Ha and I just saw that @rich responded around the same time I did. Thanks! Looks like we have similar-ish answers
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Enormously. The problem we are fighting is oxidation and other chemical effects. All chemical processes are accelerated by heat. Dropping the temperature dramatically reducing the reaction.
Rich
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@rich and @ChrisGammell Thank you both so much!
I thought I may be overthinking this.
A couple of things that I should have probably stated from the beginning:
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I am using a Hakko FX-888d with a 2.4mm chisel tip (T18-D24 I believe, although I have the T18-D type tips in all possible sizes except 3mm and 3.2mm), lead free SN100C solder (not the original, but one by Balver Zinn, I don’t remember on top of my head their particular model number, I believe something like LN5357NC) in 0.3mm thickness with flux core (I believe 2.2% but don’t remember the type of flux) and I solder at 350C, I believe the tips are genuine.
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My tip and brass sponges are new (have been used a couple of times so far
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I seem to be getting good joints and no weird behavior from the tip or the solder joints, except 1 thing:
Sometimes touching the solder to the pad after holding the tip to the pad and component leg/lead for about a second, the solder doesn’t start instantly (but i believe i may have not touched the component lead with it as well, not sure, need to get a magnifying glass or something) and i either have to touch the solder to the tip to get it started or wait about a second and a half loger. Although I have been soldering eBay practice boards with questionable quality and who knows what kind of plating.
Is this normal?
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My tip tinning paste is again by Hakko, can’t remember the model number. I beliene FS-100?
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When I talk about retinning the tip after every couple of joints, I should have mentioned that I also clean it after every couple of joints (before and after retinning it).
I am sure I am missing something but I can’t remember right now.
Let me recap to see if I’m understanding the what would be a good procedure (perhaps not the only viable one). Let me know if this seems corret/a good way to do/keep doig things:
I turn on the iron, wait for it to reach the 350 (or chosen temperature), when I am ready to start soldering, clean the blob of solder I left on the tip last time before shutting the station off, clean it so there’s not much solder left on the tip but doesn’t have to neccessarily be “coating tin”, solder a couple of joints, clean it again, re-thin it (and it’s ok if you put a lot of solder) covering the whole iron plated part of the tip, clean it again, so at least there’s not a blob of solder on it?
Also, any time you notice oxidation on the tip or part of it and you can’t tin it with just solder so it starts forming bubbles instead, don’t be afraid to “shove it” into the tinning paste?
Clean not right after every couple of solder joints but right before the next one (after those few ones) to not leave it hot and exposed?
Also, once again, thank you so much! Everyone makes videos about tin, solder, clean, tin, etc but it’s hard findig info on how much should you clean and tin, which of the two should be the last step and whether it actually matters.
Also, thank you for the NASA guide! I have been wondering about building, soldering, making, etc hardware for space and extreme conditions, ever since I found out that the requirements are different than the regular.
Would you be able to make a video with your concerns? Doesn’t need to be public
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Besides the question above asking if this is normal:
Sometimes touching the solder to the pad after holding the tip to the pad and component leg/lead for about a second, the solder doesn’t start instantly (but i believe i may have not touched the component lead with it as well, not sure, need to get a magnifying glass or something) and i either have to touch the solder to the tip to get it started or wait about a second and a half loger. Although I have been soldering eBay practice boards with questionable quality and who knows what kind of plating.
Is this normal?
The rest was my explanation of what I understood and asking for confirmation to make sure i understood right.
No concerns besides that, also out of things to solder atm to be able to make a video.
Sounds fairly normal to me. It is a stochastic process. Could be reduced cross section area of contact with tip, how the tip plating solder just happened to deform on contact, trapped gas or oxides, or a host of alternatives. High speed thermal camera video would be fantastic. 
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@ifohancroft
I use higher temperatures with Pb-free solder. I set it to 375C to 400C, not 350C.
Have you tried add a little flux with a flux pen?
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@quozl Can you please ellaborate on:
Could be reduced cross section area of contact with tip
Also, yeah, it would be nice to have a high speed thermal camera.
@cgervasi I just set it up according to Hakko’s recommendations.
