The Impact of Static Electricity on LED Chip Luminance Failure

Release Date:

2020-12-15

　　Often encounter LED light bead The phenomenon of non-illumination can occur in packaging companies, application firms, and among the end users—both organizations and individuals—and is commonly referred to in the industry as “dead LED” or “dead lamp” failure. There are generally two primary causes: 1) Leakage in the LED die; excessive current can cause the PN junction to fail, resulting in the LED not lighting up. This type of failure typically does not affect the operation of other LEDs in the same string; 2) Breakage of the internal interconnections within the LED die, which prevents current from flowing and causes the LED to go dark. Such a failure will impact the normal operation of all other LEDs in the string. The underlying reason is the relatively low operating voltage of LEDs: red, yellow, and orange LEDs operate at 1.8–2.2 V, while blue, green, and white LEDs typically require 2.8–3.2 V. To accommodate these differing voltages, LEDs are often connected in series or in parallel; the more LEDs connected in series, the greater the impact. If even a single LED in a series string opens circuit, the entire string will fail to light. As such, this second scenario is far more serious than the first. Dead LEDs represent a critical factor affecting product quality and reliability. Therefore, reducing and eliminating dead LEDs to enhance product quality and reliability is a pressing need for both packaging and application companies. To address this key issue, the following section provides an analysis and discussion of the common causes of dead LEDs.

 

oKQ4cLmkTaOMbysMKIDJzQ.jpg

 

　　1. Electrostatic discharge can damage LED chips, causing the LED’s PN junction to fail and increasing leakage current, effectively turning the junction into a resistor. Electrostatic discharge is highly detrimental; countless electronic components worldwide have been damaged by it, resulting in economic losses amounting to tens of millions of U.S. dollars. Therefore, preventing electrostatic damage to electronic components is a critical task in the electronics industry, and companies engaged in LED packaging and applications must take it seriously. Any issue at any point in the production or application chain can lead to LED damage, degraded performance, or even failure. Human-body static electricity can reach as high as 3 kV—enough to break down and destroy LED chips. It is also crucial to ensure that the grounding resistance of LED packaging lines and various pieces of equipment meets the required specifications. Typically, the grounding resistance should be no more than 4 ohms; in some cases, the requirement is even stricter, with a maximum allowable value of ≤2 ohms. These standards are well known within the electronics industry, but the key lies in whether they are properly implemented and maintained during actual operations.

　　According to available information, most private enterprises do not implement adequate electrostatic protection measures. In fact, the majority lack documented records of ground resistance testing; even when such tests are conducted, they are typically performed only once a year, once every few years, or only when a problem is suspected. However, ground resistance testing is a critical task that should be carried out at least four times annually—once each quarter—and in certain high-demand environments, it must be performed monthly. This is because soil resistivity varies with the seasons.

　　Human static electricity also affects LED light bead This can cause significant damage. Personnel must wear antistatic clothing and an antistatic wrist strap, which should be properly grounded. There are also antistatic wrist straps that do not require grounding. If an employee violates operating procedures, they should receive appropriate warnings and training, and this should serve as a reminder to others. The amount of static electricity carried by the human body depends on the types of fabrics worn and individual physiological characteristics. On autumn and winter evenings, it is easy to observe static discharge between garments when removing clothes; the voltage of such discharges can reach 3,000 volts. This level of static electricity is sufficient to cause LED chips to fail.

 

More information

What is a light-emitting diode?

Light-emitting diodes are commonly referred to as LED beads. They are used in a wide range of applications and can be seen on streets and in alleys everywhere. For example, traffic lights at intersections remind people to obey traffic rules; remote controls transmit or receive signals; they can be used to display images on ultra-large screens; and various streetlights provide warm illumination at night. Even everyday household appliances rely on their contributions.

What are the tips for selecting LED chips?

1. Brightness: LED brightness varies, and so does the price. LEDs used in LED lighting must comply with laser safety classification standards.

What factors influence the price differences of LED light beads?

LED chips are a well-known product in the LED industry; however, many people are less familiar with their pricing. What causes such wide variations in LED chip prices? Below, we will outline the factors that influence LED chip prices.

What is the light-emitting principle of LED chips?

An LED chip is a light-emitting diode, and an LED bulb is simply the common, colloquial term for an LED.

Are you familiar with full-color LED chip-on-board modules for side mounting?

The brightness of full-color LED surface-mount devices is closely related to the LED’s viewing angle. The narrower the viewing angle, the higher the brightness; moreover, differences in manufacturing processes can lead to significant variations in service life. For a 5-mm LED with a 180-degree viewing angle, the white-light luminous intensity is only a few hundred mcd, whereas for a 15-degree viewing-angle LED, the luminous intensity exceeds 10,000 mcd. When high-power LEDs are used outdoors, the brightness is even greater. Single-power LEDs include 1 W, 3 W, and 5 W models; some high-power LEDs can be combined to form a single high-power LED with output up to several hundred watts. Color temperature is independent of brightness, but brightness is directly related to the lumen value.

Key Considerations for Full-Color SMD LEDs on the Side

Side-view full-color LED chips, also known as surface-mount LEDs, are a type of simple lighting device. Their light-emitting principle is based on passing an electric current through a compound semiconductor; when electrons and holes recombine, the excess energy is released in the form of light, thereby producing illumination.