Eurocard is a European standard format for PCB cards, 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.
The Eurocard packaging system is a complex mixture of English and metric dimensions.
Eurocard subracks have standardized sizes in the vertical and horizontal directions. Height is specified by the rack unit 'U', with 1 U being 1.75 inches (44.45 mm), the same unit used with 19-inch racks. Width is specified by the horizontal pitch unit 'HP', with 1 HP being 0.20 inches (5.08 mm). A 3U subrack is 5.25 inches (133.35 mm) high and accepts a 3U Eurocard which is 100 millimetres (3.937 in) high. Another popular size is the 6U high subrack which is 10.5 inches (266.70 mm) high and accepts 6U (Double) Eurocards which are 233.35 millimetres (9.187 in) high. Note that front panel sizes are slightly less than the subrack sizes: for example a 3U front panel may only be 130 millimetres (5.118 in) high whereas the 3U subrack itself is 133.35 millimetres (5.250 in) high.
The Eurocard height starts at 100 millimetres (3.937 in) and increments by 5.25 inches (133.350 mm) increments. This arrangement allows two 3U high (100 millimetres (3.937 in)) Eurocards to be supported properly next to a 6U high (233.35 millimetres (9.187 in)) Eurocard. The 33.35 millimetres (1.313 in) space is required for the card guide structure that would be between the two 3U high cards.
Eurocards come in modular depths that start at 100 millimetres (3.937 in) and then increase in 60 millimetres (2.362 in) increments. The 160 millimetres (6.299 in) depth is the most common today, however standard hardware is available to accommodate depths of 100 millimetres (3.937 in), 160 millimetres (6.299 in), 220 millimetres (8.661 in), 280 millimetres (11.024 in), 340 millimetres (13.386 in), and 400 millimetres (15.748 in).
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.
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.
The Eurocard standard is also the basis of the "Eurorack" format for modular electronic music synthesizers, popularized by Doepfer and other manufacturers.