Click to view our Accessibility Statement or contact us with accessibility-related questions
Showing 1 of 51 conversations about:
ming.geekhackers.org
62
Nov 2, 2014
bookmark_border
I've already said most of my piece about Aoyue above. Soldering irons are extremely hot sticks and broken soldering irons can be extremely dangerous. Many manufacturers of said hot sticks cut corners that should not be cut, maybe because they are in a situation in which they know they are immune to liability, or because they want to win a given manufacturing contract above wanting to manufacture quality product. I really don't care. When working with dangerous temperatures, chemicals, pressures, etc. I don't believe in cutting corners that sacrifice safety.
But anyway, there is an interesting and fun scientific point to be made regarding that 469 product.
POWER VS TEMPERATURE
Power is a unit of _work_ in the physical sense. Temperature is a _property of matter_, again, in the physical sense. Power can do work such as raising the temperature of something. Power is also necessary to lower the temperature of something. Power is measured in Watts, also known as Joules per second. A Joule is a unit of energy. Hence, power is energy expended over time.
On the other hand, think of temperature as the "disorderliness" of matter. The higher the temperature of a compound, the more the little atomic bits of the compound are actively moving around. If they move around _too_ fast, you can get into trouble, but metals can typically tolerate very very high temperatures (think 1200C) before they start causing trouble. This is not true for the chemicals that we call "flux", but let's ignore that for now.
HENCE, we expend energy over time, with our soldering irons, to raise the temperature of metal soldering alloys. The more energy we use per unit time, the more quickly the things we use the energy on will get hot. Cool!
However, there's an important corollary here. Variable _power_ tools are not the same as variable _temperature_ tools, and fixed power tools are not the same as fixed temperature tools. Further, when soldering, what is important is _temperature_, not power.
Why? Matter changes phase (solid to liquid, liquid to gas) at temperature boundaries. 63/37 tin to lead ratio soldering alloy changes from solid to liquid at 287C. Note that we have made no statement about the amount of power required. However, all else equal, more energy per unit time will raise the temperature of the soldering alloy faster. However, it will also raise the temperature of all the things that are thermally connected to the soldering alloy faster as well.
One of the most common discouraging mistakes that I typically see in people who are dipping their feet into soldering is accidental burning of components or circuit boards or skin (and more power turned a 1st degree burn into a 3rd degree burn ever so quickly..). Less power makes it harder to burn components. However, we still need to reach the melting point of the solder, so there is a balance between power and temperature.
This is thephysical principal that guided my choice of soldering irons. The Edsyn CL1481 iron is rated at 30W, that is, 30 Joules of energy per second. However, the heater that expends this energy into the joint self-regulates such that the temperature of the tip stays constant at ~370C.
Hence, if I hold the CL1481 iron to a joint a period of time that is not arbitrarily long, the iron will expend enough energy to bring the joint up to 370C (which we call equilibrium), and then the rate of temperature increase will actually plateau.
The upshot of this is that the designer of this iron, who is not me, but who was quite brilliant, designed an iron that will bring soldering joints up to processing temperature, but not much higher, making burning of components very difficult.
With both variable temperature and especially variable power irons, especially with poor quality control and components of dubious origin, the property above is extremely hard to achieve.
Nov 2, 2014
View Full Discussion