LTST-C195TBKFKT-5A Dual Color SMD LED Datasheet - Blue & Orange - 0.55mm Height - 3.2V/2.3V - 38mW/50mW - English Technical Document

1. Product Overview

This document provides the complete technical specifications for the LTST-C195TBKFKT-5A, a dual-color Surface-Mount Device (SMD) Light Emitting Diode (LED). This component integrates two distinct semiconductor chips within a single, ultra-thin package: one emitting blue light (based on InGaN technology) and the other emitting orange light (based on AlInGaP technology). It is designed for automated assembly processes and applications where space conservation and reliable performance are critical.

1.1 Key Features and Target Market

The primary advantages of this LED include its compliance with RoHS directives, an exceptionally low profile of 0.55mm, and high brightness output. It is packaged in 8mm tape on 7-inch reels, conforming to EIA standards, making it compatible with automated pick-and-place equipment and standard infrared (IR) reflow soldering processes. Its design is also I.C. compatible.

Typical application areas span across telecommunications, office automation, home appliances, and industrial equipment. Specific uses include backlighting for keypads and keyboards, status indication, integration into micro-displays, and signal or symbol illumination.

2. Technical Parameters: In-Depth Objective Interpretation

This section provides a detailed, objective analysis of the LED's operational limits and performance characteristics under standard test conditions.

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. They are not intended for normal operation.

• Power Dissipation (P_d): 38 mW for the Blue chip; 50 mW for the Orange chip. This parameter indicates the maximum power the LED can dissipate as heat without degradation.
• Peak Forward Current (I_FP): 40 mA for both colors, permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width).
• DC Forward Current (I_F): 10 mA for Blue; 20 mA for Orange. This is the recommended maximum continuous forward current.
• Operating & Storage Temperature: The device is rated for an ambient temperature (T_a) range of -20°C to +80°C during operation and -30°C to +100°C during storage.
• Infrared Soldering Condition: Withstands a peak temperature of 260°C for a maximum of 5 seconds, which is standard for Pb-free reflow processes.

2.2 Electrical and Optical Characteristics at T_a=25°C

These parameters define the typical performance of the device when driven under specified conditions (I_F = 5mA unless noted).

• Luminous Intensity (I_V): Minimum 11.2 mcd for both colors. The typical maximum is 45 mcd for Blue and 71 mcd for Orange. This is a measure of the perceived brightness by the human eye.
• Viewing Angle (2θ_1/2): Typically 130 degrees. This wide angle indicates a diffuse, non-directional light emission pattern suitable for area illumination.
• Peak Emission Wavelength (λ_P): Typically 468 nm (Blue) and 611 nm (Orange). This is the wavelength at which the spectral power output is highest.
• Dominant Wavelength (λ_d): Ranges from 465-475 nm (Blue) and 600-610 nm (Orange) at 5mA. This is the single wavelength perceived by the human eye, defining the color.
• Spectral Line Half-Width (Δλ): Typically 25 nm (Blue) and 17 nm (Orange). This indicates the spectral purity; a smaller value means a more monochromatic color.
• Forward Voltage (V_F): Typically 2.80V (Blue, max 3.20V) and 2.00V (Orange, max 2.30V) at 5mA. This is the voltage drop across the LED when conducting current.
• Reverse Current (I_R): Maximum 100 µA for both at V_R = 5V. LEDs are not designed for reverse bias operation; this parameter is for test purposes only.

3. Binning System Explanation

The LEDs are sorted (binned) based on their measured luminous intensity to ensure consistency within a production batch.

3.1 Luminous Intensity Binning

Each color has defined intensity ranges assigned a bin code. The tolerance within each bin is +/-15%.

Blue LED Binning (@5mA):

• Bin L: 11.2 - 18.0 mcd
• Bin M: 18.0 - 28.0 mcd
• Bin N: 28.0 - 45.0 mcd

Orange LED Binning (@5mA):

• Bin L: 11.2 - 18.0 mcd
• Bin M: 18.0 - 28.0 mcd
• Bin N: 28.0 - 45.0 mcd
• Bin P: 45.0 - 71.0 mcd

This system allows designers to select LEDs with a guaranteed minimum brightness for their application, aiding in achieving uniform visual performance across multiple units.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1 for spectral distribution, Figure 6 for viewing angle), their implications are critical for design.

