Predicted Bow of Plastic Packages Due to the Nonuniform Through-Thickness Distribution of Temperature

1992 ◽  
Vol 114 (3) ◽  
pp. 329-335 ◽  
Author(s):  
E. Suhir ◽  
L. T. Manzione
Keyword(s):  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Thickness Distribution ◽  
Edge Length ◽  
Nonuniform Distribution ◽  
Temperature Gradients ◽  
Molding Compound ◽  
Thermally Induced ◽  
Plastic Packages ◽  
Selection Of

Warpage of molded plastic packages becomes a more serious consideration as their size increases. In this analysis we develop an analytical stress model for the evaluation of the thermally induced bow of large plastic packages due to the nonuniform distribution of temperature in the through-thickness direction after the molding cycle. This model enables one to determine the effects of the package geometry and material properties on the induced warpage. We show that the bow of the package is proportional to the edge length squared, and is inversely proportional to the package thickness. We show also that the coefficient of thermal expansion (contraction) of the molding compound has a strong effect on the bow, while its Young’s modulus has a small effect. The performed experimental work has indicated that different procedures for handling the packages after molding result in different temperature gradients leading to different bows. The obtained results are useful in the selection of the appropriate molding compound and rational physical design of thick plastic packages, as well as in the optimization of the handling procedures after molding and post-curing.

Investigation of Transfer Mold Process Effects on Semiconductor Package Warpage

2009 ◽  
Author(s):  
Jason M. Brand ◽  
Myung J. Yim ◽  
Ravi Kumar
Keyword(s):  
Solder Joint ◽  
Material Property ◽  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Filler Concentration ◽  
Packaging System ◽  
Property Variation ◽  
Molding Compound ◽  
Fea Model ◽  
Die Attach

In recent years, Package on Package (PoP) is increasingly used for high density package solutions. Generally the top package is a stacked memory packaging system connected to a bottom logic packaging system via solder joint: this is representative of PoP configurations. To guarantee the assembly yield and reliability of the solder joint between the top package and bottom package, mechanical compliance between these two packages is crucial during package stacking. Henceforth package warpage needs to be understood and controlled to meet the assembly yield targets. The complexity of the package configuration increases by thinner package thickness, higher number of stacking dies and large package size. Controlling the warpage within the target requirement is very challenging, especially when the material behaviors of substrate, die, molding compound and die attach film are different and also changing as a function of temperature. Certainly, the material properties of key components in top PoP package plays a crucial role in warpage performance. Among various material properties, the chemical cure shrinkage, coefficient of thermal expansion and storage modulus for the molding compounds are determining factors on the temperature dependant warpage control of top PoP package. Warpage variation still exists within parts processed at the same time mainly due to slight material property variation. In this paper, the cause of the warpage variation is investigated. The main cause was found to be filler migration effect in narrow gaps with in the stacked die package during the mold process, which resulted in different filler concentration and distribution, and finally different local molding compound material property among the package unit location in the substrate strip. The findings indicate that mold pressure is not a major modulator of warpage, while filler distribution can dramatically alter the warpage behavior. FEA model results and warpage data are presented to validate the filler migration phenomena and warpage behavior impact. The findings and results provide some clues and design/process guideline for warpage control in Top PoP package, which influence the PoP assembly yield and reliability.

Warpage Analysis of FBGA (Fine Ball Grid Array) Package by the Altered EMC (Epoxy Molding Compound) Filler Contents

2006 ◽  
Vol 306-308 ◽  
pp. 625-630 ◽  
Author(s):  
Yong Tae Park ◽  
Yoo Kyoung Whang ◽  
Joon Ki Hong ◽  
Kwang Yoo Byeon
Keyword(s):  
Numerical Analysis ◽  
Material Properties ◽  
Filler Content ◽  
Coefficient Of Thermal Expansion ◽  
Ball Grid Array ◽  
Structure Design ◽  
Actual Measurement ◽  
Molding Compound ◽  
Semiconductor Packaging ◽  
Adhesive Materials

