Cure shrinkage characterization and its implementation into correlation of warpage between simulation and measurement

Zhu, Wenhui; Li, Guang; Sun, Wei; Che, F.X.; Sun, A.Y.S.; Wang, C.K.; Tan, Henry; Zhao, Baozong; Chin, N.H.

doi:10.1109/esime.2007.359966

Cited by 34 publications

(15 citation statements)

References 5 publications

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“…On the other hand, zero warpage occurs at 189 °C and above this temperature a reversal of the warpage direction could be observed. Consequently the stressfree or zero warpage temperature (T z ) is shifted to higher temperatures than T m as a result of elastic cure shrinkage [13]. With a value obtained for T z , the cure shrinkage can be deduced from (3) which was found to be 10.1 % of the expected ϵ m at 15 °C as calculated via (2).…”

Section: A Measurementsmentioning

confidence: 91%

“…Although small compared to , the cure shrinkage occurring at T m is not negligible [13] and can be derived using (3), valid for molding compounds with a glass transition temperature lower than T m :…”

Section: Problem Overviewmentioning

confidence: 99%

“…On the other hand isotropic elastic properties were considered for EMC varying linearly from room temperature to T m (in accordance with EMC properties published by de Vreugd [16]). In the case of the linear isotropic thermal expansion properties of EMC, CTE EMC,1 and CTE EMC,2 were constant while the cure shrinkage was included in the model by shifting the reference temperature for the calculation of the thermal expansion of both silicon and EMC from T m to T z [13]. The value for T G used to prescribe the thermal expansion of EMC was provided by the material supplier.…”

Section: B Finite Elements Modellingmentioning

confidence: 99%

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Investigation of warpage in wafer-level Molding: Measurements and FE analysis

Farrugia

Grech

Casha

et al. 2015

2015 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS (DTIP)

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Novel 3D packaging technologies which require largearea mold embedding are being developed in order to achieve further minimization and cost reductions. Compression molding using epoxy molding compounds is one technique being considered for wafer-level encapsulation. However significant warpage in molded wafers is a critical issue which may hinder successive processes from being carried out. Cases of both symmetric (spherical) and asymmetric (cylindrical)-shaped warpage have been reported in wafer-level compression molding trials on blank wafers. This paper presents finite element models of the molded wafer, with and without embedded dies, which take into account the observed complex multi-state warpage characteristics. Molded wafer warpage measurements were carried out in order verify the applicability of the small and large deformation theories for layered plates, to deduce the cure shrinkage molding compound properties and to validate the finite element model of the molded blank wafer. The latter was used to analyze possible factors (nonplanar mold layer thickness, anisotropic wafer elastic properties) leading to asymmetric warpage. The numerical model will thus enable the prediction of the optimum process and material conditions for the warpage to be minimized together with the expected deformation of the molded wafer model with embedded dies. Keywords-3D packaging; wafer-level molding; asymmetric warpage; bifurcation; epoxy molding compound 2015 Symposium on Design Test Integration and Packaging of MEMS and MOEMS 978-1-4799-8625-5/15/$31.00 ©2015 IEEE

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Section: A Measurementsmentioning

confidence: 91%

Section: Problem Overviewmentioning

confidence: 99%

Section: B Finite Elements Modellingmentioning

confidence: 99%

See 1 more Smart Citation

Investigation of warpage in wafer-level Molding: Measurements and FE analysis

Farrugia

Grech

Casha

et al. 2015

2015 Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS (DTIP)

View full text Add to dashboard Cite

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“…In this paper, we back calculated the cure shrinkage of EMC using the warpage at 175C. The cure shrinkage can be modeled by shifting the reference temperature [5] in simulation or adding a residual stress in the structure at 175C. In this paper, the residual stress approach was used.…”

Section: Figure 10 Warpage Of Two Bilayer Structuresmentioning

confidence: 99%

“…How this structure can be used to characterize the cure shrinkage induced warpage is discussed extensively in this paper. The bilayer structure could be analytically calculated [2,3] and similar studies on EMC cure shrinkage were done using EMC/Cu bilayers [4,5]. The EMC/substrate bilayer in this paper was built with the same process used on a molded package but with the silicon die excluded.…”

Section: Introductionmentioning

confidence: 99%

Relative and absolute warpage modeling on molded packages

Zheng

Zhou

Wang

et al. 2015

2015 IEEE 65th Electronic Components and Technology Conference (ECTC)

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Package warpage is an important consideration for mobile device applications. With thinner packages and PoP applications, it is critical that both room temperature and high temperature warpage of the package are measured. Design optimization and material selection also requires simulations to predict warpage, which requires model calibration. Historically, warpage model calibration has been an issue in the industry for many reasons: measurement accuracy, package assembly process, material properties, simulation methodology, etc. This paper addresses these factors and presents a methodology for measured warpage data analysis and its correlation with finite element models. Absolute Warpage versus Relative WarpageWarpage measurement, generally done by shadow moiré, is needed for model calibration. It is important to differentiate the relative warpage from the absolute warpage for correct model calibration.The warpage reported from shadow moiré is almost always the absolute warpage, i.e., the actual shape of the package at a given temperature. The absolute warpage is a combination of process induced warpage and thermal warpage. Depending on the package and assembly processes, the process induced warpage can be a significant portion of the total warpage. Also process induced stress could generate an asymmetric warpage shape even for a symmetric structure.An example is shown in Figure 3 where the absolute warpage at 25°C on top of a molded package along two diagonals is plotted. In Figure 3, diagonal-1 is a concave (viewed from top of the package) while diagonal-2 tends to be 978-1-4799-8609-5/15/$31.00 ©2015 IEEE

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