Author Topic: Soldering iron buying choice: watt vs. temperature?  (Read 448 times)

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Offline analogix

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Soldering iron buying choice: watt vs. temperature?
« on: December 07, 2017, 12:51:58 AM »
Recently I've been running into unexpected problems when soldering (cold joints etc.) and wonder if my trusty old Japanese 25W Goot soldering iron has reached its end-of-life after a couple of decades (or more) use. I've changed its tip but that didn't help. To further confuse matters I had to buy a new roll of solder, but being quality branded (Multicore/Loctite) 0.71mm 60/40 leaded I don't think that's it (unfortunately the labelling of my old solder has long since gone).

I'm a hobbyist (building kits or solder ready made PCBs, all through-hole so far), soldering a bit now and then, and although I did consider a soldering station at some stage I'm leaning more towards a new quality soldering iron as I just can't justify the costs for something I don't use very often. And I don't like buying cheap stuff which breaks and needs to be thrown away after a little use either. So I'm looking into another Goot soldering iron, this time a PX-201 temperature adjustable (250-450 C) 70W type costing around US$ 43 plus shipping. There are also around 20 replacement tips to be found for it. Hakko has a similar type (FX-600) but it's (not surprisingly with that brand) more expensive.

What confuses me is the relationship between temperature and wattage in soldering irons. I always thought that for delicate electronic components you'd need a low wattage soldering iron around 20-30W, and for more durable stuff and where heat is quickly dissipated (wires, grounding planes etc.) a higher wattage was needed. But then I read somewhere that the amount of watts has to do with how quickly the soldering iron can regain heat when having lost a lot (i.e. soldering something to a large ground plane), and that the temperature adjustment has to do with its application (lower for electronic components on PCBs, higher for cables, connectors etc.)
Is this correct, and will this type of adjustable soldering iron be suitable for the same type of work as before (through-hole soldering of resistors, capacitors, transistors, ICs etc. to PCBs as well as wires, cables etc)?
And is such a soldering iron something similar to, but not quite, a soldering station with its temperature adjustment?
 

Offline sstepane

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #1 on: December 07, 2017, 01:35:52 AM »
Hi there,

I think You're looking for temperature recovery time. I don't know about Hakko mentioned, but this Goot iron is quite good since its heat up time is approx. 30-45 seconds (as far as I remember) which is better than usual chinese irons, but far too long compared to Hakko T12 or JBC, Ersa, Metcal (3 to 12 seconds). Best recovery times are in irons mentioned and it comes with price. But if You do soldering all the time - these, in price 10 times more than 45 usd are worth every penny.
As for wattage, I think 70W will fit most needs in electronics.
 

Offline Brumby

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #2 on: December 07, 2017, 01:38:12 AM »
This is the key bit of information:

But then I read somewhere that the amount of watts has to do with how quickly the soldering iron can regain heat (when having lost a lot)

Everything else descends from that - plus a thing called "thermal mass".

Greater thermal mass allows an iron to lose heat at a lesser rate, which means temperature drop will be slower.  Unfortunately, this requires physical bulk - and that's just not always convenient.

The answer to not having the temperature drop too far is to have greater power which can put more heat in and help keep the temperature up ... BUT there is a problem with this.  Left to its own devices the temperature will rise to levels that create a risk of cooking components and boards, so the way to address this is to have a system where the power is controlled to maintain a steady temperature.  This is where we end up with temperature controlled soldering stations.

But that isn't the end of the considerations...

Temperature control systems must have a point where the temperature is measured - and you will be hard pressed to find one that does that at the actual solder joint where it matters.  In most (affordable) systems, the temperature sensor will be closer to the element than the tip - which means there is going to be a temperature difference from what the sensor is registering and what the actual temperature of the puddle of solder around the tip.  This can be mitigated by good thermal contact between the element, sensor and tip - plus greater thermal mass in this region.

The better units will have more refined design of the whole element/sensor/tip structure to keep the temperature differences to a minimum, which will also result in smaller temperature fluctuations.  How well they do this - and for the range of scenarios from SMD to ground plane metalwork - is usually reflected in the price.

Choosing the one that's best for you is then the challenge.
« Last Edit: December 07, 2017, 01:41:55 AM by Brumby »
 

Offline jgalak

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #3 on: December 07, 2017, 02:31:19 AM »
I have an older Chinese temp controlled soldering station (Aoyue 2901).  It was my first controlled iron - before that, I always used the cheap pencils.  What a difference!  But then I got a chance to use a friend's Hakko.  Blows it away, for exactly the reason mentioned - temp recovery time is shorter, so it's much faster to use.