In a semiconductor packaging process, the warpage greatly has influenced the reliability of the package as well as the workability. The strip warpage in FBGA package result from the structure of constitutes and the thermal mismatch by the mechanical or thermal properties such as CTE (Coefficient of Thermal Expansion) and Modulus of EMC, substrate, chip and adhesive materials. Therefore, the optimization of material properties and the package structure design has been needed by the numerical analysis. EMC used as one of the package constituents has a decisive effect on the trend of warpage, and the filler content is dominant in the EMC property. In this research, firstly the effect of the filler contents is evaluated in the warpage of FBGA package and the numerical analysis is performed with the high temperature – material properties to deal with the warpage under the actual measurement value.

Numerical and Experimental Study of Interface Delamination in Flip Chip BGA Package

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Hu Guojun ◽  
Andrew A. O. Tay ◽  
Luan Jing-En ◽  
Ma Yiyi
Keyword(s):  
Thermal Expansion ◽  
Material Properties ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Element Analysis ◽  
Epoxy Molding Compound ◽  
Molding Compound ◽  
Interface Delamination ◽  
Underfill Material ◽  
Die Thickness

The reliability of the flip chip package is strongly influenced by underfill, which has a much higher coefficient of thermal expansion (CTE) compared with other packaging materials and leads to large thermomechanical stresses developed during the assembly processes. Thermal expansion mismatch between different materials causes interface delamination between epoxy molding compound and silicon die as well as interface delamination between underfill and silicon die. The main objective of this study is to investigate the effects of underfill material properties, fillet height, and silicon die thickness on the interface delamination between epoxy molding compound and silicon die during a lead-free solder reflow process based on the modified virtual crack closure method. Based on finite element analysis and experiment study, it can be concluded that the energy release rates at reflow temperature are the suitable criteria for the estimation of interface delamination. Furthermore, it is found that underfill material properties (elastic modulus, CTE, and chemical cure shrinkage), fillet height, and silicon die thickness can be optimized to reduce the risk of interface delamination between epoxy molding compound and silicon die in the flip chip ball grid array package.

Application of an Epoxy Cap in a Flip-Chip Package Design

1989 ◽  
Vol 111 (1) ◽  
pp. 16-20 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Thermal Expansion ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Preliminary Test ◽  
Elastic Stability ◽  
Thermally Induced ◽  
Package Design ◽  
Silicone Gels ◽  
Low Modulus ◽  
Supporting Frame

In order to combine the merits of epoxies, which provide good environmental and mechanical protection, and the merits of silicone gels, resulting in low stresses, one can use an encapsulation version, where a low modulus gel is utilized as a major encapsulant, while epoxy is applied as a protecting cap. Such an encapsulation version is currently under consideration, parallel with a metal cap version, for the Advanced VLSI package design which is being developed at AT&T Bell Laboratories. We recommend that the coefficient of thermal expansion for the epoxy be somewhat smaller than the coefficient of thermal expansion for the supporting frame. In this case the thermally induced displacements would result in a desirable tightness in the cap/frame interface. This paper is aimed at the assessment of stresses, which could arise in the supporting frame and in the epoxy cap at low temperatures. Also, the elastic stability of the cap, subjected to compression, is evaluated. The calculations were executed for the Advanced VLSI package design and for a Solder Test Vehicle (STV), which is currently used to obtain preliminary information regarding the performance of the candidate encapsulants. It is concluded that in order to avoid buckling of the cap, the latter should not be thinner than 15 mils (0.40 mm) in the case of VLSI package design and than 17.5 mils (0.45 mm) in the case of STV. At the same time, the thickness of the cap should not be greater than necessary, both for smaller stresses in the cap and for sufficient undercap space, required for wirebond encapsulation. The obtained formulas enable one to evaluate the actual and the buckling stresses. Preliminary test data, obtained by using STV samples, confirmed the feasibility of the application of an epoxy cap in a flip-chip package design.

