For CapSense applications, following are the basic two considerations while selecting an adhesive:
1. Since the dielectric constant of air is very low, an air gap between the overlay and sensor degrades the performance of the sensor. Thus, the adhesive should be used to properly stick the overlay with the PCB.
2. The adhesive must be nonconductive.
A transparent acrylic adhesive film from 3M™ called 200MP is qualified for use in CapSense applications. This special adhesive is dispensed from paper-backed tape rolls (3M™ product numbers 467MP and 468MP).
Refer "getting started with CapSense" design guide for CapSense design guidelines.