Query: “Cure Shrinkage Analysis of Epoxy Molding Compound,”

Candidate papers:

abstract: BGA (ball grid array) one of the structures used for semiconductor packages, involves a laminated structure. BGA inevitably involves significant warpage, owing to differences in shrinkage among constituent materials. The extent of warpage is governed by total shrinkage cure shrinkage thermal shrinkage of the epoxy molding compound that encapsulates the IC chip. In particular, the cure shrinkage exerts great influence on warpage. Cure shrinkage has been understood as the decrease in free volume at the time of curing. However, the cure shrinkage rate cannot be sufficiently explained by the free volume of the cured epoxy resin. We have developed an evaluation method based on the epoxy group reaction ratio, and have eventually confirmed that cure shrinkage depends on the reaction ratio of the epoxy group after curing, and on epoxy group density.
author_names: Ken Oota

Masumi Saka
title: Cure shrinkage analysis of epoxy molding compound
year: 2001

abstract: Finite element analysis (FEA) is widely used throughout the electronics industry to understand the thermal and thermo mechanical behavior of electronic packages and interconnect during their manufacture and lifetime. After encapsulation, thermo mechanical stress builds up within the package due to temperature coefficient of expansion mismatch between the respective materials within the package as it cools to room temperature. Due to the complexity and time consuming of the calculation, it is almost impossible for industry to carry out the numerical simulation using viscoelastic property which is the most close to the real material property of polymer material. However, FEA using temperature dependent elastic property, temperature dependent thermal expansion coefficient and accurate chemical cure shrinkage can help to improve the accuracy on the stress and warpage prediction. This study has developed an evaluation method for the chemical cure shrinkage based on the measurement of the warpage of bimaterial model. The results show that FEA simulations without chemical cure shrinkage fail to accurately predict the package warpage. On the other hand. FEA simulations with chemical cure shrinkage is outlined which show fair agreement with experimental measurements of package warpage over a range of temperatures.
author_names: Guojun Hu

Spencer Chew

B Singh
title: Cure Shrinkage Analysis of Green Epoxy Molding Compound with Application to Warpage Analysis in a Plastic IC Package
venue: 2007 8th International Conference on Electronic Packaging Technology
year: 2007

abstract: After encapsulation, thermomechanical deformation builds up within the electronic packages due to the temperature coefficient of expansion mismatch between the respective materials within the package as it cools to room temperature. At the same time, the chemical cure shrinkage exerts important influence on the total deformation. Due to the complexity and time consuming of the calculation, it is almost impossible for an industry to carry out the numerical simulation using viscoelastic property, which is the most close to the real material property of polymer material. However, finite element analysis (FEA) using temperature dependent elastic property, temperature dependent thermal expansion coefficient, and accurate chemical cure shrinkage can help to improve the accuracy on the stress and warpage prediction. This study has developed an evaluation method for the chemical cure shrinkage based on the measurement of the warpage of bimaterial model. The results show that FEA simulations without chemical cure shrinkage fail to accurately predict the package warpage. On the other hand, FEA simulations with chemical cure shrinkage are outlined, which show fair agreement with experimental measurements of package warpage over a range of temperatures. Furthermore, this study has evaluated the effect of silica filler percentage on the chemical cure shrinkage and confirmed that the chemical cure shrinkage decreases with the increase in silica filler percentage.
author_names: Guojun Hu

Jing-en Luan

Spencer Chew
title: Characterization of Chemical Cure Shrinkage of Epoxy Molding Compound With Application to Warpage Analysis
year: 2009

