CBGA Solder Fillet Shape Prediction and Design Optimization

1998 ◽  
Vol 120 (2) ◽  
pp. 118-122 ◽  
Author(s):  
Y. Li ◽  
R. L. Mahajan
Keyword(s):  
Mathematical Method ◽  
Fatigue Life ◽  
Solder Ball ◽  
Surface Model ◽  
Underlying Assumption ◽  
Eutectic Solder ◽  
Factors Affecting ◽  
Ball Size ◽  
Solder Volume ◽  
Set Up

In this paper, we first present a mathematical method that can be used to predict the eutectic solder fillet shape for ceramic ball grid array joints. An underlying assumption is that the solder fillets on both the module and the card sides can be represented as arcs. The fillets’ profiles are then calculated for the factors affecting the shape including solder volume, pad size, solder ball size, the wetting angle between eutectic solder and solder ball, and the gap between solder ball and pad. The second part of the paper focuses on design for reliability and investigates the effect of the interactions between the card-side and the module-side solder fillets on CBGA solder joint reliability. To this end, a central composite design of experiment is set up to systematically vary the pad size and the eutectic solder volume on both the module and the card sides. For each of the design settings, the proposed mathematical method is used to calculate the solder fillet shape. Using ABAQUS and the modified Coffin-Manson relationship, the mean fatigue life is predicted. The implications of the simulations are discussed. In addition, a response surface model is presented to find the optimum settings for maximum reliability. Finally, a comparison is made for the fatigue life predictions obtained using the proposed mathematical method and the linear solder fillet assumption.

The Effect of Stencil Printing Optimization on Reliability of CBGA and PBGA Solder Joints

1998 ◽  
Vol 120 (1) ◽  
pp. 54-60 ◽  
Author(s):  
Y. Li ◽  
R. L. Mahajan ◽  
G. Subbarayan
Keyword(s):  
Fatigue Life ◽  
Solder Joints ◽  
Maximum Strain ◽  
Stencil Printing ◽  
Eutectic Solder ◽  
Printing Process ◽  
Ceramic Ball ◽  
Ball Grid Arrays ◽  
Solder Volume ◽  
Plastic Ball

As a follow-up and conclusion to previous work in stencil printing process modeling and optimization (Li et al., 1996), we investigate the effect of stencil printing optimization on the reliability of the ceramic and plastic ball grid arrays. For ceramic ball grid arrays, the eutectic solder fillet shape is calculated using a series of simple mathematical equations. The thermal strain distributions within the solder joints after two cycles of accelerated thermal cycling test are estimated using three-dimensional finite element models. The modified Coffin-Manson relationship is applied to calculate the mean fatigue lives of the solder joints. The results reveal that an optimized stencil printing process significantly reduces variation in the fatigue life of ceramic ball grid arrays. The results also show that the fatigue life of ceramic ball grid arrays is very sensitive to the card-side solder volume. The maximum strain region shifts from the card-side eutectic solder to the module side as the card-side eutectic solder volume increases. This shift in maximum strain suggests that there exists an optimum ratio between the card-side solder volume and the module-side solder volume for the reliability of a given ceramic ball grid array design. The implications of this for the package developers and users are discussed. The calculations indicate that the fatigue life of plastic ball grid arrays is almost insensitive to the card-side solder volume.

Biodynamic Modeling of a Pedestrian Impact With a Rigid Frontal Guard of a Utility Vehicle

2010 ◽  
Author(s):  
Rasoul Moradi ◽  
Chandrashekhar K. Thorbole ◽  
Michael McCoy ◽  
Hamid M. Lankarani
Keyword(s):  
Front Surface ◽  
Body Region ◽  
Computational Technique ◽  
Surface Model ◽  
Published Data ◽  
Factors Affecting ◽  
Light Trucks ◽  
Accident Data ◽  
Facet Surface ◽  
The Impact

