LED assembly requires various manufacturing processes that include fluid dispensing. Typical applications are:
Lens attachment requires exact adhesive amounts dispensed at specific locations, which are sometimes in the bottom of cavities due to the optics structure. Optics alignment between lens and LED die is critical and the assembly needs to avoid contamination of the lens. The proper amount of adhesive is also critical to ensure the proper parallelism of the lens during bonding.
Flip chip LEDs need tight keep-out-zones and tiny dots dispensed for underfill. Many packages have multiple dies and the spacing of die is tight for optimum performance. The underfill material cannot interfere with the light production and the underfill materials must have high thermal conductivity for good LED heat dissipation; silicone material is often selected.
Outdoor LED displays need protection from environments such as humidity for reliability of electrical circuits. Conformal coating is used to protect electronics from hostile environments with moisture exposure, temperature extremes, and adverse chemical conditions. Many outdoor applications for LEDs, such as signage, traffic lights, automotive and architectural illumination are made reliable with the application of conformal coatings. Equipment from Nordson ASYMTEK is ideal for applying conformal coating to selective areas of the circuits with tight keep-out-zones.
Requirements for LED assembly material dispensing are:
- Consistent, exact fluid amounts, often using silicone which is difficult to dispense due to elasticity
- Accurate location
- Tiny fluid dot size
- Tight keep-out-zone
- Selective area conformal coating
- Fast throughput—high unit per hour (UPH)