SMD LED Chip LTST-C171TBKT Datasheet - Size 1.6x0.8x0.6mm - Voltage 2.8-3.8V - Blue Color - 76mW Power - English Technical Document

1. Product Overview

The LTST-C171TBKT is a surface-mount device (SMD) chip LED designed for modern electronic assembly. It belongs to a family of super-thin components, featuring a compact form factor with a height of only 0.80 mm. This makes it suitable for applications where space constraints and low profile are critical design factors. The device utilizes an InGaN (Indium Gallium Nitride) semiconductor material to produce blue light, encapsulated in a water-clear lens package. It is engineered for compatibility with automated pick-and-place equipment and standard reflow soldering processes, including infrared (IR) and vapor phase methods, facilitating high-volume manufacturing.

2. Technical Parameter Deep Dive

2.1 Absolute Maximum Ratings

The device's operational limits are defined under an ambient temperature (Ta) of 25°C. The maximum continuous DC forward current is rated at 20 mA. For pulsed operation, a peak forward current of 100 mA is permissible under a 1/10 duty cycle with a 0.1ms pulse width. The maximum power dissipation is 76 mW. The reverse voltage withstand capability is 5 V, but continuous operation under reverse bias is prohibited. The operating temperature range spans from -20°C to +80°C, while the storage range is wider, from -30°C to +100°C. The device is rated for soldering at 260°C for 5 seconds in IR/wave processes and 215°C for 3 minutes in vapor phase.

2.2 Electrical & Optical Characteristics

Key performance parameters are measured at Ta=25°C and a forward current (IF) of 20 mA. The luminous intensity (IV) has a typical range from a minimum of 28.0 mcd to a maximum of 180.0 mcd. The forward voltage (VF) ranges from 2.80 V to 3.80 V. The device emits blue light with a typical peak emission wavelength (λP) of 468 nm and a dominant wavelength (λd) range of 465.0 nm to 475.0 nm. The spectral line half-width (Δλ) is typically 25 nm, indicating the spectral purity. The viewing angle (2θ1/2) is 130 degrees, providing a wide field of illumination. The reverse current (IR) is a maximum of 10 μA at a reverse voltage (VR) of 5V.

3. Binning System Explanation

The product is classified into bins based on three key parameters to ensure consistency in application design.

3.1 Forward Voltage Binning

Forward voltage is binned in 0.2V steps from 2.80V to 3.80V. Bin codes are D7 (2.80-3.00V), D8 (3.00-3.20V), D9 (3.20-3.40V), D10 (3.40-3.60V), and D11 (3.60-3.80V). A tolerance of ±0.1V applies within each bin.

3.2 Luminous Intensity Binning

Luminous intensity is categorized into four bins: N (28.0-45.0 mcd), P (45.0-71.0 mcd), Q (71.0-112.0 mcd), and R (112.0-180.0 mcd). A tolerance of ±15% applies to each intensity bin.

3.3 Dominant Wavelength Binning

The blue color is defined by two dominant wavelength bins: AC (465.0-470.0 nm) and AD (470.0-475.0 nm). The tolerance for each bin is ±1 nm.

4. Performance Curve Analysis

The datasheet references typical performance curves which are essential for design engineers. These curves graphically represent the relationship between forward current and luminous intensity, the effect of ambient temperature on luminous intensity, and the spectral power distribution of the emitted blue light. Analyzing the IV curve helps in selecting the appropriate current-limiting resistor to achieve desired brightness while maintaining efficiency. The temperature derating curve shows how luminous output decreases as ambient temperature rises above 30°C, at a rate defined by the derating factor. The spectral distribution curve confirms the peak and dominant wavelengths, ensuring the emitted color meets application requirements.

5. Mechanical & Packaging Information

5.1 Package Dimensions

The chip LED follows EIA standard package dimensions. All critical dimensions are provided in millimeters, with a general tolerance of ±0.10 mm unless otherwise specified. The super-thin profile of 0.80 mm is a key mechanical feature.

5.2 Polarity Identification & Pad Design

The component has anode and cathode terminals. The datasheet includes a suggested soldering pad layout (land pattern) to ensure reliable solder joint formation and proper alignment during reflow. Adhering to this footprint is crucial for mechanical stability and thermal management.

5.3 Tape and Reel Specifications

The device is supplied in 8mm tape on 7-inch diameter reels, compatible with automated assembly equipment. Standard reel quantity is 3000 pieces. Packaging follows ANSI/EIA 481-1-A-1994 specifications, with empty component pockets sealed by a top cover tape.

