LTST-S110KFKT Orange SMD LED Datasheet - Side View - AlInGaP Chip - 20mA - English Technical Document

1. Product Overview

This document details the specifications for a high-brightness, side-view surface-mount device (SMD) light-emitting diode (LED). The primary application for this component is LCD backlighting, where its side-emitting profile is specifically advantageous. The LED utilizes an Aluminum Indium Gallium Phosphide (AlInGaP) semiconductor chip, which is known for producing efficient and bright orange light. The device is packaged on 8mm tape wound onto 7-inch diameter reels, making it fully compatible with automated pick-and-place assembly systems used in high-volume electronics manufacturing.

The product is designed to be compliant with RoHS (Restriction of Hazardous Substances) directives, classifying it as a "Green Product." It is engineered for compatibility with standard infrared (IR) and vapor phase reflow soldering processes, which are common in printed circuit board (PCB) assembly. Its electrical characteristics are also compatible with integrated circuit (IC) logic levels, simplifying drive circuit design.

2. Absolute Maximum Ratings

The following table lists the stress limits that must not be exceeded under any operating conditions. Exceeding these values may cause permanent damage to the device. All ratings are specified at an ambient temperature (Ta) of 25°C.

• Power Dissipation (Pd): 75 mW. This is the maximum amount of power the LED package can safely dissipate as heat.
• Peak Forward Current (IFP): 80 mA. This is the maximum allowable instantaneous forward current, typically specified under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to prevent overheating.
• DC Forward Current (IF): 30 mA. This is the maximum continuous forward current that can be applied to the LED.
• Derating Factor: The DC forward current must be linearly reduced by 0.4 mA for every degree Celsius the ambient temperature rises above 50°C.
• Reverse Voltage (VR): 5 V. Applying a reverse voltage greater than this can break down the LED's semiconductor junction.
• Operating & Storage Temperature Range: -55°C to +85°C. The device can be stored and operated within this full temperature range.
• Soldering Temperature Tolerance: The LED can withstand wave or infrared soldering at 260°C for up to 5 seconds, or vapor phase soldering at 215°C for up to 3 minutes.

3. Electro-Optical Characteristics

The following parameters define the LED's performance under typical operating conditions at Ta=25°C. "Typ." denotes typical values, while "Min." and "Max." define the guaranteed limits for specific parameters.

• Luminous Intensity (Iv): 45.0 mcd (Min.), 90.0 mcd (Typ.) at a forward current (IF) of 20mA. Intensity is measured using a sensor filtered to match the human eye's photopic response (CIE curve).
• Viewing Angle (2θ1/2): 130 degrees (Typ.). This is the full angle at which the luminous intensity drops to half of its value measured on the central axis.
• Peak Wavelength (λP): 611 nm (Typ.). This is the wavelength at which the optical output power is maximum.
• Dominant Wavelength (λd): 605 nm (Typ.). Derived from color coordinates on the CIE chromaticity diagram, this single wavelength best represents the perceived color of the light.
• Spectral Bandwidth (Δλ): 17 nm (Typ.). This is the full width at half maximum (FWHM) of the emission spectrum, indicating color purity.
• Forward Voltage (VF): 2.0 V (Min.), 2.4 V (Typ.) at IF=20mA. This is the voltage drop across the LED when conducting current.
• Reverse Current (IR): 10 μA (Max.) at VR=5V. This is the small leakage current that flows when the LED is reverse-biased.
• Capacitance (C): 40 pF (Typ.) measured at 0V bias and 1MHz frequency. This is the junction capacitance of the LED.

4. Binning System

To ensure consistency in applications, LEDs are sorted into bins based on their measured luminous intensity. The bin code is part of the product identification. The following binning structure applies for the LTST-S110KFKT at IF=20mA:

• Bin Code P: Luminous Intensity range from 45.0 mcd to 71.0 mcd.
• Bin Code Q: Luminous Intensity range from 71.0 mcd to 112.0 mcd.
• Bin Code R: Luminous Intensity range from 112.0 mcd to 180.0 mcd.
• Bin Code S: Luminous Intensity range from 180.0 mcd to 280.0 mcd.

A tolerance of +/-15% is applied to the intensity values within each bin. This binning allows designers to select LEDs with the required brightness level for their specific application, ensuring visual uniformity when multiple LEDs are used together.