Accident data reveals that in most pedestrian accidents, the pedestrian head and lower extremity are vulnerable to serious injuries. The vehicle front geometry profile as well as the impact speed are important factors affecting the pedestrian kinematics and injury potential. In the US, accident data also shows that the fatality rate for pedestrian/light trucks and vans (LTV) impact is greater than that for the pedestrian/passenger-car impact. Addition of a front guard on light trucks and sports utility vehicles to mitigate damage during off-road activity or to provide mounting points for extra lights, makes the pedestrian more vulnerable to the impact. In this paper, a computational technique is utilized to study the influence of the added front guard on the impacted pedestrian. A CAD model of a typical commercial frontal guard is developed and converted into a rigid facet model, and attached to the vehicle front. The validated standing dummy model in the MADYMO code is used to simulate a pedestrian, and the rigid facet-surface model of a pickup truck is used to generate a vehicle front surface. This computational model is validated by comparing the pedestrian kinematics with the published data. This study demonstrates that the pedestrian mid body region is more vulnerable with the addition of guard on the vehicle. The result from this study facilitates a better understanding of a guard design and its geometry profile as required to protect vulnerable road users.

Ticket Income Distribution of Urban Rail Transit in Network Operating Condition

2011 ◽  
Vol 243-249 ◽  
pp. 4375-4380
Author(s):  
Yuan Chun Huang ◽  
Jian Li ◽  
Haize Pan
Keyword(s):  
Income Distribution ◽  
Urban Rail Transit ◽  
Ratio Method ◽  
Rail Transit ◽  
Matching Algorithm ◽  
Factors Affecting ◽  
Urban Rail ◽  
Set Up ◽  
Urban Rail Transit Network ◽  
Factor Matching

Through analyzing the factors affecting passengers’ path-choice, the corresponding principles and rules of the ticket income distribution are put forward and the new model of the Urban Rail Transit Network in Beijing is set up in the paper. Through the deformation of the urban rail transit and the simplification of the lines, the topology of the urban rail transit lines is abstracted into an undirected connection graph. Breadth-priority optimization algorithm is applied to search the effective paths between the OD and the flow-matching ratio is acquired by calculating based on multi-factor matching algorithm, in which many relevant numerical examples are analyzed to verify the feasibility of the dual-ratio method and to summarize the characteristics of the project.

The Influencing Factors and Assessment Rule of Fatigue Life of Shaft Based on Product Lifecycle Management

2007 ◽  
Vol 561-565 ◽  
pp. 2253-2256 ◽  
Author(s):  
You Tang Li ◽  
Ping Ma ◽  
Jun Tian Zhao
Keyword(s):  
Fatigue Life ◽  
Influencing Factors ◽  
Axial Stress ◽  
Assessment Method ◽  
Product Lifecycle Management ◽  
Product Lifecycle ◽  
Fatigue Design ◽  
Main Factors ◽  
Set Up ◽  
Lifecycle Management

Product lifecycle management is one of the main developmental aspects of advanced manufacturing technology. Anti-fatigue design is the key content in product lifecycle management. For designing the fatigue life of shaft exactly and determining the assessment method, the influencing factors must be realized roundly. The mechanical model of shaft is set up at first, and then the main factors that affect the fatigue life of shaft is discussed, the interrelations of the main factors and the framework are founded. The assessment equation of fatigue life for shaft is put forward and the influencing coefficient of multi-axial stress to fatigue life is analyzed. The results of this paper will establish the base of anti-fatigue and assessment life of shaft.

Development of Foot Structure for Humanoid Robot Using Topology Optimization

2018 ◽  
Vol 29 ◽  
pp. 34-45
Author(s):  
Van Tinh Nguyen ◽  
Daichi Kiuchi ◽  
Hiroshi Hasegawa
Keyword(s):  
Topology Optimization ◽  
Humanoid Robot ◽  
Differential Evolution Algorithm ◽  
Optimization Method ◽  
Gait Pattern ◽  
Surface Model ◽  
Foot Structure ◽  
Adaptive Differential Evolution ◽  
Reaction Forces ◽  
Set Up

This paper addresses the development of a foot structure for 22-Degree of Freedom (DoF) humanoid robot. The goal of this research is to reduce the weight of the foot and enable the robot to walk steadily. The proposed foot structure is based on the consideration of cases where the ground reaction forces are set up in different situations. The optimal foot structure is a combination of all the topology optimization results. Additionally, a gait pattern is generated by an approximated optimization method based on Response Surface Model (RSM) and Improved Self-Adaptive Differential Evolution Algorithm (ISADE). The result is validated through dynamic simulation by a commercially available software called Adams (MSC software, USA) with the humanoid robot named KHR-3HV belonging to Kondo Kagaku company.

