◽  
Quality Models ◽  
Model Parameter ◽  
Water Quality Models

<p>Water quality models offer to study dissolved oxygen (DO) dynamics and resulting DO balances. However, the infrequent temporal resolution of measurement data commonly limits the reliability of disentangling and quantifying instream DO process fluxes using models. These limitations of the temporal data resolution can result in the equifinality of model parameter sets. In this study, we aim to quantify the effect of the combination of emerging high-frequency monitoring techniques and water quality modelling for 1) improving the estimation of the model parameters and 2) reducing the forward uncertainty of the continuous quantification of instream DO balance pathways.</p><p>To this end, synthetic measurements for calibration with a given series of frequencies are used to estimate the model parameters of a conceptual water quality model of an agricultural river in Germany. The frequencies vary from the 15-min interval, daily, weekly, to monthly. A Bayesian inference approach using the DREAM algorithm is adopted to perform the uncertainty analysis of DO simulation. Furthermore, the propagated uncertainties in daily fluxes of different DO processes, including reaeration, phytoplankton metabolism, benthic algae metabolism, nitrification, and organic matter deoxygenation, are quantified.</p><p>We hypothesize that the uncertainty will be larger when the measurement frequency of calibrated data was limited. We also expect that the high-frequency measurements significantly reduce the uncertainty of flux estimations of different DO balance components. This study highlights the critical role of high-frequency data supporting model parameter estimation and its significant value in disentangling DO processes.</p>

Targeting G-quadruplexes in the rhinovirus genome by Pyridostatin inhibits uncoating 3 and highlights a critical role for sodium ions.

2021 ◽  
Author(s):  
Antonio Real-Hohn ◽  
Martin Groznica ◽  
Georg Kontaxis ◽  
Rong Zhu ◽  
Otávio Chaves ◽  
...  
Keyword(s):  
Common Cold ◽  
Critical Role ◽  
Sodium Ions ◽  
Structural Elements ◽  
Temperature Dependent ◽  
Physiological Conditions ◽  
Metastable Structures ◽  
G Quadruplex ◽  
The Common ◽  
Secondary Structural Elements

Abstract The ~ 2.4 µm long rhinovirus ss(+)RNA genome consists of roughly 7,200 nucleotides. It is tightly folded to fit into the ~ 22 nm diameter void in the protein capsid. In addition to previously predicted secondary structural elements in the RNA, using the QGRS mapper, we revealed the presence of multiple quadruplex forming G-rich sequences (QGRS) in the RV-A, B, and C clades, with four of them being exquisitely conserved. The biophysical analyses of ribooligonucleotides corresponding to selected QGRS demonstrate G-quadruplex (GQ) formation in each instance and resulted in discovering another example of an unconventional, two-layer zero-nucleotide loop RNA GQ stable at physiological conditions. By exploiting the temperature-dependent viral breathing to allow diffusion of small compounds into the virion, we demonstrate that the GQ-binding compounds PhenDC3 and pyridostatin (PDS) uniquely interfere with viral uncoating. Remarkably, this inhibition was entirely prevented in the presence of K+ but not Na+, despite the higher GQ stabilising effect of K+. Based on virus thermostability studies combined with ultrastructural imaging of isolated viral RNA, we propose a mechanism where Na+ keeps the encapsidated genome loose, allowing its penetration by PDS to promote the transition of QGRS sequestered in alternative metastable structures into GQs. The resulting conformational change then materialises in a severely compromised RNA release from the proteinaceous shell. Targeting extracellularly circulating RVs with GQ-stabilisers might thus become a novel way of combating the common cold.

Strengthening and Retrofitting of Motín de Oro II Bridge in Mexico

2020 ◽  
pp. 193-209
Author(s):  
Jose M. Jara ◽  
Bertha A. Olmos ◽  
Guillermo Martínez
Keyword(s):  
Material Properties ◽  
River Flow ◽  
Dynamic Properties ◽  
Flow Characteristics ◽  
Ambient Vibration ◽  
Structural Elements ◽  
Box Girder ◽  
Prone Area ◽  
Scour Protection ◽  
Ambient Vibration Measurements

This chapter presents the studies conducted to retrofit an existing bridge in a seismic prone area of Mexico. The Motín de Oro II Bridge was built in the 1970s with a continuous box girder superstructure and wall-type substructure. From the 1970s to nowadays, the design truck loads in Mexico have been substantially incremented and many bridges built in that period have required to be evaluated and, in some cases, rehabilitated and retrofitted. Firstly, the study presents the results of visual inspections of all parts of the bridge and a description of the preliminary studies conducted to determine the material properties, to evaluate the river flow characteristics and to calculate the scour depth. Secondly, the chapter discusses the initial structural analyses of the bridge subjected to the original gravitational and seismic loads and to the current loads before the intervention. These analyses allow to select the structural elements that require to be retrofitted and the best strategy to follow. Finally, the study presents results of the numerical retrofitted model and the experimental assessment of the dynamic properties based on ambient vibration measurements. Additionally, the scour protection and the general construction procedure are also described.

Highly Flexible Die Attach Adhesives for MEMS packages

2012 ◽  
Vol 2012 (1) ◽  
pp. 001169-001177 ◽  
Author(s):  
Tobias Königer
Keyword(s):  
Mechanical Stress ◽  
Young’S Modulus ◽  
Young's Modulus ◽  
Assembly Process ◽  
Processing Times ◽  
Heat Curing ◽  
Die Attach ◽  
Negative Effect ◽  
Dual Curing ◽  
Flexible Die

Die attach materials for most MEMS packages must be highly flexible as temperature changes during the assembly process and application may lead to thermo-mechanical stress as a consequence of dissimilar coefficients of thermal expansion of substrate, chip and adhesive. Thermo-mechanical stress results in a distortion of the signal characteristics of the extremely stress-sensitive MEMS device. Within the scope of this paper, highly flexible heat-curing adhesives with a Young's modulus down to 5 MPa (0.725 ksi) at room temperature were developed. DMTA measurements show that temperature storage at +120 °C (+248 °F) does not cause the adhesive to embrittle, which would have a negative effect on the MEMS package's reliability. After storage at +120 °C (+248 °F) for up to 1000 h, no increase in Young's modulus can be observed. The adhesives cure at extremely low temperatures down to +100 °C (+212 °F), which reduces stress development during the assembly process. In addition, the adhesives have very process-friendly properties. Processing times of more than one week can be achieved. The option of dual curing enables preliminary light fixation of the chip within just seconds.

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