Light intensity and uniformity is determined by the LED array method employed.
LED arrays are assemblies of LED packages or dies that can be built using several methods. Each method hinges on the manner and extent to which the chips themselves are packaged by the LED semiconductor manufacturer. The intensity and uniformity of light output from an array depends upon the method of LED array manufacturing used.
Examples of packaged LEDs are shown in Figures 1 and 2. A packaged LED has an optical lens, bonding wire, electrodes, and resin to encapsulate the LED for protection.
Figure 1: Through hole (T-pack) LED
Figure 2: Surface Mount LED
These packages can be affixed to a heat-sinking substrate using either “through hole” mounting or surface mounting. The through-hole mounted devices are often referred to as T-pack LEDs. Arrays built of through-hole LEDs are shown in Figure 3.
Figure 3: LED Array comprised of T-packs
Chip-on-Board LED Arrays
In Chip-on-Board LED Arrays, the bare chip is placed in direct contact with the substrate. This method offers a number of advantages over the use of Packaged LED arrays:
Compactness, due to the small size of the LED chip
High intensity, particularly at close distance
High uniformity, even at close working distances
Best thermal performance for better lifetime, stability and reliability
Using automated pick-and-place machines, ProPhotonix attaches individual LED chips directly to a printed circuit board, creating “chip-on-board” LED arrays.
Figure 4: Chip-on-Board Array
Packaged LED array vs. Chip- On -Board LED Array
Due to the small size of the LED chip, Chip-on-Board technology allows for a much higher packing density than surface mount technology. This results in higher intensity and greater uniformity for the user. The table shows the number of LEDs that can be placed on a 10mm square area and the resulting array power.
As you can see, the number of LEDs that can be placed using COB technology is 38 times higher than that of T-Pack technology and 8.5 times higher than with surface mount technology. Consequently, the output power is orders of magnitude greater with COB versus Packaged placement technology.
ProPhotonix designs & manufactures custom LED arrays for OEMs across a wide range of industries. For more information on our custom LED Solutions, contact us.
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