Solder Joint Formation in Surface Mount Technology—Part II: Design

1990 ◽  
Vol 112 (3) ◽  
pp. 219-222 ◽  
Author(s):  
S. M. Heinrich ◽  
N. J. Nigro ◽  
A. F. Elkouh ◽  
P. S. Lee
Keyword(s):  
Surface Tension ◽  
Solder Joint ◽  
Solder Joints ◽  
Cross Sectional Area ◽  
Surface Mount Technology ◽  
Sectional Area ◽  
Cross Sectional ◽  
Joint Formation ◽  
Surface Mount ◽  
Surface Tension Model

In this paper dimensionless design curves relating fillet height and length to joint cross-sectional area are presented for surface-mount solder joints. Based on an analytical surface tension model, the advantage of these dimensionless curves is that they may be used for arbitrary values of solder density and surface tension. The range of applicability of previously developed approximate formulae for predicting joint dimensions is also investigated. A simple example problem is included to illustrate the use of both the design curves and the approximate formulae.

Effects of surface tension and intraluminal fluid on mechanics of small airways

1997 ◽  
Vol 82 (1) ◽  
pp. 233-239 ◽  
Author(s):  
Mark J. Hill ◽  
Theodore A. Wilson ◽  
Rodney K. Lambert
Keyword(s):  
Surface Tension ◽  
Bending Stiffness ◽  
Liquid Interface ◽  
Cross Sectional Area ◽  
Pressure Curve ◽  
Small Airways ◽  
Sectional Area ◽  
Cross Sectional ◽  
Inner Surface ◽  
Air Liquid Interface

Hill, Mark J., Theodore A. Wilson, and Rodney K. Lambert.Effects of surface tension and intraluminal fluid on the mechanics of small airways. J. Appl. Physiol.82(1): 233–239, 1997.—Airway constriction is accompanied by folding of the mucosa to form ridges that run axially along the inner surface of the airways. The muscosa has been modeled (R. K. Lambert. J. Appl. Physiol. 71: 666–673, 1991) as a thin elastic layer with a finite bending stiffness, and the contribution of its bending stiffness to airway elastance has been computed. In this study, we extend that work by including surface tension and intraluminal fluid in the model. With surface tension, the pressure on the inner surface of the elastic mucosa is modified by the pressure difference across the air-liquid interface. As folds form in the mucosa, intraluminal fluid collects in pools in the depressions formed by the folds, and the curvature of the air-liquid interface becomes nonuniform. If the amount of intraluminal fluid is small, <2% of luminal volume, the pools of intraluminal fluid are small, the air-liquid interface nearly coincides with the surface of the mucosa, and the area of the air-liquid interface remains constant as airway cross-sectional area decreases. In that case, surface energy is independent of airway area, and surface tension has no effect on airway mechanics. If the amount of intraluminal fluid is >2%, the area of the air-liquid interface decreases as airway cross-sectional area decreases, and surface tension contributes to airway compression. The model predicts that surface tension plus intraluminal fluid can cause an instability in the area-pressure curve of small airways. This instability provides a mechanism for abrupt airway closure and abrupt reopening at a higher opening pressure.

Solder Joint Reliability — Design Implications From Finite Element Modeling and Experimental Testing

1990 ◽  
Vol 112 (2) ◽  
pp. 135-146 ◽  
Author(s):  
H. K. Charles ◽  
G. V. Clatterbaugh
Keyword(s):  
Fracture Toughness ◽  
Finite Element ◽  
Fatigue Life ◽  
Solder Joint ◽  
Solder Joints ◽  
Experimental Testing ◽  
Sectional Area ◽  
Stress Concentrations ◽  
Cross Sectional ◽  
Power Cycling