The Aoyue, I have to pause, momentarily, to allow it to heat back up - especially after cleaning the tip.  The Hakko just worked. 

I'm used to the Aouye, and it works acceptable, so I'll probably keep using it until it dies, but after that, I'm shelling out the money for Hakko.  Kind of wish I'd gotten it in the first place - my advice is to get the Hakko if you can afford it.
 

Offline kalel

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #4 on: December 07, 2017, 06:56:49 AM »
The Aoyue, I have to pause, momentarily, to allow it to heat back up - especially after cleaning the tip.  The Hakko just worked. 

I would recommend trying to clean the tip with one of those brass shaving type of cleaners, using a twisting motion it is usually very easy. I can't say if it's better than the sponge (or when following up with the sponge) but it's the easiest method by far, since you don't need to add water. It should not take much heat away from the soldering iron at all, so you may not have the recovery issue.
 

Offline analogix

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #5 on: December 07, 2017, 07:22:02 AM »
I'm used to the Aouye, and it works acceptable, so I'll probably keep using it until it dies, but after that, I'm shelling out the money for Hakko.  Kind of wish I'd gotten it in the first place - my advice is to get the Hakko if you can afford it.

Are you referring to Hakko soldering stations, or that FX-600 adjustable temperature soldering iron?
Like I said, I really just can't justify (at least not at the moment) a complete soldering station mainly because of the cost, but also the extra bulk/storage space it demands. I figure that since I've gotten by with a normal soldering iron for so many years I can do fine with a similar (but slightly more powerful) soldering iron.
As for the Hakko FX-600 I just haven't come across any dealers anywhere selling a European 220/240V version.
 
sstepane: Where did you read about the fast heatup time? For what I'm used to, waiting 3-5 minutes before being able to solder is no problem, so that's not an issue at all. I've been using a 25W Goot CS-30 (an older version of the Goot CS-31) up to now, which has for the most part done the job (a little weak for soldering larger surfaces) but for some reason doesn't work that well any longer. This is what I'll be comparing a replacement with. So you're saying 70W should be able to handle everything I've used the 25W iron for as well as soldering bigger surfaces?

Brumby: Do you think the temperature control of this particular iron is to be trusted?
If it doesn't measure the actual tip temperature I don't mind, as long as it measures consistently from somewhere else. I really have no idea what to set the temperature dial at for "normal" PCB/component soldering for instance, so I would just set it at a low setting, then go up from there until it melts the solder sufficiently and take a note of that. Or have I misunderstood what you're saying? I take it that a good soldering station with a digital readout actually outputs 250C at the tip when it says 250C on the display.

But regarding the wattage, do I understand it correctly that this 70W iron is suitable for delicate work (through hole, or even SMD components to PCBs) when the temperature dial is set to a low temperature, and at the same time being suitable for soldering larger surfaces, cables etc. when the temperature dial is cranked up for a higher temperature?


 

Offline analogix

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #6 on: December 07, 2017, 07:38:28 AM »
The Aoyue, I have to pause, momentarily, to allow it to heat back up - especially after cleaning the tip.  The Hakko just worked. 

I would recommend trying to clean the tip with one of those brass shaving type of cleaners, using a twisting motion it is usually very easy. I can't say if it's better than the sponge (or when following up with the sponge) but it's the easiest method by far, since you don't need to add water. It should not take much heat away from the soldering iron at all, so you may not have the recovery issue.

I got myself a sturdy Velleman stand with one of those brass cleaners for the reason above (not needing to add water) but mostly because I've read that a sponge "shocks" a soldering iron tip, thereby shortening its life.


But how about the abrasive effect this has to a soldering iron tip? Won't cleaning it this way scratch away the outer layer?
 

Offline sstepane

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #7 on: December 07, 2017, 07:52:28 AM »
sstepane: Where did you read about the fast heatup time? For what I'm used to, waiting 3-5 minutes before being able to solder is no problem, so that's not an issue at all. I've been using a 25W Goot CS-30 (an older version of the Goot CS-31) up to now, which has for the most part done the job (a little weak for soldering larger surfaces) but for some reason doesn't work that well any longer. This is what I'll be comparing a replacement with. So you're saying 70W should be able to handle everything I've used the 25W iron for as well as soldering bigger surfaces?

