Importance of molding compound chemical shrinkage in the stress and warpage analysis of PQFPs

Kelly, G.; Lyden, C.; Lawton, W.; Barrett, J.; Saboui, A.; Pape, H.; Peters, Hildegard

doi:10.1109/96.496032

Cited by 83 publications

(30 citation statements)

References 9 publications

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“…The condition of the displacements (2) compatibility can be written as (7) Here (8) is the compliance of one of the bonding layers, h a is its thickness, and G a is shear modulus of the attachment material. Introducing the equations (2) into the condition (7), the following equation for the shearing stress function can be obtained: (9) +HUH ǻĮ = Į 0 í Į 1 LV WKH GLIIHUHQFH LQ WKH HIIHFWLYH FRHI¿FLHQWV RI expansion of the inner and the outer components, (10) is the parameter of the interfacial shearing stress, (11) is the total axial compliance of the assembly, and (12) is its total longitudinal interfacial compliance.…”

Section: Shearing Stressmentioning

confidence: 99%

“…Ability to predict and minimize warpage is critical for the product fabrication (soldering requirements and assembly) and operation [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35]. Warpage is affected by package geometries, properties of the molding compound, mechanical characteristics of the employed materials and, certainly, the direction and level of temperature excursions.…”

Section: Introduction ([Fhvvlyh Zdusdjh Erz LV D Vljql¿fdqw Frqfhuq Rmentioning

confidence: 99%

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Bow-Free Tri-Component Mechanically Pre-Stressed Failure-Oriented-Accelerated-Test (FOAT) Specimen

Suhir¹,

Bensoussan²,

Nicolics³

2015

SAE Technical Paper Series

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OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 18140 Any correspondence concerning this service should be sent to the repository administrator: staff-oatao@listes-diff.inp-toulouse.fr AbstractIn some today's and future electronic and optoelectronic packaging systems (assemblies), including those intended for aerospace applications, the package (system's component containing active and passive devices and interconnects) is placed (sandwiched) between two substrates. In an approximate stress analysis these substrates could be considered, from the mechanical (physical) standpoint, identical. Such assemblies are certainly bow-free, provided that all the stresses are within the elastic range and remain elastic during testing and operation. Ability to remain bow-free is an important merit for many applications. This is particularly true in optical engineering, where there is always a QHHG WR PDLQWDLQ KLJK FRXSOLQJ HI¿FLHQF\ The level of thermal stresses in bow-free assemblies of the type in question could be, however, rather high. High thermal stresses are caused by the thermal contraction mismatch of the dissimilar materials of the assembly components and occur at low temperature conditions. These stresses include normal stresses acting in the component cross-sections and interfacial shearing and peeling stresses. The normal stresses in the component cross-sections determine the reliability of the component materials and the devices embedded into the inner component (package). The interfacial stresses affect the adhesive and cohesive strength of the assembly, i.e. its integrity.It should be pointed out that although the assembly as a whole is bow-free, the peeling stresses in it, whether thermal or mechanical, are not necessarily low: the two outer components (substrates) might exhibit appreciable warpage with respect to the bow-free inner component (package).While there is an incentive for using bow-free assemblies, there is also an incentive for narrowing the temperature range of the accelerated reliability testing: elevated temperature excursions might produce an undesirable shift in the modes and mechanisms of failure, i.e. lead to failures that will hardly occur in actual operation conditions. Failure oriented accelerated test (FOAT) specimens are particularly vulnerable, since the temperature range in these tests should be broad enough to lead to a failure, and, if a shift in the PRGHV DQG PHFKDQLVPV RI IDLOXUHV WDNHV SODFH GXULQJ VLJQL¿FDQW temperature excursions, the physics of such failures might be quite different of those in actual operation conditions. Mechanical pre-stressing can be an effective means for narrowing the range of temperature excursions during accelerated testing and, owing to that, -for obtaining consistent and trustworthy information. If prestressing is considered, the ability to predict the thermo-mech...

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Section: Shearing Stressmentioning

confidence: 99%

Section: Introduction ([Fhvvlyh Zdusdjh Erz LV D Vljql¿fdqw Frqfhuq Rmentioning

confidence: 99%

Bow-Free Tri-Component Mechanically Pre-Stressed Failure-Oriented-Accelerated-Test (FOAT) Specimen

Suhir¹,

Bensoussan²,

Nicolics³

2015

SAE Technical Paper Series

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“…Chemical shrinkage This most intrinsic property of a polymer, "chemical shrinkage," ranges from 0.2 to 20% and it can cause a significant residual stress in an electronic packaging assembly [18]. When the polymer cures around the FBG, the chemical shrinkage, ɛ ch , will also cause a stress-induced strain in the FBG, " s f .…”

Section: Specimen Configurationsmentioning

confidence: 99%

Integrated Measurement Technique for Curing Process-Dependent Mechanical Properties of Polymeric Materials Using Fiber Bragg Grating

et al. 2007

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We propose an integrated technique to measure critical mechanical properties of polymeric materials. The method is based on a fiber Bragg grating (FBG) sensor. A polymer of interest is cured around a glass FBG and the Bragg wavelength (BW) shift is measured and documented while polymerization progresses at the curing temperature. After complete polymerization, the BW shift is monitored continuously as the temperature of the cured polymer changes. The desired material properties are then found inversely from the relationship between the Bragg wavelength shift and the deformation of the polymer caused by the changes in the material properties.

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“…This volumetric shrinkage induced by the polymerization is called "chemical shrinkage." The chemical shrinkage produces dimensional changes and residual stresses in packaged devices, which can significantly affect product reliability [1][2][3]. In some cases, the chemical shrinkage affects the functionality of special polymers.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Measurement of Effective Chemical Shrinkage and Modulus Evolutions During Polymerization

2010

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A novel method is proposed to simultaneously measure the effective chemical shrinkage and modulus evolutions of advanced polymers during polymerization. The method utilizes glass fiber Bragg grating (FBG) sensors. They are embedded in two uncured cylindrical polymer specimens with different configurations and the Bragg wavelength (BW) shifts are continuously documented during the polymerization process. A theoretical relationship is derived between the BW shifts and the evolution properties, and an inverse numerical procedure to determine the properties from the BW shifts is established. Extensive numerical analyses are conducted to provide general guidelines for selecting an optimum combination of the two specimen configurations. The method is implemented for a high-temperature curing thermosetting polymer. Validity of the proposed method is corroborated by two independent verification experiments: a self-consistency test to verify the measurement accuracy of raw data and a warpage measurement test of a bi-material strip to verify the accuracy of evolution properties.

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Importance of molding compound chemical shrinkage in the stress and warpage analysis of PQFPs

Cited by 83 publications

References 9 publications

Bow-Free Tri-Component Mechanically Pre-Stressed Failure-Oriented-Accelerated-Test (FOAT) Specimen

Bow-Free Tri-Component Mechanically Pre-Stressed Failure-Oriented-Accelerated-Test (FOAT) Specimen

Integrated Measurement Technique for Curing Process-Dependent Mechanical Properties of Polymeric Materials Using Fiber Bragg Grating

Simultaneous Measurement of Effective Chemical Shrinkage and Modulus Evolutions During Polymerization

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