Thermo-mechanical reliability during technology development of power chip-on-board assemblies with encapsulation

Wunderle, Bernhard; Becker, Karl‐Friedrich; Sinning, R.; Wittler, Olaf; Schacht, R.; Walter, H.; Schuster, Martin; Halser, K.; Simper, N.; Michel, B.; Reichl, H.

doi:10.1007/s00542-009-0907-1

Cited by 30 publications

(8 citation statements)

References 17 publications

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“…The ratio of the remaining bonded area under a die after thermal cycling to bonded area after specimen production can be used as an end-of life criterion. Criteria requiring a remaining bonded area of 80 % [3] and 90 % [8,12] were found in literature. Tn this work, the 80 % criterion was used for the evaluation of the occurrence of failures in the tests.…”

Section: Evaluation Of the Resultsmentioning

confidence: 99%

“…For the specimens investigated here, this failure mechanism was not observed. The second expected failure mechanism is fatigue, which is related to the equivalent plastic deformation per load cycle [8,12,13]. Plastic strains in the sintered material lead to damage and eventually to the formation of a crack.…”

Section: 2mentioning

confidence: 99%

“…Accordingly, thermal cycling at low temperatures should lead to virtually no damage and a lifetime in the high cycle fatigue range. Calculations of the accumulated plastic strain per cycle were carried out using an average of equivalent strain per cycle E ��g along a path in the sintered material according to [8,12,13]:…”

Section: 2mentioning

confidence: 99%

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Assessment of thermo-mechanical stresses in Low Temperature Joining Technology

Herboth

Fruh

Gunther

et al. 2012

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems

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The Low Temperature Joining Technology (L T JT) creates silver joints by a sintering process. It is an alternative die-attach technology to soldering. To initiate the sintering process the temperature has to be raised above � 215°C. The quality of a sintered joint is strongly enhanced by applying pressure to the specimen during the process, thus reducing the porosity in the sintered material. After the interconnect process, residual stresses occur in the sintered material, as well as in the joined parts.The examined specimen was a silicon MOSFET attached to a copper substrate at a sintering pressure of 50 MPa. The scope of this paper is to provide information about residual stress after production and thermo-mechanical stresses during thermal cycling. The focus is put on the investigation of the reliability of sintered silver by simulation.

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Section: Evaluation Of the Resultsmentioning

confidence: 99%

Section: 2mentioning

confidence: 99%

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Assessment of thermo-mechanical stresses in Low Temperature Joining Technology

Herboth

Fruh

Gunther

et al. 2012

2012 13th International Thermal, Mechanical and Multi-Physics Simulation and Experiments in Microelectronics and Microsystems

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“…The time constants for the 5 dies were, 0.55, 0.72, 0.62, 0.61, and 0.66 seconds which is a large variation considering the same epoxy and adhesive layer thickness was used for each die. The themal conductivity of the dies was calculated using an adhesive thickness of 50 µm a cross sectionall area of 16 mm2 and using a heat capacity of 27.2×10 -3 J·K -1 (which was calculated from a 4×4×0.5 mm 3 block of alumina with a specific heat capacity of 850 J·Kg -1 ·K -1 ). The above time constants were used to give thermal conductivity values of 0.15, 0.12, 0.14, 0.14 and 0. .…”

Section: ! !mentioning

confidence: 99%

Test Vehicle for Studying Thermal Conductivity of Die Attach Adhesives for High Temperature Electronics

Slater

Vecchio

Maeder

et al. 2012

SSP

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Abstract. Polymer adhesives offer a viable method for mounting silicon dies for high temperature applications. Here a test vehicle for comparing the thermal conductivity of different die attach materials is presented. The setup can be used to determine the degree of degradation of polymers. It consists of a mock die that has an integrated thick film heater, which is mounted onto a substrate. In operation, the substrate is placed on a heatsink and the die is heated. When the temperature reaches equilibrium the heater is switched off and the temperature of the die is measured as it cools. The time constant of the temperature decay is calculated to give the thermal conductivity. In this paper the thermal conductivity of an epoxy die attach adhesive is compared to its shear strength.

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“…Is the model still valid for chip soldered on FR4? An alternative model will be presented by Wunderle et al in [10] …”

Section: Discussionmentioning

confidence: 97%

Lifetime Prediction of SnPb and SnAgCu Solder Joints of Chips on Copper Substrate Based on Crack Propagation FE-Analysis

Deplanque

Nüchter

Wunderle

et al.

7th. Int. Conf. On Thermal, Mechanical and Multiphysics Simulation and Experiments in Micro-Electronics and Micro-Systems

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It is necessary to improve the lifetime prediction based on FE-Methods of different electronic packages in order to reduce the time and costs of new developments. This paper purposes a method describing the crack propagation of chip on copper substrate solder joints. The Chips that were studied are power transistors. They were soldered on Copper Substrate (NiAu metallization) with two different solder alloys (SnPb eutectic and SAC 305). The chip dimensions and the solder joint thickness have an influence on the lifetime, so that two different chips with two different solder thicknesses were used as test specimens. These were thermally loaded, and the state of the solder joints was regularly checked. Three different kind of methods were used to characterize the damage of solder joints: the Scanning Acoustic Microscope (SAM) detects the crack initiation and propagation; the cross section analysis can validate the results of the scanning acoustic microscope and can show the microstructure changes; and the thermal resistance which is influenced by the damage of the solder joint was measured and correlated to damage. After presenting the results of these investigations, a general FE-method predicting the crack initiation and propagation using the Paris Laws is presented.

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Thermo-mechanical reliability during technology development of power chip-on-board assemblies with encapsulation

Cited by 30 publications

References 17 publications

Assessment of thermo-mechanical stresses in Low Temperature Joining Technology

Assessment of thermo-mechanical stresses in Low Temperature Joining Technology

Test Vehicle for Studying Thermal Conductivity of Die Attach Adhesives for High Temperature Electronics

Lifetime Prediction of SnPb and SnAgCu Solder Joints of Chips on Copper Substrate Based on Crack Propagation FE-Analysis

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