Epoxy adhesives aluminum filled

Best silver-filled epoxy adhesives Aluminum-filled (50%) epoxy Epoxy filled with 75% by wt. Al,0, Epoxy filled with 50% by wt. AlA Epoxy filled with 25% by wt. AIA... 

The effect of fillers in adhesives might be considered as another general effect which may have similar responses for a variety of surface conditions. Bodnar and Wegman(96) have shown the superior resistance to natural weathering of filled polyamide-epoxy adhesive/aluminum joints as compared to the corresponding joints made with nonfilled Epon 828/Versamid 140 combinations. Minford<97) has obtained similar results comparing filled and unfilled Epon 815/Versamid 125 combinations in a variety of accelerated lab tests. Minford ) has also noted durability differences between different fillers in certain exposures. For example, aluminum-powder-filled polyamide/epoxies tested superior in four-year exposures to marine conditions. 

Other adhesives recommended hy ICI are 3M Company s Scotch Weld 2216 two-part epoxy, Amicon s Uniset A-359 one-part aluminum-filled epoxy, American Cyanamid s BR-89 one-part epoxy, Bostik s 7026 synthetic ruhher and 598-45 two-part adhesive, GE s Silgrip SR-573, and Goodyear s Vitel polyester with isocyanate curing agent. 

The best current 100% solids epoxy adhesives contain about 70% aluminum oxide by weight and give thermal conductivities in the range of 0.8-1 in the English units shown in Table 2. For convenience, a conversion chart is included in Table 2 to permit conversion to any other set of units. The k values for the best alumina-filled epoxies are 10-12 times greater than for unfilled epoxy resins, but are still much lower than for pure metals or solders. Nevertheless, heat flow is adequate for bonding most components. For example, an adhesive with a thermal conductivity of 0.91 and a bond thickness of 3 mils would be able to transfer about 20 W/cm of surface area, with a AT only about 10 C above the heat sink temperatures ... 

Kahraman R, Sunar M, Yilbas B (2008) Influence of adhesive thickness and filler conteivt on the mechanical performance of aluminum single-lap joints bonded with aluminum powder filled epoxy adhesive. J Mater Process Technol 205(1 3) 183... 

Figure 12.19 Chemical formulae of the organic compounds used to prepare a two-part silver-filled epoxy adhesive and a series of polyimide adhesives loaded with aluminum, silver, gold, diamond, or aluminum nitride.

Thermally conductive adhesives may be filled with metal, ceramic, or inorganic particles. Silver-filled epoxies have high thermal conductivities, but may not be used where there is a risk of electrical shorting. In such cases, epoxies or other polymers filled with electrically resistive, but thermally conductive materials such as aluminum nitride, boron nitride, alumina, or beryllia must be used. Some applications for thermally conductive adhesives include attachment of power devices, heat sinks, large components such as capacitors and transformers, large ceramic substrates, and edge connectors. 

Thermal-transfer adhesives that are electrically insulating also exhibit wide ranges of thermal conductivities, depending on the filler type and amount. The thermal conductivities of epoxies filled with boron nitride or diamond are approximately 4 W/m K and 12 W/m K, respectively, while those of the more common aluminum-oxide-filled adhesives range from 1 to 2 W/m K. 

Both conductive paste adhesives and pressure-sensitive tapes are widely used for EMI protection. Two-part epoxies or one-part silicones filled with silver or silver-plated copper particles are widely used as paste adhesives while acrylic conductive and nonconductive adhesives on aluminum or copper foil are used as pressure-sensitive tapes. EMI shielding tapes are suitable fortemperatures ranging from -40°Cto 121°C and are available in thicknesses from 1.5 mil to 5 miLl" Shielding effectiveness is measured as attenuation in dB at several frequencies, for example, from 1 MHz to 20 GHz. Values for several ARclad shielding tapes are given in Table 5.13. 

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