Glass transition temperature of nanoparticle-enhanced and environmentally stressed conductive adhesive materials for electronics assembly

Abstract

In our paper, the characterization of glass transition temperature (Tg) was performed for one-and two-component electrically conductive adhesive used in electronic joining technologies. Both adhesives were of the epoxy type with the silver filler. Dynamic mechanical analysis (DMA) was used to measure the Tg. The adhesives were modified with nanoparticles, namely, carbon nanotubes (concentration of 0.5 and 0.8% by weight) and silver nanoballs (2.5% by weight). The values of Tg were determined from the plot of the Tg δ parameter. Two types of environmental stresses were used for climatic aging: 125 °C/56% RH and 85 °C/85% RH. The aging of the samples at 125 °C and 56% RH caused increase Tg for all formulations. The cause of these changes is additional curing of adhesive. Aging in the combined climate 85 °C/85% RH caused a shift in Tg toward lower values for formulations based on the one-component adhesive modified by CNT and toward higher values for all other formulations. The major cause of the decrease in Tg was that CNT inhered the curing reactions and banned them from completion. In cases where Tg grew, glue hardening take place. DMA was performed to examine Tg of the samples. The DMA measurements were carried out up to 200 °C. Repeated DMA measurement confirmed that this measurement caused additional hardening and increase Tg for all samples. The results will contribute to the use of conductive adhesives with better quality and reliability in electronics manufacturing.

Synthesis and Experimental Characterization of a MWCNT-Filled Bio-Based Adhesive

“…The decrease is due to the presence of agglomerations which act as defects in the material. Similar findings regarding the negative effect of the MWCNT agglomerations have been also reported in [18,19].…”

Ultra‐Strong and Proton Conductive Aqua‐Based Adhesives from Facile Blending of Polyvinyl Alcohol and Tungsten Oxide Clusters

“…Polymer adhesives are a large family of widely used chemicals for the binding of material interfaces together in a functional manner, which possess irreplaceable advantages, including light weight, high affinity to dissimilar materials, convenient and fast processing, non‐destructive to the material structures, and the capability for energy absorption. [ 1,2 ] The compositions of adhesives can be chemically and/or physically enriched for bonusing functionality, for example, conductivity, biocompatibility, and light/electromagnetic wave transmittance, enabling their broad applications as binders for energy conversion/storage devices and electronics assembly, [ 3,4 ] bio‐adhesives for hemostatic agents and wound closure, [ 5 ] and flat panel display bonding material. [ 6 ] Solvent‐based adhesives, for example, epoxy resin, are commonly used for their low cost, ease of curing, strong adhesion to various surfaces, and good corrosion resistance; [ 7 ] however, their emission of harmful volatile organic compounds raises concerns on environmental and health safety and significantly limits their applications.…”

Monolithic Solder-On Nanoporous Si-Cu Contacts for Stretchable Silicone Composite Sensors

“… 19 – 26 Even though AgEpoxy is an excellent electrical conductor (<10 -4 Ω·cm), it is susceptible to cracking and debonding from the silicone-based stretchable strain sensors and usually the first interface to fail under rates of strain higher than 10 mm/min (2 mm/s is physiologically relevant). 27 This is due to the brittle nature of the adhesive and poor wetting of silicones by AgEpoxy. Silicones bond weakly with most adhesives due to their lower surface energy (the surface energy of epoxy is 40-50 mJ/m 2 , while silicones have a range between 19 and 25 mJ/m 2 ).…”

“…Works reported to date have optimized the sensing properties and the manufacturing of stretchable CB-PDMS sensing elements; however, reliable interfacial adhesion of the stretchable sensing element with electronic components, such as wiring, integrated circuits, or other conventional devices, still remains a problem. − Currently, the electrical connection between CB-PDMS sensors and external electronics primarily relies on brittle conductive adhesives, although some commercial products use large solid mechanical connections, such as clamps and clasps, that are not suitable for miniaturized devices (Smart Garments by Stretchsense, Zephyr Biomodule Device) . Silver-based conductive epoxy (AgEpoxy) is, by far, the most widely used adhesive to create electrical contacts between silicone-based CPC sensing elements and electrical read-out devices. − Even though AgEpoxy is an excellent electrical conductor (<10 –4 Ω·cm), it is susceptible to cracking and debonding from the silicone-based stretchable strain sensors and usually the first interface to fail under rates of strain higher than 10 mm/min (2 mm/s is physiologically relevant) . This is due to the brittle nature of the adhesive and poor wetting of silicones by AgEpoxy.…”