Diode Lead Length

[Anand P. Paralkar]

Hi,

I would like to use the 1N5283 diode in a certain application. Like
some other applications in power electronics, this diode datasheet too
mentions a certain Lead Length to be maintained.

(See http://www.datasheetcatalog.org/datasheet/motorola/1N5298.pdf)

Could someone please explain this? Why does this distance have to be
maintained? (Its got to do with the thermal characteristics alright -
but how?)

I also see thermal resistance versus lead length curve and a note which
says "(MOST HEAT CONDUCTION IS THROUGH THE CATHODE LEAD)". How's this?

I tried searching and found some other datasheets mentioning 3/8" lead
length, but no explanation.

Your inputs please?

Regards,
Anand

 

[George Herold]

Hi,

I would like to use the 1N5283 diode in a certain application.  Like
some other applications in power electronics, this diode datasheet too
mentions a certain Lead Length to be maintained.

(Seehttp://www.datasheetcatalog.org/datasheet/motorola/1N5298.pdf)

Could someone please explain this?  Why does this distance have to be
maintained?  (Its got to do with the thermal characteristics alright -
but how?)

I also see thermal resistance versus lead length curve and a note which
says "(MOST HEAT CONDUCTION IS THROUGH THE CATHODE LEAD)".  How's this?

I tried searching and found some other datasheets mentioning 3/8" lead
length, but no explanation.

Your inputs please?

Regards,
Anand

I've never used one of those. But the app note sorta spells it out.
The current is temperature dependent,
The temperature depends on power dissipation and thermal conductivity,
For best control keep power low (low forward voltage)
and thermal conductivity low... short leads.

Jim nailed the cathode part.

George H.

 

[Phil Allison]

"Anand P. Paralkar"

I would like to use the 1N5283 diode in a certain application. Like some
other applications in power electronics, this diode datasheet too mentions
a certain Lead Length to be maintained.

** No such requirement is in the data.

(See http://www.datasheetcatalog.org/datasheet/motorola/1N5298.pdf)

Could someone please explain this? Why does this distance have to be
maintained?

** There is no distance to be maintained.

FFS learn to read - it only says " keep leads short ".





..... Phil

 

[Cydrome Leader]

Hi,

I would like to use the 1N5283 diode in a certain application. Like
some other applications in power electronics, this diode datasheet too
mentions a certain Lead Length to be maintained.

(See http://www.datasheetcatalog.org/datasheet/motorola/1N5298.pdf)

Could someone please explain this? Why does this distance have to be
maintained? (Its got to do with the thermal characteristics alright -
but how?)

they assume the full lead acts as a heatsink, and if you chop it off, you
lose heatsinking, and power rating.

Of course they don't really account for a PCB with a trace also acting as
a heatsink, and that's upto you to determine if it's less or more
effective than a lead sticking out into the air.

I've seen things such as solder turrets used as heatsinks for power
diodes.