RoadTest: METCAL GT120-HP-T6 Soldering Station
Author: hlipka
Creation date:
Evaluation Type: Workshop Tools
Did you receive all parts the manufacturer stated would be included in the package?: True
What other parts do you consider comparable to this product?: I compared this to the Ersa Icon Pico
What were the biggest problems encountered?: No EU power plug was provided :)
Detailed Review:
First I would like to thank both Metcal and Element14 for making this road test possible. Working with good tools is always a joy, and this review was no exception.
When I applied for the road test my stated intention was to compare the GT120 with my Ersa i-Con pico (which I got, several years ago, from the budget of an Element14 design competition - so another thanks to E14 for making this review possible :) While the nominal power of both would be different, in its data sheet the i-Con pico is specified with up to 140W power, so I figured they should be quite comparable to each other. The main difference then is that the Metcal stations are ESD-safe, whereas the pico is not (only its bigger sister, the i-Con nano, is). When Metcal and E14 looked at the application, this idea was obviously liked, but someone thought that the GT90 might be a better match, so I will throw both the i-Con pico and the GT90 into the ring and see what happens.
In terms of prices the GT90 and i-Con nano are mostly on par - Farnell list the Metcal with 250 EUR and the Ersa with 240. The i-Con pico is a bit cheaper, with around 210 EUR, but then its not ESD-safe. Note that the prices especially for the Metcal stations can vary quite a bit - I have seen the GT90 also for around 450 EUR which would make quite difference in your buying decision.
When I received the package from Element14 I was surprised at how big it was. Every single part of the station was packaged separately, and the packaging was first class. This station will not get damaged during transport, that's for sure!
| {gallery}GT90 package contents |
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Package contents: whats in the box |
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Package contents: after unpacking everything |
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Solder tips: solder tip assortment |
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Hand piece: the hand piece needs assembling |
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hand piece: assembled hand piece |
So lets have a look at how the Metcal GT90 looks, feels and is to be used:
Directly after unboxing I realized that the GT90 will not fit into the same spot where the i-Con pico lives on my bench - its just too high for that. That's not its fault, when I built the shelves on top of my bench the lowest one was places at exactly the correct location so I can put the soldering station on top of the hot-air station. Who would have guessed that another 2cm higher would have been a good idea? But when bench real estate is limited such things might be a decision factor for you.
In term of usage, I do not really like the display, and the way temperature gets changed. While the display itself is quite large, the temperature shown is rather small. The digits are not really crisp, but somewhat washed out (which is especially noticeable when its changing fast). This gives it a cheap look. Also, one needs to be careful when changing temperatures - after about 20° of change the rate of change get really fast. I can guarantee that you will overshot your target. Since there is also no separate showing of the set temperature you need to be careful which temperature is currently shown.
For the latter annoyances I resolved to use just three preset temperatures. They can be changed easily, and only in that mode the set temperature is shown. As for the display - fortunately you don't need to look at it all the time, so its not a big deal.
Apart from that the GT90 feels really sturdy and well-made. Its metal case makes it robust, and will probably survive a drop from the bench (and I would not put the same trust in the plastic case of the i-Con pico!). The stand is similar, it feels robust and will not come up with surprises. I will probably replace the sponge with a brass wool sponge, I don't really like the one hidden behind that rubbery opening (although I totally get why its there).
So I promised a comparison with the Ersa i-Con pico. (and, since they only differ by the ground connection of the tip, the Ersa i-Con nano as well).
For soldering, we usually talk about thermal performance, and for that the power the soldering station can put into the tip is quite a big factor. The i-Con pico is rated officially as '80W soldering station', but depending on where you look a power between 68W and 140W gets claimed (with the latter being the peak draw it for rating its power outlet). The GT90 is, obviously, and 90W station, but the base station says '30W nominal, 90W max'.
So the first thing was to put both stations on a power meter to see what they really do.
First, in standby mode the Metcal draw 0.1W (because the power brick is connected always, you only turn on the base station), and the Ersa is completely shut off. When you turn them on, they heat up to their set temperature (which is usually 315°C for me), the GT90 draw around 52W and the i-Con pico around 75W. So its not a surprise that the pico reaches the target temperature about 5 seconds earlier. When just keeping their temperature they both use about 10W (but the pico has some spikes to 20W now and then). To test peak power draw, I then used a old CPU cooler heat sink (which I think was rated for sinking more than 100W of CPU power consumption) and tried to heat it up. The GT90 stayed between 40W and 50W, whereas the i-Con peaked again to 75W for several seconds and then stayed at around 45W. I will come back to this test later, but it can be seen that both stations run at about the same power level (and neither seems to reach its claimed peak power usage).