Concrete Fatigue Life Characteristics of the Different Survival Rates in the Lateral Pressure Conditions

2012 ◽  
Vol 600 ◽  
pp. 250-255
Author(s):  
Qiang Cai ◽  
Ji Ming Kong ◽  
Ze Fu Chen
Keyword(s):  
Fatigue Life ◽  
Life Stress ◽  
Failure Modes ◽  
Survival Curve ◽  
Survival Rates ◽  
Life Distribution ◽  
Fatigue Design ◽  
Set Up ◽  
Fatigue Equation ◽  
Two Parameter

Under cyclic loading of concrete structures, fatigue failure is the main failure modes of fatigue, which has become the fatigue design of concrete structure must be considered, then the concrete fatigue studies must clarify the fatigue life of concrete under different survival curve S-N curve. Based on the statistics of the two parameter Weibull distribution theory, obtain the concrete under different survival rates of fatigue life distribution, namely to improve survival, reduce the fatigue life; stress level is reduced, the fatigue life is increased; and has set up more than 50% under different survival rates of concrete fatigue equation.

The Road Less Travelled

2020 ◽  
pp. 307-327
Author(s):  
Seema S. P.
Keyword(s):  
Women Managers ◽  
Well Being ◽  
Factors Affecting ◽  
The Road ◽  
Family Balance ◽  
Education In India ◽  
Managerial Positions ◽  
Work Family ◽  
Set Up ◽  
Work And Family Roles

One of the most crucial factors affecting development in the 21st century is the increased participation of women in the economy of a country and increased entrance to managerial positions. Even though such tremendous changes have taken place, the patriarchal social set up insists on women's responsibilities towards family and children. The domestic roles of women are not shared by men despite the fact that women have shared the economic and social responsibilities of men. This causes conflict among work and family roles, which ultimately affects the physical and psychological well-being of women managers. This chapter deals with the problems and challenges faced by women managers in higher education in India and how family support and suitable coping strategies help them maintain work-family balance.

On the Critical Resolved Shear Stress and its Importance in the Fatigue Performance of Steels and other Metals with Different Crystallographic Structures

2022 ◽  
pp. 37-65
Author(s):  
M. Mlikota
Keyword(s):  
Shear Stress ◽  
Fatigue Life ◽  
Fatigue Limit ◽  
High Fatigue ◽  
Steel Aisi ◽  
Crystallographic Structures ◽  
Face Centered ◽  
Set Up ◽  
Number Of Cycles ◽  
Critical Resolved Shear Stress

This study deals with the numerical estimation of the fatigue life represented in the form of strength-life (S-N, or Wöhler) curves of metals with different crystallographic structures, namely body-centered cubic (BCC) and face-centered cubic (FCC). Their life curves are determined by analyzing the initiation of a short crack under the influence of microstructure and subsequent growth of the long crack, respectively. Micro-models containing microstructures of the materials are set up by using the finite element method (FEM) and are applied in combination with the Tanaka-Mura (TM) equation in order to estimate the number of cycles required for the crack initiation. The long crack growth analysis is conducted using the Paris law. The study shows that the crystallographic structure is not the predominant factor that determines the shape and position of the fatigue life curve in the S-N diagram, but it is rather the material parameter known as the critical resolved shear stress (CRSS). Even though it is an FCC material, the investigated austenitic stainless steel AISI 304 shows an untypically high fatigue limit (208 MPa), which is higher than the fatigue limit of the BCC vanadium-based micro-alloyed forging steel AISI 1141 (152 MPa).

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