Testing of techniques for improvement of conductivity of electrically conductive adhesives (original) (raw)
Related papers
Modification of electrically conductive adhesives for better mechanical and electrical properties
2008 31st International Spring Seminar on Electronics Technology, 2008
The goal of the work has been to check a possibility of improvement of electrical properties of electrically conductive adhesives with isotropic electrical conductivity to edge these properties toward to properties of solders. The electrical resistance and nonlinearity of I-V characteristic have been investigated. Two ways have been used for electrically conductive adhesive modification: addition of small amount of silver nanoparticles (grains) of three different dimensions into adhesive, and substitution of a part of filler flakes with the same amount of nanoparticles. It has been found that addition of silver nanoparticles increases the resistance and nonlinearity of adhesive. It has also been found that adhesives modified with nanoparticles have lower sensitivity to combined climatic ageing in comparison with adhesives without nanoparticles. The reason is other quality of contacts between flakes and contacts between nanoparticles.
Using Ozawa method to study the curing kinetics of electrically conductive adhesives
Journal of Thermal Analysis and Calorimetry, 2014
In this paper, we fabricated electrically conductive adhesives using vinyl ester resin and micro silver flakes, and then cured the adhesives by heat without any catalysts or initiators. The curing temperature was above 200°C, and the curing time about 30 min. Under these heat curing conditions, the double bonds in the adhesives reached a high conversion (a) around 98.88 % calculated from the Fourier transform infrared spectroscopy analysis. The curing kinetics of heat curing products was studied using Ozawa method and deduced by assuming a constant activation energy (E). The curing kinetic equation was obtained as da/dt = e 17.70 (1-a) 1.19 a 0.41 e (-94.32)/RT) with E = 94.32 kJ mol-1. The heat curing followed the shrinking core model from the resin-particle system. The data calculated from the kinetic equation agreed well with the experimental data, showing that the Ozawa method could evaluate the curing kinetics effectively. Furthermore, a comprehensive and in-depth understanding of the curing kinetics of heat curing electrically conductive adhesives has been achieved with this Ozawa method.
2011
In this study, the effect of amine adduct powder (AAP) on the electrical conductivity, thermal expansion, and flexural modulus of one-part system conductive adhesives are investigated. One-part system conductive adhesives are prepared using two types of silver (silver A and silver B) and different percentage of filler loadings, 10 vol.%-40 vol.%. Silver A adhesive systems exhibit higher electrical conductivity with lower percolation thresholds, high flexural moduli, and low coefficients of thermal expansion (CTE) compared silver B adhesive systems. A comparison of the electrical conductivity and thermal expansion properties of the one part and two-part of silver A adhesives system is undertaken. The one-part silver A adhesives system shows high electrical conductivity and low CTE values compared to the two-part system. This is due to the higher cross linking density of the one-part system compared to that of the two-part system.
Study of processing variables on the electrical resistivity of conductive adhesives
International Journal of Adhesion and Adhesives - INT J ADHES ADHES, 2009
In this paper, the authors explored the effects of processing variables, including carbon nanotube (CNT) concentration, assembly pressure, and processing temperature, on electrical conductivity of CNT-included electrically conductive adhesives (ECAs). The main effects of these variables were analyzed under specific range for each variable. Response surface methodology was used to investigate the cross-effects of these variables on ECA conductivity. By fitting the experimental data to the response function, minimum bulk resistivity of 1.5×10−4 Ω cm was obtained at the optimum settings of processing variables (CNT concentration 2%, processing temperature 199 °C, pressure 6000 psi).
Effect of different copper fillers on the electrical resistivity of conductive adhesives
Journal of Materials Science: Materials in Electronics, 2011
The effects of different copper fillers with different morphology and particle size have been studied in terms of electrical resistivity and thermal stability on the electrically conductive adhesives. The copper fillers used in this study were prepared by wet chemical reduction, electrolytic and gas atomization method, respectively. The as cured ECAs filled with different type of Cu fillers showed significant difference in electrical resistivity. Cu filler with smaller particle size showed higher packing density and larger surface area, which would enhance formation of conductive channels and increased conductive network in the ECAs, leading to a lower electrical resistivity. In addition, thermal stability of the ECAs were investigated under high temperature exposure at 125°C and high humidity aging at 85°C/85% RH for 1,000 h. Results showed that ECAs with Cu fillers of relatively small particle size and rough particle surface have excellent thermal stability due to enhanced adhesion and contact area between Cu fillers and the polymer matrix. A very low resistivity at an order of magnitude of 10 -4 X cm could be maintained for these ECAs after 1,000 h at 125 and 85°C/85% RH.