abstract: One of the most prominent failure modes in microelectronics devices is the delamination of epoxy materials (adhesives, molding compounds) The thermal mismatch at the interface between materials leads to stresses that build up during processing steps at different temperatures and in the following thermal cycling through use of the device or reliability testing. These stresses are well understood and are commonly investigated by finite element modeling. Epoxy molding compounds undergo a chemical reaction during processing called curing. Here the two components epoxy and hardener react to form a 3D network giving the molding compound its final material properties. During this process, the volume of the compound decreases, a phenomenon called cure shrinkage. The shrinkage itself can be experimentally determined, e.g. using volumetric measurements. However, due to relaxation processes that take place at higher temperatures and the changing thermal mechanical properties during the curing process, the stresses that build up due to chemical shrinkage are more complex to consider. In this work, the mechanically relevant cure shrinkage was investigated by a combination of experiments and finite clement simulations. Samples of molding compound on Cu leadframe material were manufactured using standard procedures. Thermal expansion experiments were performed at several temperatures recording the warpage of the samples. To extract the mechanically relevant shrinkage FE simulations were performed mimicking the process temperatures. The resulting data was evaluated and discussed with respect to: qualitative behaviour for five different molding compounds; qualitative agreement between simulation and experiment; error margins of simulation results with respect to material properties input data; and error margins of experimental data due to processing variations and experimental setup.
author_names: Marcelo Fraga de Sousa

Ole Holck

Tanja Braun

Jorg Bauer

Hans Walter

Olaf Wittler

Klaus-D Lang
title: Mechanically relevant chemical shrinkage of epoxy molding compounds
venue: 2013 14th International Conference on Thermal, Mechanical and Multi Physics Simulation and Experiments in Microelectronics and Microsystems (EuroSimE)
year: 2013

abstract: In this paper, both isothermal and dynamic differential scanning calorimetry (DSC) are employed to characterize the thermal properties of two commercial epoxy molding compounds designated as EMC A and EMC B respectively. In dynamic curing, the heat flow of uncured powder samples weighting 10+ 0.5 mg are measured at the heating rates of 5, 10 and 15 degC /min from room temperature to 220 degC. The isothermal curing tests are performed under the constant temperatures of 130, 140 and 150 degC for 30 min. The experimental results show that compared with EMC B, EMC A has smaller average curing reaction enthalpy and activation energy showing a better moldability. The parameters of autocatalytic Kamal equation for these two EMCs are obtained by the isothermal curing tests and the curing kinetic model exhibits good agreement with the experimental data generally.
author_names: Shen Hui-qiang

Qin Fei

Xia Guofeng

Bie Xiaorui
title: Characterization of thermal and curing behaviors of epoxy molding compounds
venue: 2014 15th International Conference on Electronic Packaging Technology
year: 2014

abstract: Warpage is an important issue for IC packages after molding. Due to laminated structure of IC packages, significant warpage occurs owing to differences in shrinkage among constituent materials. Thermal shrinkage is usually considered as the main cause for IC warpage. However, cure induced warpage is also important during the molding process. Analysis without considering cure induced shrinkage can not predict the amount of warpage well. In this paper, TSOP LOC54L package product, which is manufactured by ChipMos Corporation, is used as the simulation model. The P V T C (Pressure, Volume, Temperature, and Conversion) relation and CTE (Coefficients of Thermal Expansion) of an encapsulation material are used to predict the amount of warpage and experimentally verifying the results in this study. By comparing the simulations with the experiments, the preliminary results of the study indicate this approach is capable of estimating warpage in IC packages without prohibitive computational effort.Copyright (c) 2005 by ASME
author_names: Shiang-Yu Teng

Sheng-Jye Hwang
title: Simulation of Warpage Considering Both Thermal and Cure Induced Shrinkage During Molding in IC Packaging
year: 2005

abstract: The rubbery (equilibrium) modulus of thermosetting polymers dominates the mechanical behavior at elevated temperature or at long times. It also plays a major role in the residual stress induced during the curing process. In this paper, ai extensive study on the cure dependent rubbery moduli of silica spheres filled epoxy resin is carried out both experimentally and theoretically. DSC measurements were used for characterization of the cure kinetics and T/sub g/ conversion relationship. Low frequency DMA was used to measure the rubbery modulus build up during cure. A model based on scaling analysis was applied to describe the evolution of the rubbery shear modulus. A similar model was proposed for the cure dependent rubbery bulk modulus. Models from the theory of particulate filled composites were used to predict the rubbery moduli of the molding compound with different filler concentration. The effect of the filler percentage on the rubbery moduli was discussed.
author_names: D G Yang