But regarding the wattage, do I understand it correctly that this 70W iron is suitable for delicate work (through hole, or even SMD components to PCBs) when the temperature dial is set to a low temperature, and at the same time being suitable for soldering larger surfaces, cables etc. when the temperature dial is cranked up for a higher temperature?

Problem is not with waiting for it to heat up (but it is another factor that says how quick the response is), but how fast the iron will restore its hot end temperature. This is quite a problem when soldering small smd element onto big pad - small iron tip just sticks to the pad and cannot heat it up.

70W is the minimum recommended for lead free soldering, which is a standard now.

For the wattage and low-high temperatures for soldering small and large surfaces - higher temperature is cranked because the iron cannot heat it up quick enough (heat response).

High end stations do solder at any set temperature and are able to heat up quite a big surface with tiny tip.

BTW, You may want to consider getting DYI kit for Hakko T12 tips along with tips (original tips are better, but there are good copies). In my country it is number 1 selling soldering station - very good performance for the price.

While PX-201 is a good soldering iron - it is huge and quite long compared to T12 or Goot RX802AS which are more like a big pencil but with the same power and, what counts as well - very easy on the fly tip change.
« Last Edit: December 07, 2017, 07:56:15 AM by sstepane »
 

Offline jgalak

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #8 on: December 07, 2017, 08:52:24 AM »
I'm used to the Aouye, and it works acceptable, so I'll probably keep using it until it dies, but after that, I'm shelling out the money for Hakko.  Kind of wish I'd gotten it in the first place - my advice is to get the Hakko if you can afford it.

Are you referring to Hakko soldering stations, or that FX-600 adjustable temperature soldering iron?


Sorry, misunderstood.  Station.  I've not tried the FX-600.  I understand cost/space constraints, but if you've not used a station, you really should.  Even a cheaper chinese one blows any regular iron out of the water (again, don't know about the FX600). 

The problem with regular irons is that 25W or less just don't keep hot enough, and 40W or more will get too hot without regulation and damage sensitive components.
 

Offline jgalak

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #9 on: December 07, 2017, 08:54:00 AM »
I would recommend trying to clean the tip with one of those brass shaving type of cleaners, using a twisting motion it is usually very easy. I can't say if it's better than the sponge (or when following up with the sponge) but it's the easiest method by far, since you don't need to add water. It should not take much heat away from the soldering iron at all, so you may not have the recovery issue.

I actually keep both on the bench (I have a holder that has them both).  I find the wet sponge better when first getting the iron ready and every now and then as I'm working and it gets gunked up, and the brass works better to get stuff off the iron between each component.  Having both is very nice.
 

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #10 on: December 07, 2017, 08:54:56 AM »
But how about the abrasive effect this has to a soldering iron tip? Won't cleaning it this way scratch away the outer layer?

The brass wool should not have an effect on the tips, brass is a softer metal.  As I saw in video, don't push the tip in and out.  Push in and twirl the tip to clean it.  I switched from the sponge to the brass curls when I got my Hakko FX-951 a couple of years ago.  I won't go back to a sponge.
It is only when a mosquito lands on your testicles that you realize there is a way to solve problems without violence.
 

Offline kalel

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #11 on: December 07, 2017, 09:24:00 AM »
I don't know if either the sponge or brass will damage the tip significantly. I assume it would be easier to damage it by not cleaning at all. :)
 

Offline analogix

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #12 on: December 07, 2017, 10:09:48 AM »
This talk about sponge and brass wool got me thinking that the tips might be oxydized, despite being quite new and looking OK. It makes sense since solder doesn't "flow" out to the tip, but melts in a blog which doesn't stick to the tip. And I'm no longer able to create silky-smooth solder joints as before. Does this sound like an oxydized tip, a failing soldering iron or the wrong type of solder? As I mentioned before I did get some new solder (60/40 as I assume my lead-based solder from before had the same mixture), but I read something about different melting temperatures for different solder. Maybe that's it.

But back to the (possibly) oxydized tip: I read that you should use fine sandpaper to remove the dirt from the tip, then melt some solder on to it which you let stay there for a little while. But in other places (soldering iron/station manufacturer's pages I believe) they say you should avoid scratching the tip. GreyWoolfe: as you pointed out that brass is a soft type of metal, and thinking about it I've already tried cleaning the tip by twisting the soldering iron into the brass wool (as kalel suggested earlier in this thread), but to no avail. I've heard there's some sort of chemical paste or liquid to use in order to "renew" the tip, but I'm unsure of what it is. Does anyone know?
... or maybe it's just that the soldering iron has reached its end of life as I mentioned initially.