4.1 Forward Current vs. Luminous Intensity (I_F-I_V Curve)

The light output is approximately proportional to the forward current, but this relationship is not perfectly linear, especially at higher currents where efficiency may drop due to heating. Operating at or below the recommended DC current ensures stable output and longevity.

4.2 Forward Voltage vs. Forward Current (I_F-V_F Curve)

An LED exhibits a diode-like exponential I-V characteristic. A small change in forward voltage can cause a large change in current. Therefore, it is standard practice to drive LEDs with a constant current source, not a constant voltage source, to ensure stable and predictable light output and to prevent thermal runaway.

4.3 Spectral Distribution

The spectral curve shows the relative power emitted across wavelengths. The peak wavelength (λ_P) and the half-width (Δλ) are extracted from this curve. The Orange AlInGaP chip typically has a narrower spectral width than the Blue InGaN chip, resulting in a more saturated color.

5. Mechanical and Package Information

5.1 Package Dimensions and Pin Assignment

The device conforms to a standard SMD footprint. Critical dimensions include a body size and a total height of 0.55mm. The pin assignment is as follows: Pins 1 and 3 are for the Blue LED anode/cathode, and Pins 2 and 4 are for the Orange LED anode/cathode. The lens is water clear. All dimensional tolerances are ±0.1 mm unless otherwise specified.

5.2 Recommended PCB Pad Layout and Polarity

The datasheet provides a recommended land pattern (footprint) for the printed circuit board (PCB). Adhering to this pattern is crucial for achieving reliable solder joints, proper alignment, and effective heat dissipation during the reflow process. The pad design also helps prevent tombstoning (component standing up on one end). Clear polarity marking on the PCB silkscreen, matching the LED's cathode indicator, is essential to prevent incorrect installation.

6. Soldering and Assembly Guidelines

6.1 IR Reflow Soldering Parameters

For lead-free (Pb-free) solder processes, a recommended reflow profile is provided. Key parameters include:

• Pre-heat: 150-200°C for a maximum of 120 seconds to gradually heat the board and activate the flux.
• Peak Temperature: Maximum of 260°C.
• Time Above Liquidus: The component should be subjected to the peak temperature for a maximum of 10 seconds, and the reflow process should not be performed more than twice.

These parameters are based on JEDEC standards to ensure reliable mounting without damaging the LED package or the semiconductor die inside.

6.2 Storage and Handling Conditions

ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling should be performed using wrist straps, anti-static mats, and grounded equipment.

Moisture Sensitivity Level (MSL): The device is rated MSL 3. This means that once the original moisture-barrier bag is opened, the components must be soldered within one week (168 hours) under factory floor conditions (<30°C/60% RH). If this time is exceeded, a bake-out at approximately 60°C for at least 20 hours is required before soldering to remove absorbed moisture and prevent "popcorning" during reflow.

Long-term Storage: Unopened packages should be stored at ≤30°C and ≤90% RH. For opened packages or extended storage, components should be kept in a sealed container with desiccant or in a nitrogen atmosphere.

6.3 Cleaning

If post-solder cleaning is necessary, only specified alcohol-based solvents like isopropyl alcohol (IPA) or ethyl alcohol should be used. The LED should be immersed at normal temperature for less than one minute. Unspecified chemical cleaners may damage the plastic lens or the package material.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in embossed carrier tape with a protective cover tape, wound onto 7-inch (178mm) diameter reels. Standard packing quantity is 4000 pieces per reel. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies. The packaging conforms to ANSI/EIA-481 standards.

8. Application Suggestions and Design Considerations

8.1 Typical Application Circuits

Each color channel (Blue and Orange) must be driven independently. A series current-limiting resistor is the simplest drive method. The resistor value (R) is calculated using Ohm's Law: R = (V_supply - V_F) / I_F. For more stable performance, especially when V_supply varies or for precision brightness control, a constant current driver circuit (e.g., using a dedicated LED driver IC or a transistor-based current source) is recommended.

