A Numerical Study of Solder Paste Rolling Process for PCB Printing

2018 ◽  
Author(s):  
Ricardo F. Oliveira ◽  
Nelson Rodrigues ◽  
José Carlos Teixeira ◽  
Duarte Santos ◽  
Delfim Soares ◽  
...  
Keyword(s):  
Numerical Study ◽  
Flow Simulation ◽  
Rolling Process ◽  
Production Costs ◽  
Process Efficiency ◽  
Solder Paste ◽  
Filling Process ◽  
Newtonian Viscosity ◽  
Air Interface ◽  
Increasing Demand

The increasing demand for electronic devices associated with the increasing competitiveness between enterprises, pushes towards process automation to decrease production costs. The reflow soldering has proven to be effective in this regard. This is composed by a series of steps or processes, such as: (a) stencil printing, (b) component placement and (c) reflow oven soldering. Each process has its specific traits that contribute to the overall process efficiency. The present study is directed towards process (a), which includes the rolling of the solder paste over the stencil surface, followed by the subsequent filling of the stencil apertures. Several parameters influence the solder paste behaviour and thus the effectiveness of the rolling process. This work focuses on the solder paste non-Newtonian viscosity properties, with the solder paste presenting a thixotropic behaviour, necessary for the filling of the stencil apertures. Although the increase in the squeegee velocity causes extra shear in the solder paste and consequently lower viscosity, the excess of velocity may cause defects in the aperture filling process. In addition, during the rolling process, air may become entrapped in the solder paste. The complexity of this process is addressed by numerical simulation, in particular, using the work-package ANSYS to study the solder paste progress, during the rolling process, as well as the parameters influencing it. The fluid flow simulation is solved using the solver FLUENT®, a simplified 2D domain with real case dimensions, a transient prediction of the viscosity, which is a function of the solder paste solicitation, and finally by using the Volume of Fluid (VOF) method to track the solder-air interface boundary. Dynamic meshing methods are also employed to replicate the movement of the squeegee wall, in its task to push the solder paste tumble over the stencil. This study enlightens the role played by the printing velocity in the stencil aperture filling, a logarithm correlation can be found between them. It was found that lower print velocities provide better results than higher speeds. It was observed that the back tip of the squeegee blade causes a partial removal of the solder paste from the aperture, which is higher for faster print processes. An analysis of the filling process over time concluded that, independently of the printing velocity, 90% of the filling occurs in the first quarter of the process.

A NUMERICAL STUDY ON THE HEMODYNAMIC AND SHEAR STRESS OF DOUBLE ANEURYSM THROUGH S-SHAPED VESSEL

2015 ◽  
Vol 27 (04) ◽  
pp. 1550033 ◽  
Author(s):  
Mahdi Halabian ◽  
Alireza Karimi ◽  
Borhan Beigzadeh ◽  
Mahdi Navidbakhsh
Keyword(s):  
Blood Flow ◽  
Mechanical Behavior ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Flow Simulation ◽  
The Body ◽  
Sweep Angle ◽  
Abdominal Aortic ◽  
Hemodynamic Characteristics ◽  
Refined Meshes

Abdominal aortic aneurysm (AAA) is a degenerative disease defined as the abnormal ballooning of the abdominal aorta (AA) wall which is usually caused by atherosclerosis. The aneurysm grows larger and eventually ruptures if it is not diagnosed and treated. Aneurysms occur mostly in the aorta, the main artery of the chest and abdomen. The aorta carries blood flow from the heart to all parts of the body, including the vital organs, the legs, and feet. The objective of the present study is to investigate the combined effects of aneurysm and curvature on flow characteristics in S-shaped bends with sweep angle of 90° at Reynolds number of 900. The fluid mechanics of blood flow in a curved artery with abnormal aortic is studied through a mathematical analysis and employing Cosmos flow simulation. Blood is modeled as an incompressible non-Newtonian fluid and the flow is assumed to be steady and laminar. Hemodynamic characteristics are analyzed. Grid independence is tested on three successively refined meshes. It is observed that the abrupt expansion induced by AAA results in an immensely disturbed regime. The results may have implications not only for understanding the mechanical behavior of the blood flow inside an aneurysm artery but also for investigating the mechanical behavior of the blood flow in different arterial diseases, such as atherosclerosis.

scholarly journals Ferramenta para Análise e Gestão de Custos da Atividade Cafeeira em Pequenas e Médias Propriedades Rurais

