Question: What are the pros and cons of using pressure-sensitive tape adhesives in place of liquid adhesives in the assembly of electronic devices?

Answer: There are many aspects to cover when addressing this subject. Tapes have certainly made inroads into what were traditionally liquid applications. For bonding applications, tapes are supplied with adhesive coated on two sides of a carrier and having release tapes. They do not cure like liquid adhesives, but remain as viscous liquids in the bondline. They are applied by removing the release layers and then using pressure to attach them to the surfaces.

Tape adhesives have some advantages over liquids, namely instant fixture (although they often take two or three days to achieve their maximum bond strength), inherent flexibility, ability to bond different surfaces, thin and controllable bondlines, and relatively simple application without using sophisticated application equipment. Tapes can also be die-cut for precise application.

Their weaknesses include fairly low bond strength (although versions with tensile shear strength of 100 psi are available), only moderate high-temperature resistance and poor load-bearing capabilities. Liquid adhesives are harder to handle, and have to be cured with heat or UV or be mixed for two-component systems.

Tapes compete with mechanical fixturing methods and a range of well-established liquid adhesives, including epoxies, cyanoacrylates, acrylics, UV acrylics, and polyurethanes. They are expected to increase their market share as some of their weaknesses are overcome through product development and via customer awareness.  ASI