Yes, I did notice from the specs that the Goot PX-201 was a bit on the large side (210mm vs. 170mm of my current soldering iron) which might be an issue. The specs for the Hakko FX-600 says 233mm which is strange as it appears more compact than the Goot PX-201, but nevertheless I haven't found a single place where the 220V model is sold (apart from eBay and the likes of course.... if you're happy risking getting a fake one).
 

Offline kalel

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #13 on: December 07, 2017, 10:29:16 AM »
Could you show us an image?

Sure that some oxides cannot be seen, but if it looks shiny at the end (after cleaning it), most likely it's fine. Some videos mention that the inside of the barrel could be slightly oxidized, and could be cleaned with some brush. You normally shouldn't need to use anything that scratches the tip. After a while, of course, heater can be the problem as well.

After each use, it is good to clean, then apply some solder and keep it there. You could do it right after unplugging the iron. Then, oxidation will have to go through the solder first before it can cause any damage.

Also, it is good to unplug the iron (and do the clean/apply solder thing) each time the iron is not going to be used for longer than a few minutes. If you have to do it many times and there is no switch, that can be annoying. Still, it will help everything to work longer. Depending on the iron, it might be wise to take a break after each x minutes and unplug it for a little bit.

I should mention that I don't own any expensive not made in China iron. Only with one really cheap one I had a problem after a couple of years of really occasional use. In my case, it was most likely the heater. I used to have problems with tips until I started doing the tinning (applying solder) after each use and using either the sponge or brass shavings to do the cleaning. After doing that, all tips seem to last much longer, including the really cheap ones.
« Last Edit: December 07, 2017, 10:45:18 AM by kalel »
 

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #14 on: December 07, 2017, 11:10:24 AM »
I used to have a sub-20W ANTEX which served me well while in technical school and for what i was soldering back in the day.
For "heavier" work i had a soldering gun i think 60-70W no more... I also got various el-cheapo chinese irons over the years which sooner or later died on me or i through them away.. some i even paid for!!
Two years ago i went to shop for a new soldering iron and i got myself a top brand (ERSA) MULTITIP 25W for some 30 euros.
I quickly found out that i needed a different tip but for 10 euro a tip i didnt buy one... the one that came with the iron did not satisfy me at all though and it started taking solder not only in the tip but all over the surface after a few months of relatively light use.

I searched for a solution and decided to gamble with a Chinese TS100 as a lot of people praised it....
I use it with a 19,5v/4,5A laptop power supply and again i found the need to buy a second tip.. only this one has tips with embedded heating element... i got one for 9$ delivered!!!! (that was ERSA it would cost 15-20 euros when they charge 10 euro for a simple tip!!!
The tip that came with TS100 is now in storage and despite the fact that i use it heavily for several months now, is as good as new. The new one i got only a couple weeks but immediately improved my soldering/desoldering even on smd stuff.

Now, smd mentioned, i also got myself a 858D hot air station which is simply amazing for 37$ delivered from Germany (got it on 11/11)...

My opinion for any hobbyist, TS100 is a honest, reliable and proven concept, its not dirt cheap but it is worth every cent you spend on it and does the job very very well... but if you want to work with SMD you really need a hot air station and it can be really cheap these days
 

Offline Brumby

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #15 on: December 07, 2017, 12:02:09 PM »
Brumby: Do you think the temperature control of this particular iron is to be trusted?
I can't answer that from personal experience.  Sorry.

Quote
If it doesn't measure the actual tip temperature I don't mind, as long as it measures consistently from somewhere else.
That is actually one of the problems.  There is a temperature gradient between the sensor and the solder puddle - and it is dependent on how good the thermal coupling is in this region (as mentioned before) and how much heat is being drawn.  From just sitting in the stand, to soldering an SMD resistor, to soldering a metal tab to a ground plane, the heat flow increases and so does the difference between what the sensor is measuring and what the temperature of solder puddle actually is.  This difference is due to the construction of the iron and unless the sensor is something like a thermocouple you stick into the solder puddle, there will always be a difference - and that difference will change depending on the amount of heat flowing.  What only ever matters is the actual temperature of the solder puddle.