After these tests, I placed them both next to each other for a more detailed comparison of how they look and feel:
I already mentioned that the Ersa i-Con stations need less space on the bench (and the external brick makes the Metcal station need even more). But its also the stand which needs more space for the GT90. OTOH, the stand for the i-Con pico feels more flimsy, and I managed to topple it over multiple times now. So I guess its mostly a draw here, and I guess one gets used to the peculiarities of each (I need to see how much I'm annoyed by needing to look where to place the hand piece for the Metcal stand).
To get a better feeling for the difference between both, here are some measurements:
| Metcal GT90 | i-Con Pico | |
| Weight station | 970g (the PSU weights another 540g) | 1370g |
| Weight stand | 365g | 175g |
| Weight hand-piece | 44g | 28g |
| Cable length for the hand-piece | 140cm | 115cm |
| Height station | 16cm | 11cm |
| Depth station | 16,5cm (this includes the connector at the back) | 14,5 (cables come out at the bottom, so they add not to the depth) |
| Width station | 11cm | 8.5cm |
The stands are both of roughly the same size (at least with the hand-piece placed in them), so I did not include the measurements here. I should notice that the longer cable for the hand-piece that the GT90 has is not an issue. I actually like it more since it provides some more flexibility in placing the station since you have more lee-way. Also, the softer cable can be put wherever its not in the way (the one for the -Icon pico has a tendency to come to rest in the wrong spot).
Even though the GT90 hand-piece is significantly heavier then the ersa i-Tool, I did not encounter this to be a problem - I did not even notice the difference until placing them on a scale (and calling 44g 'heavy' is quite an exaggeration).
Looks and feels might be nice, but the real truth is where the solder hits the PCB. So lets have a look how these station perform at what they are designed for.
First, I took a PCB kit which I had around for a while now, and soldered most of the components (all through-hole) in. I switched between the GT90 and the i-Con pico for each type of component so I had a good feeling for how they compare. The GT90 uses a 1.8mm chisel tip, and the i-Con pico a 1.6mm chisel tip (unfortunately there is no common size between the two stations). Here we go:
From my experience I would rate them both equivalent. Most of the pads where I struggled to solder properly on the first try where because I did not find the best angle for the soldering iron - normally you will not populate so many part right at the start. The slightly larger tip of the GT90 can be a nuisance in crowed places, but I did not encounter that. The tip for the Ersa i-Con is now several years old and has seen quite a lot of use, which is something I cannot judge for the GT90 (but since both should be high quality I do not expect any bigger problems here).
For SMD soldering I tested only the GT90, but I switched between different tips this time. As mentioned in the video already its quite a hassle to switch tips in the i-Con stations (as long as you don't invest in a separate cage and nut for each tip) I'm using only the 1.6mm chisel tip for all soldering. This has proved to be a working solution so far, but since changing tips on the Metcal was so simple and fast I think I would be much more inclined to always use the proper tip for the task at hand. So I used a small SMD board, soldered one half with the 1.8mm chisel tip, and the other one with a 1.0mm chisel tip:
What a difference. Using the smaller tip worked so much better, especially when doing the SOIC part. This might really be a deal breaker, especially when switch often between SMD and PTH, or between larger and smaller parts. Maybe I will also invest in some even finer chisel tips and check how they work out for parts with a finer pin pitch. But even that 1.0mm tip felt really nice to work with.
One thing I realized after I finished this board: the GT90 never went into sleep mode even though it should (the standby timer is at 120 seconds by default). Just me working on the board, had having the hand-piece in its stand next to it was enough to prevent it from going to sleep. Depending on your needs this might be good or bad: its nice that it stays awake so its ready when you need it. OTOH it makes me a bit uncomfortable that it might wake up when you don't want it (I manage to forget to turn off the station about once a year after being done with my work, and until now it was comfort when coming after an hour to see it sitting idle at just 50°C),
Since soldering is (apart from tip size) about getting the right amount of heat into the solder joint, we also need to talk about thermal performance. This mostly means how good, and fast, the solder iron can heat up parts, and how well it keep temperature. For that I came up with two test scenarios (which then evolved into three):
So I pulled out an Arduino, added two MAX31855 thermocouple amplifiers for two measurement points, and wrote a small sketch to log temperatures (with four measurements per second to get an accurate picture).
For the first test, I fixed one of the thermocouples to the tip, using some kapton tape. Then I started my logging program and turned on the soldering station. First problem: as soon as the thermocouple touched the GT90 tip, the program did just not read any temperature. It turns out that since the tip of the GT90 is grounded (via protective earth), and the Arduino is also grounded (via its USB cable to the PC), the thermocouple input gets essentially shorted to ground so the sensor cannot read anything. Since the only USB isolator I had at hand had the wrong USB connector (Mini USB-B instead of standard USB-B) I ended up using a laptop for doing the logging.
