Orange SMD LED LTST-C150KFKT Datasheet - EIA Package - 20mA - 90mcd - English Technical Document

1. Product Overview

The LTST-C150KFKT is a high-brightness, surface-mount LED designed for modern electronic applications requiring reliable and efficient orange indicator lighting. It utilizes an advanced AlInGaP (Aluminum Indium Gallium Phosphide) semiconductor chip, which is known for producing high luminous intensity with good efficiency in the orange-red spectrum. This component is packaged in a standard EIA-compliant format, making it compatible with automated pick-and-place assembly systems commonly used in high-volume manufacturing. The device is supplied on 8mm tape mounted on 7-inch diameter reels, facilitating efficient handling and processing.

Its primary design goals are to provide consistent optical performance, compatibility with lead-free (Pb-free) soldering processes, and adherence to environmental standards such as RoHS (Restriction of Hazardous Substances). The "Water Clear" lens material allows the intrinsic chip color to be emitted without significant diffusion or color shifting, resulting in a saturated orange output.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

These ratings define the stress limits beyond which permanent damage to the device may occur. Operation under or at these limits is not guaranteed and should be avoided for reliable long-term performance.

• Power Dissipation (Pd): 75 mW. This is the maximum total power the package can dissipate as heat at an ambient temperature (Ta) of 25°C. Exceeding this limit risks overheating the semiconductor junction.
• DC Forward Current (IF): 30 mA. The maximum continuous forward current that can be applied.
• Peak Forward Current: 80 mA. This is permissible only under pulsed conditions (1/10 duty cycle, 0.1ms pulse width) to handle brief current surges.
• Derating Factor: 0.4 mA/°C above 25°C. For every degree Celsius the ambient temperature rises above 25°C, the maximum allowable DC forward current must be reduced by 0.4 mA to prevent thermal overstress.
• Reverse Voltage (VR): 5 V. Applying a reverse voltage greater than this can cause breakdown and failure.
• Operating & Storage Temperature Range: -55°C to +85°C. The device can function and be stored within this full range.
• Soldering Temperature Tolerance: The device can withstand wave or infrared soldering at 260°C for 5 seconds, and vapor phase soldering at 215°C for 3 minutes.

2.2 Electrical & Optical Characteristics

These are the typical performance parameters measured at Ta=25°C and an IF of 20mA, which is the standard test condition.

• Luminous Intensity (Iv): 45.0 mcd (Min), 90.0 mcd (Typ). This is the measured light output in millicandelas. The value is measured using a sensor filtered to match the photopic (human eye) response curve (CIE).
• Viewing Angle (2θ1/2): 130° (Typ). This wide viewing angle indicates the light is emitted in a broad, lambertian-like pattern, suitable for applications requiring wide visibility.
• Peak Emission Wavelength (λP): 611 nm (Typ). The specific wavelength at which the spectral output is strongest.
• Dominant Wavelength (λd): 605 nm (Typ). This is the single wavelength perceived by the human eye that defines the color of the LED, derived from the CIE chromaticity diagram.
• Spectral Line Half-Width (Δλ): 17 nm (Typ). This indicates the spectral purity; a narrower width means a more monochromatic (pure color) output.
• Forward Voltage (VF): 2.0V (Min), 2.4V (Typ) at IF=20mA. The voltage drop across the LED when operating. This is critical for designing the current-limiting circuitry.
• Reverse Current (IR): 10 µA (Max) at VR=5V. A small leakage current when the device is reverse-biased.
• Capacitance (C): 40 pF (Typ) at VF=0V, f=1MHz. The junction capacitance, which can be relevant in high-speed switching applications.

3. Binning System Explanation

The luminous intensity of LEDs can vary from batch to batch. To ensure consistency for the end-user, products are sorted into "bins" based on measured performance. For the LTST-C150KFKT, the primary binning is for luminous intensity at 20mA.