I.e. Solder melting temperature (for my solder that’s 227C) + 50 degrees + 70 or 100 degrees depending on the thermal conductivity of the soldering station (I believe mine has great thermal conductivity so I use 70degrees instead of 100) which gives me about 347 degrees C and since 350 is a round number and most people seem to use 350, I just set it to 350.
I still need to buy flux, as the flux pen I bought, turned out to be an empty flux pen you are supposed to fill with flux yourself.
I’ll try. But I don’t want to appear to be an expert or overdo it.
So as I understand it from your quoted text;
- your starting condition is tip hot, wetted and cleaned, pad cold, component lead cold, and solder cold,
- you hold the tip to the pad and lead for about one second, touching both with the tip,
- you touch the solder to the pad or the pad and the lead,
- you expect the solder to heat, melt, and flow, but sometimes the melt is delayed.
A number of things have to go right in step 2 and 3. Heat has to flow. Time is of the essence. The rate of heat flow depends on;
- temperature of the tip,
- temperature of the pad, lead, ground plane, component and board,
- temperature of the solder,
- the cross section of the area of contact between all these things, which for the tip is mostly the angle you are holding it and the thickness of wetting; can you see your face in it or is it so clean you can see the tip plating erosion or texture,
- if the wetting surface is clean, invisibly oxidised, dirty, or still dancing with liquid flux in brownian motion,
- ambient wind speed and air temperature; my soldering exhaust fan makes a difference,
- heat sourcing capacity of tip and control system,
- heat sinking capacity of component, trace, ground planes, vias,
- gas flow from flux evaporation; and the path the exhaust gas chooses to take,
- cross section of the area of contact between the hot surfaces and the cold solder as it hits; freshly cut solder behaves differently to previously used solder with a balled end and remnant flux.
On the heat sourcing capacity of tip and control system; larger tip will dump stored heat faster, and how faithful the control system of the FX-888d complies with demand can be a bit invisible; look at the heating indicator at the end of the temperature display, and remember that an overshot temperature is not usually displayed to you. It’s not 350°C, but at least 350°C. Heat the tip from an external source to prove that.
Another way to look at it; if you’re noticing a one second variability, that’s about as much as I had expected given what’s going on in there.
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Thank you so much!
Now I get it! I realize now that my problem understanding what you meant was because of not knowing what a cross section of an area is.
I should have said cross-sectional area. Sorry, I’m not from 'round here. 
At small scale, pushing a wetted tip against a pad and component is like pushing a balloon against a pillow on a bed. The balloon deforms a lot. The pillow less so. The heat transfer rate is mostly proportional to the area of contact.
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After gaining a bit more experience, I decided to answer some of my own questions, with the hope that it might help someone else:
The numbers below don’t follow the same order as the initial questions.
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Soldering Temperature: Lately, I have realized that when Hakko said great thermal conductivity, they mean stations like the FX-951. So, using the same formula: Solder melting temperature (227C in my case) + 50C + 70C or 100C, I have increased the temperature on my FX-888d from 347C (that I had rounded to 350C) to 377C. Judging by how the soldering iron/station behaves now - this is the perfect temperature. The difference is night and day. (Obviously, this is not a one size fits all and you still need to take into consideration what you are soldering and adjust both temperature and tip type and size accordingly).
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Tip tinning and cleaning:
2.1. Cleaning: I try to clean the tip using the brass sponge after every 2-3 joints at most. That’s important, because if you don’t you are left with a lot of solder with its flux evaporated, on the tip and this gets on what you are soldering and results in cold joints, ruining what might have otherwise been a perfectly soldered joint.
2.2. Tinning: Pretty much whenever I am about to clean the soldering iron tip, I do the following: I clean it. I tin it again with the soldering wire. I clean it. I tin it again and I clean it again, then I solder. The reason for this being: I want to clean it for the reason stated in 2.1., then I tin it so I don’t leave it exposed as well as to let the flux in the soldering wire clean any possible oxidation. I clean tin it twice (with cleaning in between) because the first time the flux will clean the soldering iron tip but the actual solder would ball up on the upper part of the tip, that’s part of the coated part of the tip but that’s not used during soldering, then I clean it and tinn it the second time and that time the solder sticks to the tip and covers it all.
