Embarked QFN16, 32 and 64 electronic devices subjected to free convection. Influence of the adhesive paste on the junction temperature

[+] Author and Article Information
Abderrahmane BAÏRI

University of Paris, Laboratoire Thermique Interfaces Environnement, LTIE-GTE EA 4415, 50, rue de Sèvres, F-92410 Ville d’Avray, France; Association Aéronautique et Astronautique de France (The French Aeronautics and Astronautics Society, 3AF), 3AF, 6, rue Galilée, F-75016 Paris, France

Bruno Chanetz

Office National d'Etudes et de Recherches Aérospatiales (ONERA), Chemin de la Hunière, BP 80100, F-91123 Palaiseau Cedex, France; Association Aéronautique et Astronautique de France (The French Aeronautics and Astronautics Society, 3AF), 3AF, 6, rue Galilée, F-75016 Paris, France

José-Antonio Millan-Garcia

University of the Basque Country, E-20018 San Sebastián, Spain

1Corresponding author.

ASME doi:10.1115/1.4038113 History: Received November 12, 2016; Revised September 28, 2017


The junction temperature of the Quad Flat Non-Lead (QFN) electronic devices equipping embarked assemblies may be controlled in order to not exceed the maximum value recommended by the manufacturer. The packaging design is then important to ensure correct operation and high reliability given the significant power generated during operation and the inclination angle of the packages during the flight. It is particularly important when thermoregulation is achieved by means of natural convection. The objective of this study is to examine the influence of the adhesive paste used to connect the Die of the QFN with its base. The study deals with three devices among the most used in the conventional arrangements: the QFN16, 32 and 64. A 3D numerical solution based on the control volume formulation allows to determine their thermal behavior for generated power ranging from 0.1 to 1.0W by steps of 0.1W and inclination angle varying between 0° (horizontal position) and 90° (vertical position) step 15°. A wide range of the paste's thermal conductivity has been considered, varying between -80% and +100% of its average value, measured by means of the Transient Plane Source method. The numerical results confirmed by measurements show that the junction temperature strongly increases when the conductivity of the paste decreases and moderately reduced when the paste is thermally more conductive. Relationships are proposed to calculate the junction temperature for the considered devices, according to the generated power, the inclination angle and the relative paste's thermal conductivity.

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