Materials & FasteningMaterials & Fastening

Heat Sink Bonding

3M 8000 Series Thermally Conductive Adhesive Transfer Tapes. These tapes spring from research 3M has conducted in heat sink packaging. "We evaluated typical heat sink configurations," explains Senior Technical Specialist Jeff McCutcheon. "And we found that many have contours and surface features which people are not fully aware of." Some of these features-like a 7-mil hill in one example-are easy not to notice but can significantly decrease the contact between tape and heat sink. Some tests found as little as 20% surface wetout (contact area) in real-world applications. The 8000 Series tapes that come out of 3M's findings have been optimized to provide better contact with heat sinks. According to McCutcheon, these tapes-at 5, 10, 15 and 20 mils-are more conformable. And these tapes have a pure adhesive construction so they have no stiff carrier to interfere with gap filling. The tapes also feature a redesigned adhesive that boosted torque-test (twist-off) strength values by about 50%, he says. For more information, and thermal data for the new tapes, visit www.3m.com/conductives. Enter 582

Tough conditions, easy use

Master Bond Polymer System Supreme10HT/S Epoxy. This electrically conductive, one-component epoxy has been formulated with tough environmental conditions in mind. It tackles service temperatures from cryogenic levels up to 400F and offers enhanced mechanical performance. Lap shear strengths on properly prepared substrates, for example, exceed 1,800 psi, reports Master Bond VP Robert Michaels. At the same time, this silver-filled epoxy meets NASA's low outgassing requirements and has improved chemical resistance, he adds. Supreme 10HT/S has a shelf life of 3 months at ambient temperatures and longer at lower temperatures. Curing typically takes place at 250F for about one hour-though faster curing routines are possible at higher temperatures. A snap-cure version called Supreme 10HTSF cures at 380-400F in less than 2 minutes. (www.masterbond.com) Enter 583

No muss, no fuss

Devcon SC 2000 Series Epoxy. These single-component epoxies-four in all-may be formulated for ease-of-use-but they offer enhanced physical properties too. "One-component systems can be a nice step up for people who want to get away from mixing and not worry about their work time," says David Bongiorni, Devcon's market development manager. "But they also offer slightly better thermal and chemical resistance than comparable two-part epoxies." Capable of withstanding service temperatures from -60 to 300F, these adhesives also hold up under exposure to oils, gasoline, potassium hydroxide solutions, aluminum sulfate solutions, and other chemicals. Self-leveling and curable by a variety of heat sources, these no-mix adhesives offer unlimited working time at room temperature. The SC 2000 Series provides structural bonds on a variety of substrates, including metals, ceramics, and glass. (www.devcon.com) Enter 584