P.S. Occasionally I also dip the whole coated part of the tip in Hakko’s own tip tinner when I haven’t followed my own procedure strictly and have left the tip to oxidize. It helps tremendously and so far I haven’t noticed it shortening the tip life, but like I said if I follow my own procedure to the T, it’s not really needed.
If I clean the tip often enough but I don’t retin it as often as I should, this ends up leaving the tip exposed, which is not good. It works great (as expected) but it leaves it open to the air.
I still don’t know if tinning just the part of the coated part of the tip that’s used for soldering will short its leave because the non-used part is leaving exposed, but I try not to leave anything exposed as I am cleaning and retiinning it anyway, it takes just slightly more solder to tin the whole coated part.
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Some good advice. I just use a wet (real) sponge to clean my tips frequently. The brass wool (aka sponge) is ok but it is a bit harder on tips than a real sponge.
By the way, Hakko tips are amazingly resilient - I have accidentally left my iron on over night several times and a quick wipe on a wet sponge cleans them up. My old Weller tips would have died.
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Thank you!
I used to use a sponge on my previous (Lidl brand) soldering iron station but it’s too much work for me having to wet it and make sure to keep it wet. You are probably right that the brass wool/sponge is harder on the tips but I haven’t had a problem so far. My only complaint is that after a certain point, you can’t get the solder out of it and you have to buy a new one and they are more expensive (if you buy genuine ones) than the wet sponges.
True. Their tips are very resilient. I haven’t left mine on for so long but I’m still using all the tips I got when I got the soldering iron station and haven’t had the need to replace a single one (although admittedly I probably haven’t used them even half as much as someone who solders every day).
My genuine hakko tips never died when I first got my 926. Then at some point, my collection of tips started including knockoffs. I lost track of which is which, but there are clearly tips that are still in very good shape and others that are shot.
If you keep the Hakko tips at 650F (uh, 343C) or so, they seem to last being left on for days…
I have heard people say they use knock-off tips because of genuine tips being expensive.
How much do they cost in other countries?
For me, a single genuine Hakko tip here in Bulgaria costs about 11BGN which using today’s exchange rate is $6.75. That doesn’t seem expensive, even if I don’t consider the fact that I don’t know of a local place to buy knock off tips so I’d have to buy from Amazon and pay probably $20 for shipping and customs and at the end, 5 or 6 knock off tips will probably only cost me $3-5 less.
In my case, it started out not because of cost but easy availability of various tip shapes in a mixed bundle. Plus, over time, I’ve accumulated various random bits from Radio Shack or included as a free gift with my PCB order, etc.
I’ve never had to replace my Hakko tips so I can’t tell you how well anything else lasts. But, honestly, I have no desire to find out. I have had my 936 for 15 years or so and use it between 10 and 15 hours a week. Based on that, I wouldn’t bother with knock-offs if I had to replace.
I have a little squirt bottle with water in it that I use to wet the sponge and refill it once a week or so. Don’t see it as particularly slowing me down.
Hi…I cleaned the tips with a Scotchbrite type kitchen scourer (fiber type) cushion prior to connecting. At that point as the iron warmed up (as Keith recommended) I applied Powerflow transition to it - I was unable to find any Tip Tinner on schedule. The tip oxidizes as the iron warms up in the event that it isn’t fluxed. At that point I applied the patch and it stuck.
It worked better on the “official” Antex substitution tips than the “independent” ones I had. I realize Powerflux is awful stuff - however better to have an iron that works and abbreviate its life than put it in the canister. I think one issue was the Phosflux 12 I was utilizing wan’t sufficient.
Just to clarify: I am not interested in how long the knock offs last, as I have no intention buying knock offs. I am curious how much do genuine Hakko tips in other countries cost, that some people buy knock offs because of the genuine ones being expensive. I mean how expensive can they be?
@LoriePetty I agree. Better have an iron with a short life but working, than not working at all.
Speaking of using Scotchbrite on the tips: In my country (Bulgaria) the DIY way of “caring” for your tips is unfortunately quite common here. If you gather people that solder, in a room, you can’t toss a coin without hitting at least one person that “cleans” their tips by sanding them, using a weird compound to solder with or something even weirder to clean their tips with. I feel like on one end of the spectrum, sandpaper is the most popular tip cleaner here, while on the other - aspirin is the most popular tip cleaner here 