A new representation for a robot grasping quality measure

Robotica ◽  
1995 ◽  
Vol 13 (3) ◽  
pp. 287-295 ◽  
Author(s):  
Venugopal K. Varma ◽  
Uri Tasch
Keyword(s):  
Objective Function ◽  
Material Properties ◽  
Graphical Representation ◽  
Contact Forces ◽  
Geometric Constraints ◽  
Objective Functions ◽  
Finger Force ◽  
Finger Forces ◽  
Robot Grasping ◽  
Selection Of

SummaryWhen an object is held by a multi-fingered hand, the values of the contact forces can be multivalued. An objective function, when used in conjunction with the frictional and geometric constraints of the grasp, can however, give a unique set of finger force values. The selection of the objective function in determining the finger forces is dependent on the type of grasp required, the material properties of the object, and the limitations of the röbot fingers. In this paper several optimization functions are studied and their merits highlighted. The paper introduces a graphical representation of the finger force values and the objective functions that enable one to select and compare various grasping configurations. The impending motion of the object at different torque and finger force values are determined by observing the normalized coefficient of friction plots.

Warpage Simulation During Fan-Out Wafer-Level Packaging Process with Uncertainty of Material Properties

2021 ◽  
Vol 21 (5) ◽  
pp. 2987-2991
Author(s):  
Geumtaek Kim ◽  
Daeil Kwon
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Input Output ◽  
Wafer Level ◽  
High Input ◽  
Element Analysis ◽  
Packaging Process ◽  
Wafer Level Packaging

Along with the reduction in semiconductor chip size and enhanced performance of electronic devices, high input/output density is a desired factor in the electronics industry. To satisfy the high input/output density, fan-out wafer-level packaging has attracted significant attention. While fan-out wafer-level packaging has several advantages, such as lower thickness and better thermal resistance, warpage is one of the major challenges of the fan-out wafer-level packaging process to be minimized. There have been many studies investigating the effects of material properties and package design on warpage using finite element analysis. Current warpage simulations using finite element analysis have been routinely conducted with deterministic input parameters, although the parameter values are uncertain from the manufacturing point of view. This assumption may lead to a gap between the simulation and the field results. This paper presents an uncertainty analysis of wafer warpage in fan-out wafer-level packaging by using finite element analysis. Coefficient of thermal expansion of silicon is considered as a parameter with uncertainty. The warpage and the von Mises stress are calculated and compared with and without uncertainty.

Development of Substrates for Through Glass Vias

2012 ◽  
Vol 2012 (DPC) ◽  
pp. 000832-000845 ◽  
Author(s):  
Aric Shorey ◽  
Scott Pollard
Keyword(s):  
Material Properties ◽  
Glass Composition ◽  
Coefficient Of Thermal Expansion ◽  
Cost Effective ◽  
High Volume ◽  
Chemical Durability ◽  
Thin Glass ◽  
Wide Range ◽  
Challenges And Opportunities ◽  
Substantial Progress

Through-substrate vias are critical for 3DS-IC integration. The choice of glass as an interposer substrate, TGV, present some interesting challenges and opportunities, making glass a compelling alternative to silicon. There are two primary challenges to begin building a precision interposer in thin glass. The first is high quality thin glass wafers (300 mm OD, thickness 0.05 to 0.10 mm, warp and TTV of 30 μm and 1 μm respectively). The second challenge is developing a process capable of providing small (5–10 μm) precision vias in a cost-effective way. “Glass” represents a large class of materials with a wide range of material properties. The first step in developing TGV is to identify the most appropriate glass composition for the application, which furthermore defines important properties such as coefficient of thermal expansion (CTE) and other mechanical properties, chemical durability and electrical properties. The manufacturing process used to develop the glass has a significant impact on quality and manufacturability. Fusion formed glass provides a solution for high volume manufacturing supply in an as-formed, ultra-thin, pristine glass manufactured to tight tolerances, and avoids the issues associated with polishing or thinning. The supply of 50 μm to 100 μm as-formed ultra-thin glass wafers can compare very favorably in cost relative to polished or thinned glass as well as thinned silicon wafer. While there are many technologies that have demonstrated vias in glass, challenges relating to via size and pitch, wafer strength and reliability remain to be resolved. However, substantial progress has been made to meet these challenges. Specific characterization data from some of these processes to demonstrate vias on the order of 10 μm diameter with a 100 μm glass thickness in alternative glass materials will be presented.

