Underflow Process for Direct-Chip-Attachment Packaging

1998 ◽  
Vol 515 ◽  
Author(s):  
P. C. Li ◽  
G. L. Lehmann ◽  
J. Cascio ◽  
T. Driscoll ◽  
Y. J. Huang ◽  
...  
Keyword(s):  
Flip Chip ◽  
Capillary Flow ◽  
Flow Behavior ◽  
Complex Function ◽  
Plane Channel ◽  
Flow Process ◽  
Wetting Properties ◽  
Solder Bumps ◽  
Flip Chip Packaging ◽  
Measured Flow

ABSTRACTIn flip-chip packaging an underfill mixture is placed into the chip-to-substrate standoff created by the array of solder bumps, using a capillary flow process. The flow behavior is a complex function of the mixture properties, the wetting properties, and the flow geometry. This paper reports on the use of a plane channel capillary flow to characterize underfill materials. The measured flow behavior provides evidence that both the contact angle (θ) and the suspension viscosity (μapp) vary with time under the Influence of changing flow conditions. This nonlinear fluid behavior is modeled for the flow of both model suspensions and commercial underfill materials using an extended Washburn model.

Investigation of the Flow Behavior of Participate Filled Fluids

1996 ◽  
Vol 445 ◽  
Author(s):  
T. E. Driscoll ◽  
P. C. Li ◽  
G. L. Lehmann ◽  
E. J. Cotts
Keyword(s):  
Large Particle ◽  
Capillary Flow ◽  
Flow Behavior ◽  
Solid Particles ◽  
Spherical Particles ◽  
Liquid Density ◽  
High Concentration ◽  
Flow Process ◽  
Fluid Mixture ◽  
Underfill Flow

AbstractUnderfill encapsulants, used in direct‐chip‐attachment (DCA) packaging of electronics, consist of an epoxy resin in which a high concentration of solid particles are suspended. As a fluid mixture key features of these encapsulants are their relatively large particle sizes and large particle‐to‐liquid density ratios (ρs/ρ0 ?2.4). Experiments have been conducted to characterize the flow behavior of model mixtures of negatively buoyant, spherical particles suspended in Newtonian liquids. Capillary flow in a parallel surface channel is used to simulate the underfill flow process. The effects of varying the channel spacing, particle size and liquid carrier are reported here. The flow behavior is contrasted with a linear fluid, effective viscosity model. Particle settling appears to be linked to the more complex behavior observed in both our model suspensions and measurements using an actual commercial encapsulant.

A Comparison of Oil-Water Flow and Oil-Gas Flow in Capillary Model

2012 ◽  
Author(s):  
Yihe Zhang ◽  
Liming Dai
Keyword(s):  
Pressure Drop ◽  
Liquid Film ◽  
Gas Flow ◽  
Capillary Flow ◽  
Flow Behavior ◽  
Thin Liquid Film ◽  
Flow Process ◽  
Capillary Model ◽  
Oil Water ◽  
Oil Gas

A capillary model is employed to study the slug flow behavior in pore structure. Oil-water system and oil-gas system are investigated in the experiments. During the flow process, it is observed that the wetting phase liquid will generate a thin liquid film on the inner surface of the tube wall, and the liquid film plays an important role in capillary flow. At the meantime, the pressure drop across the tube is recorded during the experiment, result shows that the pressure drop magnitude is proportional to the oil slug length, while it is not significantly affected by the liquid injecting velocity.

A Surface Energy Approach to Developing an Analytical Model for the Underfill Flow Process in Flip-Chip Packaging

2021 ◽  
Author(s):  
X.J. Yao ◽  
Weijie Jiang ◽  
Jiahui Yang ◽  
Junjie Fang ◽  
W.J. (Chris) Zhang
Keyword(s):  
Surface Energy ◽  
Analytical Model ◽  
Flip Chip ◽  
Cfd Simulation ◽  
Flow Front ◽  
New Approach ◽  
Solder Bumps ◽  
Regular Triangle ◽  
Filling Time ◽  
Flip Chip Packaging

Abstract This paper presents a new approach to formulating an analytical model for the underfill process in flip-chip packaging to predict the flow front and the filling time. The new approach is based on the concept of surface energy along with the energy conservation principle. This approach avoids the need of modeling the flow path to predict the flow front and the filling time and thus it is suitable to different configurations of solder bumps, including different shapes and arrangements of solder bumps in flip-chip packaging. An experiment along with the CFD simulation was performed based on a proprietarily developed testbed to verify the effectiveness of this approach. Both the experimental and simulation results show that the proposed approach along with its model is accurate for flip-chip packages with different configurations besides the configuration of a regular triangle arrangement of solder bumps and a spherical shape of the solder bump.

