Types of Photocouplers (Internal Structure)

Photocouplers have various types of internal package structure because of various restrictions such as required insulation performance, package size, and size of internal chip.

Transmissive type in single mold:

Frame-mounted LED and frame-mounted photodetector face each other in the same molded package. Silicon resin is used for the optical transmission part between LED and photodetector.

Transmissive type in single mold with film:

To raise isolation voltage, polyimide film is inserted between LED and photodetector.

Transmissive type in double mold:

In this transmissive structure, inner mold is white, and outer mold is black. Resin with high infrared light transmittance is used for white mold of the optical transmission part.

Reflective type:

Frame-mounted LED and frame-mounted photodetector are on the same plane. LED light reflected in silicon resin reaches the photodetector. Thus, it is called reflective type.

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