A. The LEDs used:

The LEDs are surely the most important quality criteria when it comes to LED video displays.
They determine the image quality of the display and are decisive in determining how the image quality is retained over time. We at deset can work with any desired LEDs, providing our customers with the option of determining the important LED characteristics themselves. Our recommendations for the use of LEDs can be found under our "Conclusion - LED quality."

The quality characteristics for LEDs are very diverse, and, here too, the maxim applies: the most expensive choice is not always the best choice. To highlight an example from the automobile industry: You are sure to be able to spontaneously list a variety of luxury sedans, though you may not generally consider these when selecting a new vehicle. Price and purpose play major roles in the decision of which model to choose. And also, luxury sedans differ in many ways, although they often all meet the highest quality standards.

The quality of an LED is determined primarily by the chip used. It determines the service life of the LED and how the lighting behavior of the LED changes over time.

Chip manufacturers of LEDs:

1. Nichia (Japan)
2. Cree (USA)
3. AXT (USA)
4. Epistar (Taiwan)
5. Silan (China)

The prevailing opinion on the market today is that LEDs made by Nichia are the best for use in LED video displays. However, they are also undeniably the most expensive LEDs on the market by a wide margin. The price of LEDs varies on average from less than one cent per LED to up to 15 cents and more, depending on the type of LED (RGB LEDs with three chips in one housing are often more expensive). For example, one model in the deset LED display line, 16N, has 6144 LEDs. An extensive price difference can arise in manufacturing, depending on the LEDs used.

So what are you paying for when purchasing an expensive LED, besides the brand name of the manufacturer?

1. 1. Brightness

   The brightness of the LEDs is measured in mcd (milli-candela).
   The higher the brightness, the better. You can run the display at a lower brightness, thus increasing the service life or increasing visibility during the day when the sun is shining.

2. 2. ESD (electrostatic discharge)

   The LED chips produced by various manufacturers differentiate themselves through a varying sensitivity to the effects of electrostatic discharge (for example due to contact).
   Display failures caused by electrostatic discharges can be prevented by implementing safeguarding measures against ESD in the production process.

   The following table indicates the voltages that the LEDs can withstand in case of electrostatic discharges:

   Cree:	2000V
   Nichia:	1000V
   Taiwanesische Chips:	800V
   Chinesische Chips:	200-800V

3. 3. Sensitivity to temperature variations

   Poor LED chips can fade faster, i.e. their service life can shorten, if they are exposed to high temperature variations. Depending on the country, temperatures can become extremely hot or cold during the summer or winter months, respectively. As a result, a poor LED quality could cause premature fading of the overall, expensive LED display.

4. 4. General service life

   The general service life of the LEDs often lies between 50,000 and 100,000 hours.
   (100,000 hours equates to 10 years of continuous display operation at full white, if no other factors exist which reduce the service life; such as increased heat in the display housing, or operating the LEDs at overvoltage in order to balance brightness reduction, for example, through matrix control or implementation of the multiscanning process (see "Control")).

5. 5. Brightness reduction due to aging

   Below is a table indicating the lighting reductions which arise within the first 10,000 hours:
   LED brightness reduction after the first 10,000 hours, sorted by manufacturer

   	Nichia (Japan)	Cree (USA)	AXT (USA)	Silan (China)	Taiwan
   Red LED	2,50%	Unknown	Unknown	Unknown	28%
   Green LED	2,50%	26%	8%	7%	28%
   Blue LED	2,50%	45%	8%	7%	28%

Conclusion - LED quality:

If money isn't an issue, choose Nichia LEDs.

Many of the quality factors for LEDs play a role in how they behave over time. Nichia LEDs are the only ones for which it is generally known that they thoroughly meet the required criteria, positively setting themselves apart from other LEDs on the market. The long-term values for some of the other manufacturers were not available. Many developments in the LED field are so new that long-term values over five, ten, or more years don't exist.

If price and performance should be balanced, we recommend LEDs with AXT chips.

In terms of overall service life, AXT LEDs are 1/3 weaker than Nichia LEDs but they cost significantly less. With the service life of AXT LEDs, you can run your display for 7 years of continuous operation at full white, although this is never done in reality. In displaying average video image content, the effective service life increases by two to four times as much, that is, 14 to 28 years, depending on the image content.

In contrast to the still very expensive Cree LEDs, AXT LEDs age more evenly and also don't have as much lighting reduction after 10,000 hours. This proves particularly lucrative when exchanging individual pixel cards, since the calibration requirement is lower.

Since we are a display manufacturer and not an LED manufacturer, you can determine the desired LEDs.

In the end, we'll work with any LED.