An extensive finite element modeling and experimental testing program has been carried out to determine the most optimum design parameters for solder joints in surface mount applications. Although the analysis and testing (power cycling and thermal cycling) has been carried out for a variety of package styles, particular attention will be paid to the result for leadless ceramic chip carriers. This package is particularly useful in certain high performance military and commercial applications. Analysis and experimentation indicate that increased fatigue life under power cycling can be attained by fabricating solder joints with large fillets and low standoff heights. The large fillet geometry significantly reduces harmful stress concentrations while increasing the net cross-sectional area within the joint. Both factors tend to improve the fracture toughness of the joint. The temperature and frequency dependencies of solder joint fatigue life under power cycling testing is discussed. The observed frequency dependence can be minimized by eliminating harmful tensile strain components thus reducing harmful stress relaxation and tensile induced oxygen embrittlement of grain boundaries. Temperature cycling studies indicate joints with slightly higher standoffs and low fillet angles are more resistant to cyclic fatigue than pillar type joints which tend to focus shear strains at the interfaces. Solder joints can be tapered to improve overall reliability but, in most cases, tapering will provide only a small increase in fracture toughness of the joint through the elimination of stress concentrations. Additional fatigue life increases can be obtained only through an enlargement of the joint cross-sectional area. Aspects of the above results will be presented in detail along with design guidelines for creating high reliability solder joints for various application scenarios.

Solder Joint Formation in Surface Mount Technology—Part I: Analysis

1990 ◽  
Vol 112 (3) ◽  
pp. 210-218 ◽  
Author(s):  
S. M. Heinrich ◽  
A. F. Elkouh ◽  
N. J. Nigro ◽  
Ping S. Lee
Keyword(s):  
Solder Joint ◽  
Laboratory Data ◽  
Integral Form ◽  
Contact Angles ◽  
Reflow Process ◽  
Cross Sectional ◽  
Joint Formation ◽  
Surface Mount ◽  
Theoretical Predictions ◽  
Joint Shape

An analytical model of solder joint formation during a surface mount reflow process is developed in the present paper, and the solution is obtained in an explicit integral form. For two limiting cases—infinitesimal and infinite solder areas—the solution is expressed in closed form. Numerical results illustrate the influence of the process parameters (surface tension, density, and cross-sectional area of the molten solder, and the contact angles between the solder andpretinning) on joint shape and overall fillet dimensions. Comparisons between theoretical predictions and laboratory data show excellent agreement.

scholarly journals Numerical Analysis of Heat Transfer Mechanism of Thermal Runaway Propagation for Cylindrical Lithium-ion Cells in Battery Module

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1010
Author(s):  
Zhiguo Tang ◽  
Anqi Song ◽  
Shoucheng Wang ◽  
Jianping Cheng ◽  
Changfa Tao
Keyword(s):  
Heat Transfer ◽  
Heat Conduction ◽  
Solder Joint ◽  
Lithium Ion ◽  
Thermal Runaway ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Joint Area ◽  
Battery Module

An electrochemical-thermal coupling model combined with an electrically connected cylindrical cell model was built to produce a structural design that prevents thermal runaway propagation of cells on the battery module. Additionally, the characteristics of different modes of heat transfer of each cell during thermal runaway propagation of the battery module in an open environment were studied by changing the spacing of adjacent cells, the solder joint area, and the cross-sectional area of the electrode tab. Heat conduction is usually the main heat transfer mode for cells directly connected to the thermal runaway cell, while radiation heat transfer is the main heat exchange mode for cells that are not directly connected to thermal runaway cell. Increasing spacing can prevent thermal runaway propagation by the three heat transfer modes. Similarly, a smaller total solder joint area and cross-sectional area of the electrode tab can inhibit thermal runaway propagation through heat conduction transfer modes if conditions permit.

Effects of Solder Joint Voiding and Seating Plane Stability on Surface Mount Lead Standoff

1994 ◽  
Vol 116 (2) ◽  
pp. 89-91 ◽  
Author(s):  
M. K. Schwiebert
Keyword(s):  
Simple Model ◽  
Solder Joint ◽  
Solder Joints ◽  
Reaction Force ◽  
Molten Solder ◽  
Surface Mount Technology ◽  
Surface Mount

This study considers the influence of solder joint voiding and seating plane stability on the lead standoffs of surface mount technology (SMT) solder joints. A model is presented for approximating the reaction force generated by a gas-filled void in molten solder which is compressed under an SMT lead. Seating plane stability is defined with a simple model. The lead standoffs of a component with an unstable seating plane are sensitive to small forces. For some SMT components, the reaction force generated by compressed voids in molten solder can tilt or rock a component, resulting in lead standoffs much greater than the measured lead coplanarity.