These first results gave a nice curve, but the maximum temperature I measured was around 260°C for both stations. This was a bits suspect, and manual verification showed that the tips in fact reach more than 300°C, as they should. So using kapton tape to fix the TC to the soldering iron did not provide good enough contact to properly measure the tip temperature. So I ended up using tweezers to clamp the thermocouple to the tips (fortunately my Engineer PTZ-51 tweezers come with ceramic tips, this is much appreciated for such tasks).
And this is how the results look like:
The orange vertical bar is when the i-Con pico claimed to have reached 315°C (15 seconds after turning on), the blue one is when the GT90 does so (20 seconds).
One part of why the GT90 is slower is that it just starts two seconds later with actually heating up. The other reason is, as mentioned above, that the i-Con pico just uses more more to heat up - it draw 75W here instead of 52W as the GT90.
Its also interesting to see that the i-Con pico is more or less correct in the temperature it show, it has some slight overshoot (somewhere between 5° and 10 °) after reaching its temperature but is stable quite fast. The GT90 too claims some overshot on its display (albeit only 4° or so), but in reality it doesn't, but the tip takes longer to reach its final temperature.
(Note: I will attach the spreadsheets with the raw data. When measuring the GT90 it seems it did not make as good contact from the thermocouple to the tip, so I added a correction factor. This is based on the temperature difference between the displayed value when reaching 315°C and the actual measured value).
I guess the pico is the winner here - it heats up considerably faster, and its ready to work when it claims to be. On the other hand, the GT90 is not that far behind, so its mostly a matter of convenience.
For the second test, I fixed the second thermocouple to the CPU heat sink, again using kapton tape. Exact measurements where not as important this time, since I was more interested in comparing the two soldering stations, so the measurements just need to be repeatable.
The only problem is that I now need to measure the temperature of the tip (to check how much it drops) I need to place the thermocouple manually on the tip, and keep it there for a minute. This took several tries, and I selected the one which was the most stable.
| {gallery:width=1200,height=450}Heating up a large heat sink |
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GT90: heating up large heat sink |
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IMAGE TITLE: THEN IMAGE DESCRIPTION |
Both graphs show the temperature of the tip as well as of the heat sink (about 5mm away from the tip). First some notes: there are some gaps in tip temperature curve - there the sensor failed to report data. I also did no keep this sensor all the time at the tip, but instead fed some more solder to the tip to get better heat transfer (that's when the tip temperature drops in the graph to 50°C).
What can be seen is how much both stations struggle to keep the temperature at level - when they dropper down to around 150° the solder did not melt anymore. It seems the heat transfer was better for the i-Con pico (there was an ever larger initial temperature drop, and the copper block did heat up faster). But we can also see that it struggled more at the end to keep this heat transfer stable. It seems the heat sink is coated in a special way - I would have expected the solder to stick to it, which it didn't. When the GT90 tip finally made better contact (around second 25) it started to work better.
Since both stations only managed to raise the temperature by about 15K in one minute, I decided to use a variation of that test. From where I had that CPU heat sink I managed to also get a heat sink used for PC chipsets. While its still way bigger than the components I usually solder (the largest so far have been some DPAK voltage regulators) it looked like being the right size to get representative numbers. So I attached the second TC again:
and repeated the tests. And sure enough, we got over 80°C his time in just one minute. And since this looked promising, I again changed tips on the GT90, and repeated the test with three different tips: the 1.0mm chisel I used for SMD soldering, a 2.5mm chisel in standard length and a 2.5mm chisel tip in shorter length (what Metcal calls 'power version'). The expectation here was that larger tips are better at transferring heat, and that the 'power tip' has better heat regulation (so it should drop less in temperature). Here are the results:
So that was interesting: the standard 2.5mm tip is not really better than the 1.8mm tip, where it should provide better heat transfer. But the power tip really shined - it ended up more than 20K hotter than its standard sibling. So this seems to be the go-to version for any complicated de-soldering jobs.
All in all the i-Con pico and the GT90, using comparable tips, also perform comparably. To me the smaller tip of the pico explains its heat transfer being a bit worse. Especially since this difference is larger at the beginning and the pico catches up the longer it heats up that heat sink. Probably its real power is just a bit higher that that of the GT90. Should I do more in-depth tests to find out?
More importantly: should you use it as your new soldering station?
Halfway into the test I would have answered 'maybe' for myself. But while writing this final paragraph, I already have re-organized my workbench to have a proper place for the GT90. The i-Con pico is still there, but mostly to do some final comparisons. I got used to selecting one of the preset temperatures (instead of dialing in the temperature directly), and I use a separate brass sponge for cleaning the tip. Being able to change the tip so easily was the final killer feature - basically it means you get the best performance for the task at hand.
Is it a station for you? I think you cannot go wrong with it - its performance is on par with the i-Con pico. It has some advantages, and some dis-advantages, and some quirks too - but whether the influence your decision in one direction or the other depends on your needs, and your circumstances. When bench space is at premium, maybe the pico is the better choice. When you switch between different tasks quite often, being able to change the tip in 30 seconds might be more important.
