Eurocard (printed circuit board)

Eurocard is a European standard format for printed circuit boards, which can be plugged together into a standardized subrack. The subrack consists of a series of slotted card guides on the top and bottom, into which the cards are slid so they stand on end, like books on a shelf. At the "back" of each card is one or more connectors, which plug into mating connectors on a backplane which closes the rear of the subrack.

Sizing and dimensions

The Eurocard packaging system is a complex mixture of English and metric dimensions. Although this may seem confusing, widespread conformance to the standard dimensions means that users are not troubled by these issues.

Standard pitch

Eurocard subracks have standardized sizes in all three dimensions. Height is specified by the unit 'U' (which stands for 'Unit'), with 1 U being 1.75 inches. Width is specified by the unit 'HP' (which stands for 'Horizontal Pitch')or 'T' with 1 HP being 0.20 inches. The smallest height is 3U.

The height of a eurocard is less than the height of rack by 33.35 mm to allow space for panels and card guides. The height of the card in a 3U rack is therefore 100 mm. As two stacked 3U cards are about the same height as a 6U card (see Notes) this scheme allows racks to be constructed which mix 3U and 6U cards.

Front panels are also slightly smaller than the rack size, and the typical panel height for a 133.35 mm 3U rack is 130 mm.

Eurocards come in modular depths that start at 100 mm and then increase in 60 mm increments.

Popular sizes

The standard allows for a vast number of permutations, but in practice there are only comparatively few sizes in use. Heights are commonly 3U or 6U, and only occasionally 9U. The 160 mm depth is the most common today, followed by 220mm. However standard hardware is also available to accommodate depths of 100 mm, 280 mm, 340 mm, and 400 mm.

Notes

A 3U high subrack is 133.35 mm (5.25 inches) high and accepts a 3U Eurocard which is 100 mm high.

A 6U high subrack is 266.7 mm (10.5 inches) high and accepts 6U Eurocards which are 233.35 mm high.

Standards and architecture

The Eurocard mechanical architecture was defined originally under IEC-60297-3. Today, the most widely recognized standards for this mechanical structure are IEEE 1101.1, IEEE 1101.10 (also known commonly as "dot ten") and IEEE 1101.11. IEEE 1101.10 covers the additional mechanical and EMI features required for VITA 1.1-1997(R2002) which is the VME64 Extensions standard as well as PICMG 2.0 (R3.0) which is the CompactPCI specification.

The IEEE 1101.11 standard covers rear plug-in units that are also called rear transition modules or RTMs.

The Eurocard is a mechanical system and does not define the specific connector to be used or the signals that are assigned to connector contacts.

The connector systems that are commonly used with Eurocard architectures include the original DIN 41612 connector that is also standardized as IEC 60603.2. This is the connector that is used for the VMEbus standard which was IEEE 1014. The connector known as the 5-row DIN which is used for the VME64 Extensions standard is IEC 61076-4-113. The VME64 Extension architecture defined by VITA 1.1-1997 (R2002).

Another popular computer architecture that utilizes the 6U-160 Eurocard is CompactPCI and CompactPCI Express. These are defined by PICMG 2.0R3 and PICMG Exp0 R1 respectively. Other computer architectures that utilize the Eurocard system are VXI, PXI, and PXI Express.

A computer architecture that used the 6U-220 Eurocard format was Multibus-II which was IEEE 1296, and IEEE 896 Futurebus used the 9U-280 format. Sun Microsystems used the 9U-400 format for their VMEbus based systems.

Because the Eurocard system provided for so many modular card sizes and because connector manufacturers have continued to create new connectors which are compatible with this system, it is a popular mechanical standard which is also used for innumerable "one-off" applications.

Conduction-cooled Eurocards are used in military and aerospace applications. They are defined by the IEEE 1101.2-1992(2001) standard.