Analysis of LED reliability verification methods and necessity

The following will briefly introduce two major parts. Regardless of whether the LED is presented in the form of components or finished products, the following model can be used and followed to achieve basic verification of LED products.

1. Product life verification

In the electronics industry, three methods are usually used to obtain product lifespan:

(1) Lifespan prediction method

Method: Based on the principles of the part count method and part stress method of MIL HDBK 217, software is used to calculate the product life.

Advantages: Short time and low cost

Disadvantages: The results may be far from the actual product life

(2) Demonstration

Method: Use the acceleration model to find the acceleration factor and provide actual samples to measure the samples using an environmental test simulator to find the product life. Currently, the most widely used acceleration models are the Arrhenius model (high temperature acceleration), the Coffin-Manson model (temperature cycle acceleration), and the Hallberg-Peck model (humidity acceleration).

Advantages: The results are more realistic than the estimation method and are more widely accepted by the industry

Disadvantages: More expensive and takes longer than expected

(3) Field return

Method: The situation of the recovered products used by users in the market.

Advantages: The result is equal to the real lifespan

Disadvantages: Longer time and cost, difficult to obtain market usage information, usually only kept by the brand itself

Of the three methods mentioned above, the actual life measurement method is the most widely used in the industry because it not only avoids the disadvantage of a large gap between the result and the actual situation, but also is obtained through actual measurement and is highly accepted by both buyers and sellers.

2. Product environmental test verification

First of all, you must analyze the life profile of the product you designed. What environment will this product be in during its life cycle? Who will use it? What are the properties of this product? Are there any other special requirements for the product? These factors may affect the specifications of the future test. Do not get lost in the specification during the process, because a good verification specification is definitely not completely copied from a certain specification. Because no matter how good the specification is, it cannot simulate the actual environmental requirements. It is just in vain and will only waste more resources and costs. For example: The designer of LED lamps designs a street lamp for use on the streets of Indonesia and formulates a verification specification of -40℃ low temperature. He is very happy to do it because the low temperature recommended in IEC is -40℃. But please recall that Indonesia is located near the equator and has a tropical climate. It is hot and humid all year round. How can it encounter a -40℃ climate? Therefore, designing a product for an environment that will never be encountered will only increase the design cost, because the cost of designing an LED lamp that can withstand a -40℃ environment must be higher than that of designing an LED lamp that can withstand a 0℃ environment.

Therefore, all product designers should return to the basics and carefully examine the products they design in order to achieve an efficient reliability verification that meets actual needs.

Finally, because LED products are different from other electronic products, their luminous characteristics must be measured before and after reliability verification. Commonly used calculus spheres or goniophotometers can measure the color temperature, luminous flux, luminous intensity, chromaticity coordinates, color rendering, wavelength, etc. of LED products to serve as the basis for the reliability verification results.