Soldering Heat vs Wattage

[Tom.Misty]

I was wondering what the different effects were on soldering with heat and wattage.
I have a weller wlc100. it is adjustable wattage from 5 to 40 watts, But from what i can tell is fixed temp at 900 f.
From what I am reading that temp is high for PCB soldering. Does wattage effect the temp? like higher temp lower watt? or higher temp higher watt so not heating as long?
Never done any soldering other than repairs or wiring to pins and other simple projects so just trying to get an idea of whats going to happen when i dive into my first PCB.

Thanks
Tom

[mlkren]

Just use 25 watt for the smaller part like resisters, capacitors, diodes, and your IC sockets and turn it up to 40W for your terminal blocks, fuse holders and triacs. This is what I did when I used a variable wattage soldering iron in my first year. In the future you might want to invest in a soldering iron with a variable temperature display.

[griffixdc]

more watts equals more power consumption(current (amps) used). Generally heat equals a loss of energy (less energy efficiency). the more heat the less energy efficient it is (thus in turn wattage used per ambient temp) In the case of heating elements where heat is the purpose. More power equals more resistance, which reveals more heat. So the answer to your questions is 5 watts equals cold and 40 watts equals hot (although i am sure non of those wattage's are actually cold to touch :) )

[David_AVD]

I just don't get a variable wattage soldering iron. If the tip temperature is set, where does the variable wattage come into it?

The only thing I can think of is that at higher wattages, the tip temperature is maintained even during prolonged usage.

ie. If you run it a 5W and start soldering a lot, the tip temperature must take a nose dive. I don't see the point of variable wattage at all.

[IdunBenhad]

Hi:
The point of a variable type soldering iron is to vary the heat at the tip. Less watts means less heat, more watts means more heat.

The higher wattage iron also has the ability to maintain the set heat at the tip when it is applied to a joint but if set too high can overheat that joint and component, possibly damaging it or pulling a land/run off the PC board.

Milkrens suggestion for soldering the various components is a good one.

The proper temperature is that which quickly transfers heat to the joint and at the same time melts and flows the solder into the joint.

Another quick note: The heat of the tip is directly related to the wattage. Variable wattage=variable heat. The variable iron should be thought of as a variable heat device rather than a variable wattage device. Think in terms of heat.

[T.D.Sutton]

Agreed, Idun,

One thing to remember though, after 50+ yrs of soldering, a low powered iron running somewhat "cool" will do more damage to a PCB and components when soldering because you have to leave it on the joint for a lot longer for the heat to transfer. During which time it transfers down to the components, and the board melting wires etc, etc. While with a temperature controlled "hot" iron may seem a bit hot, the time involved in making a good clean solder joint, is so short no heat transfers any further than the joint it'self. As one of my "bosses" once said, get in and out fast with a hot iron when soldering. My personal preferance for an iron is a variable, temperature controlled one, Weller, etc, etc. The old Wellers that had a "Curie Point" tip temperature control were good when they were going but ........

My 0.02c worth Cheers,

Terry

[underdog]

I use a Metcal STSS-001, It uses RF to heat the tip, and maintain temperature. I think I use a 750series for general purposes and then the 850 for ground planes and triacs. (The series is what temperature in Fahrenheit it will maintain). I completely agree with the guys that said "low heat for a long time is worse than high temp for short time periods". That's one of the main reasons I opted for the Metcal station, it costs a little bit more than others but they are tried an true. Best of all, it heats fast and corrects itself instantaneously, and you can adjust the temp by switching tips.

One thing to note though, If you are seriously considering a unit that uses RF to heat, like the Metcals, if it is used try it first, ABSOLUTELY and when I mean to try it, make sure the tip is seated properly in the pen, and the cord is damage free and plugged/screwed into the unit. NEVER trust someone on ebay who doesn’t have a guarantee and a guaranteed return policy. If it says "it works", still don’t trust them, the light on the unit can turn on, but doesn’t mean the unit is functional. Just like an FM transmitter, if you don't have a load on the transmitter, it will cause damage, these are IDENTICAL. No tip or no "antenna", the soldering unit is absorbing all the signal and causing damage.
With that said, I bought mine at an instrumentation surplus locally and couldn't be more pleased, The benefits far outweigh the drawbacks!

[griffixdc]

weird did no body read my post ? :) it was post #3

[IdunBenhad]

Hi:
griffixdc: It's still there as 5:10 PM Pacific time.

[Tom.Misty]

Thanks for all the replies. I feel more comfortable using this iron now that it all makes sense.

[David_AVD]

The point of a variable type soldering iron is to vary the heat at the tip. Less watts means less heat, more watts means more heat.

