LTST-C171TGKT SMD LED Datasheet - Dimensions 3.2x1.6x0.8mm - Voltage 3.2V - Green Color - 76mW Power - English Technical Document

1. Product Overview

The LTST-C171TGKT is a high-performance, surface-mount device (SMD) light-emitting diode (LED) designed for modern electronic applications requiring compact form factors and reliable operation. This component utilizes InGaN (Indium Gallium Nitride) semiconductor technology to produce green light. Its primary design goal is to provide a robust, efficient light source compatible with automated assembly processes common in high-volume manufacturing.

Key advantages of this LED include its exceptionally low profile, with a height of only 0.8 mm, making it suitable for applications with severe space constraints. It is classified as a green product and complies with RoHS (Restriction of Hazardous Substances) directives. The package is supplied on industry-standard 8mm tape mounted on 7-inch reels, facilitating efficient pick-and-place assembly. The device is fully compatible with infrared (IR) and vapor phase reflow soldering processes, ensuring reliable solder joints in mass production.

2. Technical Parameters Deep Objective Interpretation

2.1 Absolute Maximum Ratings

The absolute maximum ratings define the stress limits beyond which permanent damage to the device may occur. For the LTST-C171TGKT, these are specified at an ambient temperature (Ta) of 25°C. The maximum continuous DC forward current is 20 mA. Under pulsed operation with a 1/10 duty cycle and a 0.1ms pulse width, a peak forward current of 100 mA is permissible. The maximum power dissipation is 76 mW. The device can withstand a reverse voltage of up to 5 V. The operating temperature range is from -20°C to +80°C, while the storage temperature range extends from -30°C to +100°C. Derating for the forward current is linear above 50°C at a rate of 0.25 mA per °C, which is critical for thermal management in the application design.

2.2 Electrical and Optical Characteristics

The typical performance is measured at Ta=25°C. The luminous intensity (Iv) ranges from a minimum of 71.0 mcd to a maximum of 450.0 mcd at a forward current (IF) of 20 mA. The viewing angle (2θ1/2), defined as the full angle at which intensity is half the on-axis value, is 130 degrees, indicating a wide viewing pattern. The peak emission wavelength (λP) is typically 530 nm. The dominant wavelength (λd), which defines the perceived color, is 525 nm at IF=20mA. The spectral line half-width (Δλ) is 35 nm, describing the spectral purity. The forward voltage (VF) ranges from 2.80 V to 3.60 V, with a typical value of 3.20 V at IF=20mA. The reverse current (IR) is a maximum of 10 μA at a reverse voltage (VR) of 5V.

3. Bin Code System Explanation

The product is classified into bins based on key parameters to ensure consistency in application. This allows designers to select LEDs with tightly grouped characteristics for uniform appearance and performance.

3.1 Forward Voltage Binning

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

3.2 Luminous Intensity Binning

Luminous intensity is binned into four categories: Q (71.0 - 112.0 mcd), R (112.0 - 180.0 mcd), S (180.0 - 280.0 mcd), and T (280.0 - 450.0 mcd). A tolerance of ±15% applies to each intensity bin.

3.3 Dominant Wavelength Binning

Dominant wavelength is binned to control color consistency. The bins are AP (520.0 - 525.0 nm), AQ (525.0 - 530.0 nm), and AR (530.0 - 535.0 nm). The tolerance for each bin is ±1 nm.

4. Performance Curve Analysis

While specific graphical curves are referenced in the datasheet (e.g., Fig.1, Fig.6), their typical behavior can be described. The relationship between forward current (IF) and forward voltage (VF) is exponential, characteristic of a diode. The luminous intensity is approximately proportional to the forward current within the specified operating range. The spectral distribution curve shows a single peak around 530 nm with a defined half-width. The viewing angle pattern is typically Lambertian or near-Lambertian for this wide-angle device, meaning intensity decreases with the cosine of the angle from the axis.

5. Mechanical and Package Information

The LED conforms to EIA standard package dimensions. The package has a water-clear lens. Detailed dimensional drawings specify the length, width, height, and lead positions. The ultra-thin profile of 0.8 mm is a key mechanical feature. Polarity is indicated by the cathode mark, which is typically a notch or a green dot on the package. Recommended solder pad dimensions are provided to ensure proper solder joint formation and mechanical stability during and after the reflow process.

6. Soldering and Assembly Guidelines

6.1 Reflow Soldering Profiles

Two suggested infrared (IR) reflow profiles are provided: one for normal (tin-lead) process and one for Pb-free process. For the Pb-free process, which uses Sn-Ag-Cu solder paste, the profile must be carefully controlled. The peak temperature should not exceed 260°C, and the time above the solder liquidus temperature must be managed to prevent thermal damage to the LED package while ensuring proper solder reflow.

6.2 Wave and Hand Soldering

For wave soldering, a maximum temperature of 260°C for 5 seconds is specified. For manual soldering with an iron, the tip temperature should not exceed 300°C, and contact time should be limited to 3 seconds per joint, for one time only.

6.3 Storage and Handling

LEDs should be stored in an environment not exceeding 30°C and 70% relative humidity. Components removed from their original moisture-barrier packaging (MSL 2a) should be reflowed within 672 hours (28 days). If storage exceeds this period, a bake-out at 60°C for at least 24 hours is recommended before assembly to remove absorbed moisture and prevent \"popcorning\" during reflow.

