appliance DESIGN IAM : Page 7many other process parameters is essential. Furthermore, although a light-curable product may be considered compatible with both arc lamps and LED light sources, switching to an LED light source can result in significant differences in post-cure bond performance (see cure-results comparisons listed in Table 1). Myth No. 2—You can select LED spot-lamp systems and light-curable chemistries based on datasheet specifications and website information. Reality There are far too many variables involved in light-curable chemistry applications to use datasheet specifications and website information as the sole means for equipment and chemistry selection. Datasheet and website specifications, although useful, may lack application-specific information. When LEDs are manufactured, each batch may yield LEDs with varying spectral output. An LED curing-light manufacturer may state in a datasheet that their LED curing lights deliver an energy peak at a specific frequency, but the question remains as to the real spectral accuracy of the LED engine. Lower-quality LED curing units may actually emit over a wider range (370 to 415 nm) of ineffective peak energies. This deviation from the required curing wavelength can result in under-cured bonds, coatings, or pottings. Datasheet and web-based Figure 3. Photoinitiator absorption compared to 365 nm and 385 nm LED curing-light spectral distributions. information may have other shortcomings. Some adhesive manufacturers may not state the irradiance and spectral distribution requirements for optimum curing and performance. Some curing-light and adhesive, coating, and potting product formulators do not include substrate compatibility information in technical information on their website. Key information is often missing for specifying curing systems with confidence. There is no shortcut to success as you consider adopting LED curing technology in a MANUFACTURINGPROCESS #ONSIDER a total-solutions provider that can complete application studies using your substrates and process requirements. Application studies ensure the LED curing light and chemistry selection combination will work. Myth No. 3—Bond performance is similar whether you are using an LED or a conventional lamp light source. Reality The direct replacement of an arc lamp spot-curing system with an LED spot-curing system— without evaluation and process adjustment—can result in substandard bond performance. Differences in LED wavelength distribution and intensity necessitates the evaluation (if not formulary modification) of the chemistry and curing-energy dosage. There are some adhesives that provide the flexibility to use both types of light sources without changes to your process. Verification is strongly recommended to ensure successful results. Table 1 (on page 6) depicts various light-curable adhesives that cure with either LED or conventional light sources, but also illustrates that the cure times and post-cure properties of the chemistry may differ. Myth No. 4—UV LED light sources best cure formulations when the wavelength peak is at 365 nm. International Appliance Manufacturing 2010 7 Publication List |
