We were first introduced to the Thermaltronics range of Curie point soldering irons in September last year at the 2019 ElectroneX Electronics Design and Assembly Expo in Melbourne. What made this soldering iron different to the many other irons on display at the expo, was the fact that this iron uses a high frequency 13.56MHz RF signal in conjunction with a curie point tip to regulate the temperature. Whilst we were thoroughly impressed with the demonstration at the expo, we were certainly keen to put the iron through its paces and see how it compares to the traditional soldering irons we currently use.
Traditionally, a soldering iron is little more than a resistive element with a soldering iron tip attached to it. When AC or DC current flows into the resistive element it converts the electrical energy into thermal energy and the resistive element gets hot. This heat, in turn, is distributed to the soldering iron tip via the thermal connection between the resistive element and the iron tip. To regulate the temperature the user generally sets the desired temperature and the iron uses a microcontroller and thermocouple to measure the current temperature of the tip. If the current temperature is lower than the desired temperature the microcontroller allows current to flow into the resistive element via a Triac or MOSFET. When the temperature is higher than desired, the microcontroller restricts current to the resistive element. This regulates the temperature of the iron but relies heavily on the location of the thermocouple and the thermal resistance between the iron tip and the resistive element. This system is often prone to a significant overshoot of temperature, allowing it to exceed the desired temperature by tens of degrees in some instances.
The Thermaltronics Curie point soldering irons, however, have a completely different approach to their design. They operate by using a high frequency RF wave delivered into an induction coil, which is wrapped around the soldering iron tip. This tip is made from a special alloy designed to have a specific curie point and the coil and tip are electromagnetically coupled just like the secondary of a transformer. The skin effect causes the high frequency current to remain in the outer surface of the soldering iron tip, rapidly heating it to the curie point of the tip. At this curie point, the tip loses its magnetic properties and the tip and coil are decoupled. With the tip and coil decoupled, power is no longer being delivered to the tip, and thus, it does not continue to heat up.
However, as you begin to solder with the iron, the temperature drops below the curie point of the tip, allowing the tip and coil to recouple and once again power is delivered to the tip causing it to heat to the curie point. This process is repeated very rapidly providing a very stable soldering temperature.
The curie point of the soldering irons tip is effectively what sets the temperature. Since the tip loses its magnetic properties at this point, the heater can’t continue to heat the tip once the point has been reached / exceeded. This produces an incredibly precise level of regulation that in theory means the soldering iron cannot overshoot the rating of the tip. The curie point is a property of all ferromagnetic metals and is essentially the temperature at which point the metal loses its magnetic properties.
Here’s a table to show Curie points for various ferromagnetic metals.
In order to change the Curie point of the soldering iron tip, and therefore the iron temperature, Thermaltronics must create a special alloy (likely from Iron and Nickle) called Permalloy. To reach higher temperatures the Permalloy ratio is modified. The higher the ratio of Iron to Nickle, the higher the Curie point of the alloy, and thus, the soldering iron will reach higher temperatures. This, of course, means that the temperature is set by the specific tip being used, and as such, you must change the tip used to change temperatures.
UNBOXING & FIRST IMPRESSIONS
Upon opening the box we were greeted with the main unit, which is surprisingly heavy, weighing about 2kg. This is because it is a completely metal enclosure which presumably doubles as a heatsink for the unit. It is also quite physically large at approximately 210mm tall and 115mm long and wide. The iron holder is made from a heavy and robust plastic, which like the unit, is quite large at 200mm long, 100mm wide and 90mm tall. The power cable is a standard IEC type at approximately 2m long.
The handpiece is very light and petite at about 150mm long. The grip on the handpiece has a hard-plastic feel and can be interchanged with either of the two included spare grips. We found the green one felt much better in the hand as it’s a softer rubber feel. The handpiece cable is an impressively long 1.85m and made from a very flexible, burn resistant silicone. The short handpiece combined with the lightweight and flexible cable makes this handpiece very comfortable in the hand.
The provided tip was the M7CH176 1.78mm chisel tip, which is perfect for basic THT and SMD soldering, and is a pleasant change from the normal conical tip that comes packaged with irons. The user manual is a small multi language type with about 6 pages devoted to the English language. This isn’t a surprise as the unit requires absolutely zero user input. The kit also comes with a sponge and brass shaving tip cleaner, as well as a silicone mat used to remove hot tips from the handpiece.
The main unit has no controls or user input device at all. It simply has a 1602 LCD screen and power LED to indicate to the user the level of power being distributed to the iron tip (presumably displaying Watts) and to indicate if the device is on. It has a round rocker-style power switch on top of the unit and a large slide switch toward the bottom. This switch is used to direct the power to one of two output connectors. The main reason for dual outputs is that this system also has the options for through-hole desolder attachment (shop air required) and surface mount tweezers, making it a soldering and rework system in one.