6.4 Cleaning

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. Unspecified chemicals may damage the epoxy lens or package.

7. Packaging and Ordering Information

The standard packaging is 8mm wide embossed carrier tape on 7-inch diameter reels. Each reel contains 3000 pieces. The tape has pockets sealed with a top cover tape. Packaging follows ANSI/EIA 481-1-A-1994 specifications. For order quantities that are not a multiple of a full reel, a minimum packing quantity of 500 pieces applies for remainder parts.

8. Application Suggestions

8.1 Typical Application Scenarios

This LED is suitable for backlighting in consumer electronics (e.g., mobile devices, LCD panels), status indicators, decorative lighting, and automotive interior lighting where a thin profile is critical. Its wide viewing angle makes it good for applications requiring broad area illumination or visibility from multiple angles.

8.2 Design Considerations

Drive Circuit: LEDs are current-driven devices. To ensure uniform brightness when multiple LEDs are connected in parallel, it is strongly recommended to use a individual current-limiting resistor in series with each LED. Connecting LEDs directly in parallel without individual resistors (Circuit Model B) is discouraged, as small variations in the forward voltage (Vf) characteristic between LEDs can cause significant current imbalance, leading to uneven brightness and potential overstress of the LED with the lowest Vf.

Thermal Management: Although the power dissipation is low, proper PCB layout to dissipate heat is important, especially when operating near maximum ratings or in high ambient temperatures. The derating curve must be followed.

ESD Protection: The device is sensitive to electrostatic discharge (ESD). Proper ESD controls must be implemented during handling and assembly. This includes using grounded wrist straps, anti-static mats, and ensuring all equipment is properly grounded. An ionizer can be used to neutralize static charges in the work area.

9. Technical Comparison

The primary differentiating advantage of the LTST-C171TGKT is its ultra-thin 0.8 mm height, which is significantly lower than many standard SMD LEDs (e.g., 0805 or 1206 packages which are often over 1.0 mm tall). This allows for design into increasingly slim electronic products. The wide 130-degree viewing angle provides more diffuse light compared to narrower-angle LEDs, reducing the need for secondary optics in some applications. The defined binning structure for intensity, voltage, and wavelength offers designers predictable performance and color consistency across production batches.

10. Frequently Asked Questions (Based on Technical Parameters)

Q: Can I drive this LED with a 5V supply directly?
A: No. The typical forward voltage is 3.2V. Connecting it directly to a 5V source without a current-limiting resistor would cause excessive current to flow, potentially destroying the LED instantly. Always use a series resistor to set the appropriate current (e.g., 20 mA).

Q: What is the difference between peak wavelength and dominant wavelength?
A: Peak wavelength (λP) is the wavelength at which the spectral power output is maximum (530 nm). Dominant wavelength (λd) is the single wavelength of monochromatic light that would produce the same perceived color (525 nm). Dominant wavelength is more relevant for color specification.

Q: How do I interpret the luminous intensity bin code (e.g., \"T\")?
A: The bin code indicates the guaranteed minimum and maximum intensity for LEDs in that group. A \"T\" bin LED will have an intensity between 280.0 and 450.0 mcd when driven at 20 mA. Selecting a higher bin code generally means a brighter LED.

Q: Is this LED suitable for outdoor use?
A: The operating temperature range is -20°C to +80°C. While it could function in some outdoor environments, prolonged exposure to direct sunlight, moisture, or temperatures beyond the specified range without proper encapsulation and environmental protection is not recommended. The datasheet specifies its intended use for ordinary electronic equipment.

11. Practical Design Case

Scenario: Designing a status indicator panel for a portable medical device. The panel requires 10 uniformly bright green indicators in a very thin housing.
Implementation: Ten LTST-C171TGKT LEDs are placed on the PCB. To ensure uniform brightness, each LED is driven from a common 5V rail through its own series resistor. The resistor value is calculated using Ohm's Law: R = (Vsupply - Vf_LED) / If. Using a typical Vf of 3.2V and a target If of 20 mA: R = (5V - 3.2V) / 0.020A = 90 Ohms. A standard 91-ohm resistor is selected. All LEDs are specified from the same luminous intensity bin (e.g., \"S\" bin) to guarantee minimal brightness variation. The 0.8mm height allows the entire assembly to fit within a 1.2mm thick enclosure.

12. Principle Introduction

Light emission in this LED is based on electroluminescence in an InGaN semiconductor. When a forward voltage is applied across the p-n junction, electrons and holes are injected into the active region. When these charge carriers recombine, energy is released in the form of photons (light). The specific composition of the Indium Gallium Nitride alloy determines the bandgap energy, which in turn defines the wavelength (color) of the emitted light—in this case, green. The water-clear epoxy lens encapsulates the semiconductor die, provides mechanical protection, and shapes the light output pattern.

13. Development Trends

The trend in SMD LEDs for consumer electronics continues toward higher efficiency (more light output per unit of electrical power), smaller footprints, and thinner profiles. There is also a drive for improved color consistency and tighter binning tolerances to meet the demands of high-resolution displays and uniform lighting. Furthermore, compatibility with lead-free (Pb-free) and high-temperature reflow processes remains essential due to global environmental regulations and the adoption of advanced PCB materials. The integration of onboard current regulation or protection features within the LED package itself is an area of ongoing development to simplify driver circuit design.