Soldering D-PAK Mosfet? (TO-252)

[Hammy]

I'm using Fairchilds FCD5N60 in a D-PAK (TO-252).

Data sheet

http://www.fairchildsemi.com/ds/FC/FCD5N60.pdf

The D-PAK I'm using has a small drain tab that extends above the
plastic case; the bottom portion of the drain tab is recessed into the
plastic case Like a T0-220 .

I am unsure on how to solder the drain.

1. Are you supposed to just solder the metal tab that extends
above the plastic case?

2. Are you supposed to lay solder down on the whole drain
footprint? This includes the metal Drain that is recessed into the
plastic case. If so wouldn't this potentially damage the case?

I just soldered the tab part that extends above the case to a small
piece of PCB for testing the FET in my circuit. There is a no contact
between the drain, (the part of the drain that's recessed into the
plastic case) and the copper PCB. I pushed down to try and get contact
while soldering but either I wasn't pushing hard enough or it's not
supposed to touch the PCB. Is there supposed to be a gap for air flow
and the copper that the tab is soldered to acting as the heatsink.

Thanks

 

[Eeyore]

Hammy wrote:

I'm using Fairchilds FCD5N60 in a D-PAK (TO-252).

Data sheet

http://www.fairchildsemi.com/ds/FC/FCD5N60.pdf

The D-PAK I'm using has a small drain tab that extends above the
plastic case; the bottom portion of the drain tab is recessed into the
plastic case Like a T0-220 .

I am unsure on how to solder the drain.

You would normally apply solder paste underneath the tab and reflow solder
it.

Graham

 

[John Larkin]

On Wed, 23 Apr 2008 12:06:15 GMT, Hammy <spamme@hotmail.com> wrote:

I'm using Fairchilds FCD5N60 in a D-PAK (TO-252).

Data sheet

http://www.fairchildsemi.com/ds/FC/FCD5N60.pdf

The D-PAK I'm using has a small drain tab that extends above the
plastic case; the bottom portion of the drain tab is recessed into the
plastic case Like a T0-220 .

I am unsure on how to solder the drain.

1. Are you supposed to just solder the metal tab that extends
above the plastic case?

2. Are you supposed to lay solder down on the whole drain
footprint? This includes the metal Drain that is recessed into the
plastic case. If so wouldn't this potentially damage the case?

I just soldered the tab part that extends above the case to a small
piece of PCB for testing the FET in my circuit. There is a no contact
between the drain, (the part of the drain that's recessed into the
plastic case) and the copper PCB. I pushed down to try and get contact
while soldering but either I wasn't pushing hard enough or it's not
supposed to touch the PCB. Is there supposed to be a gap for air flow
and the copper that the tab is soldered to acting as the heatsink.

Thanks

If heat transfer isn't critical, solder it any way that's convenient.

If you need a low thermal resistance, make sure the pcb pad and solder
extend under all the metal on the part, and then make sure the heat
has somewhere to go.

Soldering the entire underside of the fet won't damage it. Fets will
cheerfully melt their own solder joints and fall off boards,
undamaged.

John

 

[Hammy]

On Wed, 23 Apr 2008 07:42:48 -0600, "Jon Slaughter"
<Jon_Slaughter@Hotmail.com> wrote:

huh? The drain needs as much cooling as it needs. If you only solder a very
small bridge between the tab and the copper then heat must flow through that
bridge... do you think thats a good idea? If you were not suppose to solder
the whole thing then why would they have it exposed?

You really need to think of why the did what the did and what is the purpose
and then it should be quite clear what to do.

I see I printed out a footprint and all became clear.I'm going to have

to put some solder on the drain pad lay the D-PAK on it and heat the
tab and push when the solder starts to flow.

Thanks

 

[Hammy]

On Wed, 23 Apr 2008 06:55:43 -0700, John Larkin
<jjlarkin@highNOTlandTHIStechnologyPART.com> wrote:

If heat transfer isn't critical, solder it any way that's convenient.

If you need a low thermal resistance, make sure the pcb pad and solder
extend under all the metal on the part, and then make sure the heat
has somewhere to go.

Soldering the entire underside of the fet won't damage it. Fets will
cheerfully melt their own solder joints and fall off boards,
undamaged.

John

Thanks John.