Consumer electronics companies are striving to create products with “infinity edges,” which maximize screen size while maintaining durability, performance, and style. With a continually shrinking bond area for phone, tablet, and other electronic device screens, infinity edges are difficult to achieve because there is less real estate for assembly components. Tapes and reactive hot melt adhesives are two technologies currently used in device assembly. Yet reactive hot melts are being used more and more frequently to create infinity edges.
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Reactive hot melt adhesives can maintain high bond strength in very small bond areas. This is especially important as device companies design toward the infinity edge, leaving minimal space for adhesive application. Reactive hot melts are up to the task, as a bead the size of a human hair has enough strength to hold the weight of two AA batteries. This enhanced strength provides a more durable and reliable bond, ensuring the product’s integrity is not compromised with repeat use and handling.
Unique bonding capability is another advantage that reactive hot melts offer over other adhesives. For example, the speed at which reactive hot melts build strength allows for immediate handling and processing, which keeps production lines moving and maximizes uptime. The reactive chemistry provides excellent end-use performance and increased reliability. Reactive hot melts also can be reworkable, even with their high bond strength and set speed. Manufacturers can rework parts instead of discarding them completely, either in process or when consumers return broken devices, which saves money on both materials and production.
Earlier generations of reactive hot melts had a few disadvantages, including large container packaging and very high application temperatures. For many applications, the processing and performance advantages outweighed these drawbacks, as an automated application process offers enhanced line efficiency, less downtime, increased productivity, and a leaner process through continuous motion.
Technology advances for adhesives and equipment have addressed previous disadvantages, with products now being packaged in small containers and applied at much lower temperatures using extremely precise equipment. After being heated to temperatures of 110°C to 130°C, reactive hot melts can be dispensed through a nozzle in a very fine line—as thin as 0.25 mm in diameter. The dispense head sits on an XYZ table and either the nozzle or the table can move (see the figure).
Manufacturers appreciate the flexibility of this application method, which allows them to swiftly and easily make any necessary adjustments in the process.
All of these factors—process efficiency, bond strength, end use performance, and more—help make reactive hot melts more cost-effective and reliable than tapes or other adhesives. With the electronics display industry trending more and more toward infinity edges, the use of reactive hot melts will continue to rise.
Elana Jacobs is the global program manager, electronics, for H.B. Fuller. She has a bachelor’s degree in mechanical engineering from the University of Minnesota.