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Intermediate Data Format (IDF) is a vendor-neutral format for exchanging printed circuit assembly (PCA) information between PCB layout design (ECAD) systems and Mechanical CAD systems such as SOLIDWORKS. CircuitWorks reads and writes IDF 2.0, IDF 3.0, and IDF 4.0.

IDF was originally developed in 1992 and continues to evolve. The current version of the format is IDF 4.0, but most systems, including CircuitWorks, supports the earlier IDF 2.0 and IDF 3.0 formats.

File Types and Extensions

Each IDF 2.0 or 3.0 "file" consists of two files on disk. The files typically have .emn and .emp extensions, but other extensions are also used (such as .brd and .lib). The .emn file contains information about the physical size and shape of the PCB (including holes and cut-outs) and component locations. The .emp file contains information about the size and shape of each component. For CircuitWorks to read  IDF 2.0 or 3.0, both files must be present in the same location with the same name (for example, samples\cellphone.emn and samples\cellphone.emp).

IDF 4.0 uses a single file with a .idf extension, such as cellphone.idf.

File Content

IDF 2.0 files contain basic information about the shape of the board, the position and size of plated and nonplated holes, and the position and basic shape of components. IDF 3.0 added support for more keep-out and outline types. IDF 2.0 and 3.0 are very similar in structure and content.

IDF 4.0 added support for traces, pads, vias, and filled areas. IDF 4.0 also allows shapes to be defined in more detail than the previous versions. Because IDF 4.0 is significantly more complex than IDF 2.0 and 3.0, its adoption in the ECAD and MCAD communities has been slow but is gaining acceptance.

How Is IDF Used?

In the typical design process, the mechanical designer defines the board shape, specifies important keep-in and keep-out regions, and pre-places critical components such as connectors, switches, displays, and LEDs using a mechanical design system. This information is passed in IDF to the PCB designer to use as the basis for the board layout in the PCB layout system. After placing the remaining components, the fully placed board assembly is passed back in IDF to the mechanical designer to make sure the board assembly fits into the final product package. Multiple iterations typically occur during the product design phase.

IDF does not provide a full design representation of a PCA. It is not intended to provide a full functional or electrical description of the PCA. Therefore, it is not appropriate to use IDF as a mechanism to convert PCA designs from one PCB layout system to another or as a mechanism to interface PCB layout with manufacturing, assembly, test, or detailed documentation systems.

Which ECAD Systems Can Produce IDF Files?

Most ECAD systems can read and write the more common IDF 2.0 and 3.0 formats. IDF 4.0 is supported by fewer ECAD systems. In some cases, third-party tools are required to generate IDF from an ECAD system. Contact SOLIDWORKS Technical Support for information about ECAD system IDF support.

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