LTW-327ZDSKS-5A SMD LED Datasheet - Side Looking Dual Color (White/Yellow) - English Technical Document

1. Product Overview

The LTW-327ZDSKS-5A is a preliminary specification for a side-looking, right-angle, dual-color Chip LED. This surface-mount device (SMD) integrates two distinct LED chips within a single package: an InGaN-based white LED and an AlInGaP-based yellow LED. Its primary design purpose is to provide a compact, dual-indication solution for applications where space is limited and side-emitting light is required. The right-angle form factor allows the light to be emitted parallel to the mounting plane, making it suitable for edge-lighting, status indicators on vertical PCBs, or backlighting in tight spaces.

The core advantages of this component include its compliance with RoHS environmental standards, compatibility with automated pick-and-place assembly equipment, and suitability for infrared (IR) reflow soldering processes. It is packaged in industry-standard 8mm tape on 7-inch diameter reels, facilitating high-volume manufacturing. The device is designed to be I.C. compatible, indicating it can be driven directly by typical logic-level signals from microcontrollers or other integrated circuits.

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 these conditions is not guaranteed. For the white LED chip, the maximum continuous DC forward current is 10 mA, with a peak forward current of 40 mA permissible under pulsed conditions (1/10 duty cycle, 0.1ms pulse width). Its maximum power dissipation is 35 mW. The yellow LED chip has higher limits: 20 mA DC forward current, the same 40 mA peak current, and 75 mW power dissipation. The device is rated for an operating temperature range of -20°C to +80°C and a storage temperature range of -30°C to +100°C. It can withstand an infrared reflow soldering profile with a peak temperature of 260°C for 10 seconds. The Human Body Model (HBM) electrostatic discharge (ESD) threshold is 2000V, necessitating standard ESD precautions during handling.

2.2 Electrical & Optical Characteristics

These parameters are specified at a standard test condition of Ta=25°C and a forward current (IF) of 5 mA, which serves as a common reference point. For the white LED, the luminous intensity (Iv) ranges from a minimum of 28.0 mcd to a maximum of 112.0 mcd, with a typical value provided. Its forward voltage (VF) ranges from 2.55V to 3.15V, with a typical value of 2.85V. The viewing angle (2θ1/2) is typically 130 degrees. For the yellow LED, the luminous intensity ranges from 7.1 mcd to 45.0 mcd, also with a typical 130-degree viewing angle. Its forward voltage ranges from 1.60V to 2.40V, with a typical value of 2.00V. The yellow LED's optical characteristics are further defined by a typical peak emission wavelength (λP) of 592 nm, a dominant wavelength (λd) of 589 nm, and a spectral line half-width (Δλ) of 20 nm. Its typical chromaticity coordinates are x=0.294, y=0.286 according to the CIE 1931 standard. The reverse current (IR) for both colors is a maximum of 100 µA at a reverse voltage (VR) of 5V. It is critical to note that the device is not designed for operation in reverse bias; this test condition is for leakage characterization only.

3. Binning System Explanation

The product is classified into bins based on key optical parameters to ensure consistency within a production lot. Two primary binning systems are defined: Luminous Intensity (Iv) bins and Hue (color) bins.

3.1 Luminous Intensity Binning

Separate bin code lists are maintained for the white and yellow LEDs. For the white LED, bins are labeled N, P, and Q, covering intensity ranges from 28.0-45.0 mcd, 45.0-71.0 mcd, and 71.0-112.0 mcd respectively, all measured at IF=5mA. For the yellow LED, bins K, L, M, and N cover ranges from 7.1-11.2 mcd, 11.2-18.0 mcd, 18.0-28.0 mcd, and 28.0-45.0 mcd. A tolerance of +/-15% is applied to the limits of each intensity bin.

3.2 Hue (Color) Binning

The hue binning applies to the yellow LED's color coordinates. Bins are defined as S1, S2, S3, and S4. Each bin specifies a quadrilateral area on the CIE 1931 chromaticity diagram defined by four (x, y) coordinate pairs. For example, bin S1 covers the area bounded by points (0.274, 0.226), (0.274, 0.258), (0.294, 0.286), and (0.294, 0.254). A tolerance of +/-0.01 is applied to each (x, y) coordinate within a hue bin. This system allows designers to select LEDs with tightly controlled color output for applications where color consistency is critical.

