PD95-21B/TR10 Photodiode Datasheet - 1.9mm Round SMD Package - Black Lens - Peak Sensitivity 940nm - English Technical Document

1. Product Overview

The PD95-21B/TR10 is a subminiature, surface-mount device (SMD) designed for high-performance light sensing applications. It is a silicon-based PIN photodiode, which is a fundamental semiconductor component that converts light energy into electrical current. The device is housed in a compact, 1.9mm diameter round package with a distinctive "Z-Bend" lead configuration, making it suitable for automated assembly processes. The top of the package features a black plastic lens that helps define the field of view and provides some environmental protection. Its primary function is to detect infrared radiation, with its spectral characteristics specifically tuned to match common infrared emitting diodes (IREDs), making it an ideal receiver component in optoelectronic systems.

2. Key Features and Applications

2.1 Core Advantages

The photodiode offers several performance benefits crucial for modern electronic design:

• Fast Response Time: The PIN structure, with its intrinsic (I) region, allows for rapid carrier collection, enabling the device to respond quickly to changes in light intensity. This is essential for data communication, pulse detection, and high-speed sensing.
• High Photo Sensitivity: It efficiently generates a measurable electrical current from low levels of incident light (irradiance), improving signal-to-noise ratio in detection circuits.
• Small Junction Capacitance: A low capacitance is critical for maintaining high bandwidth and fast response, as it minimizes the RC time constant of the detection circuit.
• Robust Manufacturing Compatibility: The device is designed to withstand standard infrared and vapor phase reflow soldering processes, facilitating reliable PCB assembly.
• Environmental Compliance: The component is lead-free (Pb-free), compliant with the EU's REACH regulation, and meets halogen-free requirements (Br <900 ppm, Cl <900 ppm, Br+Cl <1500 ppm), aligning with global environmental and safety standards.

2.2 Target Applications

This photodiode is engineered for systems requiring reliable infrared detection. Typical application areas include:

• Infrared Applied Systems: This encompasses a wide range, including remote controls, proximity sensors, object detection, and interruptive optical switches.
• Copiers and Printers: Used for paper detection, toner level sensing, and scanning mechanisms where precise detection of reflected or transmitted light is needed.
• Automotive Sensors: Suitable for non-critical sensing projects within vehicles, such as rain sensors, twilight sensors, or interior occupancy detection, where reliability across a temperature range is important.

3. Technical Parameter Analysis

3.1 Absolute Maximum Ratings

These limits define the stress conditions beyond which permanent damage may occur. Operation should always be within these bounds.

• Reverse Voltage (V_R): 32 V. The maximum voltage that can be applied in reverse bias across the diode without causing breakdown.
• Operating Temperature (T_opr): -25°C to +85°C. The ambient temperature range over which the device is specified to function correctly.
• Storage Temperature (T_stg): -40°C to +85°C. The temperature range for non-operational storage.
• Soldering Temperature (T_sol): 260°C for a maximum of 5 seconds. This defines the peak temperature tolerance during reflow soldering.
• Power Dissipation (P_d): 150 mW at 25°C. The maximum power the device can safely dissipate as heat.

3.2 Electro-Optical Characteristics (Ta=25°C)

These parameters define the device's performance under typical operating conditions.

• Spectral Bandwidth (λ_0.5): 730 nm to 1100 nm. This is the wavelength range where the photodiode's responsivity is at least half of its peak value. It confirms the device is sensitive across the near-infrared spectrum.
• Peak Sensitivity Wavelength (λ_P): 940 nm (Typical). The wavelength of light at which the photodiode is most sensitive. This aligns perfectly with the emission peak of many standard GaAlAs infrared LEDs.
• Short-Circuit Current (I_SC): 4 µA (Typical) at E_e=1 mW/cm², λ=875 nm. The current generated when the photodiode terminals are short-circuited (zero bias voltage). It is a direct measure of photocurrent generation efficiency.
• Reverse Light Current (I_L): 4 µA (Typical) at E_e=1 mW/cm², λ=875 nm, V_R=5V. The current flowing under reverse bias when illuminated. Operating in reverse bias (photoconductive mode) generally offers faster response and more linear output than zero-bias (photovoltaic mode).
• Reverse Dark Current (I_D): 10 nA (Max) at V_R=10V. The small leakage current that flows under reverse bias conditions in complete darkness. A low dark current is critical for detecting weak light signals, as it represents the noise floor of the device.
• Reverse Breakdown Voltage (V_BR): 32 V (Min), 170 V (Typical). The voltage at which the reverse current increases sharply. The device should never be operated near this point.

4. Performance Curve Analysis

The datasheet references typical performance curves which provide deeper insight than single-point specifications.

4.1 Spectral Sensitivity (Fig. 1)

This curve graphically represents the photodiode's responsivity as a function of the wavelength of incident light. It will show a bell-shaped curve, peaking at approximately 940 nm and tapering off towards the specified 730 nm and 1100 nm points at half the peak sensitivity. This curve is essential for matching the photodiode to a specific light source, ensuring maximum signal strength.

4.2 Reverse Light Current vs. Irradiance (Fig. 2)

This plot illustrates the relationship between the generated photocurrent (I_L) and the incident light power density (E_e). For a well-designed PIN photodiode operating in its linear region, this relationship should be highly linear. The slope of this line represents the photodiode's responsivity (typically in A/W). This linearity is crucial for analog light measurement applications.

