LTST-C295TBKSKT Dual Color SMD LED Datasheet - 0.55mm Thin - Blue/Yellow - 20mA/30mA - English Technical Document

1. Product Overview

This document details the specifications for the LTST-C295TBKSKT, a dual-color, surface-mount device (SMD) LED. This component integrates two distinct LED chips within an exceptionally thin package, making it suitable for space-constrained applications requiring multiple indicator colors or status signals.

1.1 Core Advantages and Target Market

The primary advantages of this LED include its ultra-thin profile of 0.55mm, which allows for integration into slim consumer electronics, portable devices, and modern, compact PCB designs. It combines an InGaN (Indium Gallium Nitride) chip for blue emission and an AlInGaP (Aluminum Indium Gallium Phosphide) chip for yellow emission. The product is compliant with ROHS (Restriction of Hazardous Substances) directives, qualifying it as a \"Green Product.\" Its design is compatible with automatic placement equipment and standard infrared (IR) reflow soldering processes, aligning with high-volume manufacturing requirements. The target market encompasses general electronic equipment, including office automation devices, communication equipment, and household appliances where reliable, dual-color indication is needed.

2. In-Depth Technical Parameter Analysis

The performance characteristics are defined under standard ambient temperature conditions (Ta=25°C).

2.1 Absolute Maximum Ratings

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

• Power Dissipation: Blue: 76 mW, Yellow: 75 mW.
• Peak Forward Current (1/10 Duty Cycle, 0.1ms Pulse): Blue: 100 mA, Yellow: 80 mA.
• DC Forward Current (Continuous): Blue: 20 mA, Yellow: 30 mA. This is the recommended operating current for each color.
• Operating Temperature Range: -20°C to +80°C.
• Storage Temperature Range: -30°C to +100°C.
• Infrared Soldering Condition: Withstands 260°C peak temperature for 10 seconds, which is typical for lead-free (Pb-free) solder processes.

2.2 Electrical and Optical Characteristics

These parameters define the expected performance under normal operating conditions (IF = 20 mA).

• Luminous Intensity (Iv):
  • Blue: Minimum 18.0 mcd, Typical value not specified, Maximum 180 mcd.
  • Yellow: Minimum 28.0 mcd, Typical value not specified, Maximum 180.0 mcd.
  The wide range indicates a binning system is used (see Section 3).
• Viewing Angle (2θ1/2): Typically 130 degrees for both colors, providing a wide, diffuse light pattern.
• Peak Emission Wavelength (λP): Blue: 468 nm (Typical), Yellow: 591 nm (Typical).
• Dominant Wavelength (λd): Blue: 470 nm (Typical), Yellow: 589 nm (Typical). This is the perceived color.
• Spectral Line Half-Width (Δλ): Blue: 25 nm (Typical), Yellow: 15 nm (Typical). Yellow light has a narrower spectral bandwidth.
• Forward Voltage (VF): Maximum 3.80V for Blue, Maximum 2.40V for Yellow at 20mA. Designers must account for this voltage difference when driving the LEDs.
• Reverse Current (IR): Maximum 10 μA for both at VR = 5V. Important: The device is not designed for reverse-bias operation; this test condition is for leakage characterization only.

3. Binning System Explanation

To ensure consistent color and brightness in production, LEDs are sorted into bins based on measured performance.

3.1 Luminous Intensity Binning

The luminous intensity for each color is categorized into specific code ranges with a tolerance of ±15% within each bin.

• Blue LED Bins (mcd @ 20mA): M (18.0-28.0), N (28.0-45.0), P (45.0-71.0), Q (71.0-112.0), R (112.0-180.0).
• Yellow LED Bins (mcd @ 20mA): N (28.0-45.0), P (45.0-71.0), Q (71.0-112.0), R (112.0-180.0).

This system allows designers to select a brightness grade suitable for their application's requirements, from lower-intensity indicators to brighter status lights.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Figure 1, Figure 5), their typical behavior can be described based on semiconductor physics.

4.1 Current vs. Voltage (I-V) Characteristic

The forward voltage (VF) is not constant but increases with forward current (IF). The Blue LED, based on InGaN technology, will exhibit a higher VF (~3.2V typical) compared to the Yellow AlInGaP LED (~2.0V typical) at their respective operating currents. Driving circuits should use current-limiting resistors or constant-current drivers to prevent thermal runaway.

4.2 Temperature Dependence

LED performance is temperature-sensitive. Typically, the forward voltage (VF) decreases as the junction temperature increases (negative temperature coefficient). Conversely, luminous intensity generally decreases with rising temperature. The specified operating range of -20°C to +80°C ensures reliable operation within these variations.

4.3 Spectral Distribution

The peak and dominant wavelengths are specified. The Blue LED's emission centers around 468-470 nm, while the Yellow LED centers around 589-591 nm. The half-width values indicate the spectral purity; the yellow LED's narrower 15nm bandwidth suggests a more saturated yellow color compared to the blue's 25nm bandwidth.

5. Mechanical and Packaging Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an EIA standard SMD package footprint. The key feature is its height of 0.55mm. The pin assignment for the dual-color LED is: Pins 1 and 3 are for the Blue LED anode/cathode, and Pins 2 and 4 are for the Yellow LED anode/cathode. The exact pinout (which pin is anode vs. cathode) must be confirmed from the package diagram for correct PCB layout.