6. Soldering & Assembly Guide

6.1 Reflow Soldering Profiles

Detailed suggested reflow profiles are provided for both normal (tin-lead) and Pb-free solder processes. The Pb-free profile is specifically calibrated for SnAgCu solder paste. Key parameters include pre-heat temperature and time, time above liquidus, peak temperature (max 260°C), and time at peak temperature (max 5 seconds).

6.2 Storage and Handling Precautions

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. Components removed from their original moisture-barrier bag should be reflow-soldered within 672 hours (28 days). For storage beyond this period, baking at approximately 60°C for at least 24 hours is recommended before assembly to prevent moisture-induced damage (popcorning) during reflow.

6.3 Cleaning Instructions

If cleaning is necessary after soldering, only specified solvents should be used. Immersing the LED in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute is acceptable. The use of unspecified chemicals can damage the package material.

7. Application Suggestions

7.1 Typical Application Scenarios

This blue SMD LED is suitable for backlighting in consumer electronics (e.g., keypads, indicator lights), status indicators in communication and office equipment, and decorative lighting applications. Its thin profile makes it ideal for slim devices like smartphones, tablets, and ultra-thin displays.

7.2 Drive Circuit Design

LEDs are current-driven devices. To ensure uniform brightness when multiple LEDs are used in parallel, it is strongly recommended to use a dedicated current-limiting resistor in series with each LED. Driving multiple LEDs in parallel directly from a single current source (Circuit Model B) is discouraged, as slight variations in the forward voltage (Vf) characteristic of individual LEDs can lead to significant differences in current sharing and, consequently, uneven brightness.

7.3 Electrostatic Discharge (ESD) Protection

The LED is sensitive to electrostatic discharge. Proper ESD control measures must be implemented during handling and assembly. These include the use of grounded wrist straps or anti-static gloves, ensuring all workstations and equipment are properly grounded, and maintaining a controlled humidity environment in the assembly area.

8. Technical Comparison & Differentiation

The primary differentiating feature of this component is its ultra-low height of 0.80 mm, which is advantageous compared to standard LED packages. The combination of a wide 130-degree viewing angle and a well-defined binning structure for intensity, voltage, and wavelength provides designers with predictable performance. Its compatibility with standard IR, vapor phase, and wave soldering processes offers flexibility in manufacturing without requiring specialized equipment.

9. Frequently Asked Questions (FAQs)

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the emission spectrum has its maximum intensity. Dominant wavelength (λd) is derived from the CIE chromaticity diagram and represents the single wavelength that best matches the perceived color of the light. For design, dominant wavelength is more relevant for color specification.

Q: Can I drive this LED without a series resistor?
A: It is not recommended. The forward voltage has a range (2.8-3.8V). Connecting it directly to a voltage source near this range can cause excessive current if the LED's Vf is at the low end, potentially damaging it. A series resistor is necessary to set and limit the operating current reliably.

Q: How does temperature affect performance?
A: As ambient temperature increases, the luminous intensity typically decreases. The datasheet specifies a derating factor for forward current above 30°C. Also, the forward voltage has a negative temperature coefficient, meaning it decreases slightly as temperature rises.

10. Design-in Case Study

Consider a design for a portable device requiring multiple blue status indicators. The designer selects the LTST-C171TBKT for its low profile. To ensure uniform brightness across all 5 indicators, they specify LEDs from the same luminous intensity bin (e.g., Bin Q) and forward voltage bin (e.g., Bin D9). A constant voltage source of 5V is available. Using the typical Vf of 3.3V (mid-point of D9) and a target current of 20 mA, the series resistor value is calculated as R = (5V - 3.3V) / 0.020A = 85 Ohms. A standard 82 Ohm or 91 Ohm resistor would be chosen, with power rating checked. The PCB layout uses the recommended pad dimensions and includes proper ESD protection zones in the assembly area.

11. Operating Principle Introduction

This is a semiconductor light-emitting diode. When a forward voltage is applied across the anode and cathode, electrons and holes are injected into the active region of the InGaN semiconductor material. These charge carriers recombine, releasing energy in the form of photons (light). The specific energy bandgap of the InGaN material determines the wavelength of the emitted photons, which in this case is in the blue region of the visible spectrum. The water-clear epoxy lens shapes the light output and provides environmental protection.

12. Technology Trends

The trend in SMD LEDs continues towards higher efficiency (more lumens per watt), smaller package sizes, and improved thermal management to allow higher drive currents. There is also a focus on tighter binning tolerances to provide more consistent color and brightness for demanding applications like display backlighting. The drive for miniaturization in consumer electronics pushes for even thinner packages than the 0.80mm featured here.