Architecture of a Soldering Tip
You have been using the basic soldering tip for years. But do you know how that tip is constructed, and why? We're
here to answer your questions.
The soldering tip is made up of a copper core, an iron layer, a chromium layer, the wettable area, and lead-free tinning. Each component of the architecture has it's own unique purpose and function.
Copper Core
The base material is comprised of machined copper. Why copper? First, copper is malleable, so it can be machined into a variety of shapes and sizes. Second, it is an excellent conductor of heat, which is of course a necessity.
Iron Layer
Although copper is an excellent conductor of heat, it is very susceptible to the corrosive qualities of tin, the main ingredient in solder. That's where the iron layer comes in. It provides protection to the copper core against the corrosive qualities of tin. So why not just make the tip out of solid iron and forget about the copper altogether? Because iron is not a good conductor of heat. For that reason, the thickness of the iron layer must be "optimized". Too little iron, and the tip will not last very long. Too much iron, and the tip will not conduct heat adequately.
Chromium Layer
Next, a thin layer of chromium is plated over the iron layer. Chromium is not "wettable", meaning molten solder will not adhere to it. So the wettable area of the tip, or the working end, is not chromium plated. This wettable area is masked during the chromium plating process. The chromium covers the non-wettable area of the tip to prevent solder from creeping to the back end of the tip.
Wettable Area
This is the front end of the tip, the business end. This area is not plated with chromium, so that the solder wets to the end. This part of the tip is responsible for the heat transfer.
Tinning (with lead-free solder)
Tin is the thin coating of solder that adheres to the working area. The reason for tinning is to produce an intermetallic bond between the iron layer and the solder alloy. When this intermetallic bond is created, the tip is tinned and remains wettable. The tip should be tinned at all times to prevent oxidation and subsequent blackening of the tip. A tip that is not tinned is exposed to oxygen, which will oxidize the tip, rendering it as "unwettable". An oxidized tip can often be rehabilitated with the use of a tip polishing bar and/or tip activator.
You can use a polishing bar that will clean it up nicely for you! (Comment this)
Thank you in advance for any help. Please e-mail your advice to wojtekskulski at yahoo dot com (sorry for the obfuscation of my e-mail, I am afraid of spam). (Comment this)
If you need a hard metal coating for your traces, you can try electoless or bright nickel. This is also difficult to solder, but not as difficult as chromium. There are several water soluable fluxes from Kester that will work with nickel.
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