There are various types of packaging sizes for optocouplers (optocouplers) to meet different application requirements, such as space limitations, isolation voltage requirements, power dissipation capacity, and production processes. Here are some of the most common and representative types of packaging sizes:
Core logic: The selection of packaging size mainly depends on three key factors:
Space limitations: Equipment volume requirements.
Electrical isolation requirements: The required insulation voltage (such as 3750Vrms, 5000Vrms).
Power consumption/heat dissipation requirements: The heat generated by the internal LED and output devices (such as transistors, thyristors, ICs) of the optocoupler.
Main packaging size types
Dual in-line package
DIP-4/DIP-6: This is the most classic and widely used through-hole plug-in package. Usually 4-pin (single channel) or 6-pin (may include base lead out or dual channel variants). Relatively large in size, easy to manually weld and prototype. Provide good isolation performance and moderate heat dissipation capability.
DIP-8: wider than DIP-4/6, typically used for devices that require higher isolation voltages (such as 5000Vrms) or have more complex integrated circuits (such as logic gate output optocouplers). It is also common in dual channel optocouplers. The heat dissipation capability is usually better than DIP-4.
Features: Through hole installation, easy to use, good isolation performance, relatively large volume.
Small form factor packaging
SOP/SOIC: This is the most mainstream surface mount packaging.
SOP-4/SOIC-4: Standard 4-pin SMD package, significantly smaller in size than DIP-4, making it the preferred choice for modern compact electronic devices. The pin spacing is usually 1.27mm.
SOP-5/SOIC-5: Add a pin on top of SOP-4 (commonly used for base extraction or special functions).
SOP-6/SOIC-6: Commonly used in dual channel optocouplers or single channel optocouplers with additional functions.
SOP-8/SOIC-8: Used for SMD optocouplers that require higher isolation, more complex functionality, or dual channels.
Features: Surface mount, space saving, suitable for automated production, is currently the mainstream packaging.
Micro flat packaging
SSOP/TSOP/USOP: These are packages that are narrower and have smaller pin spacing than standard SOP (such as 0.65mm), aimed at further reducing PCB footprint.
For example: SSOP-4, TSOP-4, etc.
Features: Ultra small surface mount, high space utilization, higher requirements for PCB layout and soldering processes (such as SMT equipment accuracy).
Wide body packaging
DIP-4 Wide/DIP-6 Wide/DIP-8 Wide/SOP-8 Wide: On the basis of standard DIP or SOP, the width (and sometimes height) of the plastic package is increased. The main purpose is to:
Significantly improve creepage distance and electrical clearance: thus supporting higher isolation voltages (such as 5000Vrms, 7500Vrms or even higher), meeting stricter safety requirements (such as medical and industrial control).
Improving heat dissipation: A larger plastic casing helps dissipate more heat, making it suitable for optocouplers that drive larger loads such as MOSFETs and IGBT gates.
Features: Large size (especially width), focused on high isolation voltage and/or better heat dissipation performance.
Axial lead packaging
Mainly used for optocoupler thyristors and optocoupler three terminal bidirectional thyristors.
The appearance is similar to a large glass diode (DO-41, DO-15, etc.), but it integrates LED and output thyristor/three terminal bidirectional thyristor internally. Usually there are three leads (LED anode, LED cathode, output MT1/MT2).
Features: Designed for direct driving of AC loads, easy to install on heat sinks or utilize lead wires for heat dissipation, commonly used in solid-state relay modules or independent incandescent lamp dimming and motor control applications.
Special/power type packaging
DIP-16 (similar size): Some high-power optocouplers or optically isolated IGBT/MOSFET drivers may use larger and more pin packed packages, which may integrate more circuits internally or provide better heat dissipation paths (sometimes with metal heat sinks at the bottom).
SMD packages with heat sinks/exposed solder pads: Some high-power optocouplers or drivers are designed with metal heat sinks or exposed thermal pads at the bottom of SOP, DIP, and other packages to enhance thermal conductivity to the PCB copper foil.
Modular packaging: Some manufacturers integrate optocouplers with other power devices (such as MOSFETs) in one module to form a complete isolated driving solution. These types of packaging sizes vary and are relatively large.
Summarize key selection points
Ultimate space saving: Prioritize micro SMD packages (such as TSOP, USOP) or standard SMD (SOP/SOI).
High isolation voltage requirement: Wide DIP (Wide SOP) packaging must be selected.
Medium to high power drive applications: Choose wide body packages, packages with heat sinks, DIP-8 or larger power type packages. Axial packaging is suitable for thyristor drives.
Prototype production/small batch/easy to manually weld: Standard DIP packaging is more convenient.
Large scale automated production: SMD packaging (SOP, SSOP, TSOP, etc.) is the standard choice.
Important Notice:
The same package name (such as SOP-8) may have slight size differences (length, width, height, pin spacing) between different manufacturers. When making specific selections, it is necessary to refer to the "Package Outline Drawing" or "Mechanical Dimensions" section in the official data manual of the target optocoupler model, where accurate dimensional drawings will be provided.
The packaging size directly affects the creepage distance and electrical clearance, thereby determining its maximum rated isolation voltage, which is a key parameter for safety compliance.
When choosing optocoupler packaging, it is necessary to comprehensively consider space, isolation level, power requirements, and manufacturing process, and refer to the data manual of specific devices to obtain accurate dimensions and performance parameters.