Adhesives that cure in a short time tend to be unstable during storage, while adhesives that are stable during storage tend to cure slowly. As a result, either heat or ultraviolet radiation is often used to hasten curing. However, both methods have some limitations. For example, some substrates might not be able to tolerate extended time in a curing oven. Similarly, the obvious disadvantage of UV curing is that the radiation must be able to reach all parts of the assembly.
Microwaves represent an alternative energy source for curing adhesives. Like UV radiation, microwaves consist of electromagnetic waves. Unlike UV radiation, however, microwaves are radio waves rather than light waves. As such, there are no components that microwaves cannot reach. And, since only materials that absorb microwave energy undergo self-heating, selective heating is possible. In fact, selective heating with microwaves makes it possible to cure an adhesive while simultaneously cooling other parts of the substrate by external means.