What's better, a ceramic or a metallic heating element?

[Panacea]

Hi guys,

I'm willing to buy some el'cheapo soldering iron with sensing, that I can use with something like this, initially:

http://code.google.com/p/avr-pid-solder-station/

I've seen, however, two different types of heating elements broadly used (for these cheap things), each using different tips. The first, is the typical ceramic heating element, as seen in here:

http://static.tme.eu/katalog_pics/6/7/e/67e976e0cca81d3ba2da384130a7afa6/pensol%20sl20c-h.jpg

And which I seem to prefer over the usual hakko-alike soldering iron variants, due to being easier to change in a future.

The other type is this one:

http://static.tme.eu/katalog_pics/6/0/a/60a0cf80de49f23c4cff5741e5a4479d/pensol-sl10-ihn.jpg

It does also have thermocouple, but it's drilled at it's end, such that it can make use of these tips:

http://static.tme.eu/katalog_pics/0/d/9/0d99805518d1479a9b2c700f660a8598/sr-623.jpg

Can somebody tell me which would be better than the other, and why?

As I've got workshop, my original idea is to buy one whose heating element I can (hopefully) refit with nichrome wire the day it gets blown, but I'm acutally more concerned with reliability of operation (to the extent applicable to the soldering iron's temperature itself), consumption, and overall durability.

So far, the drawback I've read regarding the ceramic element, is that it can get broken if one puts some pressure on the tip.

By looking at the finish of these irons (metalic enclosure fitting the tip itself), I reckon it shouldn't break under normal circumstances, but can't really tell as I've never had one in my hands. 

Regards,

[saturation]

Hakko is a big proponent of ceramic heaters and uses it in most of their soldering irons.  Weller, OTAH, uses a lot of nichrome wire based as well as ceramic. 

Ceramic heats faster, evenly and recovers better than nichrome wire mainly because the whole element heats up as one entire element, and more evenly from the inside.  Nichrome wire are wound around a core, so it heats from the outside in and the heat distribution depends on the spacing of the wires. 

Hakko says:

 http://www.tequipment.net/Hakko455-16.html

But a lot depends on the quality of the ceramic element, thus many clones of Hakko stations often mention they can use genuine Hakko elements and tips, not just anyone else's. 

This Weller station is popular, and is a nichrome equivalent in terms of functionality, of the Hakko FX888.  However, I don't think there is a formal description of the Weller's recovery time, start up time and other fine features of stations.  However, both stations meet IPC standards.

http://www.tequipment.net/WellerWES51.html

This is the iron for it:

http://www.tequipment.net/WellerPES51.html

[SgtRock]

Greetings EEVBees:

--Dear Panacea:

--I highly recommend you spend a few more dollars and get a real Hakko, new or used. The used 936s have been disappearing from eBay. This is a testament to their quality. If you strike while the iron is hot you can still get a new Hakko 936-4, which is the digital model of the 936, at a very good price. I have tested some of the 936 clones, and I am not impressed with the fit, finish or the tolerances of the parts that make up the wands.

--If you plan on doing more that and "hour at at time soldering" buy one of the real brands, and not cloned junk. Get a Hakko, Weller, or something better.

"The telegraph is a kind of a very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Radio operates the same way, except there is no cat." Albert Einstein

Best Regards
Clear Ether

[IanB]

This is an interesting question, and I have no idea what the answer is!

From what I read, a nichrome wire heating element is usually bigger and heats up a larger "body" part of the iron, which in turn conducts heat to the tip. On the other hand, a ceramic heating element is typically smaller and heats up a smaller body of metal that is much closer to the tip.

Where this gets complicated is that there is a large body of metal acting as a capacitance between the heating element and the tip. If you consider changes in heat load (you touch the soldering tip to a heat drain like a big lump of copper) then more heat capacity in the iron is good--the tip temperature will drop more slowly. On the other hand, if you consider changes in temperature demand (the heater must react to a drop in temperature) then a less heat capacity in the iron is good since the heater can change the temperature faster.

On balance, I suspect these effects cancel out and it becomes six of one and half a dozen of the other. Since quality irons can use either ceramic elements or nichrome elements I suspect the difference is mostly marketing and very little physics.

If you are considering a PID controller for the temperature, then what you really need to consider is power of the heater. A heater with more power can create a greater rate of change of temperature and this will allow the PID controller to have faster tuning without saturating (controller saturation will turn your PID controller into an on/off controller).

Overall, it seems like you have an interesting experimental project in prospect. On the other hand you could just buy a Hakko FX-888 and enjoy soldering! (There is more to a quality iron than just temperature regulation.)

[Panacea]

Thanks guys,

So ceramic heating elements use other than nichrome inside?

I actually assumed both used nicrome wire, being ceramic used instead of metal due to it not being conductive while propagating heat in a "controlled" or focal manner.

For example, I've seen pictures of this ceramic resistors at work on the net, and they seem to heat at +/- 1 cm from it's end, such that what really is at the tip is the thermocouple.