5.2 Soldering Pad Layout

The datasheet includes suggested soldering pad dimensions. Following these recommendations is crucial for achieving a reliable solder joint, proper self-alignment during reflow, and managing thermal stress. The pad design accounts for the package's thermal mass and the need for a robust electrical and mechanical connection.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profile

A detailed suggestion for an IR reflow profile is provided, tailored for lead-free (Pb-free) solder processes. Key parameters include: a pre-heat zone (150-200°C), a controlled ramp to a peak temperature of 260°C maximum, and a time above liquidus (TAL) to ensure proper solder joint formation. The component must not be exposed to 260°C for more than 10 seconds. This profile is based on JEDEC standards to ensure reliability.

6.2 Hand Soldering

If hand soldering is necessary, it should be performed with a soldering iron tip temperature not exceeding 300°C, and the contact time should be limited to a maximum of 3 seconds for a single operation only. Excessive heat can damage the LED chip or the plastic package.

6.3 Cleaning

If post-solder cleaning is required, only specified solvents should be used. The datasheet recommends immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Unspecified chemicals may damage the package material, leading to discoloration, cracking, or reduced light output.

6.4 Storage and Handling

ESD Precautions: LEDs are sensitive to electrostatic discharge (ESD). Handling should be done with anti-static measures such as wrist straps and grounded equipment.

Moisture Sensitivity: The devices are packaged in moisture-barrier bags with desiccant. Once the original bag is opened, the LEDs should be used within one week. For longer storage outside the original packaging, they must be kept in a dry environment (≤30°C, ≤60% RH) or rebaked (approx. 60°C for 20 hours) before soldering to prevent \"popcorning\" during reflow.

7. Packaging and Ordering Information

7.1 Tape and Reel Specifications

The LEDs are supplied in standard 8mm carrier tape on 7-inch (178mm) diameter reels. Each reel contains 4000 pieces. This packaging is compatible with automated pick-and-place machines used in high-speed PCB assembly lines. The tape has a cover seal to protect components.

8. Application Suggestions

8.1 Typical Application Scenarios

This dual-color LED is ideal for status indication where two states need to be communicated (e.g., power on/standby, charge status, network activity, error/warning signals). Its thin profile makes it perfect for modern smartphones, tablets, ultra-thin laptops, wearable devices, and slim control panels.

8.2 Design Considerations

• Current Driving: Always use a series current-limiting resistor for each LED color. Calculate the resistor value based on the supply voltage (Vcc), the LED's forward voltage (VF), and the desired operating current (IF). Use separate calculations for Blue and Yellow due to their different VF values.
• Thermal Management: Although power dissipation is low, ensuring adequate PCB copper area around the thermal pads (if any) or traces helps dissipate heat, maintaining LED longevity and stable light output.
• Optical Design: The 130-degree viewing angle provides wide visibility. For focused light, external lenses or light guides may be required.

9. Technical Comparison and Differentiation

The key differentiator of this product is the combination of two high-performance LED technologies (InGaN for blue, AlInGaP for yellow) in an industry-standard, ultra-thin (0.55mm) package. Compared to using two separate single-color LEDs, this solution saves PCB space, reduces component count, and simplifies assembly. The high luminous intensity bins (up to 180 mcd) offer brightness competitive with many standard SMD LEDs.

10. Frequently Asked Questions (Based on Technical Parameters)

10.1 Can I drive both LED colors simultaneously at full current?

Yes, but you must consider total power dissipation and thermal effects. Driving both at their maximum DC current (Blue 20mA, Yellow 30mA, total 50mA) will generate heat. Ensure the application's ambient temperature and PCB layout can handle the combined thermal load without exceeding the maximum junction temperature.

10.2 Why is the forward voltage different for Blue and Yellow?

The forward voltage is a fundamental property of the semiconductor material's bandgap. InGaN (Blue) has a wider bandgap than AlInGaP (Yellow), requiring a higher voltage to \"push\" electrons across the junction, resulting in higher-energy (shorter wavelength) photons.

10.3 How do I select the right bin code?

Choose based on your application's brightness uniformity requirements. For a panel of indicators, specifying a tighter bin range (e.g., all P bin) ensures consistent appearance. For cost-sensitive applications where absolute brightness is less critical, a wider bin or mix may be acceptable.

11. Practical Design and Usage Case

Scenario: Dual-Status Indicator for a Portable Battery Charger. The Blue LED can indicate \"charging in progress,\" and the Yellow LED can indicate \"charge complete.\" The designer would lay out the PCB with the recommended pad footprint. Two separate driver circuits would be designed: one with a current-limiting resistor calculated for the Blue LED's VF (e.g., (5V - 3.2V)/0.02A = 90Ω) and another for the Yellow LED (e.g., (5V - 2.0V)/0.03A ≈ 100Ω). The microcontroller would control transistors to switch each circuit. The thin package allows it to fit into the charger's slim enclosure.

12. Operating Principle Introduction

An LED is a semiconductor diode. When a forward voltage is applied, electrons from the n-type material recombine with holes from the p-type material within the active region. This recombination releases energy in the form of photons (light). The color (wavelength) of the emitted light is determined by the energy bandgap of the semiconductor material used in the active region. The InGaN chip produces blue light, and the AlInGaP chip produces yellow light. The package incorporates a water-clear lens that minimally alters the emitted color.

13. Technology Trends

The development of this component reflects broader trends in optoelectronics: Miniaturization (thinner packages), Multi-Function Integration (combining multiple chips/colors), and Manufacturing Compatibility (compliance with automated, lead-free processes). Future trends may include even thinner profiles, higher efficiency (more light output per mA), and the integration of more than two colors or combined with photodetectors in a single package.