Bonding Tape
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ARclean DEV 8906 is an acrylic acid-free, electronically clean, low-outgassing bonding tape that has a permanent adhesive on one side and a cleanly strippable adhesive on the other. The adhesive is exposed upon removing the white polyester film release liner; it can also be made available with a silicone-free polyester film release liner. It reportedly eliminates the contamination and labor costs associated with adhesive residue during rework and also minimizes HDD system crashes due to contamination. It features ultralow total VOCs and low extractable ions. Adhesives Research Inc., Glen Rock, Pa.
Connector Adhesive
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Tra-Bond F112 is a two-part, low-viscosity adhesive that can be used in fiber optic connector applications. The product is said to have a long pot life and provide impact resistance. The viscosity of this adhesive reportedly remains below 3,000 cps for at least 40 minutes. It can be cured overnight at room temperature or as quickly as 15 minutes at 90°C, making it suitable for both multimode and singlemode connectors where excessive curing temperatures may cause cracking. Tra-Con Inc., a National Starch & Chemical Co., Bedford, Mass.
Electrically Resistant Adhesive
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Resbond 919 is an electrically resistant adhesive that reportedly maintains its high electrical resistance up to 2,800°F. Users mix, apply and let dry. The product is said to cure at room temperature to bond, seal, insulate and protect delicate electronic components against electricity, high heat, chemicals, corrosion and moisture. Applications include bonding, protecting and electrically insulating high-watt resistors, electrodes, extension wires, thermocouples and more. Cotronics Corp., Brooklyn, N.Y.
Single-component Adhesive
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The MB600 adhesive is a single-component, storage-stable inorganic compound that reportedly features heat resistance and adhesion to metals, ceramics, glass, most plastics and rubbers. It is said to cure readily at ambient temperatures and more quickly at moderately elevated temperatures. The product is odorless, nontoxic and nonflammable. The cured adhesive is water-soluble and reportedly does not leave any contaminants on the previously bonded surfaces. Master Bond Inc., Hackensack, N.J.
Epoxy System
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Aremco-Bond 2310 is a flexible, ceramic-filled, high-strength, structural epoxy adhesive system that reportedly provides a lap shear strength to aluminum of 4,560 psi and T-peel strength of 24 pli. This product is said to offer impact and vibration resistance and low-temperature flexibility. It also exhibits electrical, mechanical and thermal properties, and is suitable for bonding engineered thermoplastics and sheet-molded compounds used in aerospace and automotive applications. Aremco Products Inc., Valley Cottage, N.Y.
Surface-mount Adhesive
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Loctite 3615 is a single-component epoxy adhesive designed for bonding surface-mounted devices to PCBs prior to wave soldering. Said to be moisture-tolerant and formulated for high adhesion to low-stress molding compounds, it reportedly is suitable for high-speed dispense in positive displacement and pressure-time dispense systems. The adhesive cures completely in 60 to 90 seconds at 150°C, or in 3 to 5 minutes at 125°C. Loctite Corp., Rocky Hill, Conn.
Film Adhesives
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TechFilm preforms and film adhesives are predispensed on carrier sheets, continuous rolls or preforms to the manufacturers' specifications. Once the film adhesive is applied to one component or substrate, the carrier sheet is removed and another component can be mated. The application process is said to be accurate and reliable from part-to-part and lot-to-lot. The adhesive is activated with heat to produce a uniform bond that is reportedly free of squeeze-out and undesirable contact between substrates and components. APS TechFilm, Peabody, Mass.
Adhesives
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Methacrylate Adhesives are said to be high-performance adhesives designed for hard-to-bond plastics, composites and dissimilar substrates. These structural adhesives reportedly require minimal surface preparation and cure rapidly at room temperature to high-strength bonds that are resistant to weathering, humidity and variations in temperature. Said to be environmentally friendly, these adhesives are recyclable and reduce VOC emissions. Devcon, Danvers, Mass.
Adhesives
The 800 Series adhesives form high-strength bonds to 3,000 psi on metal, ferrite, ceramic and glass surfaces that pass severe thermal shock testing from -55° to 230°C. This resistance is said to result in bonds that are able to endure various conditions for DC motor, speaker, alternator, flywheel and transformer assemblies. Typical set speed for the adhesives is between 20 and 40 seconds. This polymerization is said to allow for in-line quality testing and eliminate the need for large heat-curing chambers. Dymax Corp., Torrington, Conn.