The first thing we wanted to know regarding this new soldering iron was the temperature of the soldering iron tip. The datasheet for the provided tip suggested the tip will have a temperature range between 350°C and 398°C.
To test this, we used the Hakko FG-100 soldering iron tip temperature thermometer. This showed that the tip provided with our unit was self-regulating at around 380°C. Usually, we solder at about 360°C using our old iron so whilst this iron is a little hotter it isn’t by a significant amount. However, this means that we need to take slightly less time soldering each joint to avoid overheating the component.
We then wanted to test to see how quickly the soldering iron can heat up. It became glaringly apparent upon power-up that this iron heats up incredibly quick. On average, it took about 8.5 seconds to go from room temperature to the melting point of 0.9mm 60/40 leaded solder. This is much quicker than the conventional soldering iron we have been using for about 5 years. This much quicker heat up means it’s much more convenient to just “flick the soldering iron on” for that simple quick soldering task.
Of course, a soldering iron that heats up quickly is only a small part of what makes a soldering iron great.
Arguably, the most important feature of a soldering iron is its ability to rapidly transfer the heat from the soldering iron tip into the lead of the component and the PCB pad that you’re soldering the component too, while simultaneously providing enough power to keep the tip at the regulated temperature. This process needs to be done as quickly as practical, as the heat can easily travel up the lead of the component into the device and damage it. Some component datasheets even state the maximum time a soldering iron can apply heat to the lead before doing damage. As a rule of thumb, the ideal soldering time will be less than 3 seconds for any lead of any component.
The issue is, when you put the tip of a soldering iron against the lead and pad of the PCB, the heat is very quickly wicked away from the soldering iron tip into the much colder pad and lead. This causes the temperature of the tip to drop dramatically and needs time to recover. This is greatly increased when either the pad you’re soldering too is large, such as a PCB ground plane, a component attached to a heatsink, etc. This has historically been a bit of an issue for our previous iron and was very obvious when soldering the PCB for the servo tester in issue 024. When soldering components to the ground plane we would increase the temperature of our iron from 360°C to 460°C to be able to solder the components quickly. At the lower temperature, the soldering iron struggled to flow solder and took much longer risking damage to the components. To avoid overheating the component you need an iron that can quickly recover from that shock, preferably without increasing the soldering temperature.
To test how quick this iron was able to deal with large ground planes and large components, we tested it against some single sided copper clad PCB material, which was roughly 100mm x 70mm. This copper board simulated a large ground plane. and heatsinks heat away from the soldering iron tip and disperses it over the surface of the copper PCB. Despite this large heatsinking area, the soldering iron had no issues in flowing solder onto the board within a second or two.
To test how this would affect parts situated close to this solder joint we attached a K type thermocouple to the PCB using a small piece of Kapton tape. We measured the temperature of the PCB surface using the Digitech QM1323 multimeter while we soldered 10mm away from the thermocouple sensor. During the test, the temperature increased 5°C from 32.8°C to 37.8°C with the soldering iron making contact with the PCB for about 2 seconds.
We repeated the above test several times, each time adding more solder which subsequently took longer each time to cool and longer to flow.
The image shown here shows the large bead of solder with an approximate diameter of 10mm reflowing the solder after 3 seconds. The temperature of the PCB about 10mm away is still less than 10°C above ambient.
Overall, we have been blown away by the performance of the iron. Its ability to rapidly solder without losing temperature is unsurpassed by any iron we have previously used. In every test we performed to evaluate the thermal capacity of the iron we were impressed. From reflowing the solder tabs of a large heatsink to even soldering a TO-220 5V regulator to a PCB ground plane via the ground tag. This iron had no drama with any of it.
Reflowing solder on the mounting tabs for a large heatsink took little effort from the Thermaltronics TMT 9000s.
We were even able to easily solder a TO-220 5V linear regulator to the ground plane of the Datalogger PCB from Issue 031. This is quite the feat, given the large ground plane and tag of the package.
To test the power output and thermal capacity of the iron, we decided to create a little torture test. This way, we can use the results to compare future irons as practically as possible. For the test, we wanted to use a medium sized piece of copper with uniform size and weight so that the test could be easily repeated. For this, we figured the Australian one or two-cent pieces would be ideal. They will all weigh about 5.2g and have the same dimensions, which means they will all have the same thermal absorption characteristics.
Note: The Australian 1 and 2 cent pieces can sometimes be quite valuable to coin collectors. We advise you do some interim research regarding the date the coins you’re intending on using to ensure you’re not destroying a valuable coin.
We can calculate the thermal absorption characteristics using the formula: Q = m x c x Δt
Q = Thermal Absorption
M = Weight in grams of the material
C = The specific heat capacity of the material
Δt = Change in temperature required. i.e. final - ambient
Note: the Australian 2 cent piece is 97% copper, the remaining 3% is a mixture of zinc and tin. Pure copper would be ideal however, for the purpose of this experiment and calculation we will assume the coin is 100% copper.
