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Soldering Station Confusion


TekNoir

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I just started learning about electronics last year and at the time I bought myself a very cheap soldering iron to start out with. (When I say "cheap," I mean that I gave the clerk a ten-dollar bill and received change back in exchange for the item.) I would like to upgrade, preferably to a complete station, but I am having a slight bit of difficulty with advertising terms.

What confuses me is the connection between temperature and advertised wattage.

From my understanding, it takes a tip temperature of somewhere around 361F (183C) to melt 63/37 solder efficiently. However, a great number of soldering irons and soldering stations, as well, only advertise a wattage rating, some give both, and some only give their temperature. I'm not exactly certain how wattage translates directly into temperature rating.

I realize that electricity moves through the heating element and the resistance causes heat and that the power dissipated can be measured in watts. Am I missing some simple connection? I would think that the two were unconnected, sort of like the marketing scheme of lighbulbs in watts which have nothing to do with their light output (in lumens). It could be assumed, of course, that higher wattage produces more heat (or light), but this is simply not always true. Thermal properties of the substances involved, basic construction, as well as other factors have to be figured in as well.

As an aside, I have noticed soldering stations advertised with tip temperatures adjustable between 350F and 800F, yet their advertised wattage were completely different (42W for one as compared to 80W for the other). I have been told (and read in a number of places online) that twenty-five to thirty-five watts was good enough for electronics work. Yet, I cannot comprehend "good enough." Does that mean that I should not get anything over thirty-five watts for fear of ruining components (which I, once again, would tend to believe has more to do with temperature than actual wattage) or that something with lower wattage simply won't get hot enough? (I should note that I saw some 15W soldering irons with tip temperatures of 600F.)

The only connection that I can somehow attribute from research is in the transfer of heat into the joint itself. Higher wattages would transfer the same amount of heat faster than a lower wattage would for the same temperature. I would think that this would be conducive to better and faster soldering so long as you didn't decide to daydream at the exact moment you decided to solder a joint. This is another reason that I question the 25W to 35W "rule." Shouldn't any soldering tool capable of delivering an appropriate amount of it's 360F+ tip temperature be "good enough?"

In closing, the two soldering stations that I am considering purchasing (the Hakko FP-102 and the CooperTools/Weller WSL, both comparably priced at 200$ USD and what I have budgeted to spend on a new soldering station) are both well over the 35W recommended for electronics work. I was trying to put together a clearer picture of what I should look at when purchasing my soldering companion for the next number of years.

Sorry for the long post and thank you all in advance...

Edit: I had inadvertently copied the melting point for lead alone. I have now corrected my data to correctly represent "ideal" electronics solder's melting point.

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Hi TekNoir,
Welcome to our forum. ;D
I have used Weller WTCP irons at home and at work for about 40 years. They don't have instant temperature adjustment nor a fancy display that I have seen on much more expensive ones fail during a lightning storm like my cheap clock radios.

At first I tried various tip sizes and temperatures but quickly decided on 700 degrees F and chisel tips of 1/16th inch for normal soldering and 1/4 inch for the occasional heavy stuff.
Since it is temperature controlled it goes to full power (42W) when needed. It can be running all day every day and the tip seems to last forever. After 40 years of a lot of work the mechanism certainly lasted. I didn't even have to replace its burn-proof super-flexible silicon rubber cord.

I hope you don't purchase an expensive iron with fancy un-needed gadgets that fail prematurely. ;D

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Hi TekNoir,
If you only want to have one soldering station, a good digital iron which is adjustable is good for all occasions.

A preset wattage type of iron will give different results for soldering on different materials. You will notice varying amounts of time for solder flow when using one of these irons. These can leave you with undesirable results in many situations. More noticeable is varying time to do the same job on different media.

