Most electronic components come in standardized packages. A package type has well a defined set of physical dimensions that the component has to conform to. For each package, normally the pitch spacing, height and general shape is defined.
Standardizing components sizes and shapes makes it easier for the component manufacturer, the PCB manufacturer, and the design engineer. Although most components are standardized, there are still plenty of packages out there. This pages purpose is to hopefully make some sense of the most common and widely used packages and to help anyone choosing a component package or designing a PCB.
Basically, the packages are used to define the shape and size of the particular components. a single components can be found in different packages.
For Example, resistors contain TWO most widely used packages:
SURFACE MOUNT RESISTORS
Resistors are available in a large amount of different packages. Nowadays the most used are the rectangular surface mount resistors, but also the good old axial resistor is still used extensively in through hole designs. This page will inform you about the dimensions of SMD, axial and MELF packages and about the required land patterns for SMD components.
The shape and size of surface mount resistors are standardized . The size of SMD resistors is indicated by a numerical code, such as 0603. 0403 1206. This code contains the width and height of the package.
So in the example of 0603 Imperial code, this indicates a length of 0.060″ and a width of 0.030″. in general the Imperial code is used more often to indicate the package size. The SMD resistor size depends mainly on the required power rating. The following table lists the dimensions and specifications of commonly used surface mount packages.
The size of axial resistors is not as standardized as the SMD resistors and different manufacturers often use slightly different dimensions. Furthermore the size of an axial resistor depends on the power rating and the type of resistor such as carbon composition, wirewound, carbon or metal film. The following drawing and table give an indication of the dimensions of common carbon film and metal film axial resistors. Whenever the exact size needs to be known, always check the manufacturer datasheet of the component.
Sometimes surface mount resistors are also used as MELF packages (Metal Electrode Leadless Face). The main advantage of using MELF in stead of standard SMD packages is the lower thermal coefficient and better stability. This cylindrical construction also gives the package distinct disadvantages, mainly when the components have to be placed using pick and place machines. Because of their round shape a special suction cup and more vacuum is required. There are three common MELF package sizes: MicroMELF, MiniMELF and MELF.