I'm in the market for a simple hot air station, and I've noticed that they seem to vary quite a lot wattage-wise. One apparently decent-looking unit is 320W, while another very popular one is 700W. Is more power better, or is it just wasted energy? Is there added heat capacity with the higher consumption?

Thanks,
Jonah

 

Larger heat capability allows working on larger pieces and shorter times.

 

I've understood this is with soldering irons, where the heat gets dissipated in ground planes through physical contact, but it also applies to air? And how do I actually benefit from a higher thermal capacity? Shorter/safer working time for the components?

 

Higher wattage allows higher air flow and/or higher temperature. The device is a heater with a blower. More power can go to both.

Your need for wattage depends on what you're doing. For small work, a smaller gun might be more convenient. Big work calls for a bigger gun. (insert joke here )

 

Hi,
Maybe this will help you my little information.....
I have here a MODEL-Quick 850 smd workstation 220vac unit made from china,wattage not mention.
In the front panel a two knobs control.
control knob no1-- Air -Adjustable pressure from no1 to no8.
control knob no2- Heating-Adjustable temperature from 150degrees to 500 degrees.
You can use this not only for soldering/resoldering purposes but for drying wet areas.

 

Thanks for the reponses! Both of the stations I'm looking at have the typical controls for heat and air flow. Ironically enough the 320W Zhongdi station claims to be able to reach 500C, where as the 700W Atten promises only 450C. I'll be using it for occasional SMT reflow and the odd heat shrinking tube and what not, so not looking for huge airflow...I suppose?

Zhongdi: http://www.reichelt.de/Various-Rewo...&artnr=STATION+ZD-939L&SEARCH=hot+air+station

(The infamous) Atten: http://www.gratten.eu/solder-rework/hot-air-stations/at858d-hot-air-rework-station.html

Can't choose. Though in the end — as with most dithering — it's most likely not going to make any practical difference.

 

Soldering Temperature Chart
Solder Type Lead / Non-Lead Temperature °C
63/37 lead 183
60/40 lead 183-188
50/50 lead 183-212
45/55 lead 183-224
40/60 lead 183-234
96S lead 221
95A lead 236-243
Alloy No. 1 lead 183-215
Alloy No. 2 lead 183-190
HMP 5S lead 296-301
LMP 62S lead 179
TLS/5 lead 296-301
TIN tin 232
99C non-lead 227
97C non-lead 230-250
SAC3 non-lead 217-219
MC1 non-lead 232

The highest temperature on that chart is 301 C.
You don't have to get very much above that to melt solder and account for losses.
As for air flow and temperature, if the air flow approaches zero, the temperature approaches infinity. In practical terms, slow down the air enough and you can get to any temperature you want. Still, a little whisper of air isn't going to heat 4 square inches of board and a great huge blast of air is going to blow surface mount components right off the board. It's a matter of balance.

What doesn't matter is the difference between 450 C and 500 C. Both of those are not necessary.

 

And trust me.. Getting anywhere close to 450-500deg C and you will be watching the plastic housing on the handles of those units just melting in front of your eyes..

 

/snip
What doesn't matter is the difference between 450 C and 500 C. Both of those are not necessary.

Although 450-500C might not make much of a difference, temperatures this high can be useful. Desoldering operations on large or metallic connectors and even surface mount parts with lots of thermal contact can make the desoldering process difficult. Higher temperature, shorter duration, lower airflow reduces heat wicking to unwanted portions of the board while removing, say, a damaged TO-263 FET. For large connectors (think, long double row headers), I've rarely found I can have too much heat to get from one side of a large header to another all while keeping the solder in liquid form.

And trust me.. Getting anywhere close to 450-500deg C and you will be watching the plastic housing on the handles of those units just melting in front of your eyes..

I have a overseas brand reflow gun (Aoyue) much like what has been suggested so far. It has a max setpoint of 480C and I have yet to see any type of melting while regularly operating at this setpoint.

 

temperatures this high can be useful

I did not know that.
I know I romp my Weller 250 as hot as it will go when soldering a ground to the steel case of a Fender amplifier. That's a lot of steel, but I couldn't imagine taking a circuit board to 450C when 350C is more than enough to melt the solder. A circuit board just doesn't wick heat like steel does.

So, thanks for the information. The present scenario exceeded my ability to imagine what the limits are.

 

I did not know that.
...I couldn't imagine taking a circuit board to 450C when 350C is more than enough to melt the solder.

The air temp has to be quite a bit higher than the board temp, to drive heat from the air to the board. With an iron, most heat transfer is by conduction. With moving air, it's primarily convection. That's a much less effective heat conduit, so you need a much larger ∆T to quickly move the heat.

 

Just be careful with reasoning. Heat is not temperature.

 

I also use an ox-acetylene torch which is obviously hotter than necessary. That is a gas transfer of heat, but the heat wicking by the copper pipes is the reason. (You can't braze copper larger than 3/4 inch with a turbo-torch.) I didn't think a circuit board would present much of a heat wicking problem, but I can imagine why "fast" would be important.