SO Flat-Pak IC Package Drawing

SO Flat Package [Small Outline]

SO IC Package Style

An SO IC device is a surface mount component that has a body width that is small compared to other packages of the same style, which is why the term Small Outline is used.
The leads appear to be different than normal, compared to other styles. The SO Flat Package also appears to allow the bottom of the IC body to touch the surface of the printed wiring board. It may well be that a pad resides under the IC body; however no graphic is available.
A Small Out-Line IC is normally a Surface Mount Device [SMD], but could be any semiconductor package using a DIP package.
So the term Small Out-line is relative, as in, what does small refer to, or what is defined as small. However if you were to compare two identical functions having the same number of pins in the same package, than the small out-line package would be the one with a thinner component body.

The abbreviation SO IC is being used here, but in reference to a Flat-Pack IC. There is another more common IC package style that uses the acronym SOIC, again meaning Small-Outline, and also using a different lead attachment.

The dimensions shown for the IC are above are just one example. Another IC with more or less pins will have a different package body length, to accommodate the number of pins. The width of the body could also change depending on the complexity of the semiconductor die contained in the package.

This topic is one of a number in this series, just informative. In some cases the designer can determine the package type used in a board design and in some cases when an IC is only offered in one format, designs with what's offered. In many cases a function is available in more than one format, but if its not and the function is still required, there is no option than to use the format offered by the vendor.

Note the difference in how two different flat packages are depicted, as shown in the 2 diagrams. The major difference being the length of the pins, otherwise the packages appear similar, with the same style terminals. Check the data sheet for the exact dimensions of the package used in your application, and any special mounting requirements.

Dimensions of a 54-pin SO Flat Package.
Other packages may use different dimensions.

Note the metal pad on the top side of the IC.
Sometimes called a Thermal Pad.
Not all packages use a thermal pad.

Related topics:
Surface Mount Packages
IC Package styles
IC Socket Manufacturers.

Flat Pack IC Package Style

For simplicity no dimensions are shown.
The size varies with the pin count.
Other styles are also possible.

PC motherboard

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Modified 1/17/12
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