• Bin Code P: 45.0 - 71.0 mcd
• Bin Code Q: 71.0 - 112.0 mcd
• Bin Code R: 112.0 - 180.0 mcdBin Code S: 180.0 - 280.0 mcd

A tolerance of +/-15% is applied to each intensity bin. When designing a system where uniform brightness is critical (e.g., multi-LED displays or backlights), specifying a single bin code or understanding the bin range is essential to avoid visible brightness mismatches.

4. Performance Curve Analysis

While specific graphs are referenced in the datasheet (Fig.1, Fig.6), their implied characteristics are standard for AlInGaP LEDs and crucial for design.

4.1 Forward Current vs. Forward Voltage (I-V Curve)

The relationship is exponential. A small increase in voltage beyond the turn-on threshold (~1.8V) causes a large increase in current. This is why LEDs must be driven by a current-limited source, not a constant voltage source, to prevent thermal runaway and destruction.

4.2 Luminous Intensity vs. Forward Current

Light output is generally proportional to forward current within the operating range. However, efficiency (lumens per watt) typically peaks at a current lower than the maximum rating and decreases at higher currents due to increased heat.

4.3 Temperature Dependence

Luminous intensity and forward voltage are temperature-dependent. As junction temperature increases:

• Luminous Intensity Decreases: The output can drop significantly, a factor that must be accounted for in thermal management.
• Forward Voltage Decreases: The VF has a negative temperature coefficient (typically around -2 mV/°C for AlInGaP). This can affect the current in a simple resistor-limited circuit if the ambient temperature varies widely.

4.4 Spectral Distribution

The spectral output curve will be centered around the 611 nm peak. The 17 nm half-width indicates a relatively narrow spectrum, characteristic of direct-bandgap semiconductors like AlInGaP, resulting in a pure orange color.

5. Mechanical & Packaging Information

The device conforms to a standard EIA surface-mount package outline. Key dimensional notes include:

• All primary dimensions are in millimeters.A standard tolerance of ±0.10 mm applies unless otherwise specified.

The datasheet includes detailed dimensioned drawings for the LED body, which are essential for creating the PCB footprint (land pattern). A suggested soldering pad layout is also provided to ensure a reliable solder joint and proper alignment during reflow. The polarity is indicated by a cathode mark on the device, typically a notch, green line, or other visual indicator on one side of the package.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Profiles

The datasheet provides two suggested infrared (IR) reflow profiles:

1. For Normal Process: A standard profile suitable for tin-lead (SnPb) solder.
2. For Pb-Free Process: A profile optimized for lead-free solder pastes like SAC (Sn-Ag-Cu). This profile typically has a higher peak temperature (up to 260°C) to accommodate the higher melting point of lead-free alloys. The time above liquidus (TAL) and ramp rates are critical to prevent thermal shock and ensure proper solder joint formation without damaging the LED's epoxy package.

6.2 Storage Conditions

LEDs are moisture-sensitive devices. Prolonged exposure to ambient humidity can lead to "popcorning" (package cracking) during the high-temperature reflow soldering process due to rapid vaporization of absorbed moisture.

• Recommended Storage: Not exceeding 30°C and 70% relative humidity.
• Out-of-Bag Time: If removed from the original moisture-barrier bag, LEDs should be reflowed within one week.
• Extended Storage/Baking: For storage beyond one week outside the original packaging, store in a sealed container with desiccant or in a nitrogen ambient. LEDs stored this way for over a week should be baked at approximately 60°C for at least 24 hours before soldering to drive out moisture.

6.3 Cleaning

Only specified cleaning agents should be used. Unspecified chemicals may damage the epoxy lens or package. If cleaning is necessary post-soldering, immersion in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is recommended.

7. Packaging & Ordering Information

The product is supplied in industry-standard packaging for automated assembly:

• Tape & Reel: 8mm wide embossed carrier tape.
• Reel Size: 7-inch diameter.
• Quantity per Reel: 3000 pieces.
• Minimum Order Quantity (MOQ): 500 pieces for remainder quantities.
• Packaging Standards: Complies with ANSI/EIA-481-1-A-1994 specifications. Empty pockets in the tape are sealed with cover tape.

