Flip-Chip Underfill Packaging Considering Capillary Force, Pressure Difference, and Inertia Effects

2006 ◽  
Vol 129 (1) ◽  
pp. 48-55 ◽  
Author(s):  
Chao-Ming Lin ◽  
Win-Jin Chang ◽  
Te-Hua Fang
Keyword(s):  
Capillary Force ◽  
Pressure Difference ◽  
Driving Force ◽  
Flip Chip ◽  
Inertia Force ◽  
Inertia Effects ◽  
Filling Time ◽  
Circular Rotation ◽  
Gap Height ◽  
Force Pressure

This study aims to enhance the flow rate and reduce the filling time in flip-chip underfill packaging by combining capillary force, pressure difference, and inertia effects. In the designed underfill apparatus, the capillary force effect is developed by surface tension, the pressure difference between the inlet and the outlet is established using a pump or a vacuum, and the inertia force is achieved via circular rotation. The governing equations containing the three analyzed effects are derived and solved using a dimensionless technique. The analytical results indicate that for the general gap height of approximately 10-1000μm, the pressure difference and inertia effects dominate the driving force and provide a significant reduction in the filling time. However, for a gap height of less than 1μm, the driving force is dominated by the capillary effect. The present results confirm that the productivity of the flip-chip underfill packaging process can be enhanced through the appropriate control of the capillary force, pressure difference, and inertia effects.

A Theoretical Analysis of the Concept of Critical Clearance Toward a Design Methodology for the Flip-Chip Package

2007 ◽  
Vol 129 (4) ◽  
pp. 473-478 ◽  
Author(s):  
J. W. Wan ◽  
W. J. Zhang ◽  
D. J. Bergstrom
Keyword(s):  
Flip Chip ◽  
Solder Bump ◽  
Flow Characteristics ◽  
Quantitative Relation ◽  
Package Design ◽  
Solder Bumps ◽  
Filling Time ◽  
Encapsulation Process ◽  
Advanced Packaging ◽  
Gap Height

In this article, we present a theoretical study on the concept known as critical clearance for flip-chip packages. The critical clearance phenomenon was first observed in an experiment reported by Gordon et al. (1999, “A Capillary-Driven Underfill Encapsulation Process,” Advanced Packaging, 8(4), pp. 34–37). When the clearance is below a critical value, filling time begins to increase dramatically, and when the clearance is above this value, the influence of clearance on filling time is insignificant. Therefore, the optimal solder bump density in a flip-chip package should be one with a clearance larger than the critical clearance. The contribution of our study is the development of a quantitative relation among package design features, flow characteristics, and critical clearance based on an analytical model we developed and reported elsewhere. This relation is further used to determine critical clearance given a type of underfill material (specifically the index n of the power-law constitutive equation), the solder bump pitch, and the gap height; further the flip-chip package design can be optimized to make the actual clearance between solder bumps greater than its corresponding critical clearance.

Influence of Gap Height in Flip Chip Underfill Process With Non-Newtonian Flow Between Two Parallel Plates

2012 ◽  
Vol 134 (1) ◽  
Author(s):  
C. Y. Khor ◽  
M. Z. Abdullah ◽  
M. Abdul Mujeebu
Keyword(s):  
Pressure Drop ◽  
Flip Chip ◽  
3D Model ◽  
Fluid Dynamic ◽  
Power Law Model ◽  
Parallel Plates ◽  
Newtonian Flow ◽  
Filling Time ◽  
Gap Height ◽  
Volume Method

In this paper, the finite volume method (FVM) is used for the simulation of flip chip underfill process by considering non-Newtonian flow between two parallel plates that emulate the silicon die and the substrate. 3D model of two parallel plates of size 12.75 mm × 9.5 mm with gap heights of 5 μm, 15 μm, 25 μm, 35 μm, 45 μm, and 85 μm are developed and simulated by computational fluid dynamic (CFD) code, fluent 6.3.26. The flow is modeled by using power law model and volume of fluid (VOF) technique is applied for flow front tracking. The effect of change in height of the gap between the plates on the underfill process is mainly studied in the present work. It is observed that the gap height has significant influence on the melt filling time and pressure drop, as the gap height decreases filling time and pressure drop increase. The simulation results are compared with previous experimental results and found in good conformity.

