Magnetically Aligned Novel ACA Revolutionizes 3D Chip Stacking

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The use of anisotropic conductive adhesive (ACA) is not new within the electronics industry; however, drop-in replacements don't exist for lead-based and lead-free solder assemblies. Current ACAs require pressure and sequential assembly of components. Sunray Scientific's Novel ACA (ZTACH) is an excellent drop-in ACA replacement that will revolutionize the packaging industry and make electronic products more sustainable and green. ZTACH has been proven to enable the use of existing SMT equipment, lower the processing temperatures (75–150°C), and also eliminate the need to apply pressure, thereby eliminating the need to invest in new equipment and processes and reducing energy consumption.

ZTACH is composed of conductive, ferromagnetic particles in an epoxy matrix, which is printed or dispensed on the individual pads or the entire footprint of the components. The material is cured in a reflow oven, after all components are in place, in the presence of a magnetic field. The magnetic field aligns the conductive particles in the Z-axis direction, during curing, thereby eliminating the need for pressure. The formation of conductive columns within the adhesive matrix during cure provides a very high insulation resistance between adjacent conductors and also eliminates the need for precise printing or dispensing of adhesives onto individual fine pitch pads. Modification of the filler size and filler proportion enables control of the column density, column spacing and the required contact pad area for minimum resistance. ZTACH can be mass cured, eliminating the need for sequential component assembly. The formation of many parallel columns especially with micron and sub-micron sized particles between mating pads reduces the resistance considerably.

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Editor's Note: This article originally appeared in the February 2016 issue of SMT Magazine.