Definitive guide to SMT resistor dissipation?

L

Lostgallifreyan

Guest
I tried a search on Google:
1206 resistor power dissipation

I thought I'd get lots of helpful reults. I got lots of UNhelpful results,
and further searching made matters worse, not better!

Is there a definitive guide to standards for parts of size 0603, 0805,
1206, 1210? If so, can anyone help me with direct linkage? I guess the
contruction materials affect this, and things are always changing, but any
stable or currently accurate references will do.

I'm used to axial metal film resistors where you got 1/8 W, 1/4 W, or 0.5W
and 0.6W, and 1W and 2W. With SMT, finding references is harder than
finding actual non-SMT resistors themselves!
 
Sod it, I'll rephrase that. What are the best 1% tolerance resistors in SMT
to replace 0.6W and 2W metal film? (0.5W is also acceptable).
 
Lostgallifreyan <no-one@nowhere.net> wrote in
news:Xns99EBBFE4E1F8Czoodlewurdle@140.99.99.130:

Sod it, I'll rephrase that. What are the best 1% tolerance resistors
in SMT to replace 0.6W and 2W metal film? (0.5W is also acceptable).
Click to expand...
Better rephrase that too... I want metal film. Just not axial lead types.
 
On Sat, 17 Nov 2007 18:42:42 GMT, the renowned Lostgallifreyan
<no-one@nowhere.net> wrote:

I tried a search on Google:
1206 resistor power dissipation

I thought I'd get lots of helpful reults. I got lots of UNhelpful results,
and further searching made matters worse, not better!

Is there a definitive guide to standards for parts of size 0603, 0805,
1206, 1210? If so, can anyone help me with direct linkage? I guess the
contruction materials affect this, and things are always changing, but any
stable or currently accurate references will do.
Click to expand...
Usually 250mW at 70°C "Ta" derated to zero at or around 155°C. The
exact definition of Ta is another question.

I'm used to axial metal film resistors where you got 1/8 W, 1/4 W, or 0.5W
and 0.6W, and 1W and 2W. With SMT, finding references is harder than
finding actual non-SMT resistors themselves!
Click to expand...
All the reputable makers have data sheets.


Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
speff@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
 
Spehro Pefhany <speffSNIP@interlogDOTyou.knowwhat> wrote in
news:14euj3le31v3ug53ghmo7t69r2r0d4b2pk@4ax.com:

Usually 250mW at 70°C "Ta" derated to zero at or around 155°C. The
exact definition of Ta is another question.
Click to expand...
Thanks. 250 mW is what I've seen enough times to think it's reasonable to
assume most will match that. Same with 1210 doing 500 mW, I think, but I
haven't seen enough examples.

I guess Ta means the actual temperature of the resistor, as opposed to
ambient, which really could mean anything depending how proximate it was,
or whether the air moved...

All the reputable makers have data sheets.
Click to expand...
I don't even know who they are, with SMT resistors, and specific maker's
guides should never be relied on for general standards, which is why I
asked the question about general guides. Asking in a place where people
have direct experience of various standards is the best thing, rather than
blundering on Google for days...

Most resistors found on eBay might have a size declared but no hint of who
made them.
 
Lostgallifreyan <no-one@nowhere.net> wrote in
news:Xns99EBBE5647666zoodlewurdle@140.99.99.130:

Is there a definitive guide to standards for parts of size 0603, 0805,
1206, 1210? If so, can anyone help me with direct linkage? I guess the
contruction materials affect this, and things are always changing, but
any stable or currently accurate references will do.
Click to expand...
Ok, found one answer to this:
http://www.rcd-comp.com/rcd/press/SM%20Guide%20Resistors%20page.pdf
Might be useful to other people, it's nice... Any others out there?
 
On Sat, 17 Nov 2007 18:42:42 +0000, Lostgallifreyan wrote:

Is there a definitive guide to standards for parts of size 0603, 0805,
1206, 1210
Click to expand...
The numbers are dimensions in 10-mil (thou) units:

0603 is .06" x .03" (60 mil by 30 mil)
0805 is likewise .080" x .050"
etc. etc.

Power dissipation depends to a large extent on how they are mounted,
size of pad/trace, proximity, the type of resistor construction and
material.

Consult the manufacturers' data for recommended dissipation limits, it's
freely available (Vishay, Yageo, etc).

--
"Electricity is of two kinds, positive and negative. The difference
is, I presume, that one comes a little more expensive, but is more
durable; the other is a cheaper thing, but the moths get into it."
(Stephen Leacock)
 
Fred Abse <excretatauris@cerebrumconfus.it> wrote in
news:pan.2007.11.17.19.39.11.667142@cerebrumconfus.it:

On Sat, 17 Nov 2007 18:42:42 +0000, Lostgallifreyan wrote:

Is there a definitive guide to standards for parts of size 0603, 0805,
1206, 1210

The numbers are dimensions in 10-mil (thou) units:

0603 is .06" x .03" (60 mil by 30 mil)
0805 is likewise .080" x .050"
etc. etc.

Power dissipation depends to a large extent on how they are mounted,
size of pad/trace, proximity, the type of resistor construction and
material.

Consult the manufacturers' data for recommended dissipation limits, it's
freely available (Vishay, Yageo, etc).
Click to expand...
Thankyou. Vishay I discovered in the last half hour. :) Looked like a good
reference capable of being extended to other firms parts, in many cases I
saw.

I noticed that the dissipation specs are conservative, so I guess it's
possible to increase it in the case of one or two with a good anchorage on
broad pads. I might just try a test to see what it takes to overheat them
in an actual-size test mounting. Can't do that till I get them though,
hence the questions...

Is there any SMT resistor that is ideal to substitute for an 0.6W metal
film type? Something standardised enough that it won't matter exactly who I
buy it from?
 
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