scholarly journals Material properties and structure of natural graphite sheet

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Martin Cermak ◽  
Nicolas Perez ◽  
Michael Collins ◽  
Majid Bahrami
Keyword(s):  
Material Properties ◽  
Coefficient Of Thermal Expansion ◽  
Electrical Contact ◽  
Sheet Thickness ◽  
Electronics Cooling ◽  
Forming Process ◽  
Electrical Contact Resistance ◽  
Natural Graphite ◽  
Graphite Sheet ◽  
Thermally Conductive

Abstract Natural graphite sheet (NGS) is compressible, porous, electrically and thermally conductive material that shows a potential to be used in fuel cells, flow batteries, electronics cooling systems, supercapacitors, adsorption air conditioning, and heat exchangers. We report the results of an extensive material characterization study that focuses on thermal conductivity, thermal diffusivity, electrical conductivity, coefficient of thermal expansion (CTE), compression strain, and emissivity. All the properties are density-dependent and highly anisotropic. Increasing the compression from 100 to 1080 kPa causes the through-plane thermal and electrical conductivities to increase by up to 116% and 263%, respectively. The properties are independent of the sheet thickness. Thermal and electrical contact resistance between stacked NGS is negligible at pressures 100 to 1080 kPa. In the in-plane direction, NGS follows the Wiedemann-Franz law with Lorenz number 6.6 $$\times $$ × 10$$^{-6}$$ - 6 W $$\Omega $$ Ω K$$^{-2}$$ - 2 . The in-plane CTE is low and negative (shrinkage with increasing temperature), while the through-plane CTE is high, increases with density, and reaches 33 $$\times $$ × 10$$^{-6}$$ - 6 K$$^{-1}$$ - 1 . Microscope images are used to study the structure and relate it to material properties. An easy-to-use graphical summary of the forming process and NGS properties are provided in Appendices A and B.

scholarly journals Shape-Memory Polymers for Biomedical Applications

2008 ◽  
Vol 54 ◽  
pp. 96-102 ◽  
Author(s):  
Andreas Lendlein ◽  
Marc Behl
Keyword(s):  
Shape Memory ◽  
Material Properties ◽  
Biomedical Applications ◽  
Traditional Approach ◽  
Shape Change ◽  
Shape Memory Polymers ◽  
Thermally Induced ◽  
Wide Range ◽  
Multifunctional Polymers ◽  
Suitable Process

Most polymers used in clinical applications today are materials that have been developed originally for application areas other than biomedicine. On the other side, different biomedical applications are demanding different combinations of material properties and functionalities. Compared to the intrinsic material properties, a functionality is not given by nature but result from the combination of the polymer architecture and a suitable process. Examples for functionalities that play a prominent role in the development of multifunctional polymers for medical applications are biofunctionality (e.g. cell or tissue specificity), degradability, or shape-memory functionality. In this sense, an important aim for developing multifunctional polymers is tailoring of biomaterials for specific biomedical applications. Here the traditional approach, which is designing a single new homo- or copolymer, reaches its limits. The strategy, that is applied here, is the development of polymer systems whose macroscopic properties can be tailored over a wide range by variation of molecular parameters. The Shape-memory capability of a material is its ability to trigger a predefined shape change by exposure to an external stimulus. A change in shape initiated by heat is called thermally-induced shape-memory effect. Thermally, light-, and magnetically induced shape-memory polymers will be presented, that were developed especially for minimally invasive surgery and other biomedical applications. Furthermore triple-shape polymers will be introduced, that have the capability to perform two subsequent shape changes. Thus enabling more complex movements of a polymeric material.

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