4. Performance Curve Analysis

The datasheet references typical electrical and optical characteristic curves, although the specific graphs are not detailed in the provided text. Based on standard LED behavior, these curves would typically include:

• Forward Current vs. Forward Voltage (I-V Curve): Shows the exponential relationship, crucial for designing current-limiting circuitry.
• Luminous Intensity vs. Forward Current (I-L Curve): Demonstrates how light output increases with current, often becoming sub-linear at higher currents due to thermal effects.
• Luminous Intensity vs. Ambient Temperature: Shows the decrease in light output as junction temperature rises, which is a key consideration for thermal management.
• Spectral Power Distribution: For the yellow LED, this would show the narrow emission peak around 592 nm, confirming its monochromatic nature.
• Viewing Angle Pattern: A polar plot illustrating the 130-degree angular distribution of light intensity.

These curves are essential for predicting real-world performance under conditions different from the standard test point of 5mA and 25°C.

5. Mechanical & Packaging Information

5.1 Package Dimensions and Pin Assignment

The device conforms to an EIA standard package outline. The pin assignment is clearly defined: Pin A1 is assigned to the AlInGaP Yellow LED anode, and Pin A2 is assigned to the InGaN White LED anode. The common cathode is not explicitly labeled in the snippet but is standard for this type of dual LED in a 2-pin package. A detailed dimensioned drawing would specify the length, width, height, lead spacing, and lens geometry, with all dimensions in millimeters and a typical tolerance of ±0.10 mm unless otherwise noted.

5.2 Suggested Soldering Pad Layout and Direction

The datasheet includes a section with suggested soldering pad dimensions and a recommended soldering direction. This guidance is vital for PCB layout designers to ensure reliable solder joint formation during reflow, proper mechanical stability, and correct alignment for the side-looking emission. Following these recommendations helps prevent tombstoning (component standing up on one end) and ensures optimal thermal and electrical connection.

6. Soldering & Assembly Guidelines

6.1 Reflow Soldering Process

The component is compatible with infrared reflow soldering. A suggested reflow profile is indicated, with the critical parameter being the ability to withstand 260°C at the solder joints for 10 seconds. This aligns with common lead-free (Pb-free) solder process requirements. Adherence to this profile is necessary to prevent package cracking, delamination, or damage to the LED chips.

6.2 Cleaning and Handling

Specific cleaning instructions are provided. Unspecified chemical liquids should not be used as they may damage the LED package. If cleaning is necessary post-solder, the recommended method is to immerse the LEDs in ethyl alcohol or isopropyl alcohol at normal temperature for less than one minute. Strict ESD precautions are emphasized due to the device's 2000V HBM rating. Handling with grounded wrist straps, anti-static gloves, and properly grounded equipment is strongly recommended to prevent damage from electrostatic discharge.

6.3 Storage Conditions

Storage conditions differ based on whether the moisture-sensitive device is in its original sealed packaging or has been opened. When sealed with desiccant, it should be stored at ≤30°C and ≤90% Relative Humidity (RH) and used within one year. Once the moisture-proof bag is opened, the storage ambient should not exceed 30°C or 60% RH. LEDs removed from their original packaging should ideally undergo IR reflow within one week. For longer storage outside the original bag, they must be kept in a sealed container with desiccant or in a nitrogen desiccator. If stored open for more than a week, 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.

7. Packaging & Ordering Information

7.1 Tape and Reel Specifications

The product is supplied in an 8mm wide embossed carrier tape wound onto 7-inch (178mm) diameter reels. The packaging conforms to ANSI/EIA 481 specifications. Each full reel contains 3000 pieces. For quantities less than a full reel, a minimum packing quantity of 500 pieces applies for remainders. The tape uses a top cover tape to seal empty component pockets. Quality specifications state that the maximum number of consecutive missing components (empty pockets) in the tape is two.

7.2 Part Number Interpretation

The part number LTW-327ZDSKS-5A follows the manufacturer's internal coding system. While the full breakdown is not provided, typical elements in such part numbers can denote series, color, package, bin codes, and other attributes. The \"(Preliminary)\" suffix indicates this is a pre-release or prototype specification, which may be subject to change before final release.

8. Application Suggestions

This side-looking dual-color LED is designed for ordinary electronic equipment applications. These include, but are not limited to, office automation equipment, communication devices, and household appliances. Its right-angle design makes it particularly suitable for:

• Panel-Mounted Status Indicators: Where LEDs are mounted on a daughter board perpendicular to the main board, shining through a panel.
• Edge-Lighting for Displays or Buttons: Providing backlighting from the side of a light guide.
• Dual-State Indication: Using white for one status (e.g., \"power on\") and yellow for another (e.g., \"standby\" or \"warning\") in a single component footprint.
• Space-Constrained Consumer Electronics: Such as smartphones, tablets, or portable gaming devices where height and side emission are critical.

Design Considerations: The different forward voltages of the white (typ. 2.85V) and yellow (typ. 2.00V) LEDs must be accounted for in the driving circuit, typically requiring separate current-limiting resistors for each color if they are to be driven independently from the same voltage rail. Thermal management is also important, as exceeding the maximum junction temperature will reduce light output and lifespan.