Extended Finite Element Analysis of Journal Bearing Dynamic Forced Performance to Include Fluid Inertia Force Coefficients

2012 ◽  
Author(s):  
Luis San Andrés
Keyword(s):  
Finite Element ◽  
Test Data ◽  
Small Amplitude ◽  
Forced Response ◽  
Inertia Force ◽  
Fluid Inertia ◽  
Inertia Effects ◽  
Force Coefficients ◽  
Reaction Forces ◽  
Bearing Stiffness

Reynolds equation governs the generation of hydrodynamic pressure in oil lubricated fluid film bearings. The static and dynamic forced response of a bearing is obtained from integration of the film pressure on the bearing surface. For small amplitude journal motions, a linear analysis represents the fluid film bearing reaction forces as proportional to the journal center displacements and velocity components through four stiffness and four damping coefficients. These force coefficients are integrated into rotor-bearing system structural analysis for prediction of the system stability and the synchronous response to imbalance. Fluid inertia force coefficients, those relating reaction forces to journal center accelerations, are routinely ignored because most oil lubricated bearings operate at relatively low Reynolds numbers, i.e., under slow flow conditions. Modern rotating machinery operates at ever increasing surface speeds to deliver more power in smaller size units. Under these operating conditions fluid inertia effects need to be accounted for in the forced response of oil lubricated bearings, as recent experimental test data also reveal. The paper presents a finite element formulation to predict added mass coefficients in oil lubricated bearings by extending a basic formulation that already calculates the bearing stiffness and damping force coefficients. That is, a small amplitude perturbation analysis of the lubrication flow equations keeps the temporal fluid inertia effects and develops a set of equations to obtain the bearing stiffness, damping and inertia force coefficients. The method does not impose on the cost of the original formulation which makes it very attractive for ready implementation in existing software. Predictions of the computational model are benchmarked against archival test data for an oil-lubricated pressure dam bearing supporting large compressors. The comparisons show fluid inertia effects cannot be ignored for operation at high rotor speeds and with small static loads.

Spatial analysis of underfill flow in flip-chip encapsulation

2020 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Fei Chong Ng ◽  
Mohd Hafiz Zawawi ◽  
Mohamad Aizat Abas
Keyword(s):  
Spatial Analysis ◽  
Formation Mechanism ◽  
Flip Chip ◽  
Void Formation ◽  
Past Research ◽  
Air Entrapment ◽  
Time Model ◽  
Content Type ◽  
Filling Time ◽  
Underfill Flow

Purpose The purpose of the study is to investigate the spatial aspects of underfill flow during the flip-chip encapsulation process, for instance, meniscus evolution and contact line jump (CLJ). Furthermore, a spatial-based void formation mechanism during the underfill flow was formulated. Design/methodology/approach The meniscus evolution of underfill fluid subtended between the bump array and the CLJ phenomenon were visualized numerically using the micro-mesh unit cell approach. Additionally, the meniscus evolution and CLJ phenomenon were modelled analytically based on the formulation of capillary physics. Meanwhile, the mechanism of void formation was explained numerically and analytically. Findings Both the proposed analytical and current numerical findings achieved great consensus and were well-validated experimentally. The variation effects of bump pitch on the spatial aspects were analyzed and found that the meniscus arc radius and filling distance increase with the pitch, while the subtended angle of meniscus arc is invariant with the pitch size. For larger pitch, the jump occurs further away from the bump entrance and takes longer time to attain the equilibrium meniscus. This inferred that the concavity of meniscus arc was influenced by the bump pitch. On the voiding mechanism, air void was formed from the air entrapment because of the fluid-bump interaction. Smaller voids tend to merge into a bigger void through necking and, subsequently, propagate along the underfill flow. Practical implications The microscopic spatial analysis of underfill flow would explain fundamentally how the bump design will affect the macroscopic filling time. This not only provides alternative visualization tool to analyze flow pattern in the industry but also enables the development of accurate analytical filling time model. Moreover, the void formation mechanism gave substantial insights to understand the root causes of void defects and allow possible solutions to be formulated to tackle this issue. Additionally, the microfluidics sector could also benefit from these spatial analysis insights. Originality/value Spatial analysis on underfill flow is scarcely conducted, as the past research studies mainly emphasized on the temporal aspects. Additionally, this work presented a new mechanism on the void formation based on the fluid-bump interaction, in which the formation and propagation of micro-voids were numerically visualized for the first time. The findings from current work provided fundamental information on the flow interaction between underfill fluid and solder bump to the package designers for optimization work and process enhancement.

