Handling difficulties Metal electrode leadless face

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zener diode high-reliability applications in quadromelf package.


because of cylindrical shape , small size, in cases these components can roll off workbench or circuit board before have been soldered place. such, there joke suggests alternate meaning acronym: end lying on floor. additionally, melf components called roll away package.


during automated smt pick-and-place, happens if mechanical pressure of smd placer nozzle low. if melf components placed solder paste enough pressure, problem can minimized. care must taken glass diodes less mechanically robust resistors , other melf components.


also, when building pcbs via manual assembly using tweezers (e.g., prototyping) pressure @ end of tweezers can cause melf component slip , shoot out ends... thereby making placement more difficult, compared other flat component packages.


another reason nickname of melf components production engineers not use melf nozzles on smt pick-and-place machine. them waste of time change flat nozzles melf nozzles. micro-melf , mini-melf smd placers able use flat chip nozzles if vacuum high enough; i.e., higher flat chip components. melfs case size of 0207 or less, recommended use original melf nozzle supplied smt machine. each supplier of such smd pick-and-place machines offers these types of nozzles.


in order overcome of difficulties encountered when mounting these devices, there variants square electrodes (e.g. sq melf, quadromelf , b-melf). these variants used in semiconductor diodes applications high-reliability of hermetically sealed voidless-glass packages required.


these handling difficulties prompted development of alternative smt packages common melf components (like diodes) power handling capability needed similar melf components (superior low-power 0805/0603, etc. smt components) improved automated pick-and-place handling characteristics. resulted in various squared-off packages fold-over contacts, similar rectangular inductor/tantalum capacitor packages.








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