Kaspar M B Jansen

Leo J Ernst

G -Q Zhang

H J L Bressers

J H J Janssen
title: Measuring and modeling the cure dependent rubbery moduli of epoxy molding compound
venue: EuroSimE 2005. Proceedings of the 6th International Conference on Thermal, Mechanial and Multi Physics Simulation and Experiments in Micro Electronics and Micro Systems, 2005.
year: 2005

abstract: This paper is to study the warpage impact of filler content and special additives on BGA packages. The special additives have significant impact on the warpage. The additive A has great influence on the warpage at different temperature; the warpage will flatten when more additive A is added. From the warpage study of single unit from room temperature to 260degC, all the warpage is in 50um when additive A is about 1% The additive A can flatten the warpage of the package and keep the warpage at same level even with different silicon occupation in the package. The filler content shows great impact on the warpage by control the shrinkage after cured, the lower shrinkage; the package will move to more crying.
author_names: Wei Tan

Fang Zhou

Xingming Cheng

D H Ding

Juan Wu
title: The warpage control method in epoxy molding compound
venue: 2009 International Conference on Electronic Packaging Technology High Density Packaging
year: 2009

abstract: The isothermal and isobaric volume shrinkage is measured by a single plunger type dilatometer for epoxy molding compound (EMC) This device has been found suitable for measuring volume change of thermosetting materials such as commercial EMC under isothermal and isobaric conditions. Moreover, the degree of cure (conversion) was determined by a differential scanning calorimetry (DSC) Combining volume change and conversion, a mathematic pressure volume temperature cure (P V T C) model is proposed to describe the relationship between volume shrinkage, pressure, temperature and conversion. The P V T C equation can be simply expressed as VS(P,T,C)=F/sub 1/(P,T)/spl middot/C/sup F2(P,T) This equation can well describe historical profiles of volume shrinkage under specified isothermal and isobaric states. From the predicted results, volume shrinkage under different pressure levels in any specified temperature can be approximated as and it obeys the principle of linearity. With the help of this model, together with three dimensional mold filling simulation, engineers will be able to predict warpage and residual stresses for a package after molding.
author_names: Sheng-Jye Hwang

Yi-San Chang
title: P V T C equation for epoxy molding compound
venue: IEEE Transactions on Components and Packaging Technologies
year: 2006

abstract: The cure process of epoxy prepreg used as composite pipe joints was studied by means of differential scanning calorimetry (DSC) Bohlin Rheometer and other techniques. Isothermal DSC measurements were conducted between 110 and 220 C, at 10 C intervals. The results show that the complete cure reaction could be achieved at 220 C. The isothermal cure process was simulated with the four parameter autocatalytic model. Except in the late stage of cure reaction, the model agrees well with the experimental data, especially at high temperatures. To account for the effect of diffusion on the cure rate, a diffusion factor was introduced into the model. The modified model greatly improved the predicated data at the late stage of cure reaction. The dynamic cure process was different from the isothermal cure process in that it is composed of two cure reactions. For dynamic cure process, a three parameter autocatalytic model was used. The parameters in the model were determined by two methods. One was based on Kissinger and Ozawa approach. The whole curing process was modeled with two reactions. Another method was based on Borchardt and Daniels kinetic approach with the whole curing process modeled with one reaction. The fitted results by the first and second methods agreed well with the experimental values in the late and early cure stages, respectively. Rheological properties of epoxy prepreg are closely related to the cure process. With the development of the cure reaction, gelation occurs and epoxy prepreg becomes difficult to process. As the temperature increases, the gel time decreases. Viscosity profiles were described by different models. Except for the first and nth order viscosity
author_names: Liangfeng Sun
title: Thermal rheological analysis of cure process of epoxy prepreg
year: 2002