5. Soldering and Assembly Guidelines

5.1 Reflow Soldering Profiles

The LED is designed to withstand standard SMD reflow processes. Two suggested infrared (IR) reflow profiles are provided: one for standard tin-lead (SnPb) solder processes and another for lead-free (Pb-free) solder processes, typically using SAC (Sn-Ag-Cu) alloys. The lead-free profile requires a higher peak temperature, typically up to 260°C, but with carefully controlled ramp-up and cooling rates to prevent thermal shock to the component and PCB.

5.2 Cleaning

If cleaning after soldering is necessary, only specified solvents should be used. Unspecified chemicals may damage the plastic lens or package. The recommended method is to immerse the LED in ethyl alcohol or isopropyl alcohol at room temperature for less than one minute. Aggressive or ultrasonic cleaning is not recommended unless specifically validated.

5.3 Storage and Handling

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. Once removed from their original moisture-barrier packaging, components should ideally be soldered within one week. For longer storage outside the original bag, they must be kept in a sealed container with desiccant or in a nitrogen atmosphere. If stored unpackaged for more than a week, a bake-out at approximately 60°C for at least 24 hours is required before assembly to remove absorbed moisture and prevent "popcorning" during reflow.

6. Package and Mechanical Information

The LED conforms to an industry-standard SMD package outline. Detailed dimensioned drawings are provided in the datasheet, including the body size, lead dimensions, and recommended PCB land (pad) pattern. The side-view design means the primary light emission is parallel to the plane of the PCB, which is critical for edge-lighting applications like LCD panels. The device is supplied on embossed carrier tape, 8mm wide, wound onto 7-inch reels. Each reel contains 3000 pieces. Packaging follows ANSI/EIA 481-1-A standards.

7. Application Notes and Design Considerations

7.1 Drive Circuit Design

LEDs are current-driven devices. To ensure stable operation and consistent brightness, especially when multiple LEDs are used in parallel, it is strongly recommended to use a current-limiting resistor in series with each LED. The resistor value is calculated based on the supply voltage (Vcc), the LED's forward voltage (VF), and the desired forward current (IF): R = (Vcc - VF) / IF. Driving multiple LEDs in parallel without individual series resistors is not recommended (Circuit Model B in the datasheet), as small variations in the forward voltage (VF) characteristic between individual LEDs can cause significant differences in current sharing and, consequently, uneven brightness.

7.2 Electrostatic Discharge (ESD) Protection

The semiconductor junction in LEDs is sensitive to electrostatic discharge. ESD can cause immediate failure or latent damage that degrades performance over time. To prevent ESD damage:

• Personnel should wear grounded wrist straps or anti-static gloves when handling LEDs.
• All workstations, tools, and equipment must be properly grounded.
• Use ionizers to neutralize static charges that can build up on the plastic lens during handling.

7.3 Thermal Management

While the LED itself does not have an integrated heatsink, effective thermal management at the PCB level is important for long-term reliability. The 0.4 mA/°C derating above 50°C highlights the need to manage the ambient temperature around the LED. In high-density backlight arrays, ensuring adequate airflow or thermal relief in the PCB layout can help maintain performance and lifespan.

8. Typical Performance Curves Analysis

The datasheet includes several graphs depicting the relationship between key parameters. While the specific curves are not reproduced in text, they typically show:

• Relative Luminous Intensity vs. Forward Current: This curve shows how light output increases with current, usually in a sub-linear fashion at higher currents due to heating effects.
• Forward Voltage vs. Forward Current: This shows the diode's I-V characteristic, which is exponential at low currents and becomes more resistive at the operating current.
• Relative Luminous Intensity vs. Ambient Temperature: This curve demonstrates the decrease in light output as the junction temperature rises, a key consideration for applications operating in warm environments.
• Spectral Distribution: A plot of relative intensity versus wavelength, showing the peak at ~611 nm and the ~17 nm bandwidth, confirming the orange color emission.

These curves are essential for designers to predict performance under non-standard conditions (different currents or temperatures) and to optimize their driver circuits for efficiency and stability.

9. Comparison and Technology Context

The use of an AlInGaP chip is significant. Compared to older technologies like Gallium Arsenide Phosphide (GaAsP), AlInGaP LEDs offer substantially higher efficiency and brightness for red, orange, and yellow wavelengths. The side-view package differentiates this product from top-emitting LEDs. This mechanical orientation is not merely a packaging choice but a functional one, enabling thin, edge-lit display designs where light is coupled into a light guide plate. The combination of a high-performance chip material with this specific package geometry makes it a specialized component optimized for a dominant application area: LCD panel backlighting, particularly in consumer electronics like smartphones, tablets, and monitors where space is at a premium.