The Electronics Soldering Thread

[Hohn]

If the cost continues to drop, we'll all eventually have some of these video microscopes:

 

[pofen62594]

As a continuation, let's talk about heat flow and soldering station performance. Or, why the Metcal and Hakko and other stations are basically all the same in terms of thermal capability.

I've actually measure the current draw in real time of my soldering stations under different load conditions. I've testing them to an extreme case using a footlong scrap of 1" copper pipe as a brutal test as to whether a soldering station can get it hot enough to melt solder at the end. I learned a lot from that copper pipe testing, including the startling observation that a 400W station was barely-- and I mean barely-- better than a 40w station in its ability to heat the pipe up and get solder flowing.

What you find pretty early in testing is that the station isn't the limiting factor at all to thermal performance. This is why a 40W Metcal and a 120w Hakko end up performing similarly.

Stations are always reactive. If the set operating temperature is achieved, the the power dissipation of the station is just whatever is required to overcome the convective cooling at the tip. On a Curie-point station like the Metcal, the reaction is that a decrease in tip temperature take the tip below the curie point, the heating element becomes magnetic again until the Curie temperature is achieved and the cycle repeats. You can see the power demand cycle off and on as the element become magnetic or not.

On a cartridge station, the temperature drop is seen by a thermocouple which signals the station to send more juice to the heating element. In effect, it works the same as the Metcal, it just uses a thermocouple for temp sensing and PID control instead of using the induction heating tech of the Metcal. Unlike the Metcal, the PID control can find the steady state open-air current draw and so it converges to a steady state dissipation.

With either station, the only way to get more-than-idle power out of the station is for the tip temperature to drop. If you use a tiny tip, it's easy for the temperature to drop (very little mass) but the tiny tip also has tiny surface area and so it a poor thermal conductor. That means that while it's very responsive, it's also a horrible bottleneck for energy transfer. And importantly-- it won't pull heat away from the sense point and signal to the station to send more power.

The thermal gradient between the working contact area (where the heat is being lost) and the and sensing location is *critical*. If you had a long enough soldering tip (picture a long heavy wire), you could actually hold the tip in your fingertips and not see ANY increase in current draw from the station. From the perspective of the station, it's just idle current.

Until you drop the temperature at the SENSE LOCATION, the station contributes NOTHING.

So the first critical takeaway is that the tip geometry and proximity to the sensing element is absolutely paramount to station response and performance. This is why the Metcals don't have as big an advantage as one might think. While they are very sensitive to heat loss electrically, they are NOT thermally sensitive-- the heating element is the sensor and it's pretty far back up away from the tip. The cartridge stations, by contrast, have a thermocouple as close to the tip as they can place it (and it's separate from the heating element.

As a result, there are situations where either station will "outperform" the other even with similar tip geometry. If you are doing lots of work on small thermal masses, the Metcal style works brilliantly. Think of small pad PCBs and such where you won't be sustaining any kind of major load. Metcal stations work best when you are making lots of small joints and sustaining a modest power draw. If the tip size you using is 2.4mm or smaller, the Metcal can work very, very well.

But when you get into larger tip size and get off PCBs and into discrete things like heavier lugs, potentiometers and such the Metcal style will fall on its face a bit. When you can apply a higher load to the tip, that's when you will really start to see the difference between a 40w Inductive station (Metcal) and a 120w Cartridge Station (JBC/Hakko).

The vast majority of the time, there's no real world difference between them because you simply cannot load the station above 40w.

And above all remember that the TIP is the place to store energy, not the station. There's no station on earth capable of overcoming a tiny and inferior choice of tip. Always use the biggest a shortest tip you can physically fit on the workpiece. If you are using that large and short tip, you will have maximum performance regardless what station the iron is plugged into.

I have to totally disagree with you on a couple points.

Point 1
"...heavier lugs, potentiometers and such the Metcal style will fall on its face a bit. When you can apply a higher load to the tip, that's when you will really start to see the difference between a 40w Inductive station (Metcal) and a 120w Cartridge Station (JBC/Hakko)."

Here is a big 150W JBC station getting easily beaten on a larger mass test by a Metcal (running at only 40W). Skip to 22:14 to see the comparison.

Point 2
"The vast majority of the time, there's no real world difference between them because you simply cannot load the station above 40w."

If point 1 doesnt prove enough real world difference and you think you need more than 40w from a Metcal, you can absolutely load the station above 40w with a High Thermal Demand handpiece and cartridge to get 80w.

Here is a test of the Metcal HTD handpiece, using it to solder to a sheet of copper. It destroys a Pace 120w system.

I hope these two points prove the complete superioty of inductive heating stations vs resistive. Dont get me wrong, there are plenty of good resistive systems out there, but the best technology is induction due to the instant reaction time.

 

[theoldwizard1]

I just recently bought a TS101. I have only used it a couple of times, but I am very IMPRESSED. Amazing amount of power from such a small iron. If you are going to use it on a bench, buy a decent holder



The standard tip is NOT good for very small work, like soldering SMD. Get the TS-I tip for that.

 

[WildBill]

I have to totally disagree with you on a couple points.

Point 1
"...heavier lugs, potentiometers and such the Metcal style will fall on its face a bit. When you can apply a higher load to the tip, that's when you will really start to see the difference between a 40w Inductive station (Metcal) and a 120w Cartridge Station (JBC/Hakko)."

Here is a big 150W JBC station getting easily beaten on a larger mass test by a Metcal (running at only 40W). Skip to 22:14 to see the comparison.

Point 2
"The vast majority of the time, there's no real world difference between them because you simply cannot load the station above 40w."