9. Technical Comparison & Differentiation

While a direct comparison with other part numbers is not provided in the datasheet, the key differentiating features of this component can be inferred:

• Dual Color in Right-Angle Package: Combines two colors in one side-emitting package, saving space compared to using two separate side-view LEDs.
• Chip Technology: Uses advanced InGaN for white and AlInGaP for yellow, which typically offer higher efficiency and reliability compared to older technologies like phosphor-converted yellow or standard GaAsP.
• Tin-Plated Leads: Improves solderability and compatibility with lead-free processes.
• Comprehensive Binning: Offers detailed intensity and hue binning, allowing for precise color and brightness matching in production.

10. Frequently Asked Questions (Based on Technical Parameters)

Q1: Can I drive the white and yellow LEDs simultaneously from the same pin?

A: No, they have separate anodes (A1 for Yellow, A2 for White). They must be driven independently to control each color separately. A common cathode configuration is typical.

Q2: Why is the maximum DC current different for the two colors (10mA vs 20mA)?

A: This is due to differences in the semiconductor materials (InGaN vs. AlInGaP), chip size, and thermal characteristics. Each chip has its own maximum power dissipation rating (35mW vs 75mW), which limits the allowable current.

Q3: What does the \"I.C. compatible\" feature mean?

A: It indicates that the LED's forward voltage and current requirements are within the typical output voltage and current sourcing/sinking capabilities of standard digital integrated circuits (like CMOS or TTL logic gates or microcontroller GPIO pins), often when paired with a suitable current-limiting resistor.

Q4: How critical is the 1-week floor life after opening the moisture barrier bag?

A: Very critical for reliable assembly. Moisture absorbed by the plastic package can vaporize rapidly during reflow soldering, causing internal cracks or delamination (\"popcorning\"). If the exposure time is exceeded, the mandatory bake-out procedure must be followed.

11. Practical Use Case Example

Scenario: Dual-Status Indicator for a Network Router.

A designer is creating a compact router with status LEDs on a front vertical panel. A single LTW-327ZDSKS-5A LED is mounted on a small PCB perpendicular to the main board, directly behind a small diffused window on the panel. The microcontroller on the main board has two GPIO pins available. Pin 1, connected to the white LED anode via a 150Ω resistor (calculated for ~3.3V supply and ~5mA target), indicates \"Internet Connection Active.\" Pin 2, connected to the yellow LED anode via a 68Ω resistor (for the same 3.3V supply), indicates \"Data Transfer Activity\" by blinking. This solution uses only one component footprint on the vertical board, simplifies assembly, and provides clear, two-color status indication in a very limited space.

12. Operating Principle Introduction

Light Emitting Diodes (LEDs) are semiconductor devices that emit light when an electric current passes through them. This phenomenon is called electroluminescence. In the LTW-327ZDSKS-5A:

• The White LED uses an InGaN (Indium Gallium Nitride) chip. Typically, a blue-emitting InGaN chip is combined with a yellow phosphor coating inside the package. The blue light from the chip excites the phosphor, which then emits yellow light. The combination of the remaining blue light and the generated yellow light appears white to the human eye.
• The Yellow LED uses an AlInGaP (Aluminum Indium Gallium Phosphide) chip. This material system directly emits light in the yellow/orange/red part of the spectrum. For this component, the epitaxial layer structure is engineered to emit photons with a peak wavelength of approximately 592 nm, which is perceived as yellow.

When a forward voltage exceeding the diode's threshold is applied, electrons and holes recombine in the active region of the semiconductor, releasing energy in the form of photons (light). The wavelength (color) of the light is determined by the bandgap energy of the semiconductor material.

13. Technology Trends

The development of LEDs like the LTW-327ZDSKS-5A follows several key industry trends:

• Miniaturization & Integration: Combining multiple functions (two colors) into a single, ever-smaller package to save PCB real estate.
• Higher Efficiency: Ongoing improvements in InGaN and AlInGaP materials lead to higher luminous efficacy (more light output per electrical watt), reducing power consumption and thermal load.
• Improved Color Consistency: Advanced binning systems, as seen in this datasheet, allow for tighter control over color and brightness, which is crucial for applications requiring uniform appearance.
• Enhanced Reliability & Robustness: Designs that withstand higher temperature reflow profiles (like 260°C) and have better ESD protection are essential for compatibility with modern, automated assembly processes.
• Specialized Form Factors: The growth of side-view and right-angle LEDs caters to the design needs of slim, modern consumer electronics where light must be directed laterally rather than upwards.