DPAK and D2PAK power dissipation

[jasen]

On Sat, 16 Dec 2006 05:43:59 +0000, Eeyore

So maybe half a dozen 30 mil holes would get down below 10 k/w net,
pretty good considering the thermal resistance of the surface copper
itself. Using internal planes helps a lot, as the theta to them is
less and they can help spread the heat laterally, especially if you
can include a second ring of holes further out.

I haven't figured out if it's better to use a few big vias or a lot of
smaller ones, or what the optimum pattern might be.

many small holes have more surface surface area, and so without solder
filling will have more conductivity,

with it's probably faily close.


Ofcourse the best is one huge hole and solder a copper heatsink into it.





Bye.
Jasen

 

[John Larkin]

?? drilled via sizes of 15-20 thou are pretty common with. 4 thou or
less is possible these days (0.1mm) but I don't think they are
conventionally drilled (laser).

Consider these drill sizes:

#77 = 0.018" (0.45mm)
#78 = 0.016"
#79 = 0.0145"
#80 = 0.0135" (0.34mm)

Which make up roughly 50% of the sizes in an assortment of carbide
bits which I picked up, presumably representing how frequently they
are used.

I'd hate to think of 2.5, 3 or 4 mil lines and spaces with 31 mil
vias.


Best regards,
Spehro Pefhany

Hi, Speff,

What sort of drill do you use? My drill presses have enough runout to
snap off small carbide drills after just a few holes.

Right, a high-density board tends to be via limited, no matter how
many routing layers are available. The good board houses around here
seem to feel that a 10 mil drill and a 6 mil trace is non-premium
turf.

John

 

[vasile]

Does anybody sell that ground? I've been looking for it on some of my
recent projects.

Well, if you have a noisy digital ground from a 2Ghz running processor
with an 133Mhz memory bus, some fast 200Mhz buses tied to a DSP, a
switching power supply at 2Mhz, some analogic transcievers running in
2.4Ghz + every garbage is comming from the PC ground, then no one from
this earth will sell you a ground-ground.
Maybe only the guys from Nigeria ?

greetings,
Vasile

 

[Eeyore]

One big plane!

If you don't mind crosstalk.

Graham