Predicted Thermal Stresses in a Circular Assembly With Identical Adherends and With Application to a Holographic Memory Package Design

2011 ◽  
Vol 79 (1) ◽  
Author(s):  
E. Suhir ◽  
C. Gu ◽  
L. Cao
Keyword(s):  
Elevated Temperature ◽  
Thermal Stresses ◽  
Memory Systems ◽  
Stress Model ◽  
Adhesively Bonded ◽  
Holographic Memory ◽  
Thermally Induced ◽  
Package Design ◽  
Induced Stresses ◽  
Lower Temperature

A simple, easy-to-apply and physically meaningful analytical (“mathematical”) stress model is developed for the prediction of the thermally induced stresses in a circular adhesively bonded assembly with identical adherends. The assembly is fabricated at an elevated temperature and is subsequently cooled down to a lower temperature. The developed model can be helpful for stress-strain analyses and physical design of electronic and photonic assemblies of the type in question, and particularly those employed in holographic memory systems.

Analysis and Optimization of the Input/Output Fiber Configuration in a Laser Package Design

1995 ◽  
Vol 117 (4) ◽  
pp. 261-265 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Small Angle ◽  
Allowable Stress ◽  
Input Output ◽  
Transverse Axis ◽  
Thermally Induced ◽  
Package Design ◽  
Induced Stresses ◽  
Straight Fiber ◽  
Final Selection ◽  
Selection Of

The mechanical and thermally induced stresses in the input/output (I/O) fiber in a laser package design are evaluated for different fiber configurations. It is shown that, if the fiber experiences bending deformations, the mechanical stresses can be minimized by applying a proper end off-set. It is found also that, if the optical device can be rotated around the transverse axis by a small angle, this rotation can be effectively used for minimizing the stresses. The smallest fiber span can be achieved, if necessary, by making the fiber straight. In this case the fiber should be short enough to avoid buckling under the action of the compressive stress. We suggest that such a configuration be employed when the appropriate rotation of the device is possible, fiber ends can be easily aligned, and the support structures are strong enough to withstand the elevated thermal force from the compressed fiber. Although the results of the performed analysis can provide guidance for optimizing the I/O fiber configuration, the final selection of such a configuration can be made only after the allowable stress and the achievable end alignment (in the case of straight fiber) are established experimentally.

Predicted Thermal Mismatch Stresses in a Cylindrical Bi-material Assembly Adhesively Bonded at Its Ends

1997 ◽  
Vol 64 (1) ◽  
pp. 15-22 ◽  
Author(s):  
E. Suhir
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Coefficient Of Thermal Expansion ◽  
Stress Model ◽  
Adhesively Bonded ◽  
Thermal Mismatch ◽  
Adhesive Material ◽  
Thermally Induced ◽  
Local Stresses ◽  
Material Assembly

A simple analytical stress model, based on the strength-of-materials approach, is developed for the evaluation of thermally induced shearing stresses in a long cylindrical bi-material assembly adhesively bonded at its ends and subjected to the change in temperature. The emphasis is on the interaction of the “global” thermal mismatch stresses, counted with respect to the mid cross section of the assembly as a whole, and the “local” stresses, counted with respect to the mid cross sections of the bonded regions. The effect of the coefficient of thermal expansion of the adhesive material itself is also considered. We show also how to evaluate the fundamental frequency of vibrations of the inner cylinder with consideration of the thermally induced tension, if any.

Development of a SiC SSPC Module with Advanced High Temperature Packaging

2010 ◽  
Vol 2010 (HITEC) ◽  
pp. 000310-000315
Author(s):  
Douglas C Hopkins ◽  
Yuan-Bo Guo ◽  
Herbert E Dwyer ◽  
James D. Scofield
Keyword(s):  
Thermal Stresses ◽  
System Modeling ◽  
Electrical System ◽  
Power Module ◽  
Packaging System ◽  
Thermally Induced ◽  
Dc System ◽  
Transient Heat Flow ◽  
Induced Stresses

Development of a multi-chip power module (MCPM) is reported that uses advanced metal-matrix composite aluminum packaging to manage high thermally induced stresses in devices that incur 350°C transients. The MCPM uses parallel SiC devices to control 120A DC nominal, 1200A fault in a 270V DC system. Electrical system modeling is presented to characterize electrical fault transients that induce electrical and thermal stresses in the semiconductors and packaging. The characterization of the advanced aluminum-based packaging system, which uses composites, such as AlSiC, and direct bonded aluminum (DBA), is discussed to manage the thermal stresses and transient heat flow.

Morphologies of Nonadherent Al2O3 and Matching Substrate Surfaces

1972 ◽  
Vol 30 ◽  
pp. 524-525
Author(s):  
C. S. Giggins ◽  
J. K. Tien ◽  
B. H. Kear ◽  
F. S. Pettit
Keyword(s):  
Electron Microscopy ◽  
Oxide Scale ◽  
Oxidation Resistance ◽  
Substrate Surface ◽  
Morphological Features ◽  
Thermally Induced ◽  
Oxide Spallation ◽  
Oxidation Resistant ◽  
Induced Stresses ◽  
Substrate Surfaces

The performance of most oxidation resistant alloys and coatings is markedly improved if the oxide scale strongly adheres to the substrate surface. Consequently, in order to develop alloys and coatings with improved oxidation resistance, it has become necessary to determine the conditions that lead to spallation of oxides from the surfaces of alloys. In what follows, the morphological features of nonadherent Al2O3, and the substrate surfaces from which the Al2O3 has spalled, are presented and related to oxide spallation.The Al2O3, scales were developed by oxidizing Fe-25Cr-4Al (w/o) and Ni-rich Ni3 (Al,Ta) alloys in air at 1200°C. These scales spalled from their substrates upon cooling as a result of thermally induced stresses. The scales and the alloy substrate surfaces were then examined by scanning and replication electron microscopy.The Al2O3, scales from the Fe-Cr-Al contained filamentary protrusions at the oxide-gas interface, Fig. 1(a). In addition, nodules of oxide have been developed such that cavities were formed between the oxide and the substrate, Fig. 1(a).

Heat Transfer and Thermal Stress Analysis of an Optoelectronic Package

1991 ◽  
Vol 113 (3) ◽  
pp. 258-262 ◽  
Author(s):  
J. G. Stack ◽  
M. S. Acarlar
Keyword(s):  
Heat Transfer ◽  
Thermal Management ◽  
Power Dissipation ◽  
Point Of View ◽  
Optical Data ◽  
Data Link ◽  
Element Analysis ◽  
Thermally Induced ◽  
Temperature Changes ◽  
Induced Stresses

The reliability and life of an Optical Data Link transmitter are inversely related to the temperature of the LED. It is therefore critical to have efficient packaging from the point of view of thermal management. For the ODL® 200H devices, it is also necessary to ensure that all package seals remain hermetic throughout the stringent military temperature range requirements of −65 to +150°C. For these devices, finite element analysis was used to study both the thermal paths due to LED power dissipation and the thermally induced stresses in the hermetic joints due to ambient temperature changes

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.

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