What are MELF metal electrode face diodes and resistors used for? I see MELF diodes used in SMD/SMT circuit boards mostly in the power supply but why use MELF diodes and resistors.

 

to solder to. surface mount parts have no leads, just metal faces to flow solder to boards.

 

From the datasheets of MELF diodes and resistors, is there any thing different about them than normal resistors and diodes?

Anything special about MELF components

 

From the datasheets of MELF diodes and resistors, is there any thing different about them than normal resistors and diodes?

Anything special about MELF components

The ones I encountered that were described as MELF, were in a range of Thorn Consumer CTVs.

The parts on the board were actually regular round bodied components with very short stub leads pressed into "mushrooms" at the ends - its hard to put into words, but think of the head of a chisel that's been used a lot. These parts are placed and soldered just like regular SMD parts, but originally came off the same production line as regular leaded components.

AFAIK: MELF is a distinctly separate sub-family of SMD parts than the most common type you usually see.

 

Melf resistors are more stable and more resistant to mechanical stress.
Often You can find them in high reliable industrial stuff.

 

I hate MELF. They roll off the pads when you try to solder them by hand.

And the glass MELF diodes slip out of the tweezers.

 

I hate MELF. They roll off the pads when you try to solder them by hand.

And the glass MELF diodes slip out of the tweezers.

Doncha just love the way they pop out of the tweezers and disappear across the room at 90+ MPH.

 

Doncha just love the way they pop out of the tweezers and disappear across the room at 90+ MPH.

No. I. Don't.

In fact, I believe the MELF package was developed by Satan himself -- just to give you an idea what Hell will be like.

 

MELF: "Most End up Lying on the Floor"

 

Melf resistors are more stable and more resistant to mechanical stress.

But I always see the MELF diodes and MELF resistors in the power supply sections of of SMT/SMD circuit boards. The MELF must have a higher wattage rating?

 

But I always see the MELF diodes and MELF resistors in the power supply sections of of SMT/SMD circuit boards. The MELF must have a higher wattage rating?

Probably not. MELF diodes look a lot like their leaded counterpart, most heat for a D02 diode is radiated from the leads, since MELF has no leads they radiate heat from the endcaps. Read earlier in this thread and elsewhere that they're higher reliability than typical SMT parts.

 

higher reliability than typical SMT parts.

Why do they have a higher reliability than SMT parts? I don't get it

 

Why do they have a higher reliability than SMT parts? I don't get it

Looking for items recently I found these, so they are fairly versatile.

 

MELF components are more stable with temperature, that is why they are used in smd smt power supply circuit boards. 5pp is really good for temperature in power supplies.

 

Why do they have a higher reliability than SMT parts? I don't get it

For the diodes: Glass is more stable and the springformed lead absorbs thermal stress.
For resistors: the metal caps are not a part of the resistor body itself and can relief stress from expansion when the body heats up.

 

For the diodes: Glass is more stable and the springformed lead absorbs thermal stress.
For resistors: the metal caps are not a part of the resistor body itself and can relief stress from expansion when the body heats up.

I'd go along with the glass bit.

Of the old germanium devices, more glass encapsulated types have survived to this day than metal ones. Although some metal types have suffered internal shorts from tin whiskers - which probably isn't what's meant by "stability".

In those days, the epoxy encapsulations available then weren't good enough for germanium.