One thousand LED people have one thousand people do not know the knowledge: protective material with LED Life Association

LED is a very reliable, but the harsh application may make solid-state lighting risk. This paper expounds how to choose the right protection materials to improve the service life and performance of LED.

With the rapid development of LED and solid-state lighting industry, product developers are using technology to harsh environments. Now, we discuss in harsh environments (such as marine applications) the necessity of protection of LED and circuit components. Life and performance of coating and other protection technology can be extended to a solid state lighting system.

With the rapid development of the LED market, choose the right product is the key to ensure the performance and service life LED. In this paper, we will emphasize the use of LED in various environments, and introduces how to adopt appropriate protection under these circumstances. The development process must ensure reliability, while ensuring good optical properties of solid-state lighting system (Figure 1).

Figure 1. (UR5635) and diffusion (UR5634) optical properties of transparent polyurethane resin in the solid-state lighting systems are quite different.

The LED application is more and more diversified; the design requirements, position or function of products can prove LED designers face challenges in changing. Like most electronic devices like LED, good performance, until the external influence began to reduce their performance. These effects can include electrostatic dust, wet or corrosive environment to attract, chemical or gas pollution and many other possibilities. Therefore, need to be carefully considered to end use environment, to ensure that you can choose the right products.

Opportunity and Application

Due to the development of LED lighting LED lighting in the form of adaptability, lifetime and efficiency advantages than traditional lamp. Therefore, it is easy to understand why LED lighting is widely used in many applications, including household lamps factory, industrial lighting, lighting and architectural lighting and marine environment design etc..

The standard of building lighting applications in the environmental conditions and marine environment comparison can help us understand the potential causes of deterioration of LED. In the application of architectural lighting, the design of the lighting unit, LED itself may be covered, or toward the LED so that it is generally only possible exposure to the changes of temperature and humidity in the environment. In the marine environment, the LED lamp may be splashed or soaked in brine. In addition, in all cases, the most light service life is work in salt fog environment. High salt conditions may cause corrosion of printed circuit board (PCB), which is generally faster than humidity changes will reduce its performance. Usually, in these environments, conformal coating and encapsulation resin can provide a high level of protection.

Protection options

Conformal coating is the first protective measures we discussed. The coating is usually thin paint with PCB contour, provide good protection and does not significantly increase the weight or volume of circuit board. They are usually the thickness of 25-75 microns, and easily by spraying or dipping technology can easily use.

In order to protect the top of the LED, the use of coating must have good transparency, and in the required environment in the entire product life keep clear. If used outdoors, coating may need good stability with UV. Therefore, the best type of conformal coatings are based on an acrylic chemical material, provide clarity and color stability and excellent humidity and salt fog protection. Figure 2 depicts the salt spray test, the acrylic coating provides excellent protection.

Figure 2. when exposed to salt fog test, different chemical matrix coatings can provide different levels of performance based on.

Usually, acrylic conformal coating is solvent based products, including the use of solvent is a liquid carrier, a resin film is deposited on the substrate. The solvent used for volatile organic compounds (VOC). Because of the solvent in the application stage only in a few minutes on the LED, so for most systems, this is not a long-term problem. In some cases, the use of LED to manufacturers of products containing VOC and other specific chemicals have specific requirements, these are listed in the LED manual. Usually, the chemical compatibility check is helpful to identify the solvent type conformal coating is suitable for specific LED.

Color problem

In addition to considering the influence of coating on the LED, also need to understand the effects of coating on color temperature. Figure 3 depicts the temperature common in LED lighting (CCT) with. The temperature changes with time, also known as color maintenance, when considering the type of protective medium, which has been a problem. It is understood that no matter what material is placed directly on LED crystal, will lead to the interaction, resulting in color offset.

Figure 3. LED in some typical color bands in.

CCT usually changes to the colder temperatures from warmer temperatures and changes between different types of LED and color temperate. In addition, it will be because of the protection of material application and different. This is another area of acrylic conformal coating than other chemical materials and the types of products have more advantages.

Figure 4 depicts a typical color offset warm white LED. In order to highlight the color changes possible, it has included the thickness and curing mechanism of different, to highlight the possible changes in temperature. The red line represents the LED type specific color boundary; that is to say, when the purchase of LED, its color may be anywhere in between these lines.

Figure 4. color temperature deviation depends on the coating thickness and curing time.

The thin coating referred to in Figure 4 and represent the thick coating conformal coating thickness of the minimum and maximum level, namely 25 and 75 microns. Through the application of this