Diode Package Styles

Melf Component

SMD Diode Packages

Diode Package URS Case style, Surface Mount

URS Style Surface Mount Package
URS Diode, Surface Mount

The URS package is a Surface Mount Device [SMD]. This package style is also called a Melf package; metal Electrode Leadless Face. The DO-213 is another style of Melf package.
MELF packages are widely used for surface mount diodes and resistors. The DO-213 is the commercial JEDEC designation, while this package is using a Department of Defense designation. Although both references are relating to the same basic body style.

Square Body Surface Mount Package
Square Body Diode, Surface Mount Package

Design Hint; Use a larger pad on the PWB to act as a heat sink.
The larger the copper pad the lower the thermal resistance.
Also refer to Thermal Resistance vs Pad Area [FR4 board material].
Of course if no space is available on the component side of the board, a copper pad could be added to one or more internal layers. Using an internal layer as a heat sink is not as efficient as a top layer copper pad, but any heat sink is better than no heat sink at all.

D-5B Package [Government Designation];
Hermetic, Rectifier, Schottky Barrier Diode, 1N6826US, 1N6831US

Editor note: I think the term URS refers to a part number suffix to indicate a MELF package and not a package style in its own right. However in some government documents the term URS is referred to as a Package Identifier and not a Package Outline. In fact one particular document makes reference to the URS as; Surface mount diode with one round and one square endcap [endcap meaning terminal]. So a URS Identifier is not a package type in its own right, but the means to identify a package style. However it's only important because the military uses it to identify the package style shown in the graphic, and also the sizes that are called out in the dimensions table. In addition the package style D-5B called out for the diodes listed above could also be meaningless. In that, package designation is just a unique number to identify this package, but has no meaning outside of that, and no comparison can be made with other package styles. However a better explanation is that the DOD document using these numbers generates it own package type because no commercial alternative is available.

Surface Mount DO213

metal Electrode Leadless Face Component
MELF Package

Related Diode topics:
Types of Diode cases
Diode Derating Guidelines
Diode Derating Curves
Diode Manufacturers

The URS term seems common with DOD,
Not so common on the commercial side.

Note the picture shows round terminals.
The graphic shows square terminals.

URS packages hold any 2-lead component;
Having a low power dissipation.

Physical Dimensions
are provided for the
D-5A and D-5B packages.
Other Dimensions may be possible.

PC motherboard

Distributor rolodex Electronic Components Electronic Equipment EDA CDROM Software Engineering Standards, BOB card Cabled Computer Bus Electronic Engineering Design Table Conversion DB9-to-DB25.
DistributorsComponents Equipment Software Standards Buses Design Reference
Modified 6/13/15
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