Regional Segregation With Spatial Considerations-Based Analytical Filling Time Model for Non-Newtonian Power-Law Underfill Fluid in Flip-Chip Encapsulation

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Fei Chong Ng ◽  
Aizat Abas ◽  
M. Z. Abdullah
Keyword(s):  
Power Law ◽  
Flip Chip ◽  
Current Model ◽  
Process Time ◽  
Time Model ◽  
Package Design ◽  
Absolute Value ◽  
Filling Time ◽  
Underfill Flow ◽  
Encapsulation Process

Abstract This paper presents a new analytical filling time model to predict the flow of non-Newtonian underfill fluid during flip-chip encapsulation process. The current model is formulated based on the regional segregation approach, instead of the conventional porous media approximation. In this approach, the filling times were computed separately at different filling stages, before being summed up till the required filling distance. The non-Newtonian property of underfill fluid is modeled using the conventional power-law constitutive equation. Additionally, the spatial aspects of the underfill flow were incorporated into the present analysis. For instance, the evolution of underfill menisci from convex to concave was analytically developed and the contact line jump (CLJ) criterion was improved using minimal flow assumption. Upon validated with three distinct past underfill experiments, the current analytical model is found to have the best performance as it predicted the filling times with the least discrepancy among other existing filling time models. Quantitatively, the discrepancies were averagely reduced by an absolute value of at least 8.68% and 4.90%, respectively, for the first two set of validation studies. Generally, this model is particularly useful in manufacturing lines to estimate the process time of flip-chip underfill, as well as for the optimizations of process and package design.

scholarly journals Analysis of Leakage Model of All-Metal Screw Pump

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Heng Zhang ◽  
Xiaodong Wu ◽  
Yongsheng An
Keyword(s):  
Inertia Force ◽  
Fluid Inertia ◽  
Breakdown Pressure ◽  
Screw Pump ◽  
Leakage Model ◽  
Annular Gap ◽  
Gap Flow ◽  
Petroleum Equipment ◽  
Gap Height ◽  
Main Factor

Traditional rubber screw pumps use an interference method to engage. When the pressure is less than the breakdown pressure of the pump, there is no leakage in the pump. The all-metal screw pump stator and rotor are made of metal, and the stator and rotor adopt a gap-fitting engagement method, so even when the pump is working normally, the leakage is objective. Based on the concentric annular gap flow, the pressure drop leakage caused by the fluid inertia force is fully considered, and the calculation formula of the leakage of the all-metal screw pump is studied from the three aspects of transverse leakage, longitudinal leakage, and oblique leakage. This model was experimentally verified by a commercial all-metal screw pump produced by Shihong Petroleum Equipment Company. The model results show that the leakage of the all-metal screw pump is mainly affected by the structure parameters of the pump itself and the density of the pumped fluid, and the gap height is the main factor affecting the leakage.

