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New Adhesives, Encapsulants, and Other Non-solder Assembly Materials
April 12, 2010 |Estimated reading time: 6 minutes
— In the surface mount materials sector, ECM introduced rubber-like adhesives; Henkel re-engineered Macromelt encapsulant for medical and auto uses; Creative Materials has silver-filled epoxy adhesives; Fujipoly debuted Sarcon TIMs; Zymet offers reworkable underfill; Dymax put out a new adhesives guide; Cotronics makes a high-purity adhesive to resist high temperatures; and Permabond introduced an instant-attach adhesive.Electrically Conductive Epoxy Adhesives
These electrically conductive epoxy adhesives are 100%-solids silver-filled epoxy systems, designed for attachment of electronic components. They have a one-to-one mix ratio by weight, are fast-curing, have a long pot life, and are resistant to thermal shock. In addition, they have a long shelf life in the two-component system, have low cure temperatures (as low as 80°C), are RoHS compliant, and have low ionics. With good rheological properties, these products are dispensable via syringe or using high-speed jet dispensing systems, allowing dispensing in dots or lines as narrow as 1 to 3 mils. These products can be used for electrical component attachment in a range of application areas, including solar assembly, medical device and automotive manufacture, electronics and components production. Applications include mounting LEDs, chip attachment, solar cell assembly, metal-to-glass bonding, attachment of leads, and lid attachment. The products in this epoxy family share many of the same characteristics, each with specialized features. 118-15A/B and 118-15C are fast-curing with excellent conductivity. 123-39A/B and 123-39C are stencilable, with higher viscosity and bond strength. 124-08A/B and 124-08C have greater thermal shock resistance and flexibility. 124-08LVA/B and 124-08LVC offer lower viscosity for jet dispensing systems. 125-18A/B and 125-18C have increased bond strength. All are available as two-component (A/B) systems or as single-component precatalyzed (C) products. Creative Materials Inc., www.creativematerials.com/datasheets.html
Electrically Conductive Interconnect Adhesives
Sol-Ag Series interconnect adhesives were developed to exhibit rubber-like flexibility, reducing stress in the interconnect bond line and imparting resistance to thermal cycling. The rubber-like properties are said to increase the overall peel strength of the assembly. The adhesives are designed to withstand accelerated damp heat conditions when tested to IEC standards. Sol-Ag Series also has demonstrated unchanged electrical performance after 1000 hours at 85°C/85RH on tin/silver (SnAg) and copper (Cu) surfaces. ECM LLC, mfrancis@emsadhesives.com
Encapsulant Re-engineered for Auto and Medical Applications
As an alternative to traditional potting and encapsulation techniques, Macromelt offers automated processing, throughput and cure time advantages, and fewer processing steps. The polyamide hotmelt quickly encapsulates exposed circuitry to form the outer shell of the device and delivering a self-contained integrated assembly. With a low application pressure of between 20 to 500psi within the mold cavity, there is no risk of damage to sensitive circuitry or fragile devices. When in a liquid state, Macromelt flows in and around the tightest dimensions without the high levels of pressure used with traditional injection molding or potting techniques and significantly reduces stress even for the most highly miniaturized components. Macromelt OM341 was designed for the hybrid automobile market and Macromelt 2384 for the medical electronics sector. Safety orange-colored Macromelt OM341 required modifications to meet color, viscosity, and UV stabilization specifications. Macromelt OM341 will be used for easy identification and access to the main power connector for a new hybrid vehicle. Other Macromelt formulations will also be part of the vehicle’s electrical sensor system, as the hotmelt products are used for seven different components within this automobile: the main electrical outlet, seatbelt tension sensor, occupancy sensor, steering position sensor, strain relief receptacle and base, CCID board and the vehicle plug for the travel set and charge station. The UV stabilization chemistry used in safety-orange Macromelt OM341 ensures that the color remains vibrant, without discoloration from exposure to UV light. This same UV stabilization characteristic, along with solvent-resistant technology, has also been incorporated into Macromelt materials used by the medical industry. Used to encapsulate numerous medical monitoring devices, Macromelt 2384 is highly solvent resistant for sterilization. Henkel, www.henkel.com/electronics
Reinforced Gap Filler Pads
Sarcon GR-HF gap filler thermal interface materials (TIM) are pads manufactured with a hardened top surface as well as a reinforced nylon mesh layer. The added reinforcement and less tacky surface treatments reduce tearing, elongation and damage during complex assembly and rework operations. These characteristics also make the TIM ideal for applications that require intricate die cutting. Depending on the selected formulation, Sarcon GR-HF exhibits a thermal conductivity up to 2.8 W/m°K and a thermal resistance as low as .67°Cin2/W. This flame retardant gap filler pad is manufactured in sheets up to 200 × 300 mm with thickness options from 1.0 to 5.0 mm. Fujipoly America Corporation, a wholly owned subsidiary of Fuji Polymer Industries Co. Ltd., http://www.fujipoly.com.