Epoxy Adhesive
The 121-20A/B is a two-component, low-temperature-curing, silver-filled epoxy adhesive. It is designed for making electrical and mechanical attachments of electrical components and devices when shorts between closely spaced contact pads are a concern. The product reportedly provides for electrical conductivity in the Z-axis while remaining electrically insulating in the X- and Y-axis. Applications include conductive splicing of ribbon cables, bonding of flex circuits to PCBs and bonding of electrical components. Creative Materials Inc. (CMI), Tyngsboro, Mass.
High-temperature Epoxy
Epo-Tek 353ND epoxy is an industry standard with biocompatible, nontoxic, Class VI-approval, optically clear adhesive with low viscosity and a 2:1 mix ratio. The company's optical adhesives are designed for optics, lasers, amplifiers, filters, fiber-to-ferrule, fiber terminations, splicing and various other fiber optic applications for high-speed communication. Epoxy Technology Inc., Billerica, Mass.
Adhesive Films
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Z-Axis Adhesive Films are anisotropic conductive films for the flex interconnect industry. They reportedly use the company's adhesive technologies and a variety of different conductive particles to connect to multiple substrates including flexible circuit, LCD glass and printed wiring board. Several of the adhesives are said to balance performance and processing requirements and offer fine-pitch capabilities to 70 mm. 3M Bonding Systems Div., St. Paul, Minn.
High Thermal Adhesive
A process ((J-2) has been developed for achieving low thermal resistance across large-area, large-CTE-mismatched components. It uses the company's high thermal adhesives with k values greater than 60 W/mK. In addition to attaining low thermal interfacial resistance, the process reportedly minimizes the shear stress due to CTE mismatches. The first large application for this new technology is expected to be attachment of heat spreaders to the backside of high-power flip chip devices. Diemat Inc., Byfield, Mass.
Electrically Conductive Adhesive
Eccobond LE 2099-78-2 adhesive is a high-purity, silver-filled paste that is designed for die and component bonding. It reportedly can cure in as little as 15 minutes or at a temperature as low as 80°C. The product is available in both two-component and premixed, frozen, single-component formulations. Emerson & Cuming, a National Starch & Chemical Co., Billerica, Mass.
TECHNOLOGY UPDATE
By William M. Stratton, III
Pressure-sensitive adhesive (PSA) technology has helped hard disk drive (HDD) manufacturers significantly control contamination. Clean PSAs are useful in the critical components that are used for HDD assembly. Changes in the design of HDDs — particularly the advancement from MR to GMR head technology with higher spindle speeds that generate more heat — have increased sensitivity to chemical contamination and set the stage for raw materials to outgas more. Design, supply and contamination control engineers are requesting PSAs that incorporate electronically clean, low-outgassing technology and higher bond strengths while maintaining strippability after burn-in.
The first generation of electronically clean PSAs for the HDD market reduced outgassing and eliminated acrylic acid to control the possibility of media fogging and head corrosion. The next generation of electronically clean technology was not only cleaner but strippable, allowing for clean removal of seals, labels and filters from stainless steel, cast aluminum, stamped aluminum and e-coated aluminum with no adhesive residue after exposure to high temperatures. Strippable PSAs have eliminated extra labor costs associated with removing adhesive residues during the rework process and reduced the probability of contamination and leaks associated with the application of replacement seals.
Electronically clean, low-outgassing PSAs provide the HDD industry with a consistent method for bonding component parts while minimizing contamination and increasing HDD reliability. They are acrylic acid-free and organotin-free, have low extractable ions, offer excellent resistance to environmental aging and are suitable for use as a tape seal after passing leak tests. HDD engineers recognize the many benefits of using PSAs during manufacturing and are now commonly specifying them on blueprints for each new HDD platform.
The next generation of PSA technology will be more electronically clean and ultralow outgassing, with improved adhesion that maintains strippability. HDD engineers are also requesting specialty liner development, including silicone-free release liners that reduce the possibility of cross-contamination during manufacturing. HDD engineers want PSAs that can be used with both small and large surface area parts and that are compatible with the new silicone-free liners. PSA manufacturers will continue to customize and develop products that meet the growing, stringent requirements of the industry as the need to control component contamination remains crucial and plays a larger role in the manufacturing process.
WILLIAM M. STRATTON, III is general manager, Electronics Business Unit, Adhesives Research Inc., 400 Seaks Run Road, Glen Rock, PA 17327; (717) 235-7979 ext. 3254; Fax: (717) 235-8466; Web site: www.adhesivesresearch.com.
