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http://dx.doi.org/10.6117/kmeps.2013.20.3.037

Measurement of Thermal Expansion Coefficient of Package Material Using Strain Gages  

Yang, Hee-Gul (Department of Mechanical Engineering, Chungbuk National University)
Joo, Jin-Won (Department of Mechanical Engineering, Chungbuk National University)
Publication Information
Journal of the Microelectronics and Packaging Society / v.20, no.3, 2013 , pp. 37-44 More about this Journal
Abstract
It is well known that thermal deformation of electronic packages with Pb-Sn solder and with lead-free solder is significantly affected by material properties consisting the package, as well as those of the solder itself. In this paper, the method for determining coefficient of thermal expansion(CTE) of new material is established by using temperature characteristic of strain gages, and the CTE of molding compound are obtained experimentally. The temperature-dependent CTE of molding compound for Pb-Sn solder and that for lead-free solder are obtained by using strain measurements with well known steel specimen and aluminium specimen as reference specimens, and the CTE's are also measured non-contactly by using moire interferometry. Those results are compared, and the agreement between the two types of strain gage experiment and the moire experiment show the strain gage method used in this paper to be reliable. In the case of the molding compound for Pb-Sn solder, the CTE is measured as approximately $15.8ppm/^{\circ}C$ regardless of the temperature. In the case for the lead-free solder, the CTE is measured as of approximately $9.9ppm/^{\circ}C$ below the temperature of $100^{\circ}C$, and then the CTE is increased sharply depending on the temperature, and reaches to $15.0ppm/^{\circ}C$ at $130^{\circ}C$.
Keywords
WB-PBGA package; Coefficient of thermal expansions; Strain gage; Moir$\acute{e}$ Interferometry; Molding compound; Lead-free solder;
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