Material selection requirements for LED package brackets for different applications

1. Requirements of LED packaging factory for LED bracket:

LED (visible light) can be divided into: LED display , LED lighting , LED backlight , LED indicator light, automotive lighting applications, etc. Different applications have different requirements for LEDs. As one of the three most important raw materials for LEDs, LED brackets have an important impact on the performance of LEDs. Therefore, different LED applications have different requirements for LED brackets.

1. LED display

LED display screens can be divided into outdoor LED display screens and indoor LED display screens. Outdoor LED display screens must have high brightness and a high level of protection (must have windproof, rainproof, and waterproof functions), so they are generally implemented using Lamp LED or Display dot matrix, with an area of ​​tens to hundreds of square meters and low cost; while indoor LED display screens have smaller light points and require good color consistency, wide viewing angle, and especially require very good color mixing effects, so they are generally implemented using SMD LEDs . Due to the high cost, the display area is generally a few to tens of square meters.

Since indoor screens are relatively expensive, no consumer is willing to buy one that will dim or have different brightness and color after only a few thousand hours of use due to a significant attenuation of brightness . Therefore, in addition to requiring the use of larger and higher-quality chips when packaging indoor screen LEDs, the PPA reflector cup of the LED bracket must also have good long-term yellowing resistance. It must be able to maintain a high reflection for a long time without absorbing light due to the yellowing of the reflector cup, causing rapid brightness attenuation. It must also be able to withstand long-term exposure to trace amounts of ultraviolet light emitted by the blue light chip without aging and yellowing in the short term. Therefore, most LED brackets used for indoor screen applications will be injection molded with PPA materials that have good long-term yellowing resistance, rather than just pursuing initial whiteness and brightness. 2. LED backlight

It can be divided into small-sized backlight sources and medium-sized and large-sized backlight sources.

A. Small-sized backlight: generally refers to LED backlight used in small-sized consumer electronic products such as mobile phones, MP3, MP4, etc. Because these small-sized backlights are generally not used continuously for a long time, and there are no strict requirements for long-term performance, and they are not sensitive to light decay. Therefore, when encapsulating, most of them will use PPA materials with good initial whiteness (brightness) and high reflectivity to make LED brackets. The requirements for long-term yellowing resistance are not as strict as those for medium and large-sized backlights. Therefore, when selecting LED brackets, both high initial brightness and low cost will be considered.

B. Medium and large size backlight: generally refers to LED TV backlight, laptop backlight and some medium and large size display screen backlight. Laptop backlight and some medium and large size display screen backlight are generally used for a long time in a day, and the cost is also high. No one wants their laptop, display or LED TV to have a large light decay and inconsistent brightness and color, or even dead light within one or two years. They have strict requirements on the long-term performance of the product, especially LED TV backlight.

Therefore, when encapsulating LED brackets, most people will choose brackets made of PPA materials with good long-term yellowing resistance, rather than just pursuing initial whiteness and brightness. Because materials with good long-term yellowing resistance generally have light stabilizers added, they can resist the irradiation of trace ultraviolet light emitted by blue light chips for a long time and delay the speed of aging and yellowing. Moreover, the brightness difference of LED brackets with good initial whiteness and LED brackets with good long-term yellowing resistance under the same conditions is very small (less than 5%).

3. LED lighting

It can be divided into LED street lighting, commercial lighting, landscape lighting and indoor lighting.

A. LED commercial lighting has developed rapidly due to its long service life (lit for more than 12 hours a day, and some even lit for 24 hours a day), energy saving, environmental protection, and fast cost recovery . At present, high-power and COB LEDs are mostly used to achieve this. High brightness, but limited by the influence of heat dissipation technology, the current cost is high and the service life cannot meet the expected requirements. At present, when LED packaging uses LED brackets, most of them will use PPA material brackets with good initial whiteness and high brightness. Because the cost of commercial lighting is recovered quickly, there is no strict requirement for long-term reliability. B. LED street lighting and landscape lighting are both municipal engineering lighting. The working hours are generally less than 12 hours a day. They have developed rapidly under the support of low-carbon energy saving, green environmental protection and the government. High light brightness and good illumination , but affected by heat dissipation technology, the current cost is high and the service life cannot meet the expected requirements. At present, when high-power LED packaging uses LED brackets, most of them will use PPA material brackets with good initial whiteness and high brightness.

C. Indoor lighting (general lighting): Currently, T8, T5, etc. are the mainstream, and there are different sizes according to different powers. Both SMD and High Power LEDs are used for indoor lighting, and SMD is still the mainstream. Indoor lighting generally requires uniform light output, good consistency, good color rendering and long service life, but due to the uneven quality of LEDs, as well as the influence of heat dissipation technology and consumer concepts, most of them are currently sold to foreign markets. However, in terms of indoor lighting requirements, it is recommended that LED packaging factories use LED brackets made of PPA materials with good long-term yellowing resistance when selecting LED brackets, and do not ignore their long-term reliability in pursuit of high initial brightness.

The lack of industry standards and specifications in the domestic LED lighting market has resulted in a low entry threshold for the LED lighting industry. This has led to some packaging companies ignoring product quality for the sake of temporary benefits, turning the long service life of LED into a shortcoming of LED lighting. If ordinary people no longer believe in LED general lighting, the entire domestic LED general lighting market will collapse, which will be a disaster for the entire LED industry. As for the LED brackets currently available for lighting, the ceramic LED bracket has the best heat dissipation, and the LCP plastic bracket has the best long-term yellowing resistance. However, the former is expensive, about 10 times more than the PPA bracket, and cannot be widely promoted due to cost considerations; the latter cannot currently achieve the whiteness that PPA can achieve, and the initial brightness is poor and cannot be widely promoted.

Therefore, as far as the current situation is concerned, the urgent problem to be solved is the light output efficiency and heat dissipation of LED. At the same time, the LED bracket made of PPA material with good long-term yellowing resistance should be injection molded to ensure product quality.