If point 1 doesnt prove enough real world difference and you think you need more than 40w from a Metcal, you can absolutely load the station above 40w with a High Thermal Demand handpiece and cartridge to get 80w.

Here is a test of the Metcal HTD handpiece, using it to solder to a sheet of copper. It destroys a Pace 120w system.

I hope these two points prove the complete superioty of inductive heating stations vs resistive. Dont get me wrong, there are plenty of good resistive systems out there, but the best technology is induction due to the instant reaction time.

I agree but it didn't seem worth it trying to convince Hohn otherwise, so good luck with that. We have seen a big increase in quality, a reduction in scrap, and a reduction in tip costs after switching our whole company from Hakko to Metcal last fall. I appreciate his effort in making informative posts about soldering though, even if they are not 100% accurate they are probably pretty helpful to the average person.

 

[mv213]

Here's a pic of some guitar soldering work. Note how "wet" the solder on the potentiometer is, and that you can see the strands of the wire. This is all but impossible to do with a typical iron with a small conical point. By the time you melt the solder this thoroughly, you will have overheated the pot and ruined it because the heat transfer rate is too slow. But if you have a massive 6.5mm chisel tip on a Hakko FX-601, you can dump an enormous amount of heat into the part nearly instantly and get off and on right away. The result is a nicely wetted joint with very little total heat into the pot. I can't tell you how much I love that Han-Solo-in-carbonite look of well-wetted solder that still lets you see everything under it.

@Hohn This is a great thread. Thanks for sharing your knowledge, I appreciate it. I’ve done a lot of electronics soldering over the years (my dad bought me my first Heathkit at age 12). I always like to improve and learn more.

 

[Hohn]

I see this is your first post, so WELCOME!

I have to totally disagree with you on a couple points.

Point 1
"...heavier lugs, potentiometers and such the Metcal style will fall on its face a bit. When you can apply a higher load to the tip, that's when you will really start to see the difference between a 40w Inductive station (Metcal) and a 120w Cartridge Station (JBC/Hakko)."

Here is a big 150W JBC station getting easily beaten on a larger mass test by a Metcal (running at only 40W). Skip to 22:14 to see the comparison.

Did you watch the entire video? Including the part at 23:54 where the large 7mm tip let the JBC knockoff crush the Metcal 5mm as well as the JBC 5mm tips? "Certainly, that big tip was able to put way more power into the coin" he says. This is exactly what I'm talking about it. With big tips or big heat loads, the induction stations falter a little partly because they top out at 5.3mm tips.


This testing is exactly consistent with my own experience-- the smaller the tip and the smaller the thermal mass, the better the induction units are because the tip and not the station is the factor limiting the system's thermal performance. At lower demands, the response is super important and the power behind it almost completely irrelevant.

But at higher thermal demands, the tables turn. Which is why the 7mm JBC tip crushes all the smaller tips--including the Metcal. No station is powerful enough to overcome the limitations of a small tip.

I bought a separate iron that can make use of 6.5mm chisel tips because I have some high-load applications where the 5.2mm size isn't quite enough heat capacity. And my cheap big iron with the 6.5mm tip will crush both my induction AND my cartridge stations that max out at 5.2mm width on the chisel. Things like chassis grounds on Fender amps, guitar tremolo grounds, etc all require a big tip that can store and discharge a lot of heat FAST to get in and out.

For that kind of usage, the doesn't matter how responsive the station is because every station ***** compared to storing heat in the tip ready for immediate discharge.

I'm a fan of induction stations but I've used them and others enough to know where different stations have different strengths. And for my money, the $170 add-on accessory to a $650 station is not even close to justified for home hobby usage compared to what my T12 cartrige station does for $250.

For @WildBill usage in a business setting, I'd recommend Metcals or comparable induction stations every time (I'm partial to the Thermaltronics as more cost effective). Business tools are different than home gamer tools, and you can justify much higher budgets when having to deal with less skilled labor and expensive rework/warranty costs. The only exception would be if that business was solar panels or such where no induction stations of sufficient power are available.

 

[Hohn]

I have to totally disagree with you on a couple points.

Point 1
"...heavier lugs, potentiometers and such the Metcal style will fall on its face a bit. When you can apply a higher load to the tip, that's when you will really start to see the difference between a 40w Inductive station (Metcal) and a 120w Cartridge Station (JBC/Hakko)."

Here is a big 150W JBC station getting easily beaten on a larger mass test by a Metcal (running at only 40W). Skip to 22:14 to see the comparison.

Point 2
"The vast majority of the time, there's no real world difference between them because you simply cannot load the station above 40w."

If point 1 doesnt prove enough real world difference and you think you need more than 40w from a Metcal, you can absolutely load the station above 40w with a High Thermal Demand handpiece and cartridge to get 80w.

Here is a test of the Metcal HTD handpiece, using it to solder to a sheet of copper. It destroys a Pace 120w system.

I hope these two points prove the complete superioty of inductive heating stations vs resistive. Dont get me wrong, there are plenty of good resistive systems out there, but the best technology is induction due to the instant reaction time.

I'd also like to add something I didn't want to disappear in an edit: there is a real-world difference between induction units and cartridge stations. The response of induction units is superior. Rather, this real world difference is 1) small, when present and 2) comes often at a massive cost premium and 3) is less significant in practice than people might think, and 4) becomes a disadvantage under particular uses with high thermal loads (chassis grounds on fender amps, for example-- not even an 80W Metcal with a 5.3mm tip can do these very well, the tips are too small and the power too low. A JBC with 7mm tip, on the other hand, performs much better, as does my inexpensive Hakko FX601 with the large 6.5mm tip).

I was wrong to state there is no "real world" difference when there is. I should have characterized it in the manner of the preceding paragraph.