I still don't understand why you can have a variable wattage soldering iron if the tip is set at a specific temperature.

The ultimate goal of the soldering iron is to maintain the tip temperature at a very specific point.

If the tip temperature varies, that's just poor heat regulation or insufficient wattage to maintain it.

[IdunBenhad]

Hi:
The purpose of a variable iron is to set and maintain a tip temperature. The tip temperature is NOT a constant temperature over a range of wattage settings on the iron.

Example: An iron has a variable wattage range of 0 to 50 watts. Setting the iron to 25 watts results in a temperature of 600 F. degrees. Increasing the wattage setting to 50 watts sets the tip temperature to 900 degrees. These are just examples as I do not know the actual wattage/temperature readings.

The temperature of a variable iron IS NOT set at one temperature, but as the name implies, is variable according to the wattage setting.

Once a wattage has been set, the tip temperature will be maintained by the iron. So many watts=so many degrees. It takes a certain amount of power (watts) to reach a certain temperature.

Again, think heat and not watts.

[David_AVD]

So these irons have a wattage control instead of a temperature setting control?

I've always used soldering irons that have a fixed tip temperature (early Weller units) or settable temperature (Hakko 926, 936 & FX888).

Why (in the electronics world) you'd specify the wattage as a way to set the temperature is beyond me.

[mrpackethead]

pffft!

So, i'm soldering a large 18uH inductor. Its physically large and has a good deal of copper. One side of it is attached to a large track ( read lots of copper ).. I don't want to overheat it, in fact i want to stick to the manufacturers specified temps. So i start soldering at say 15W.. The problem is that its simply not getting hot.. Grrr. Ok, i'll give up on that and i move onto a 0402 resistor.. its pretty small in fact its tiny.. I touch the component, and wamm. its soldered but i've melted the flux way past useful, and i think i thermally damaged the part.. Same old 15W that i was'nt enough for the big inductor...



Once a wattage has been set, the tip temperature will be maintained by the iron. So many watts=so many degrees. It takes a certain amount of power (watts) to reach a certain temperature.


The moment you start using it, the heat transfers off the iron onto the work ( ie a transfer of energy ).. This means that the iron starts getting colder.. In the case of the big inductor, rapidlly ( same applys for big wires/connectors ).. The power going into the iron now has to heat the iron and all the bits your working on.. The temp certainly does not stay consistent.. The amount of energy that it takes to keep something at a temperture is related to how much energy its loosing.. The amount of power is a related function of that.


With a temp controlled iron, a thermostat does keep it at a consistent temp ( as close as it can ).. When its sitting in its holder, it will be using minimal power to hold it at temp.. The moment it starts dropping in temp, the power comes on to hold it at temp.







I have seen a variable power soldering iron. I never could figure out why i'd use it. To me its one step up from a really cheap iron that just is on or off and not temp controlled. I recalibrate all our soldering irons every month using a Hakko FG-100. ( we use Hakko 888 and 951 irons in the factory ).. If you want to do a decent job, then a good iron is mandatory.. I'd highly recommend the Hakko FX-888 they are about $99 as a great iron for the semi-serious hobbyist.. )

[IdunBenhad]

Hi:
There is a bit of confusion here.

The reason for wattage rating is to indicate the maximum amount of power the iron will consume or convert to heat The ability to vary the power or watts is so that in turn, the temperature can be set to what is desired or necessary to get the job done. When you vary the power being applied to the heating element, you are changing or setting the temperature of the iron. That iron has a rating of say 0 to 50 watts. That means the temperature will vary from zero or very low to whatever the maximum temp the iron can obtain.

By turning the knob, which may be rated in watts or temperature, the power being used by the heating element is varied. It is the same as setting the heat control knob on your kitchen range. The amount of heat generated is proportional to the amount of watts consumed, either by the iron or the kitchen range.

Again, I will repeat. Think heat/temperature and not watts.

[David_AVD]

The heat control on your kitchen range varies the temperature point at which the element cycles on and off. The wattage (current consumed) while heating is exactly the same.

A smaller wattage element means that it will take longer to reach that set point, so it ends up staying on longer to maintain a given temperature.

Sure, a larger wattage element consumes more power while it's active, but it only needs to be active for a shorter length of time. This is something that seems to be lost on a lot of people.

[Matt_Edwards]

Tom,
I hope the argument hasn't put you off.
The weller wlc100 is a variaiable temperature soldering statio. 'The tip temperature can be adjusted by varying the power level of the heater. The power can be adjusted anyway from 5 to 40 watts with the knob on base unit ......' (extract from user manual)
In my opinion this wording is unfortunate. Having temperature scale would be more useful.