What difference does the wattage of a hot air station make?

Discussion in 'General Electronics Chat' started by Yonah, Jan 10, 2017.

  1. Yonah

    Thread Starter New Member

    Jan 2, 2017
    7
    0
    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
     
  2. Externet

    AAC Fanatic!

    Nov 29, 2005
    781
    58
    Larger heat capability allows working on larger pieces and shorter times.
     
  3. Yonah

    Thread Starter New Member

    Jan 2, 2017
    7
    0
    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?
     
    Last edited: Jan 10, 2017
  4. wayneh

    Expert

    Sep 9, 2010
    12,406
    3,256
    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 :p)
     
    #12 likes this.
  5. JUNELER

    Member

    Jul 13, 2015
    64
    10
    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.
     
  6. Yonah

    Thread Starter New Member

    Jan 2, 2017
    7
    0
    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.
     
  7. #12

    Expert

    Nov 30, 2010
    16,705
    7,358
    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.
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,798
    979
    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..
     
  9. Stuntman

    Active Member

    Mar 28, 2011
    189
    50
    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.

    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.
     
    #12 likes this.
  10. #12

    Expert

    Nov 30, 2010
    16,705
    7,358
    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.
     
  11. wayneh

    Expert

    Sep 9, 2010
    12,406
    3,256
    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.
     
    #12 likes this.
  12. Externet

    AAC Fanatic!

    Nov 29, 2005
    781
    58
    Just be careful with reasoning. Heat is not temperature.
     
  13. #12

    Expert

    Nov 30, 2010
    16,705
    7,358
    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.
     
Loading...