AEROSIL® for Adhesives and Sealants - Adhesives & Sealants by ...

SMD AdhesivesSMD componentadhesivewired componentSMD adhesives attach the electronic device to the circuit board beforethe completed circuit boards are turned upside down for immersion in the soldering bathAEROSIL® – Advantages in Adhesivesfor Electronic ComponentsAEROSIL® helps the electronics industry in sticky situationsFor decades now, the electronics industryhas been the fastest growing and fastestchanging industry worldwide. Adhesivesare used in the electronics industry toadhere electronic components to printedcircuit boards and to seal electroniccomponents (e.g. relays). Miniaturizationis the main trend in the development ofcircuit boards and in manufacturingtechnology. The introduction of SMDtechnology (Surface Mounted Device)in the 1980s, replacing the then standardwired elements, made it possible toachieve further miniaturization of thecomponents and a higher degree ofrationalization during fabrication. TheSMD process involves the direct solderingof the device contacts onto solder spotslocated on the surface of the circuit board.SMD adhesives play an important role inthe mounting of circuit boards withsubsequent soldering. They attach theelectronic devices to the circuit boardbefore the completed circuit boards areflipped for immersion in the solderingbath. The adhesive is dispensed from acartridge; this requires the adhesive tohave a suitable drop profile. The volumeapplied must be sufficient to bridge thegap between the circuit board and theSMD components. The diameter of theglue spot must remain within the spacebetween the solder spots, withoutinadvertently wetting the connectionspots with glue. The drop profile of theadhesive is defined by the thixotropy,the viscosity in a state of resting, andthe surface tension. Furthermore, theadhesive has to fulfill additional highrequirements during application:• Thixotropic flow behavior,high viscosity in resting state• Sag-resistance during thecuring process• High drop profile, no strings• Constant drop profile and volume• High green strength• High cure strength• Rapid cure rate• Guaranteed rapid applicationof very small drops• Bubble-free application, lowmoisture adsorptionBoth epoxy resin and acrylate-basedadhesives are available for use as SMDadhesives. The hydrophobic gradesAEROSIL® R 972, AEROSIL® R 202, andAEROSIL® R 805 are very effectivethixotropic agents for these adhesives.SMD adhesives can be adjusted usingAEROSIL® R 972, AEROSIL® R 202, andAEROSIL® R 805, to fulfill the demandsfor thixotropic flow behavior, highviscosity in resting state, high dropprofile, and anti-sagging during the curingprocess.15