Measurement of Temperature-Dependent Young’s Modulus at a Strain Rate for a Molding Compound by Nanoindentation

T. Xu, Y. Du, H. Luo, G. H. Kim, Z. Xu, M. Minary-Jolandan, L. Stark, T. Baughn, H. Lu

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

The mechanical properties of a molding compound on a packaged integrated circuit (IC) were measured by spherical nanoindentation using a 50 μm radius diamond tip. The molding compound is a heterogeneous material, consisting of assorted diameters of glass beads embedded in an epoxy. Statistical analysis was conducted to determine the representative volume element (RVE) size for a nanoindentation grid. Nanoindentation was made on the RVE to determine the effective viscoelastic properties. The relaxation functions were converted to temperature-dependent Young’s modulus at a given strain rate at several elevated temperatures. The Young’s modulus values at a given strain rate from nanoindentation were found to be in a good agreement with the corresponding data obtained from tensile samples at or below 90 °C. However, the values from nanoindentation were significantly lower than the data obtained from tensile samples when the temperature was near or higher than 110 °C, which is near the glass transition. The spatial distribution of the Young’s modulus at a given strain rate was determined using nanoindentation with a Berkovich tip. The spatial variation of the Young’s modulus at a given strain rate is due to the difference in nanoindentation sites (glass beads, epoxy or the interphase region). A graphical map made from an optical micrograph agrees reasonably well with the nanoindentation results.

Original languageEnglish (US)
Pages (from-to)1135-1147
Number of pages13
JournalExperimental Mechanics
Volume57
Issue number7
DOIs
StatePublished - Sep 1 2017
Externally publishedYes

Keywords

  • Elevated temperatures
  • Molding compounds
  • Nanoindentation
  • Viscoelasticity
  • Young’s modulus

ASJC Scopus subject areas

  • Aerospace Engineering
  • Mechanics of Materials
  • Mechanical Engineering

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