Electrically conductive adhesive filled with mixture of silver nano and microparticles
2008
Electrically conductive adhesive with isotropical electrical conductivity modified with addition of silver nanoparticles has been investigated. The electrical resistance, nonlinearity of a current vs. voltage characteristic and the tensile strength of adhesive joints formed of this adhesive have been measured. The specimens have also been aged at the temperature of 125°C and at the combined climate 80°C/80 % relative humidity for 700 hours. It has been found that silver nanoparticles added into the electrically conductive adhesive cause decrease of its conductivity, increase of its nonlinearity and increase of the tensile strength.
Synthetic Metals, 2004
Electrical conductivity and percolation concentrations of epoxy and polyurethane (PU) resins filled with Ag-coated particles and short fibers were studied in this paper. Percolation concentrations were determined to be as follows: 29 vol.% for epoxy/Ag-coated fibers and PU/Ag-coated particles and fibers and 28 vol.% for epoxy/Ag-coated particles. The highest values of electrical conductivity were found for PU/Ag-coated fibers.
Development of conductive adhesives for solder replacement
IEEE Transactions on Components and Packaging Technologies, 2000
With the phasing out of lead-bearing solders, electrically conductive adhesives (ECAs) have been identified as an environmentally friendly alternative to tin/lead (Sn/Pb) solders in electronics packaging applications. Compared to Sn/Pb solders, conductive adhesive technology offers numerous advantages. However, this new technology still has reliability limitations. Two critical limitations are unstable contact resistance on non-noble metals and poor impact performance. Our previous study proved that galvanic corrosion is the dominant mechanism for the unstable contact resistance during elevated temperature and humidity aging. The ultimate goal of this study is to develop conductive adhesives with stable contact resistance and desirable impact performance. In this study, effects of purity of the resins and moisture absorption on contact resistance are investigated. Several different additives (oxygen scavengers and corrosion inhibitors) on contact resistance stability during elevated temperature and humidity aging are studied, and effective additives are identified based on this study. Then, several rubber-modified epoxy resins and two synthesized epoxide-terminated polyurethane resins are introduced into ECA formulations to determine their effects on impact strength. The loss factor, tan , of each formulation is measured using a dynamic mechanical analyzer (DMA) and impact strength is evaluated using the National Center for Manufacturing Science (NCMS) standard drop test procedure. Finally, high performance conductive adhesives are formulated by combining the modified resins and the effective additives. It is found that 1) purity of the resins and moisture absorption of the formulation affect the contact resistance stability of an ECA; 2) the oxygen scavengers and corrosion inhibitors can delay contact resistance shift; 3) one of the corrosion inhibitors is very effective in stabilizing the contact resistance; 4) some rubbermodified epoxy resins and the epoxide-terminated polyurethane resins can provide the conductive adhesives with superior impact performance; and 5) conductive adhesives with stable contact resistance and desirable impact performance are developed.
Synthetic Metals, 2002
Electrical conductivity and elongation at break of polyurethane (PU) filled with two different grades of graphite, Ag-coated basalt particles and fibres were investigated in this paper. Percolation concentrations were determined to be as follows: 21 or 22 vol.% for PU/graphite composites, 29 vol.% for both PU/Ag-coated particles and PU/Ag-coated fibres composites. It was found that the steepest increase in electrical conductivity and the more pronounced decrease in elongation at break occurs at the same filler concentration range for all investigated systems. A good correlation between phenomenological model, introduced in [J. Mater. Sci. Lett. 18 (1999) 1457], and experimental data for all investigated systems was also observed. #