You will want a different heat setting for different items. Things that have a mass of metal will need more. On the other side, you will not want to overheat fragile items. Also, when you are doing re-work, you will want more heat for this task than when you are soldering components to the board. This will help to remove your chips and other components quickly.
You can get different tip sizes for most of these stations and this adds even more flexibility when soldering a wide range of media from larger masses and wiring, to soldering small surface mount components and fragile items such as the wires on thermistors. After a few practice runs, you will have favorite settings for the different things you are soldering.

Some might call this unneeded gadgets, but I have heard the same argument by those who refuse to drive cars because the technology is unneeded or because a bicycle has less to go wrong. Personally, I enjoy technology and the way it makes life easier.  8)

...bottom line here is that there is no right and wrong way to go about this. You will have to find your own personal preference through trying out different methods.

MP

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You will want a different heat setting for different items. Things that have a mass of metal will need more. On the other side, you will not want to overheat fragile items. Also, when you are doing re-work, you will want more heat for this task than when you are soldering components to the board. This will help to remove your chips and other components quickly.

The heat setting on my simple, long lasting temperature controlled soldering iron is automatic. For a mass of metal and rework, it automatically goes to full power until the desired temperature is reached very quickly. For fragile items or at idle, it uses very little power but is ready to switch to full power when needed. ;D
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I agree audioguru, if you have a temperature controlled iron and you set its temperature to 300oC for example it will remain at this temperature regardless of the load  by the same way a switching regulator keeps the output voltage constant.

My first temperature control was a phase controller made with a triac and I had to do as MP says and adjust the setting depending on the object I was soldering.

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Maybe there is some confusion there, but I was referring to a temperature controlled iron in my description.

Set it to a certain temperature and leave it there for your work. My preference is to have the digital display. The reason you have this option (settable temp) is so that you can use it in different circumstances. The "so called" automatic ones can certainly give you control when there is a different mass of metal, but they cannot differentiate between the leg of a resistor or the lead of a fragile thermistor. There are many circumstances where having complete control over temperature settings is preferable. 700 degrees for everything might work for your circumstance, but it would never work in my business.

MP

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The heat setting on my simple, long lasting temperature controlled soldering iron is automatic. For a mass of metal and rework, it automatically goes to full power until the desired temperature is reached very quickly. For fragile items or at idle, it uses very little power but is ready to switch to full power when needed. ;D


After doing some research, the Weller WTCPT purports utilizing a unique closed loop method of controlling maximum tip temperature which protects temperature sensitive components. Does this basically act as if you were to lower the tip temperature in any other iron or does it, in fact, remain at whatever temperature was already determined by the tip (700F for the supplied tip)? Having used this particular station for so long, what are your opinions as to how effective it is in actually protecting temperature sensitive components?

Thank you all for your knowledge and opinions and please keep it up. I am learning quite a bit between my personal research and here.
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Having used this particular station for so long, what are your opinions as to how effective it is in actually protecting temperature sensitive components?

My Weller WCTP's have never caused thermal damage to anything with their tips that keep their temp at 700 degrees F. Most of the time I don't even bother using pliers as a heat shield.

Many thermally-sensitive components have a duration limit for their exposure to a high temp. A lower temp of a soldering iron would extend the soldering time to beyond the duration limit. 700 degrees solders items very quickly.
I guess it is similar to the reason that straps are flash-welded on batteries with plastic inside instead of soldering them.

I know, I've also seen guys solder batteries together. They get away with it because they use a very hot soldering iron with two big flat faces and the soldering is completed in only a moment. ;D 
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The guy was soldering LI-Po cells together. They have polyester inside and all around them. Even their heat-shrink plastic case didn't melt.
I soldered button cells when I was young and didn't know anything about danger. About as crazy as soldering a car battery. Did you use a blow-torch? ;D

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For anyone who is curious and based upon information I have gotten here and elsewhere, I decided to go with a Metcal PS-800 soldering system. It operates much like the Weller WCTP series in that the tip temperature is fully regulated and set according to which tip you have inserted. The tip temperature is held constant (within 1C) while the power adjusts to the load. More information can be found in the link given.

Thank you all for your help. I truly do appreciate it.

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