COMPONENT PACKAGES

SOIC Component Package

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Overview

NameSOIC (Small Outline Integrated Package)
Synonyms
  • R-PDSO (JEDEC wide body SOIC, 7.5mm width, 0.65mm pitch)
  • SO (ST Microelectronics)
  • S8 (SOIC-8, Analog Devices)
  • S8E (Linear Technologies, SOIC-8 with exposed pad)
  • WSON (SST, this is a package which shares the same footprint as a SOIC but has a smaller height, not to be confused with the different SON package)
Variants

The SOIC family contains packages with a varying number of pins.

There are also two width's for SOIC packages, narrow width (3.9mm wide body, `SOICx_N`) and wide width (7.5mm wide body, `SOICx_W`). The width is usually expressed by the addition of `_N` or `_W` to the end of the package name. If the width is not mentioned, it is most likely going to be narrow width.

Relevant Standards
  • JEDEC MS-012-AA (SOIC Narrow)
  • JEDEC MS-013 (SOIC Wide)
Similar ToSOJ
MountingSMD
Pin Count8, 14, 16, 18, 20, 24, 28, 32
Pitch
  • 0.65mm (e.g. R-PDSO)
  • 1.27mm (50mill)
SolderabilityRelatively easy to hand solder compared to other SMT packages.
Thermal Resistance
  • SOIC-8: 70.6K/W (pads only, no copper fill)
  • SOIC-8: 55K/W (6cm2 of copper, ground pins attached internally to die)
  • SOIC-8: 33.5K/W (1 square inch of copper surrounding package, connected to ground)
Land Area
  • SOIC-8: 29.4mm2
  • SOIC-28W: 186.4mm² (10.3x18.1mm)
Height1.50-2.54mm
3D Modelsn/a
Common Uses
  • Linear regulators
  • Drivers/buffers
  • High-power MOSFETs (normally in a SOIC-8N, with one pin for the gate, and either 3 or 4 pins for the drain and source)

Dimensions

The dimensions for the SOIC-8N package are shown below:

The dimensions for the SOIC-8N component package.

The dimensions for the SOIC-8N component package.

The dimensions for the SOIC-16N component package are shown below:

The dimensions for the SOIC-16N component package.

The dimensions for the SOIC-16N component package.

Pitch

Most SOIC packages have a pitch of 1.27mm (50mil) and usually have Gullwing leads. When used for regulators, sometimes the many ground pins are connected internally to the die attach flag, providing better heat sinking capabilities. SOIC packages use leadframe technology.

The SOIC package R-PDSO defined by JEDEC has a non-standard pitch of 0.65mm (and the standard wide body width of 7.5mm).

Pin Numbering

Pin numbering is the same as a DIP package, in that pin 1 is at the top left, and then pins are numbered sequentially down the left-hand side, then up the right hand-side.

Polarity Marks

There are three ways of indicating the polarity on a SOIC package. The first two, a dot or a notch, indicate pin 1 or the top of the chip. The third way is not so obvious, and features a bevelled edge along the side that pin 1 is on (so for SOIC-8, the bevelled edge would be on the side with pins 1 to 4).

The WSON package by SST is lower in height than a standard SOIC package, but is designed to use the same PCB footprint.

Adapter PCBs

Adapter PCBs for the SOIC family of packages are widely available due to the popularity of the package.

SparkFun makes a SOIC-8 to DIP-8-300 adapter PCB.

A SOIC-8 to DIP-8-300 adapter PCB by SparkFun.

A SOIC-8 to DIP-8-300 adapter PCB by SparkFun.

Thermal Resistance And Power Dissipation

This graph shows the maximum power dissipation for the SOIC-8N component package, for various PCB copper areas.

Maximum power dissipation graphs for the SOIC-8N component package.

Maximum power dissipation graphs for the SOIC-8N component package.

Standard Pinout For MOSFETs

The SOIC-8 component package is commonly used for medium-power N and P-channel MOSFETs. Most of these MOSFETs have the exact same pinout (both N and P-Channels!), as shown in the below diagram.

Note: As far I’m aware, this is not specified in any standard, but is just an industry default. Also, this only applies to SOIC-8 packages with 1 MOSFET inside them.

The standard pinout for a single MOSFET (N or P-channel) in a SOIC-8 package.

The standard pinout for a single MOSFET (N or P-channel) in a SOIC-8 package.

Examples that follow this pinout include the ST STS25NH3LL (N-channel), the International Rectifier IRF8721PbF-1 (N-channel), and the Vishay SI9407BDY-T1-GE3 (P-channel).

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