That explains why the tips are that long and makes a lot of sense to me at both, the architectural and thermal-transfer point of views.

About spending money on a weller or better, that's what I should do indeed, but I haven't got funds for it, unfortunately.

I'm also with you, SgtRock, when you mention clones are gonna heat my hand on the long term, and the finish won't be as expected, but I can always use the original to turn a piece of baquelite, PTFE or other to have a proper handle until funds are present.

But in general, I prefer ceramic over metal or even the magnetic type of control used by wellers (which I haven't looked in depth, I must admit).

At least by now, it is important for me to be able to fix whatever happens to the soldering iron in a future, easily and at a low cost.

Regards,

[saturation]

Hakko tried both and ended up with ceramic.  Its not heated with a wire inside, those heaters are found in space heaters or traditional heaters like Calrod elements in stove tops.

http://en.wikipedia.org/wiki/Heating_element

Ceramic heating elements are made of a special material such as MoSi2 and heat up entirely like a resistive wire.

IMHO Hakko's ceramic based stations feel better in at least, providing heat faster than my older Weller, while making the pencil less hot, although I've never tried the Weller WES51 to know its just as good with nichrome 

[SiBurning]

Are you more concerned about the DIY side or getting a good iron for the money? For the DIY side, it might be cheaper to experiment with wire, assuming you have a low cost source of small quantities of wire of different composition and diameters. It'll definitely be easier fashioning an element from wire than from ceramics.

I'm just confused about the goals you mention in the OP. If you want a good iron, there's not much sense in comparing ceramic vs wire. Instead, you want to just compare the irons, and maybe look at cost of total cost of replacement parts over its life. While it's theoretically true that ceramic lasts longer but is subject to break under physical shock, it's hard to extrapolate that to how often you might need to replace a heating element when used for typical soldering. In other applications where there's more exposure and direct contact with materials--lighters and vaporizers--there are significant differences that have no little or relevance to soldering. Also, if you DIY the element, you might be willing & able to clean the film off the nichrome wire, extending its life--something I doubt any of us soldering-only folks are doing.

[alexwhittemore]

I have the digital version of that weller station (WESD51) and it works beautifully. It doesn't heat up instantly, but it's pretty fast - 15-20 seconds tops, even at relatively high temp settings. I think when it comes down to metallic vs ceramic, they have pretty similar characteristics. And I'd argue that it doesn't really matter how evenly the element heats up, since it's relatively far away from the tip you'll actually be using. Most who've used cheap firestarters know they tend to have hotter and colder spots on the tip, but that's much more a function of the tip construction than anything. Use really high quality tips and I bet you could even wind your own heater.

I think the only time you notice really different heating characteristics is when you're talking about a technology that's not resistive at all. Take Metcal stations, which use RF to dissipate power in the tip. Those things heat instantly and work flawlessly.

[saturation]

That's great to know.  Can you do us a favor?  With the iron fully at room temp, such as not used overnight, time in seconds how long it takes from cold at turn on until it reaches 350C.  This is a simple index of how fast it will respond to maintian temp during soldering.

For comparison a Hakko 936 takes ~ 40 sec.  A Metcal takes ~ 6 sec.


The WESD51 is better in that it never needs calibration.

I have the digital version of that weller station (WESD51) and it works beautifully. It doesn't heat up instantly, but it's pretty fast - 15-20 seconds tops, even at relatively high temp settings. I think when it comes down to metallic vs ceramic, they have pretty similar characteristics. And I'd argue that it doesn't really matter how evenly the element heats up, since it's relatively far away from the tip you'll actually be using. Most who've used cheap firestarters know they tend to have hotter and colder spots on the tip, but that's much more a function of the tip construction than anything. Use really high quality tips and I bet you could even wind your own heater.

I think the only time you notice really different heating characteristics is when you're talking about a technology that's not resistive at all. Take Metcal stations, which use RF to dissipate power in the tip. Those things heat instantly and work flawlessly.

[nukie]

Saturation - get some thin copper sheet from K&S metals, wrap it around the heating element, you can decrease 936 heating time to less than 20seconds. My room temperature is 25c. Don't wrap too thick, let room for expansion. My tip is  the smd 0.2mm so it might heat up faster than yours because it has less thermal mass. Are you using a big tip?

I have posted this info a few years ago in another forum I am going to re-post this. If you are thinking of buying a clone 936, then be prepared to spend as much as you can because there are many grades of clones out there. Top grade clones are so well made you won't be able to tell the difference. Most if not ALL clones don't have foam grip. Most of the grips are rubber/sticky types. I have never seen a clone with foam grip in China.