The part number LTST-C150KFKT follows a typical manufacturer coding system where elements likely indicate series, color, intensity bin, lens type, and packaging.

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is suitable for a wide range of applications requiring orange status indication, backlighting, or decorative lighting, including:

• Consumer electronics (audio/video equipment, appliances).
• Industrial control panels and instrumentation.
• Automotive interior lighting (non-critical).
• Signage and decorative lighting.
• General-purpose indicator lights on PCBs.

Important Note: The datasheet explicitly states this LED is intended for "ordinary electronic equipment." For applications requiring exceptional reliability where failure could jeopardize life or health (aviation, medical, transportation safety systems), consultation with the manufacturer is required prior to design-in.

8.2 Design Considerations & Circuit Configuration

Drive Method: LEDs are current-operated devices. The most critical design rule is to control the forward current.

• Recommended Circuit (Circuit A): Use a series current-limiting resistor for each LED. This is essential when connecting multiple LEDs in parallel, as it compensates for natural variations in the forward voltage (VF) of individual LEDs. Without individual resistors, LEDs with a slightly lower VF will draw disproportionately more current, leading to uneven brightness and potential overcurrent failure.
• Non-Recommended Circuit (Circuit B): Connecting multiple LEDs directly in parallel with a single shared current-limiting resistor is discouraged due to the risk of current hogging described above.

The value of the series resistor (R) is calculated using Ohm's Law: R = (V_supply - VF_LED) / I_desired. Always use the typical or maximum VF from the datasheet for a conservative design.

8.3 Electrostatic Discharge (ESD) Protection

LEDs are sensitive to electrostatic discharge. ESD can cause latent or catastrophic damage, manifesting as high reverse leakage current, low forward voltage, or failure to light at low currents.

Prevention measures include:

• Using conductive wrist straps or anti-static gloves when handling.
• Ensuring all workstations, equipment, and storage racks are properly grounded.
• Using ionizers to neutralize static charge that may build up on the plastic lens.

To test for potential ESD damage, check if the LED lights up and measure its VF at a low test current (e.g., 1-5mA). Abnormal readings indicate possible damage.

9. Technical Comparison & Differentiation

The LTST-C150KFKT's key differentiators are rooted in its material system and package design:

• AlInGaP Chip Technology: Compared to older technologies like standard GaAsP, AlInGaP offers significantly higher luminous efficiency and brightness, better temperature stability, and longer operational lifetime. This makes it superior for applications demanding high visibility and reliability.
• Water Clear Lens: Provides a more saturated, vivid color compared to diffused or tinted lenses, which scatter light and can mute the color purity. This is ideal for applications where color definition is important.
• Pb-Free & RoHS Compliance: Meets modern environmental regulations, which is a mandatory requirement for most electronics sold today.
• Wide Viewing Angle (130°): Offers excellent off-axis visibility, which is advantageous for panel indicators that need to be seen from various angles.

10. Frequently Asked Questions (Based on Technical Parameters)

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

Peak Wavelength (λP) is the physical wavelength where the LED emits the most optical power, measured directly from the spectrum. Dominant Wavelength (λd) is a calculated value based on human color perception (CIE chart) that best represents the single color we see. For monochromatic LEDs like this orange one, they are often close, but λd is the more relevant parameter for color specification in design.

10.2 Why is a 20mA test current used?

20mA has historically been a standard drive current for many small-signal LEDs, providing a good balance between brightness, efficiency, and power dissipation. It serves as a common reference point for comparing different LED models. Your application can use a different current, but all performance parameters (Iv, VF) will scale accordingly, and you must stay within the Absolute Maximum Ratings.