You might get a better feel for things if you look at what is happening as a thermal resistance exercise - with the element being analogous to the die in a transistor, the joint analogous to the heatsink with all the intermediate boundaries that exist (element/barrel/tip/solder/joint/ambient as a minimum) and paying particular attention to where the temperature is being measured by the sensor.

Quote
I really have no idea what to set the temperature dial at for "normal" PCB/component soldering for instance, so I would just set it at a low setting, then go up from there until it melts the solder sufficiently and take a note of that.
We all go through a 'familiarisation' stage when we get a new iron - so what you are saying here is pretty normal thinking.  After a time, you will get to know how your iron deals with different jobs and how to adjust it to perform properly in different situations.

Quote
Or have I misunderstood what you're saying? I take it that a good soldering station with a digital readout actually outputs 250C at the tip when it says 250C on the display.
That is an "ideal" soldering station.  There will always be a temperature drop - especially during soldering - but the really good stations will have a more accurate control system.

Quote
But regarding the wattage, do I understand it correctly that this 70W iron is suitable for delicate work (through hole, or even SMD components to PCBs) when the temperature dial is set to a low temperature, and at the same time being suitable for soldering larger surfaces, cables etc. when the temperature dial is cranked up for a higher temperature?
This is where the "ideal" gives way to the real world.

A 70W iron doing SMD is not too far from the ideal.  You set a temperature and because there is not a lot of mass to suck away heat, the actual temperature is not too far away.  As such, you set the temperature closer to the actual melting point of your solder and the temperature control system is switching the element on and off to keep it there.

However, when you are soldering heavier joints, there is a lot of heat getting sucked out - so you need more heat in.  Setting your iron to the same temperature as you would for SMD means that the temperature at the tip would drop very quickly and the temperature control circuitry would switch on when the sensor dropped below the set point.  What happens next is important...

Once the element is turned on, it heats up, then it's surrounds heat up, the sensor heats up and eventually the tip heats up - followed by the solder.  The temperature control system monitors the sensor - so when the sensor reaches the set point, the control system switches off the element.  The problem with this is, that the tip and the solder haven't been heated up enough - because the joint is sucking away heat big time.

The simple response to this is to do exactly what you have said - crank up the temperature.  This allows the element to be kept on long enough to deliver the heat required to get the solder and joint up to temperature.  The risk is that you now have to take responsibility for the actual temperature at the joint - something that will come only with experience.
 

Online Audioguru

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #16 on: December 07, 2017, 12:22:39 PM »
Some cheap soldering "stations" use a simple light dimmer circuit for you to adjust the power but not the temperature. They get too cool while soldering and get too hot when not soldering then the next solder joint is with the flux incinerated, a poor solder joint and the tip burnt.

You need a soldering station with temperature control and you probably never need to adjust anything. My Weller soldering iron has its tip always at the correct temperature.
 

Offline KL27x

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Re: Soldering iron buying choice: watt vs. temperature?
« Reply #17 on: December 07, 2017, 10:12:11 PM »
Quote
But regarding the wattage, do I understand it correctly that this 70W iron is suitable for delicate work (through hole, or even SMD components to PCBs) when the temperature dial is set to a low temperature, and at the same time being suitable for soldering larger surfaces, cables etc. when the temperature dial is cranked up for a higher temperature?

It sounds like the iron is truly thermostatic. It is decribed as temp-controlled. And furthermore that it has a temperature sensor (i.e. feedback). So I would hope it is not just a variable power iron.

If it is a temp-controlled iron, and if the response time is fast enough, and if it is truly 70W, then you shouldn't have to change the temp dial much, at all, going from delicate things to fairly larger things. (Tip changes maybe more important than temp changes). But as others have already stated, response time is one factor. Another factor, which is often overlooked is the fact that power ratings are somewhat... flexible.

For instance, Hakko 888 is listed at 65W. I have measured resistance of the heater when cold and when hot. I have recorded voltage over time, with heater switched on/off. Cold and hot. And IMO, 65W is a remarkably moderate power rating. This is truly close to the actual power drawn when at soldering temp. (And I was completely shocked to see how stable the transformer is in this station.) When Goot says 70W, that could mean something else entirely. It could be 70W max, when the heater is cold. But then it could drop to 30W after it warms up, due to heater resistance increasing with temperature. And that would not be lying.

And this doesn't even take into account where that power goes. Some irons are better at putting that power into heating the tip. Others are better at heating up your hand.
 


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