Process induced residual stresses in isotropically conductive adhesive joints

Wu, S.X.; Mel, Yuhai; Yeh, Chao-Pin; Wyatt, K.

doi:10.1109/3476.558551

Cited by 11 publications

(8 citation statements)

References 4 publications

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“…It offers a lead-free, low temperature, and low cost process with fine pitch capabilities. However, the degradation mechanisms during ageing are not completely understood and assembly process parameters and adhesive material properties are not fully optimized which has so far limited its use [1][2][3][4][5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

Zhang

Wong

Rajoo

et al. 2005

Microelectronics Reliability

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Section: Introductionmentioning

confidence: 99%

Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

Zhang

Wong

Rajoo

et al. 2005

Microelectronics Reliability

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“…The results were given in the form of temperature dependence of the dynamic shear modulus as well as time dependence of the relaxation modulus at two temperatures. The data of Wu et al [7] seem to obey quite well a very simple expression for the creep strain ycr as a function of temperature T, time t and shear stress 7:…”

Section: Viscoelastic Properties Of Conductive Adhesivesmentioning

confidence: 90%

“…Unfortunately there are very little such data available about the electrically conductive adhesives used in electronics. Wu et al [7] have reported measurements made for one isotropically conductive adhesive of unknown composition. The results were given in the form of temperature dependence of the dynamic shear modulus as well as time dependence of the relaxation modulus at two temperatures.…”

Section: Viscoelastic Properties Of Conductive Adhesivesmentioning

confidence: 99%

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Reliability testing and stress strain estimations of flip-chip joints made by stud-bump-bonding technique

Lenkkeri

Vähäkangas²

Proceedings of 3rd International Conference on Adhesive Joining and Coating Technology in Electronics Manufacturing 1998 (Cat.

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The stud bumping with ball bonder is a flexible method for making bumps suitable for adhesive joining of flip-chips. We have made test structures with stud bumped chips onto alumina and FR4-substrates using isotropically conduc Live adhesives and underfill materials selected to be compat ble together and with the type of substrate used. The chips protected by underfill dispensing were tested to remain sti.ble up to 500 cycles in thermal cycling between -40 and 120 'C. Because of the limited mechanical strength of adhesive joints especially when the area of joints is very small compared with the chip area, good reliability in temperature cycling requ res an underfill material to increase the mechanical strength of joining and to reduce the thermally induced deformation caused by different thermal expansion of the chip m d substrate.Calculations have been made to estimate the stress-stmin behavior of adhesive joints in temperature cycling usin:: a developed 1 -dimensional model together with assumption: of the material behavior. The effects of various geometr cal factors on the reliability have been studied. The application of underfill material, temperature dependence of its e h t i c modulus, difference of the thermal expansion coefficients of the chip and substrate as well as the stiffness of the structure adjacent to joints seem to have large effects on the deformation of the joints in temperature cycling.

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“…In recent years, extensive studies have been conducted fix conductive adhesives in various areas such as joint reliability testing [4], electrical properties and microstructure development [ 5 ] , and joint residual stress analysis [6]. The physical, electrical and mechanical properties of conductive adhesives depend to a large extent on the degree of cure of the epoxy composition in the conductive adhesives.…”

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confidence: 99%

Cure kinetics and mechanical properties of conductive adhesive

Zhang²,

Yeh³

et al.

1997 Proceedings 47th Electronic Components and Technology Conference

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The curing reaction of a conductive adhesive was studied with a differential scanning calorimeter (DSC) under isothermal conditions in the range of 10O-16O0C. An autocatalyzed kinetic model was used to describe the curing reaction. The rate constant and the reaction orders were determined and used in the model to predict the progress of the curing reactions. A good agreement is found between the proposed kinetic model and the experimental reaction rate data. The reaction rate constants were correlated with the isothermal temperature by the Arrhenius equation. The activation energy for the curing reaction is determined to be 94.9 kJ/mol. The reaction order which represents the effects of the unreacted materials is found to be a parabolic h c t i o n of temperature. But the effects of the reacted materials on the reaction rate change sharply at around 120 "C. Unlike some previous results on epoxy curing kinetics, the sum of the two reaction orders is not a constant for this conductive adhesive. Thermogravimetric Analyzer (TGA) was used to study the weight loss during thermal processes. The degradation temperature of the conductive adhesive was found to be 250 "C. The properties of the corresponding unfilled Epoxy were also studied with the DSC and TGA. Results were compared with those obtained from the conductive adhesive. Tests were conducted to investigate the mechanical and electrical property changes during cure.Conductive adhesives have become an attractive altemative to solder joints as the interconnect medium since they provide many advantages such as low processing temperatures and less environment contamination [ 1-31. In recent years, extensive studies have been conducted fix conductive adhesives in various areas such as joint reliability testing [4], electrical properties and microstructure development [ 5 ] , and joint residual stress analysis [6]. The physical, electrical and mechanical properties of conductive adhesives depend to a large extent on the degree of cure of the epoxy composition in the conductive adhesives. Thus, a hlly understanding of the cure mechanisms of conductive adhesives and their effects on the properties of adhesives can provide tools to optimize cure schedule so that residual stresses in the conductive adhesive joint are minimal. In this study, the curing reaction of an isotropically conductive was studied with a differential scanning calorimeter (DSC) under isothermal and dynamic conditions. An autocatalyzed kinetic model was used to describe the curing reaction. Thermogravimetric Analyzer (TGA) was used to study the O -7 8 O~-~5 7 -~9 7 $4.00 01 997 IEEE 550 weight loss during thermal processes. The properties of the corresponding unfilled Epoxy were also studied with the DSC and TGA and results were compared with those obtained from the conductive adhesive. A dynamic mechanical analyzer (DMA) was used to study the mechanical property change during dynamic cure process. It was found that the adhesive starts to become rigid when the degree of cure reaches about 0.75 and the ri...

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Process induced residual stresses in isotropically conductive adhesive joints

Cited by 11 publications

References 4 publications

Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

Development of process modeling methodology for flip chip on flex interconnections with non-conductive adhesives

Reliability testing and stress strain estimations of flip-chip joints made by stud-bump-bonding technique

Cure kinetics and mechanical properties of conductive adhesive

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