Low CTE Reworkable Underfill
Silica-filled reworkable board-level underfill encapsulant, X2825 has a coefficient of thermal expansion (CTE) of 26 ppm/°C. The underfill reportedly enhances drop and shock reliability and has better thermal cycle performance than higher CTE underfills. Thermal cycling of a BGA between -20° and +85°C had no failures after 1500 cycles. Addition of silica filler to an otherwise reworkable underfill ordinarily damages reworkability. X2825 is easily reworked, despite the presence of filler. Rework is accomplished by use of elevated temperature, 170° to 180°C, to remove the underfill fillet. Underfill residue is easily scraped off. Zymet Inc., info@zymet.com
Adhesives Selector Guide
DYMAX Corporation released an enhanced version of its Selector Guide for Industrial Assembly Adhesives. The company manufactures a wide range of light-curable materials and equipment. This reference tool provides detailed guidance for selecting the best DYMAX adhesive and curing equipment for glass, metal, and plastic bonding applications in the appliance, automotive, aerospace, solar, fuel cell, and alternative energy manufacturing and assembly markets. Selector tables in the guide list glass, metal, and plastic bonding adhesives, their properties (such as viscosity and durometer hardness), and the unique applications for each product. The tables detail typical substrates and the bonding capabilities of DYMAX products. Also described in this guide are the types of light-curable products available and their chemistries, as well as compatible light-curing and dispensing systems. Dymax, www.dymax.com
High-purity Alumina Adhesive
Resbond 989 high-purity, alumina adhesive offers continuous protection to 3000ºF, protecting critical electronic components against moisture and humidity. It is a one component product applied directly to metals, glass, ceramics, graphite, and silicon carbide. Resbond 989 cures at room temperature and provides high bond strength and electrical, moisture, chemical and solvent resistance. Applications include bonding and protecting thermocouples, heat sensors, critical electronic components, heaters, heating elements, resistors, instrumentations, strain gauges, electrical feed-throughs, optical fibers, etc. Cotronics Corporation, www.cotronics.com
High-performance Thermal Putty
A high-performance thermal interface silicone putty, SARCON XR-Um-Al is a gap filler compound that has a putty-like consistency. This physical property contributes to the material’s low contact and thermal resistance while maintaining a thermal conductivity of 17 W/m-k. SARCON XR-Um-Al is manufactured with a thin aluminum carrier film for application. The low adhesion aluminum barrier enables users to remove the carrier film after installation with no pull-out effect. This thermal interface material is available in sheets up to 50 × 50 mm with thicknesses ranging from 0.2 to 0.5 mm. SARCON XR-Um-Al complies with UL 94 V-0 flame retardancy specifications and is most commonly used to transfer heat from between CPUs and semiconductors to close proximity heatsinks. Fujipoly America Corporation, www.fujipoly.com
High-temperature-resistant Instant Adhesive for Component Tacking
Permabond 820 quick-setting, instant adhesive resists temperature ranges up to 200ºC, compared to typical ethyl cyanoacrylates that resist temperatures to 82ºC. Permabond 820 is a modified ethyl cyanoacrylate that has a fast fixture time and high-temperature resistance, suiting bonding components in position on dual-sided PCBs prior to wave soldering. The adhesive is colorless with a viscosity of 100cPs. Cyanoacrylate adhesives are single-component adhesives that cure by reacting to small traces of moisture on the surface of the substrates being bonded. Permabond, www.permabond.com
Check out more surface mount materials:New Conformal Coatings, Encapsulants, Adhesives, and Other Assembly Materials New Surface Mount Assembly Materials New Thermal Management ProductsNew Materials: Thermal Interfaces, Encapsulants, Adhesives, and More
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