Die Shear Testing of a Novel Isotropic Conductive Adhesive—Epoxy Filled With Metal-Coated Polymer Spheres

Abstract

Isotropic conductive adhesives (ICAs) filled with metal-coated polymer spheres (MPS) are introduced to improve the mechanical reliability compared with conventional ICAs filled with silver (Ag) flakes. This paper deals with the die shear performance of an MPS-based ICA; an epoxy filled with 45 vol% of Ø 30 µm Ag-coated monodisperse polymer spheres. The curing kinetics of the ICA is also studied. The MPS-based ICA is compared with two ICAs filled with Ag flakes: an in-house prepared ICA (with the same epoxy matrix as the MPS-based ICA) and a commercially available ICA. Both ICAs with Ag flakes have a lower particle volume fraction than the MPS-based ICA. Loading 45 vol% of MPS into the epoxy matrix has no significant effect on the curing kinetics and the glass transition temperature (T g ) of the matrix. The MPS-based ICA has 140% higher die shear strength than the in-house prepared ICA with Ag flakes, and 23% higher die shear strength than the commercial ICA with Ag flakes. The MPS-based ICA also has higher shear strain at failure, and less scatter in shear strength between repeated tests. Hence, the MPS-based ICA has a good potential for demanding applications; it has better die shear performance and higher T g than the commercial ICA with Ag flakes.Index Terms-Isotropic conductive adhesive (ICA), metalcoated polymer spheres (MPS), shear test, stiffness.

Contact Resistance and Metallurgical Connections Between Silver Coated Polymer Particles in Isotropic Conductive Adhesives

“…2. The density of the polymer cores was given by the manufacturer as 1.16 g/cm 3 , and the densities of the silver coatings were assumed to be equal to that of bulk silver (10.49 g/cm 3 ). The epoxy matrix was prepared by mixing a low viscosity epoxy resin consisting of a mixture of bisphenol A and bisphenol F epoxy with a low viscosity polyetheramine curing agent at a ratio of 1:0.35 by weight.…”

“…The epoxy matrix was prepared by mixing a low viscosity epoxy resin consisting of a mixture of bisphenol A and bisphenol F epoxy with a low viscosity polyetheramine curing agent at a ratio of 1:0.35 by weight. The uncured densities of the resin and curing agent were given by the manufacturer as 1.18 g/cm 3 and 0.95 g/cm 3 , respectively. Particles were mixed into the epoxy at a volume fraction of approximately 56% using a centrifugal vacuum mixer (ARV-310, Thinky Corporation, Japan).…”

“…Nguyen et al investigated the die shear strength of AgPS-based ICA and found it to be larger than both in-house produced and commercial flake-based ICAs. 3 The rheological properties of these ICAs have also been investigated and deemed suitable for stencil/screen printing and dispensing processes. 4 Gakkestad et al investigated the thermal properties of AgPS-based ICAs.…”

Electrical characterization of individual metal‐coated polymer spheres used in isotropic conductive adhesives

“…In addition, a higher particle concentration, that is, a lower volume fraction of the adhesive matrix, may result in an MPS‐based ICA with low mechanical strength. In previous studies, we have characterized the rheological properties and the mechanical properties of an adhesive filled with 45 vol % Ag‐coated monodisperse polymer spheres (AgPS), representing a complete MPS‐based ICA. The rheological behavior of the ICA showed a high potential for processing capabilities.…”

Ternary Ag/Epoxy Adhesive with Excellent Overall Performance

“…Among the Ag fillers, Ag microflakes (Ag-MFs) are the most commonly used conductive filler for commercial ECAs because of their high conductivity and relatively stable contact resistance. Therefore, much research has been conducted based on Ag-MFs, − and the EC of the ECAs filled with Ag-MFs was higher than that filled with Ag-NSs or Ag-MSs. , Recently, one-dimensional Ag nanowires (Ag-NWs) have attracted increasing interests due to their unique electrical, optical, and thermal properties and their potential applications in microelectronic, optoelectronic devices, and sensors. − Ag-NWs possess relatively higher aspect ratio compared to Ag-NSs or Ag-MFs, which may form ideal thermally or electrically conductive paths at a relatively lower percolation threshold in polymer adhesives. ,− To lower the costs, the ECAs have also been made from metal-coated fillers, such as Ag-coated carbon nanotubes, Ag-coated graphite nanosheet, Ag-coated polymer spheres, , Ag-coated basalt particles and basalt fibers, and Ag-coated Cu particles and Cu flakes. , However, the ECAs containing metal-coated fillers usually have a relatively lower EC compared to those containing pure metal fillers. , …”