A Model for Underfill Viscous Flow Considering the Resistance Induced by Solder Bumps

2004 ◽  
Vol 126 (2) ◽  
pp. 186-194 ◽  
Author(s):  
Chyi-Lang Lai ◽  
Wen-Bin Young
Keyword(s):  
Flip Chip ◽  
External Pressure ◽  
Good Prediction ◽  
Parallel Plates ◽  
Rectangular Array ◽  
Chip Technology ◽  
Solder Bumps ◽  
Proposed Model ◽  
Filling Time ◽  
Underfill Flow

During the underfill process, polymers driven by either capillary force or external pressure are filled at a low speed between the chip and substrate. Current methods treated the flow in the chip cavity as a laminar flow between parallel plates, which ignored the resistance induced by the solder bumps or other obstructions. In this study, the filling flow between solder bumps was simulated by a flow through a porous media. By using the superposition of flows through parallel plates and series of rectangular ducts, permeability of the underfill flow was fully characterized by the geometric arrangement of solder bumps and flat chips. The flow resistances caused by adjacent bumps were represented in its permeability. The model proposed in this study could provide a numerical approach to approximate and simulate the undefill process for flip-chip technology. Although the proposed model is applicable for any geometric arrangement of solder bumps, rectangular-array of solder bumps layout was used first for comparison with experimental results of other article. Comparisons of the flow-front shapes and filling time with the experimental data indicated that the flow simulation obtained from the proposed model gave a good prediction for the underfill flow.

Integrating the analytic network process (ANP) and the driving force‐pressure‐state‐impact‐ responses (DPSIR) model for the sustainability assessment of territorial transformations

2010 ◽  
Vol 21 (5) ◽  
pp. 618-644 ◽  
Author(s):  
Marta Bottero ◽  
Valentina Ferretti
Keyword(s):  
Driving Force ◽  
Sustainability Assessment ◽  
Real Estate Market ◽  
Assessment Model ◽  
Dpsir Framework ◽  
Content Type ◽  
Network Process ◽  
Impact Responses ◽  
Pressure State ◽  
Force Pressure

PurposeThe paper, which is based on an integrated approach that is able to aid the comprehension of complex phenomena, aims to investigate innovative models and tools in the field of sustainability assessment of territorial transformations. The model has been applied to a real case study related to the choice of alternative projects for the requalification of a downgraded urban area in Turin (Italy).Design/methodology/approachThe work proposes the use of a comprehensive key environmental indicator framework and multi‐criteria analysis to evaluate the sustainability of different strategies. The evaluation has been performed through the application of the analytical network process (ANP) and by means of a set of indicators, which have been arranged according to the Driving Force‐Pressure‐State‐Impact‐Responses (DPSIR) framework. The assessment model provides priority lists of the importance of the considered indicators and alternatives. All the analysis elements are modelled with the ANP, taking into consideration the interconnections between the indicators and their respective cumulative importance.FindingsAccording to the aim of the paper, the most important element in the performed analysis refers to the variation of the well‐being of the population, followed by the changes in the accessibility and attractiveness of the area, then by the effects on the real estate market and the presence of new cycle tracks.Originality/valueThe work is the first study at a national level and one of the first applications at an international level in research concerning the use of the DPSIR framework integrated with an ANP analysis.

Principle Analyzing and Structure Designing for Driving and Timing of Fluid Medium Pressure Difference Pipeline Robot

2011 ◽  
Vol 211-212 ◽  
pp. 530-534
Author(s):  
Yu Feng Zhang ◽  
Sheng Yuan Jiang ◽  
Xue Wen Zhang
Keyword(s):  
Pressure Difference ◽  
Driving Force ◽  
Pipe Wall ◽  
Flowing Fluid ◽  
Fluid Medium ◽  
Friction Resistance ◽  
Medium Pressure ◽  
The Press ◽  
Push Forward ◽  
Pipeline Robot

A pipeline robot is brought forward using the energy of fluid medium transmitting within the pipeline to perform the driving and timing. The robot is soaking in the pipeline full of flowing fluid medium and getting the driving force from the press and velocity energy of medium itself to push forward it. It is discovered during the research that robot need to overcome the gravity and influence of the friction resistance with the pipe wall while driving alone, so for the different mediums and applying situation the robot required to velocity adjustment automatically. According to the condition of the hydrodynamics within the pipe and designing in reason for the size and configuration of the robot, a velocity controlling device is worked out and realized its velocity adjustable.

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