Low temperature snap cure thermoset adhesives with good worklife

Abstract

A break-through adhesive chemistry has been developed that achieves cure in seconds at temperatures below 110°C. These adhesives enable low cost RFID tag construction with low temperature substrates at extremely high assembly speed. Assemblies that require electrically conductive or non-conductive adhesives can benefit from this innovation. The cure speed of isotropic conductive paste (ICP) adhesive is demonstrated by measuring dynamic conductivity development during the heating process. Rheological stability at room temperature persists for days. The impact of rheological behavior on high speed processing is discussed. Silver ink based antenna and simulated die strap are used as test vehicles for processing and reliability tests. The integrity of the assembly is shown using a mandrel bend test to simulate downstream processing such as converting and printing. Together with a proprietary thermal radiation cure method, assembly speeds up to 300 feet/minute are achievable. The electrical stability of these bend-tested tags were evaluated in air to air thermal shock (-40°C to 80°C) and 85°C/85%RH conditions and found to be stable. The reliability results are presented and the challenge of high speed reel-to-reel processing are also discussed based on an isotropic conductive adhesive approach. This paper discusses these results and presents an adhesive technology that enables low cost RFID tag assembly.