How does the Metcal base unit convert RF energy into heat at the iron tip?

[exequor]

Does anyone know an online store that sells ECE tools for soldering/desoldering and other electronic components?... other than RadioShack.

 

[berkeman]

Try www.jameco.com

For higher-end soldering tools, check out www.metcal.com[/URL]

The Metcal irons are awesome. They use RF heating of the tip, so they warm up in less than 10 seconds, and they keep the tip temperature solid, whether you're soldering a TSSOP SMT package (tiny leads) or big 16AWG wires onto lugs. They're expensive, but worth it if you do a lot of soldering, especially SMT.

 

[faust9]

I can't second enough how gret metcal irons are. Pick one up on e-bay if you can. Get a lot of tips too. I bake a lot of my smt now but before I set up and oven I used my metcal with great results. Also, the old metcal still sees a lot of use for rework and through-hole soldering(I need a wave!)

If you don't want to shell out the money for a metcal then the next best thing is a digital pace station. 1/10 the price; however, not as good---good enough for government work literally. I'd discourage getting no-name soldering equipment BTW adn stick with eutectic solder. 60/40 'wrinkles' as it cools. 63/37 transitions from a liquid to a sold with no intermediate two phase region like 60/40, so the resulting solder joint is stronger. One thing about the Pace stations though is you can get a solder/desolder station all in one. The desolder station is good for removing large amounts of solder at once; however, I find solder-wic to be the best for small jobs(like removing solder bridges from a TQFP).

I don't know where you are, but most big cities have at least one good electronics shop. I've lived in a lot of cities and have always had access to at least one shop.

Other places to look for electronic stuff:

mouser
Newark
Allied
Digi-key

Well, good luck setting up your station.

 

[Manchot]

I can't stand shopping at RadioShack for components. "Hey everyone, let's pay a dollar for a 1 kOhm resistor!" I guess that's the price you pay for convenience.

 

[faust9]

I can't stand shopping at RadioShack for components. "Hey everyone, let's pay a dollar for a 1 kOhm resistor!" I guess that's the price you pay for convenience.

Why complain you do get 4 or 5 resistors for that dollar

 

[Ouabache]

Try www.jameco.com

For higher-end soldering tools, check out www.metcal.com

The Metcal irons are awesome. They use RF heating of the tip, so they warm up in less than 10 seconds, and they keep the tip temperature solid, whether you're soldering a TSSOP SMT package (tiny leads) or big 16AWG wires onto lugs. They're expensive, but worth it if you do a lot of soldering, especially SMT.

I do appreciate the advantage of low temperature soldering. I am curious about this thermal heating with RF. Do you know at what frequency or power level, their RF is generated?

 

[berkeman]

I do appreciate the advantage of low temperature soldering. I am curious about this thermal heating with RF. Do you know at what frequency or power level, their RF is generated?

I started at Metcal.com and found that they call their technology SmartHeat. Then a quick Google search got me here to this interesting page:

http://www.ascentconcepts.com/metcal-ps2e.htm

This system uses the Metcal SmartHeat technology. Which utilizes Skin Effect of a 13Mhz RF signal from a constant current power supply. This means the heat is generated on the surface of the tip delivering tremendous power when need at amazing accuracy. This design also means there is no internal thermo couple of heating element to fail as in other brands. Since this design uses skin effect in the tip cartridge to Generate the heat the physics of the system achieve a +/- 1.1 degree temperature stability and there is no calibration required. Tip cartridges swap easily without the use of tools.

 

[Ouabache]

Thanks for the reference. So I wonder how much RF power is a user exposed to (at 13MHz), each time the trigger is depressed? ANSI and IEEE set some maximum safety limits for SAR (specific absorption rate) of 0.08 W/kg for whole body exposure and 1.6 W/kg for exposure of limbs in that frequency range.

Ouabache
"I do appreciate the advantage of low temperature soldering. I am curious about this thermal heating with RF. Do you know at what frequency or power level, their RF is generated?"

berkeman
"I started at Metcal.com and found that they call their technology SmartHeat. Then a quick Google search got me here to this interesting page:

http://www.ascentconcepts.com/metcal-ps2e.htm "

Metcal Quote:
"This system uses the Metcal SmartHeat technology. Which utilizes Skin Effect of a 13Mhz RF signal from a constant current power supply. This means the heat is generated on the surface of the tip delivering tremendous power when need at amazing accuracy. This design also means there is no internal thermo couple of heating element to fail as in other brands. Since this design uses skin effect in the tip cartridge to Generate the heat the physics of the system achieve a +/- 1.1 degree temperature stability and there is no calibration required. Tip cartridges swap easily without the use of tools."

 

[berkeman]

Thanks for the reference. So I wonder how much RF power is a user exposed to (at 13MHz), each time the trigger is depressed? ANSI and IEEE set some maximum safety limits for SAR (specific absorption rate) of 0.08 W/kg for whole body exposure and 1.6 W/kg for exposure of limbs in that frequency range.

The Metcal base unit drives the RF energy down a flexible coax to the coaxial tip. The only RF energy outside of the system would be leakage. The exposure standing in front of a 2.4GHz microwave oven cooking dinner is probably several orders of magnitude worse.

 

[Ouabache]

The Metcal base unit drives the RF energy down a flexible coax to the coaxial tip. The only RF energy outside of the system would be leakage. The exposure standing in front of a 2.4GHz microwave oven cooking dinner is probably several orders of magnitude worse.

This is fascinating technology, I would like to understand the design aspects. Let's see if I understand so far; the base unit transmits a 13MHz signal down the coax, concentrating its energy along the surface of the center conductor (skin effect), to the load (iron tip). By that description, it sounds like the iron behaves as a poorly tuned antenna. Instead of the RF radiating into space, it is converted to heat at the iron tip, and lots of signal reflected back to the source. This is a possible explanation for generating heat. If this were the case, how might they shield that much reflected RF. I wonder if there is something else going on.

If you are familiar with non-resonant antennas (and for the benefit of our readership) any conductive load can behave as an antenna, even a trashcan, a stop sign, or the chassis of a car. With proper matching, you can even transmit and receive RF signals on these bizarre antennae.

The microwave oven analogy is interesting. I understand a fair amount of design consideration has gone into RF shielding.

Side note:
As a microwave oven ages, the seals decay and as a safety precaution, should be tested for RF leakage. At 2.4GHz frequency, RF induces heating of water not only in food, but in our body if we are too close (eyes, head).