10.3 How do I choose the right intensity bin?

Select a bin based on your application's brightness requirements and uniformity tolerance. For a single indicator, any bin may suffice. For an array where all LEDs must appear equally bright, you should specify a single, tight bin (e.g., Bin Q) and potentially implement optical diffusion to mask minor remaining variations.

10.4 Can I drive this LED directly from a 3.3V or 5V microcontroller pin?

No, not directly. A microcontroller GPIO pin is a voltage source, not a current source, and typically cannot supply a consistent 20mA while maintaining its output voltage. More importantly, it provides no protection against the LED's negative temperature coefficient. You must use a series current-limiting resistor as described in Section 8.2. The resistor value for a 3.3V supply and a target of 20mA would be approximately (3.3V - 2.4V) / 0.02A = 45 Ohms. A standard 47 Ohm resistor would be a suitable choice.

11. Practical Design & Usage Case Study

Scenario: Designing a status indicator panel for a piece of industrial equipment requiring three bright, uniform orange LEDs to signal "System Active."

1. Component Selection: The LTST-C150KFKT is chosen for its high brightness (up to 280mcd in Bin S), orange color, and SMD package suitable for automated assembly.
2. Circuit Design: The system power rail is 5V. To ensure uniform brightness, three identical drive circuits are used, one for each LED. Using the typical VF of 2.4V and a design current of 20mA, the series resistor value is calculated: R = (5V - 2.4V) / 0.02A = 130 Ohms. The nearest standard value of 130 or 120 Ohms is selected. The power rating of the resistor is (5V-2.4V)*0.02A = 0.052W, so a standard 1/8W (0.125W) resistor is more than adequate.
3. PCB Layout: The manufacturer's suggested soldering pad dimensions from the datasheet are used to create the PCB footprint. Adequate spacing is maintained between LEDs for heat dissipation.
4. Thermal Consideration: The panel is in an enclosure. To mitigate temperature rise, which would reduce light output, small thermal relief vias are placed near the LED pads to conduct heat to other PCB layers, and the enclosure has ventilation.
5. Procurement: To guarantee visual uniformity, the purchase order specifies "Bin Code S" for all 3,000 units required for production.

12. Operating Principle

Light emission in the LTST-C150KFKT is based on electroluminescence in a semiconductor p-n junction made of AlInGaP materials. When a forward voltage is applied, electrons from the n-type region and holes from the p-type region are injected across the junction. When these charge carriers recombine in the active region of the semiconductor, they release energy. In a direct bandgap material like AlInGaP, this energy is released primarily in the form of photons (light). The specific wavelength (color) of the emitted light is determined by the bandgap energy of the semiconductor material, which is engineered during the crystal growth process to be approximately 2.03 eV, corresponding to orange light around 611 nm. The "Water Clear" epoxy encapsulant protects the chip, provides mechanical stability, and acts as a lens to shape the light output beam.

13. Technology Trends

The development of LED technology continues to focus on several key areas relevant to components like the LTST-C150KFKT:

• Increased Efficiency (lm/W): Ongoing material science research aims to reduce non-radiative recombination and improve light extraction from the chip, leading to brighter LEDs at the same current or the same brightness at lower power.
• Improved Color Consistency & Binning: Advances in epitaxial growth and manufacturing process control lead to tighter parameter distributions, reducing the need for extensive binning and providing more consistent performance straight from production.
• Miniaturization: The drive for smaller electronic devices pushes for LEDs in ever-smaller package footprints while maintaining or improving optical output.
• Higher Reliability & Lifetime: Improvements in packaging materials (epoxies, silicones) and die attach techniques enhance resistance to thermal cycling, humidity, and other environmental stresses, extending operational lifetime.
• Integration: A trend towards integrating multiple LED chips (e.g., RGB), control circuitry, or even drivers into a single package to simplify end-user design and reduce PCB space.

Components like the LTST-C150KFKT represent a mature, optimized point in this evolution, offering a reliable and high-performance solution for standard indicator applications.