SMD or a leaded resistor FOR 1W Resistor

[BABESH]

Hi,
in my ckt there are two 1W leaded resistor and 1/2 W resistor, because of space constraints i want to replace the same with SMD resisors,

Even tough i have same resistors with same wattages in SMD, I feel SMD is not a good option for power resistors, because it may heat up PCB and may not dissipate heat...

Please clear my confusion...


Thx
--babesh.

 

[karesz]

Hi, SMD may exactly dissipate so heath as a leaded resistor_basically!
I think, its a trivial thing, that these components has smaller volumen, they can not dissipate same heath volumen-they will speedy glowing, or you need very good_better_ cooling as for leaded components!
Exactly that is point, what often will not clear defined on datasheets & reklam texts_all tells us only how small a 3W resistor i.e. is, but they are in revel over the NEEDED min. quadrat inch copper for that!!!
Thes is in reality worser (in relation needed place) as a usual 3W ceramics resistor...
Check every times very detailed SMD power resistors datasheets_ much of them are simple sayd: incorrect!
K.

Added after 15 minutes:

You can have a good thermal spreading in&on your PCB copper layers.
Check for versions where resistor layer is deeper to copper & the contacts are wider as usual. I think Taiyo Yuden has some such new power types in 2009; their are 2 or 3x higher in disiipation as usual versions... It wiil be conducted (of courese) to PCBs copper!
You must have very direct to the resistors leads much copper_these is SMD problematics, then with direct copper contacting you have soldering problems.._ & maybe some heat sink too.
If you need a cool PCB, you have/becomes light problems with leaded pwr resistors too...

Added after 1 hours 32 minutes:

Low Ohm Versions are real good from "IsabellenHütte", they need only the with of solder pad from connecting lines as "heat sink"!
Ok, their are a little bit bigger as some others (maybe expensiver too), but theier dissiptions capability is good! in reality is ca same volumen as a conventional! :-(
I designet i.e. w. an Panasonic 1W type; forget it (these was the 1quadrat inch copper type)...