Effect of Warpage of Flip Chip Packages Due to the Underfill Encapsulating Process on Interconnect Reliability

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
Satoru Katsurayama ◽  
Hironori Tohmyoh
Keyword(s):  
Thermal Cycling ◽  
Flip Chip ◽  
Capillary Flow ◽  
Curing Process ◽  
Assembly Process ◽  
Test Circuit ◽  
Interconnect Reliability ◽  
Flip Chip Packaging ◽  
Underfill Material

In flip chip packages, it is common practice for interconnects to be encapsulated with a liquid underfill material. This paper describes the effects of different underfill processes, i.e., the conventional capillary-flow underfill and two no-flow underfill processes, on flip chip packaging. The warpage of the package was examined, and the value of this during three different underfill encapsulating processes was measured. In addition, the interconnect reliability of the bump bonds after thermal-cycling was evaluated using a test circuit. The warpage of the package before curing varied depending on the assembly process, but that after curing was almost the same for all the processes studied. It was found that the interconnect reliability is closely related to the differences in the warpage arising from the assembly process, and that the smaller change in warpage introduced by the curing process gave a higher interconnect reliability for the bump bonds. Based on these findings, lower curing temperatures are considered to be more effective for improving the mountability of the package and the interconnect reliability.

Numerical simulation of conventional capillary flow and no-flow underfill in flip-chip packaging

2008 ◽  
Vol 37 (5) ◽  
pp. 520-523 ◽  
Author(s):  
Tomohisa Hashimoto ◽  
Tanifuji Shin-ichiro ◽  
Koji Morinishi ◽  
Nobuyuki Satofuka
Keyword(s):  
Numerical Simulation ◽  
Flip Chip ◽  
Capillary Flow ◽  
Flip Chip Packaging

A Further Study on the Analytical Model for the Permeability in Flip-Chip Packaging

2018 ◽  
Vol 140 (1) ◽  
Author(s):  
X. J. Yao ◽  
J. J. Fang ◽  
Wenjun Zhang
Keyword(s):  
Porous Medium ◽  
Analytical Model ◽  
Flip Chip ◽  
Flow Behavior ◽  
Cross Sectional Area ◽  
Sectional Area ◽  
Cross Sectional ◽  
Proposed Model ◽  
Flip Chip Packaging ◽  
Pore Permeability

The notion of permeability is very important in understanding and modeling the flow behavior of fluids in a special type of porous medium (i.e., the underfill flow in flip-chip packaging). This paper presents a new concept regarding permeability in a porous medium, namely two types of permeability: superficial permeability (with consideration of both the pore cross-sectional area and the solid matrix cross-sectional area) and pore permeability (with consideration of the pore cross-sectional area only). Subsequently, the paper proposes an analytical model (i.e., equation) for the pore permeability and superficial permeability of an underfill porous medium in a flip-chip packaging, respectively. The proposed model along with several similar models in literature is compared with a reliable numerical model developed with the computational fluid dynamics (CFD) technique, and the result of the comparison shows that the proposed model for permeability is the most accurate one among all the analytical models in literature. The main contributions of the paper are as follows: (1) the provision of a more accurate analytical model for the permeability of an underfill porous medium in flip-chip packaging, (2) the finding of two types of permeability depending on how the cross-sectional area is taken, and (3) the correction of an error in the others' model in literature.

The Use of Precision Selective Area Milling for Failure Analysis of Flip-Chip Packages

2002 ◽  
Author(s):  
George F. Gaut
Keyword(s):  
Failure Analysis ◽  
Flip Chip ◽  
Solder Bump ◽  
Selective Area ◽  
Fill Material ◽  
Solder Bumps ◽  
Time Required

Abstract Access to the solder bump and under-fill material of flip-chip devices has presented a new problem for failure analysts. The under-fill and solder bumps have also added a new source for failure causes. A new tool has become available that can reduce the time required to analyze this area of a flip-chip package. By using precision selective area milling it is possible to remove material (die or PCB) that will allow other tools to expose the source of the failure.

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