2021 ◽  
Vol 24 (40) ◽  
pp. 86-92
Author(s):  
Luiz Felipe Sacardo ◽  
Michele Ribeiro Ramos
Keyword(s):  
Production Costs ◽  
Process Efficiency ◽  
Efficiency Gain ◽  
Cash Flow Management ◽  
Financial Gain ◽  
Personal Finances ◽  
Precise Analysis ◽  
Export Volume ◽  
Coffee Farmers ◽  
The Difference

ResumoO Agronegócio é responsável por cerca de ¼ das riquezas geradas anualmente no Brasil. Dentro deste universo a cultura cafeeira é responsável por cerca de 10% do volume total das exportações deste setor. A viabilidade da produção cafeeira em qualquer escala depende fortemente da agregação de qualidade no produto final, eficiência nos processos e o controle dos custos da atividade. Os pequenos e médios cafeicultores, de maneira geral, ainda carecem de uma estrutura administrativa que lhes permita conhecer e gerencia adequadamente suas finanças, apesar de existir uma consciência da necessidade do conhecimento e gerenciamento dos custos de produção o que ainda vemos são as finanças das atividades sendo misturadas com as finanças pessoais, impossibilitando qualquer tipo de análise precisa e ainda, uma forte tendência de subjugar os custos e despesas e de inflacionar os resultados finais, mesmo que estes não estejam explícitos. Fatores como má administração do fluxo de caixa ou até mesmo menosprezo por pequenas despesas no cálculo do resultado podem ser o diferencial entre aqueles produtores que prosperam e aqueles que têm de deixar a atividade. Palavras-chave: Microanálise de Empresas Agrícolas. Modelos Econométricos e de Entrada-Saída. Investimento. Abstract Agribusiness is responsible for about ¼ of the wealth generated annually in Brazil. Within this universe, coffee culture is responsible for about 10% of the total export volume of this sector. The viability of coffee production on any scale strongly depends on the aggregation of quality in the final product, process efficiency and cost control of the activity. With the administrative modernization of the activity efficiency is gained, and with the efficiency gain opportunities for greater financial gain arise, either through cost reduction or revenue increase. Small and medium coffee farmers, in general, still lack an administrative structure that allows them to know and manage their finances properly, although there is an awareness of the need for knowledge and management of production costs. What we still see is the finances of the activity mixed with personal finances, precluding any kind of precise analysis and yet a strong tendency to subjugate costs and expenses and to inflate final results, even if they are not explicit. Factors such as poor cash flow management or even contempt for small expenses in calculating income may be the difference between those who thrive and those who have to leave the business. Keywords: Micro Analysis of Farm Firms. Econometric and Input-Output Models. Investment.

Numerical simulation of slab deformation process with different reduction values in vertical rolls of mill 2000 roughing stands

2021 ◽  
Vol 77 (6) ◽  
pp. 675-681
Author(s):  
N. L. Bolobanova ◽  
E. A. Garber
Keyword(s):  
Process Model ◽  
Surface Defects ◽  
Numerical Study ◽  
Rolling Process ◽  
Rolled Stock ◽  
Metal Consumption ◽  
Wide Face ◽  
Total Reduction ◽  
Hot Rolling Mill ◽  
Deform 3D

Perfection of rolled stock production processes at continuous wide-strip hot rolling mill (CWHRM) aimed at minimization of metal consumption, is an effective mean to decrease its cost. In the process of slabs rolling at CWHRM, the metal consumption is stipulated first of all by complicated workpiece forming in roughing stands during consecutive reduction by vertical and horizontal rolls. Results of the numerical study of slab deformation with different values of reduction in vertical rolls of roughing stands of mill 2000 are presented. The implementation of rolling process model based on application of DEFORM-3D program of finiteelement analysis described for evaluation of metal shifting from the edges of slab in the direction of the middle of the width. The convergence of the simulation results with the measurements data of workpiece forming during roughing rolling at Severstal mill 2000 was experimentally confirmed. It was found that an increase of reduction in vertical rolls has no significant effect on the metal shifting from a narrow edge to a wide one. Increase the total reduction in vertical rolls leads to an unfavorable stress-strain state of the edge region and the Cockcroft–Latham criterion rises by 20–30%. It was proposed to reduce the total reduction in the vertical rolls of the roughing stands of mill 2000 down to 40–50 mm. It was shown that increase of time of slab moving from the heating furnace to the scale breaker causes growth the Cockcroft-Latham criterion and does not affect the amount of metal shifting from a narrow face to a wide one. The proposed method of simulation the process of slab deformation in the roughing group of the mill 2000 proved by results of industrial rolling can to be used for further study of the effect of rolls profiling and forming of surface defects with the provision of minimal metal shifting onto a wide face.