8.2 Thermal Management

Although power dissipation is low, proper thermal design extends LED life. Ensure the PCB pad design provides adequate copper area to act as a heat sink. Avoid operating the LED at absolute maximum current and power ratings for extended periods, as this accelerates lumen depreciation (light output decline over time).

8.3 Optical Design

The wide 130-degree viewing angle makes this LED suitable for applications requiring broad, even illumination rather than a focused beam. For more directional light, external lenses or light guides may be necessary. The water-clear lens is optimal for true color emission.

9. Technical Comparison and Differentiation

The key differentiating factors of this component are its dual-color capability in an ultra-thin 0.55mm package. This allows for two independent status indicators or color mixing in a footprint typically occupied by a single-color LED. The use of InGaN for blue and AlInGaP for orange represents standard, high-efficiency semiconductor technologies for these respective colors, offering good brightness and reliability. Its compatibility with automated assembly and standard reflow profiles makes it a drop-in solution for modern electronics manufacturing.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive both the Blue and Orange LEDs simultaneously at their maximum DC current?

No. The Absolute Maximum Ratings specify power dissipation limits per chip (38mW Blue, 50mW Orange). Simultaneously driving both at I_F=10mA (Blue) and I_F=20mA (Orange) would result in approximate power draws of 28mW (Blue: 10mA * 2.8V) and 40mW (Orange: 20mA * 2.0V), totaling 68mW. While this is below the sum of the individual maximums, it concentrates heat in a very small area. For reliable long-term operation, it is advisable to drive below the maximum ratings and consider thermal effects on the PCB.

10.2 What is the difference between Peak Wavelength and Dominant Wavelength?

Peak Wavelength (λ_P) is the physical wavelength where the LED emits the most optical power, measured by a spectrometer. Dominant Wavelength (λ_d) is a calculated value derived from the CIE chromaticity diagram that represents the single wavelength the human eye perceives the color to be. For monochromatic LEDs, they are often close, but for LEDs with broader spectra (like white LEDs), they can be very different. In this datasheet, both are provided for precise color specification.

10.3 Why is there a reverse current (I_R) specification if the LED is not designed for reverse operation?

The I_R specification (max 100 µA at 5V) is a quality and leakage test parameter. It ensures the integrity of the semiconductor junction. During assembly or in circuit, the LED may be briefly subjected to a small reverse bias. This parameter guarantees that under such a condition, the leakage current will not exceed a defined limit, indicating a properly manufactured device. It should not be interpreted as a safe operating condition.

11. Practical Use Case Example

Scenario: Dual-State Status Indicator on a Portable Device

A handheld medical device uses a single indicator to show multiple states: Off (no light), Standby (Orange), and Active (Blue). The LTST-C195TBKFKT-5A is ideal because it saves space compared to using two separate LEDs. The microcontroller unit (MCU) has two GPIO pins, each connected to one color channel of the LED via a current-limiting resistor (e.g., 150Ω for Blue and 100Ω for Orange, assuming a 5V supply). The firmware controls the pins independently. The ultra-thin height allows it to fit behind a thin front panel. The wide viewing angle ensures the status is visible from various angles. The designer selects Bin M or N for both colors to ensure sufficient brightness under ambient light.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light through electroluminescence. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the junction region. When these charge carriers recombine, they release energy. In a standard silicon diode, this energy is released as heat. In LEDs, the semiconductor materials (InGaN for blue/green, AlInGaP for red/orange/yellow) have a direct bandgap, causing this energy to be released primarily as photons (light). The specific wavelength (color) of the emitted light is determined by the energy bandgap of the semiconductor material. The water-clear epoxy lens protects the chip and helps shape the light output pattern.

13. Technology Trends

The development of SMD LEDs like this one follows several industry trends: Miniaturization (thinner and smaller packages), Increased Efficiency (higher luminous output per unit of electrical input), and Enhanced Reliability (robustness for harsh environments and automated assembly). The integration of multiple chips (multi-color or RGB) into a single package is a common approach to save board space and simplify assembly. Furthermore, there is a continuous drive to improve color consistency (tighter binning) and to develop packages that can handle higher power densities for general lighting applications, although this specific component is optimized for low-power indicator use.