I'm sorry to tell you that the Hakko heating element in your clone station is also a fake. I have recently found out that they are making clone ceramic heating element for sometime already. It was not popular due to the cost, $3(clone) vs $4 (Hakko) at that time. With Japanese yen on the rise, it makes these ceramic clones popular today. Look closely at the silver printing on the clone ceramic, it is usually printed poorly, usually smudged. Genuine Hakko ceramic element has very sharp and high quality printing. I will take some picture for show when I am free. So far there are two clone manufacturers, probably more to come. I have no idea how they got the technology for manufacturing of these ceramic elements. Note $1 ceramic potted Nichrome heaters don't have printing on the sleeve, probably not worth the time and effort, that keeps the cost down.

These are some of the pictures I taken a few years ago regarding $1 Nichrome wire heating element potted in ceramic. These heating element flood the market. They work very well but they don't last very long because most of these are over-driven or maybe just crap build.

I also have a  few clone Nichrome wire heating element with metal sleeve. These are made in Taiwan and they are much higher quality, they work very well and they perform as good as Hakko ceramic element. Antex in the UK also make excellent and long lasting Nichrome wire heating element. I find these finely made. Finally there's this common nasty common wrap around Nichrome heating iron which clamps the tip with a screw. Hakko makes these Red series they are surprisingly long lasting, mine lasted for 15 years, rusty and nasty.

In the final picture is a genuine Hakko heating element. Notice the heating tracks through the translucent ceramic. It takes considerable amount of force to break the heating element. It is not as fragile/brittle as you think. From my misuse experience, I would say it is quite strong. Regarding the lifespan of a genuine ceramic element, the heating performance drops after many hours of operation, I haven't had a broken element yet.

If you are interested in Hakko ceramic heating element technology, have a look at the patent here
http://www.patentgenius.com/patent/6054678.html

[saturation]

Hi nukie,

I'm using the standard tip, and yes, if you use a smaller tip it will heat up faster so that's not a fair comparison.

The index I posted is the base Hakko 936 or FX888 station, and its really to compare the out of box station shipped by Hakko or Weller.  Its good to know though a small tweak can improve the heating capacity.

On the Hakko countefeits, yes, I am aware of the risks, so I buy direct from Hakko USA, the price differences from vendors is ~ nil since most items have 'free' shipping, with no minimum charge.

Those are great links!  I've always wanted to read the ceramic patent of theirs.

[alexwhittemore]

With the iron fully at room temp, such as not used overnight, time in seconds how long it takes from cold at turn on until it reaches 350C.  This is a simple index of how fast it will respond to maintian temp during soldering.

The WESD51, with the mid sized (2mm?) chisel tip I usually leave on, took 22 seconds to hit 350, then another 9 after that to get to my usual set temperature of 500.

[saturation]

Thanks Alex, is that Fahrenheit or Celsius?  Since the WES51 doesn't go to 500^oC, I presume that's F.

FYI 500^oC = 932^oF which is over the Weller's max temp.  500^oF is 260^oC and that's about the same speed as the Hakko 936, 20 sec to 250^oC then 40 sec to 350^oC.

With the iron fully at room temp, such as not used overnight, time in seconds how long it takes from cold at turn on until it reaches 350C.  This is a simple index of how fast it will respond to maintain temp during soldering.

The WESD51, with the mid sized (2mm?) chisel tip I usually leave on, took 22 seconds to hit 350, then another 9 after that to get to my usual set temperature of 500.

[alexwhittemore]

Sorry about that, right you are. I didn't even notice your C. my two temps are in F.

[Vancata]

Just bumping this old Topic to ask if anyone have any impressions from SL20C Solomon soldering station:
http://static1.tme.eu/katalog_pics/d/3/5/d35f0f05b04e5c6d576a964b44482f46/pensol%20sl20c.jpg

Just found that I can buy it for like 70 Euros here (like 95$ US) from a local supplier. Watched few Russians review in youtube, not really deep one but the unit looks kinda decent one with ceramic heating element and simple controlling unit. Hakko is not an option here, because for new one it will cost me like 200$ here, and the 2nd hand market is pretty small, so no chance there either.

[paul8f]

Sorry to resurrect this old thread, but I have a question regarding power ratings of ceramic elements.

I bought a 2nd hand appliance, and it looks like the previous owner has swapped out the OEM nichrome ignition element (left in photo), with a hollow ceramic type (pictured on the right). The original element was rated 425 watt, but unfortunately there is no power rating visible on the new ceramic one. (I did hook it up through a power-meter and it looks to only use about 220 watt).

So, my question is why is there such a difference in power ratings between the two types of element. (I wonder if it's to do with the shape, or maybe the ceramic one is slowly dying??  )

[NiHaoMike]

The ceramic heater has a PTC characteristic (much more so than nichrome) so it will reduce its power usage when warmed up. That would mean less cycling of the thermostat and better thermal regulation.

On a side note, that means ceramic heaters cannot be treated as simple resistors for the purpose of calculating power draw vs voltage.

[paul8f]

When I had the ceramic element plugged in through the power-meter, I didn't find there was any significant drop in power as it warmed up. I did notice that the element didn't glow uniformly (i.e. some areas were duller or brighter than others). Don't suppose you know if this is normal as a ceramic element ages?