Secure RFID-Enablement in Modern Companies

2012 ◽  
pp. 507-539
Author(s):  
Matthieu-P. Schapranow ◽  
Jürgen Müller ◽  
Alexander Zeier ◽  
Hasso Plattner
Keyword(s):  
Supply Chain ◽  
Supply Chains ◽  
Data Exchange ◽  
Formal Model ◽  
Mutual Authentication ◽  
The United States ◽  
Production Costs ◽  
Air Interface ◽  
Pharmaceutical Industries ◽  
Secured Data

Current RFID implementations suffer from security threats and privacy issues since the technology was not designed for secured data exchange. In emerging global RFID-aided supply chains, the need for open interfaces between supply chain partners exposes business secrets. A case study focusing on the development of detected counterfeits in the pharmaceutical industries in Europe and in the United States of America motivates the rising importance for RFID security. A formal model for describing RFID-aided supply chains is introduced to analyze flow of messages and data. Countermeasure tasks for all involved supply chain participants are defined to harden the integrity of the global supply chain. Motivated by concerns of exposing data via the air interface, two mutual authentication protocols are presented that aim to keep tag production costs low. Their applicability in context of the pharmaceutical industry is discussed.

Creep Behavior of a Solder Paste With Bi Addition

2017 ◽  
Author(s):  
Pedro E. Ribeiro ◽  
Delfim F. Soares ◽  
Maria F. Cerqueira ◽  
Senhorinha F. Teixeira ◽  
Daniel A. Barros ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Solder Joint ◽  
Mechanical Performance ◽  
Creep Behaviour ◽  
Real Life ◽  
Production Costs ◽  
Solder Paste ◽  
Creep Tests ◽  
Pcb Assembly ◽  
Solder Joint Fatigue

A common failure mode of electronic PCB’s is the appearance of cold solder joints between the component and PCB, during product life. This phenomenon is related to solder joint fatigue and is attributed mainly to the mismatch of the coefficients of thermal expansion (CTE) of component-solder-PCB assembly. Although some experiments show that newer lead-free tin-silver-copper (Sn-Ag-Cu, or SAC) solders perform better than the older SnPb ones, with today’s solder joint thickness decreasing and increasing working temperatures, among others, the stresses and strains due to temperature changes are growing, leading to limited fatigue life of the products. As fatigue life decreases with increasing plastic strain, creep occurrence should have significant impact, especially during thermal cycles. In order to improve mechanical properties, but also as an attempt to reduce maximum reflow cycle temperatures due to component damage and production costs, various SAC solder alloying additives are being considered to use in industrial production facilities. Solder paste producers are proposing new products based on new solder paste formulations, but the real life effects on thermo-mechanical performance aren’t well known at the moment. In this paper a dynamic mechanical analyser (DMA) is used to study the influence of Bismuth (Bi) addition, up to 5 wt %, on SAC405 solder paste, in terms of creep behaviour. Creep tests were made on three-point-bending configuration, isothermally at 30 °C, 50 °C and 75 °C, and three different stresses of 3, 5 and 9 MPa. The results shown not only a significant Bi concentration influence on creep behaviour but also a noticeable temperature dependence.

Solution Adaptive Grids Applied to Low Reynolds Number Flow

2002 ◽  
Author(s):  
Govert de With ◽  
Arne E. Holdo̸ ◽  
Thomas A. Huld
Keyword(s):  
Numerical Study ◽  
Turbulent Viscosity ◽  
Flow Simulation ◽  
Mesh Size ◽  
Adaptive Grids ◽  
Adaptation Algorithm ◽  
Flow Around A Cylinder ◽  
Reynolds Number Flow ◽  
Number Flow ◽  
Mesh Structures

A numerical study has been undertaken to investigate the use of a solution adaptive grid for flow around a cylinder in the laminar flow regime. The main purpose of this work is twofold. The first aim is to investigate the suitability of a grid adaptation algorithm and the reduction in mesh size that can be obtained. Secondly, the uniform asymmetric flow structures are ideal to validate the mesh structures due to mesh refinement and consequently the selected refinement criteria. The refinement criteria in this work are derived from turbulent viscosity, which is not applied to the flow simulation, but instead used as a measure for grid refinement.

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