5. Mechanical and Packaging Information

5.1 Package Dimensions

The device is a 1.9mm diameter round package. Detailed mechanical drawings are provided in the datasheet, specifying all critical dimensions including body diameter, height, lead spacing, and lead dimensions. All dimensions are in millimeters with a standard tolerance of ±0.1mm unless otherwise noted. The "Z-Bend" lead style is designed to provide a stable footprint for surface mounting and relieve mechanical stress.

5.2 Polarity Identification

The photodiode is a polarized component. The datasheet drawing clearly indicates the cathode and anode terminals. Correct polarity must be observed during circuit board assembly for proper operation in reverse-bias configuration.

5.3 Carrier Tape and Reel Specifications

For automated assembly, the components are supplied in carrier tape and reel. The datasheet includes the dimensions for the carrier tape pockets, reel diameter, and orientation. The standard packing quantity is 1000 pieces per reel.

6. Soldering and Assembly Guidelines

6.1 Storage and Moisture Sensitivity

The photodiode is moisture-sensitive. Precautions must be taken to prevent popcorning or delamination during reflow soldering:

• Store unopened bags at ≤30°C and ≤90% RH.
• Use components within one year.
• After opening, store at ≤30°C and ≤70% RH.
• Use within 168 hours (7 days) after opening the moisture barrier bag.
• If the storage time is exceeded or the desiccant indicates moisture ingress, bake at 60±5°C for 24 hours before use.

6.2 Reflow Soldering Profile

A lead-free reflow soldering temperature profile is recommended. The profile should be controlled to ensure the peak body temperature does not exceed 260°C for more than 5 seconds. Reflow soldering should not be performed more than two times to avoid thermal damage to the plastic package and semiconductor die.

6.3 Hand Soldering and Rework

If hand soldering is necessary, extreme care is required:

• Use a soldering iron with a temperature below 350°C and a power rating below 25W.
• Limit contact time per lead to 3 seconds.
• Allow a cooling interval of at least 2 seconds between soldering each lead.
• Avoid mechanical stress on the component during heating.
• Rework is strongly discouraged. If unavoidable, a specialized dual-head soldering iron should be used to simultaneously heat both leads, preventing thermal stress. The device's functionality must be verified after any rework attempt.

6.4 Circuit Board Design Considerations

After soldering, the circuit board should not be warped or bent, as this can transfer stress to the brittle semiconductor die or solder joints, potentially causing failure.

7. Application Design Considerations

7.1 Over-Current Protection

A critical design note: The photodiode itself does not have internal current limiting. When operated in reverse bias, even a small increase in voltage can cause a large, potentially destructive increase in current if the device is exposed to light. Therefore, an external series resistor must be used in the bias circuit to limit the maximum current under bright illumination conditions and prevent burnout.

7.2 Biasing and Interface Circuitry

The photodiode can be used in two primary modes:

1. Photoconductive Mode (Reverse Bias): Applying a reverse bias voltage (e.g., 5V as in the test condition) widens the depletion region, reducing junction capacitance and speeding up the response time. This is the preferred mode for high-speed and linear applications. The output is a current source, typically converted to a voltage using a transimpedance amplifier (TIA).
2. Photovoltaic Mode (Zero Bias): The photodiode generates its own voltage when illuminated, operating like a solar cell. This mode offers very low dark current but has slower response and less linearity. It is suitable for low-frequency light measurement where simplicity is key.

7.3 Optical Design

The black lens provides a defined viewing angle. For optimal performance, the system design should consider the alignment between the infrared light source (e.g., an LED) and the photodiode, as well as potential sources of ambient light interference (e.g., sunlight, incandescent bulbs) that fall within its spectral range. Optical filters may be necessary in high-ambient-light environments.

8. Technical Comparison and Selection

The PD95-21B/TR10 belongs to a category of silicon photodiodes with a black lens. When selecting a photodiode, engineers should compare key parameters against application requirements: response speed (related to capacitance and bias), sensitivity (I_L), spectral match to the light source, package size, and environmental robustness. This device's combination of small size, good sensitivity, fast response, and SMD compatibility makes it a strong candidate for space-constrained, high-volume consumer and industrial infrared sensing applications where reliability and cost are balanced.

9. Operational Principles

A PIN photodiode is a semiconductor device with a three-layer structure: P-type, Intrinsic (undoped), and N-type silicon. When photons with energy greater than the silicon bandgap strike the intrinsic region, they create electron-hole pairs. In a reverse-biased PIN diode, the electric field in the wide intrinsic region sweeps these carriers to their respective terminals, generating a photocurrent that is proportional to the incident light intensity. The wide intrinsic region is key to its performance: it creates a large depletion area for photon absorption (increasing sensitivity) and reduces junction capacitance (increasing speed).

10. Disclaimer and Usage Notes

The information provided in a datasheet represents the manufacturer's specifications at the time of publication. Typical performance curves are for reference and do not represent guaranteed minimum or maximum values. It is the responsibility of the designer to operate the device within its Absolute Maximum Ratings and to validate performance in the specific end application. This product is generally not intended for use in safety-critical, life-support, military, or automotive primary systems without explicit qualification and approval from the component manufacturer.