scholarly journals Pharyngeal mucosal wall folds in subjects with obstructive sleep apnea

2015 ◽  
Vol 118 (6) ◽  
pp. 707-715 ◽  
Author(s):  
Kristina Kairaitis ◽  
Sheryl Foster ◽  
Jason Amatoury ◽  
Manisha Verma ◽  
John R. Wheatley ◽  
...  
Keyword(s):  
Surface Tension ◽  
Obstructive Sleep Apnea ◽  
Healthy Subjects ◽  
Liquid Surface ◽  
Upper Airway ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Liquid Surface Tension ◽  
Obstructive Sleep

Mechanical processes underlying pharyngeal closure have not been examined. We hypothesized that the pharyngeal mucosal surface would fold during closure, and lowering the upper airway lining liquid surface tension would unfold areas of mucosal apposition, i.e., folds. We compared baseline pharyngeal fold numbers and response to reduction in upper airway liquid surface tension in healthy and obstructive sleep apnea (OSA) subjects. Awake, gated magnetic resonance pharyngeal airway images of 10 healthy and 11 OSA subjects were acquired before and after exogenous surfactant administration (beractant). Upper airway liquid surface tension was measured at the beginning and end of image acquisition and averaged. Velopharyngeal and oropharyngeal images were segmented and analyzed separately for average cross-sectional area, circumference, and fold number. Compared with healthy subjects, at baseline, velopharynx for OSA subjects had a smaller cross-sectional area (98.3 ± 32.5 mm2 healthy, 52.3 ± 23.6 mm2 OSA) and circumference (46.5 ± 8.1 mm healthy, 30.8 ± 6.1 mm OSA; both P < 0.05, unpaired t-test), and fewer folds (4.9 ± 1.6 healthy, 3.1 ± 1.8 OSA, P < 0.03). There were no differences in oropharynx for cross-sectional area, circumference, or folds. Reduction in upper airway liquid surface tension from 61.3 ± 1.2 to 55.3 ± 1.5 mN/m ( P < 0.0001) did not change cross-sectional area or circumference for velopharynx or oropharynx in either group; however, in OSA subjects, oropharyngeal folds fell from 6.8 ± 3.1 to 4.7 ± 1.2 ( n = 8, P < 0.05), and velopharyngeal folds from 3.3 ± 1.9 to 2.3 ± 1.2 ( P = 0.08), and were unchanged in healthy subjects. Subjects with OSA have fewer velopharyngeal wall folds, which decrease further when surface tension falls. We speculate that reduced pharyngeal wall folds contribute to an increase in pharyngeal collapsibility.

Pelvic Canal Narrowing Caused by Triple Pelvic Osteotomy in the Dog

1994 ◽  
Vol 07 (03) ◽  
pp. 110-113 ◽  
Author(s):  
D. L. Holmberg ◽  
M. B. Hurtig ◽  
H. R. Sukhiani
Keyword(s):  
Postoperative Complications ◽  
Pelvic Osteotomy ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Canal Width ◽  
Operative Complications ◽  
Post Operative Complications

SummaryDuring a triple pelvic osteotomy, rotation of the free acetabular segment causes the pubic remnant on the acetabulum to rotate into the pelvic canal. The resulting narrowing may cause complications by impingement on the organs within the pelvic canal. Triple pelvic osteotomies were performed on ten cadaver pelves with pubic remnants equal to 0, 25, and 50% of the hemi-pubic length and angles of acetabular rotation of 20, 30, and 40 degrees. All combinations of pubic remnant lengths and angles of acetabular rotation caused a significant reduction in pelvic canal-width and cross-sectional area, when compared to the inact pelvis. Zero, 25, and 50% pubic remnants result in 15, 35, and 50% reductions in pelvic canal width respectively. Overrotation of the acetabulum should be avoided and the pubic remnant on the acetabular segment should be minimized to reduce postoperative complications due to pelvic canal narrowing.When performing triple pelvic osteotomies, the length of the pubic remnant on the acetabular segment and the angle of acetabular rotation both significantly narrow the pelvic canal. To reduce post-operative complications, due to narrowing of the pelvic canal, overrotation of the acetabulum should be avoided and the length of the pubic remnant should be minimized.

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