For our coins, we know the mass is 5.2g and that the specific heat capacity of copper is 0.385J/g°C. We also know that the temperature our 60/40 leaded solder flows at is around 250°C.
Therefore, the thermal absorption is: Q = 5.2 x 0.985 x (250°C - 25°C) = 450J
This means it will take 450 joules of energy to raise the temperature of the 5.2g coin to the melting point of solder assuming perfect heat transfer. To convert joules into power we use the formula: P = E / T
P = Power(W)
E = Energy(J)
T = Time(S)
Using this formula, we can calculate the time it will take to heat the coin to 250°C if the thermal transfer between the iron heater and the coin was perfect. We know the iron is capable of delivering 40W of heating power and the total energy required to heat the coin, thus, the equation to calculate Time becomes:
T = E / P = 450J / 40W = 11.25 seconds
To reduce variables, we soaked the coins in a vinegar and salt solution for four hours before rinsing the coins thoroughly and coating them with liquid flux. This removes all existing corrosion and slows the corrosion process for the duration of the experiment. This will give the best possible heat transfer and will allow us to flow solder to the coin as quickly as practical.
On average, the Thermaltronics TMT-9000s took 25 seconds from the first application of the iron to solder flowing onto the surface of the coin. This is much lower than that calculated as the thermal calculations as they assume perfect transmission of the heat into the coin.
For comparison, we used our traditional heater cartridge soldering iron that has a reported output power of 65W (in the datasheet), which means it should take the iron 6.9 seconds to raise the temperature to the 250°C required to flow our solder. In reality, it took 54.5 seconds using this iron with a similar chisel tip. Note: We calibrated the traditional iron to match the 380°C temperature of the Thermaltronics tip.
This shows that the much lower power Thermaltronics Curie point soldering station is many times better at delivering the thermal energy into a large load than the traditional style iron. To quantify this data, we can create a single efficiency number by using the time it takes to deliver the required energy to calculate the actual power output.
Since the Thermaltronics took 25 seconds, the calculation is:
P = E / T = 450J / 25 = 18W output
To calculate the approximate efficiency, we use the equation:
n = Pout / Pin x 100 == 18/40 x 100 = 45%
This means, in this experiment, 45% of the soldering irons output power was successfully distributed into the copper coin. Whereas, with the traditional style of iron it was closer to:
n = Pout / Pin x 100 == 8.2 / 65 x 100 = 12.7%
This shows just how much more efficient the Curie point iron is at delivering heat into a load, as opposed to a traditional style iron. Now this isn’t a perfect experiment - there are factors outside of our control. For example, the position and condition of the soldering iron tip can easily affect this performance, and as such, it is only useful as a simple comparison.
We were initially hesitant about using a soldering iron that did not have any temperature adjustment capabilities, as we figured this would present a significant limitation, however, we were quick to come around. The iron’s excellent thermal capacity means you never actually feel the need to raise the temperature. Regardless of the component or PCB, the iron comfortably handles the load.
Even when under considerable and unrealistic loads such as soldering the tabs of the heatsink (shown here), where the iron was maxed out with a load of 47, the soldering iron (whilst clearly struggling) was more than capable of rapidly heating and reflowing the solder.
Note: You wouldn't normally solder tabs like this in practice. We have just done this for demonstration.
Even heating the large solder tabs for the heatsink on this traffic light power supply was an easy task thanks to the impressive thermal capacity. Whilst this is likely possible with a good quality traditional iron, this was a simple task and most importantly a quick process with this iron, and did not require the temperature to be increased. The combination of lower heat and faster soldering times means you are much less likely to damage the components.
The Thermaltronics TMT 9000s is an incredible iron that is perfectly suited for a high volume and fast-paced production environment where you need a very fast and powerful iron to perform manual through-hole PCB assembly. It has impeccably quick thermal recovery, combined with impressive thermal capacity, allowing the iron to rapidly perform heavy duty soldering tasks with ease.
The replacement tips cost about the same as our old traditional style iron and, for all intents and purposes, we would expect the lifespan to be similar. The handpiece is comfortable and lightweight allowing for long term use and iron is an absolute luxury to have on your lab bench. Of course, this luxury does come at a cost making this particular iron outside of the range for the average hobbyist, home user and or maker. With that said, Thermaltronics has a range of irons with the TMT2000s being closer to the budget of the home user and can be purchased from your local Jaycar.
- Incredible thermal capacity and recovery
- Will not overshoot temperature
- Reduces risk of damaged components
- Wide range of tips for through hole & SMT
- Optional desolder and tweezer options
- No Calibration required
- Large footprint (takes up room on a crowded lab bench)
- Relatively expensive compared to other leading brands
- Must change tip to change temperature
- Soldering Station TMT-9000S-2 RRP $585 Ex GST
See the complete range at: www.okay.com.au
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