Since there have been a bunch of questions on tip life, I thought it might be a good idea to talk about the things that will help extend the life of ALL your soldering iron tips. Most of these are common-sense soldering practices, but I thought it might be useful to some of the members of this group.
Most soldering iron tips are constructed in the following manner:- Internal Copper Core: The core of each tip is composed of copper, an excellent heat-transfer material. Unfortunately, solder has a solvent effect on copper and will rapidly dissolve it when exposed to various solder alloys (especially lead-free solder). So it must be protected by another layer of plating.
- Iron Plating: Iron plating is the protective layer electroplated over the surface of the tip, and the thicker the iron plating, the longer the life of the tip. But iron it is a terrible heat transfer medium, and if plated too much, the performance of the tip will be affected. Lead-free optimized tips are usually plated with 5-10 mils of iron plating, and any more iron plating will negatively affect heat transfer - tip will take forever to heat up or will not recover quick enough after soldering. All PACE tips are plated with 7-9 mils of iron.
- Chrome plating: a layer of non-solderable chrome plating is usually to the back portion of the tip, applied to prevent the solder from creeping too far up the tip.
- Tinning: The iron-plated working end of the tip is tinned with pure tin or solder alloy. This coating of solder protects the iron plating.
How does lead-free affect soldering? There is a higher tin content, higher melting points, tighter process window, decreased wetting, longer dwell times, duller solder joints – all these elements can affect tip life. It's been estimated that Tip life can be decreased by up to 2/3 when using lead-free!
Increased Tin Content + Higher Temperatures = Aggressive Corrosion: Lead-free solder is much more corrosive to iron-plating than standard 63/37 tin-lead alloy, especially at elevated temperatures. Higher Sn (tin) content, higher idling temperatures, greater rate of oxidation, and rapid flux degeneration all contribute to lower tip life. The most important thing to remember is the higher the tip temperature, the higher the likelihood of increased plating erosion due to iron leaching.
Oxidation is the enemy of your tip, so use low temperatures: Whether using lead-free or not, the higher the tip temperature, the more the working end of the tip will be oxidized. In practice, use the lowest possible temperature you can to do the job.
Use optimized tip geometries: You should select the
shortest and
thickest tip that will allow access to the workpiece for highest heat transfer & lowest temperatures. I realize many people prefer fine-point and necked down tips as they improve access to small components and joints. However, a fine-point conical tip severely limits your heat pathway and may force you to use higher temperatures. Copper is more evenly distributed in thicker tips – thus better heat transfer. Better heat flow = lower temperature soldering. Ultra-fine conical tips have a limited heat pathway, less copper at end of tip, heavy iron at end of tip and thus less thermal transfer.
Do not apply pressure or an abrasive scrubing motion: If you are heavy handed in your soldering, you may cause stress/cracking failures in the iron plating. You should use the same pressure as you would writing with a soft #2 pencil. Also, do not scrub the lead of a component as this can lead to a scratch in the iron plating, resulting in a pit which will start the rapid dissolution of copper, eating the core away within hours, and leading to a hollow & ruined tip!
Cover the working end of the tip with solder: this helps add a protective layer of solder (which again prevents oxidation) over the sensitive iron plating.
For leaded solder, use clean, damp sulfur-free sponges: I say
damp because a totally drenched sponge will drop the temperature of the tip too radically. Household sponges are also a no-no, as they contain sulfur, which will contaminate your tips! Also you might consider using distilled water as tap water contains additives & minerals that can damage a tip’s plating/reduce its life.
For Lead-Free solder, use Brass Wool: Lead-free solder uses some nastier fluxes which can be tough to remove using a standard sponge, so you may wish to use the “brass wool” cleaner (looks like a Brillo-Pad). It’s a little more abrasive, but in many cases necessary for proper cleaning of lead-free tips. If necessary, restore detinned tips with “Tip-Tinner” (that chemical you dip your tips in when all else fails) - yes, it's abrasive, but better than a detinned or dewetted tip that cannot be used..
Turn off the iron: When not in use, turn it off!
Use a soldering iron system with “Setback” or “Auto-Off” feature: As we’ve been discussing in this thread, use an iron that automatically “sets-back” the temperature to below solder melt (under 350°F/177°C). Setting the temperature below solder-melt is one of the best ways to eliminate oxidation of the tip, and thus extend tip life.
Do any of you have any other suggestions?
Aaron
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