R 3.10.2 MELF
This component consists of a conventional resistor for hole mount, but in a form without leads. Instead one solders direct on the press-fitted naked end caps. At wave soldering the component body should be positioned with a glue lump (epoxy) to the substrate / printed circuit board.
Because the MELF design is a modified version of well-tried, well-established hole mount types, it in this SMD component assimilates all the good characteristics that characterize the respective basic hole mount type.
For metal film MELF this means among other things
With an extra thick metal film one has in some cases improved heat dissipation and also pulse capability. High frequency capability is achieved by a so called pulsed trim cut where the spiraled conductive pattern is broken in parts, thus reducing the inductive action from the helical trim cut and thus increasing the frequency range to several GHz.
MELF components are made in metal film, carbon film and metal glaze types. Usually they are supplied with end caps of conventional components but some manufacturers use metallized terminations.
The MELF components were introduced as leadless metal film resistors in the DIN size 0207. Today 0204 (1.5 x 3.6 mm) is the most common, not least because of its smaller risk of open mode failure in the solder joints after frequent temperature changes. However, the size 0102 (1.1 x 2.2 mm) is already well established in the consumer market.
Hole mount : MELF ≈ 2 : 3.