TSSOP thermal question

[martin griffith]

Just going through the LT3439 data sheet.
It has "a thermally enhanced 16-pin
TSSOP with an exposed backside"

What gloop should I consider to thermally connect its bum to the PCB,
is the normal white silicon stuff OK?



martin

Serious error.
All shortcuts have disappeared.
Screen. Mind. Both are blank.

 

Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?

 

[Anders F]

<larwe@larwe.com> wrote in message
news:1103727474.582262.66290@f14g2000cwb.googlegroups.com...

Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?

Always!!! (If you want to benefit from it ;-)

/A

 

[martin griffith]

On 22 Dec 2004 06:57:54 -0800, in sci.electronics.design
larwe@larwe.com wrote:

Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?
I'm hand soldering the prototypes, and I'm just doing the pcb patterns

at the moment. I dont know how many will be made, so i was thinking of
the good old fashioned Dow Corning stuff that I used to use on
2n3055's as an alternative


martin

Serious error.
All shortcuts have disappeared.
Screen. Mind. Both are blank.

 

[James T. White]

"Anders F" <af-spam@hi5.dk> wrote in message
news:32tgmaF3pfj16U1@individual.net...

larwe@larwe.com> wrote in message
news:1103727474.582262.66290@f14g2000cwb.googlegroups.com...
Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?

Always!!! (If you want to benefit from it ;-)

/A


For those of us without reflow ovens, has anyone come up with a way of doing

this with just a soldering iron?

--
James T. White

 

[Paul Burke]

martin griffith wrote:

For those of us without reflow ovens, has anyone come up with a way of doing
this with just a soldering iron?

Maybe drill a hole in the PCB, beneath the center if yhe IC so you can
solder from underneath?

Yes, I've done this, make the hole big enough for a fine tipped iron,
poke it through and flood the hole. Works a treat, at least with a PTH.

Paul Burke

 

[martin griffith]

On Wed, 22 Dec 2004 09:27:43 -0600, in sci.electronics.design "James
T. White" <SPAMjtwhiteGUARD@SPAMhal-pcGUARD.org> wrote:

"Anders F" <af-spam@hi5.dk> wrote in message
news:32tgmaF3pfj16U1@individual.net...
larwe@larwe.com> wrote in message
news:1103727474.582262.66290@f14g2000cwb.googlegroups.com...
Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?

Always!!! (If you want to benefit from it ;-)

/A


For those of us without reflow ovens, has anyone come up with a way of doing
this with just a soldering iron?
Maybe drill a hole in the PCB, beneath the center if yhe IC so you can

solder from underneath?
Just an idea



martin

Serious error.
All shortcuts have disappeared.
Screen. Mind. Both are blank.

 

[John Larkin]

On Wed, 22 Dec 2004 16:23:22 +0100, martin griffith
<martingriffith@yahoo.co.uk> wrote:

On 22 Dec 2004 06:57:54 -0800, in sci.electronics.design
larwe@larwe.com wrote:

Wouldn't it normally be reflowed onto the PCB? I.e. solder paste?
I'm hand soldering the prototypes, and I'm just doing the pcb patterns
at the moment. I dont know how many will be made, so i was thinking of
the good old fashioned Dow Corning stuff that I used to use on
2n3055's as an alternative

That will work, as long as no later steps wash it out. Epoxy would be
OK, preferably the thermally-conductive kind... but almost anything
will be a hundred times better thermal conductor than air. Locktite
makes a repairable, instant-bond thermally conductive glop stuff...
just apply a little primer to one surface, a dab of glop to the other,
and press.

Solder is of course the best; apply a bit of paste and heat the whole
region.

I hope you have a lot of thermal (actually, non-"thermal"!) vias to
the ground plane or a big bottomside island.

John

 

What, can't afford a toaster oven?

 

[Rene Tschaggelar]

martin griffith wrote:

Just going through the LT3439 data sheet.
It has "a thermally enhanced 16-pin
TSSOP with an exposed backside"

What gloop should I consider to thermally connect its bum to the PCB,
is the normal white silicon stuff OK?

They usually suggest a bunch of plated holes, eg 20 mil holes with 40
mils distance in a two dimensional array fashion. It is the copper of
the PTH that conducts, less the tin filling.
And yes, they are solderable from the backside. Just fill the bunch
with tin after soldering the pins.
Then from there, you can proceed with horizontal copper, or a
heatsink.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net