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Soldering Iron Strain Sensor

Automatic temperature adjustment
  [vote for,

If you take good care of it, the tip of a soldering iron should last for a very long time, but even so most manufacturers consider the tip to be a consumable. Anyone who has used a shared workshop will know the frustration of trying to solder with an iron so encrusted with oxide that instead of wetting it, the solder blobs away on its own.

The thing that really knackers the tips is setting the iron to the maximum temperature and then not soldering with it. Perhaps the user went to get some lunch, or worse, left the iron on overnight. Without a regular re-coating of solder and flux, the oxides on the tip accumulate and harden into an impenetrable solder-phobic layer. It's usually possible to clean this off, but often it's easier to just buy a replacement tip.

I own a fairly modern soldering iron which has an accelerometer in it. When there's been no movement for more than a few minutes it drops the temperature, and eventually switches off. This goes a long way to fixing the main problem, but it's not perfect. There are times when you really need to deliver a lot of heat, and the only way to do it is to turn up to 450C, and staying at that temperature for even a minute of inactivity starts to blacken the tip. One solution is to have a "boost" button, which ups the temperature for a short period when pressed, but this can be inconvenient if you're holding multiple things in your hands, as is often the case when soldering.

Proposed is a strain sensor between the handle and the iron itself. When you're trying to deliver heat to something, you need to press the iron quite firmly against it anyway. With a strain sensor the target temperature could be set in proportion to the amount of force applied. Sensible limits could be set so that most soldering is the same as it's always been, but when a part is sucking away too much heat from the join, simply pressing harder will fix the problem.

mitxela, Apr 06 2019


       We used to just dip the hot tip in hydrochloric acid* for a second or two. Cleans the crap off very quickly.   

       *Probably not permitted, under workshop OHS regulations, nowadays.
UnaBubba, Apr 06 2019

       Why is not possible for humanity to contrive a soldering tip that doesn't oxidise? I appreciate that it has to be solder- wettable and must conduct heat well, but there must be alloys that meet those requirements and don't oxidise.
MaxwellBuchanan, Apr 06 2019

       This is going to worry me all night.
xenzag, Apr 06 2019

       "Stuff the rainforests, and the ozone layer, and whales and global warming and orangutans and microplastics and nuclear waste and tetrachlorodibenzyl-p-dioxin ... tonight I'm going to fret about soldering ..."   

       Nice one, Centurion. Donald would be so pleased, if he knew.   

       // a soldering tip that doesn't oxidise? //   

       Just work in an inert gas atmosphere. Argon is good as it's a very poor thermal conductor and helps keep the tip hot.
8th of 7, Apr 06 2019

       So, according to the internet, soldering iron tips are copper (for heat transfer) coated with a thin layer of iron (which can be wetted with solder but isn't attacked by it). All but the tip is then plated with nickel and chrome to prevent solder wicking up the bit.   

       So the problem is oxidation of the exposed iron at the very tip. Would stainless steel not be solder-wettable? Or some other corrosion-resistant alloy?
MaxwellBuchanan, Apr 06 2019

       I think the stress of not hot enough, not enough hands and not in the the right position is enough without a display saying too much 'frustration' force is being used.   

       Just make the tip constantly transfer the right temperature.
wjt, Apr 07 2019

       So have it somehow sense the (presence and) temperature of the work instead of the temperature of the inside of the tip (or, on cheap stations, the temperature of the back end of the heating element)?
notexactly, Apr 08 2019

       Surely a solid gold soldering iron tip would meet the criteria of conducting heat and resisting oxidation?
hippo, Apr 08 2019

       Yes, but I think it would also dissolve in the solder.
MaxwellBuchanan, Apr 08 2019

       //Would stainless steel not be solder-wettable? Or some other corrosion-resistant alloy?//   

       Stainless steel is largely the way it is because of a thin oxide layer. Fluxes are designed specifically to quickly remove these, usually with HCl derived from NH4Cl decomposing to NH3 and HCl. So stainless would just behave like contaminated iron.   

       //solid gold soldering iron tip would meet the criteria//   

       Maybe, physically weak and if not locked away can evaporate completely if left unattended.
bs0u0155, Apr 08 2019

       //So stainless would just behave like contaminated iron// Do you mean "so it would work as a soldering iron tip and not suffer from corrosion" or "it would work as a soldering iron tip, but would corrode like a normal iron one" ?
MaxwellBuchanan, Apr 08 2019

       What about Plutonium ? Some isotopes are autothermogenic, no need for a power supply ...
8th of 7, Apr 08 2019

       //Do you mean "so it would work as a soldering iron tip and not suffer from corrosion"//   

       It would behave like a pre-contaminated tip. Iron can exist in a reduced relatively pure state, solder and flux can really prevent oxidation forming quite effectively. Stainless steel is guaranteed to have an oxidized chromium layer under most conditions and the flux would have to burn through that every time.
bs0u0155, Apr 08 2019

       I've been thinking about this, and I'm not convinced the material choice makes a difference. My theory of tip degradation is as follows:   

       - Solder wets the surface, which means it's in molecular contact with the tip material.   

       - Once tinned, even after wiping it clean, there will be a thin layer of solder on the tip.   

       - As that thin layer of solder oxidises, it expands slightly, but it's thin enough that instead of flaking away, it clamps onto the surface and maintains close contact with it.   

       - If, instead of using acid, you mechanically clean the tip, it leaves tiny scratches that give more surface area for the oxide to grip onto.   

       There is definitely a difference between cheap and expensive soldering iron tips, but I don't know if that's to do with the thickness of the coating (perhaps a thicker coating is less likely to get damaged). By my logic, the best tip would be polished to a mirror finish to reduce the surface area for oxide to stick to.
mitxela, Apr 10 2019

       [notexactly] Use that spare hand to aim an infrared test at the work and feed data back to iron. How many hands is that now for such a small volume of work?
wjt, Apr 10 2019


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