Please recommend a good quality flux and solder

[Ian.M]

When the Weller TCP 'Magnastat' irons were king in the service and hand assembly trades, they were supplied as standard with the PTAA-7 bit which set the temperature to 700 deg F, (370 deg C).   Although you could get bits with Curie point slugs in the range 600 deg F (315 deg C) to 900 deg F (480 deg C), with the exception of a chunky 5mm PTDD-8 800 deg F bit which was always handy to have for heavy terminals, the other temperature rating bits were pretty much special purpose only - 800 deg F and hotter bits were too much of a PITA to keep tinned for general purpose work unless you religiously switched the station off for even small pauses in your workflow, and 600 deg F bits didn't deliver enough heat for anything except the lightest of work with the normal SnPb alloys that were in common use in that era.

ive brought a few reels of supposed 60/40 leaded solder from uk ebay sellers,when it is delivered,says made in china on the reel,turns out its lead free rubbish,just sommat to look out for,had one guy wanted me to send him pics of the crappy looking joints,my reply was dont you know what a dry joint looks like?,in the end i got %50 of my money back,not the ideal solution tho!!.

I personally find its nearly as easy to work with good quality SnAgCu solders as with traditional SnPb solder.   Pb-free <> rubbish.

Due to the relative market prices of Tin and Lead,  its unlikely your crap solder was actually Pb-free.  See my comments here: https://www.eevblog.com/forum/reviews/soldering-question-tinning-16-awg-wire/msg3143318/#msg3143318.

If you can also measure the melting point, you can identify the alloy supplied with a fair degree of certainty.   

Sounds like an esd-issue or a reliability problem. The datasheet says it can be soldered with 300C for 10s. I believe these ratings are conservative.

At first, I also thought that it is an ESD problem. But if this was an ESD, those MOSFETs would be damaged at the same rate at low temperature too, and other similar MOSFETs would have same problems, but they were not and the same fault mode later confirmed with a different batch of parts in different setting.

Later we dropped BSS138 completely for 2N7002K.

It may have been a moisture problem - its *rare* to get popcorning when hand soldering (excluding refow), but with a high enough soldering temperature it can happen.

[exe]

At first, I also thought that it is an ESD problem. But if this was an ESD, those MOSFETs would be damaged at the same rate at low temperature too, and other similar MOSFETs would have same problems, but they were not and the same fault mode later confirmed with a different batch of parts in different setting.

Later we dropped BSS138 completely for 2N7002K.

Hmm, the 2N7002K has esd protection on the gate, while bss138 doesn't... Anyway, I'm glad you resolved the issue.

Now here is my attempt to kill bss138 (presumably, smd marking is J1 H) with soldering it at 400C: .

I will not put spoilers, you have to watch it to see the result . And, of course, I don't want to say that soldering at 400C is good for your parts.

[wraper]

BTW Sn97Cu3 solder wire is almost guaranteed to come with some nasty corrosive and electrically conductive flux inside it. So your issue might be exactly that, not temperature.

Once I had a bunch of BSS138 that would be dead on the spot if you touch them with a hot tip, I had to go with tip as cool as it can barely melt solder or switch to low temperature solder for them, otherwise they started to conduct through the closed channel and through the gate too.

[Unixon]

It may have been a moisture problem - its *rare* to get popcorning when hand soldering (excluding refow), but with a high enough soldering temperature it can happen.

With tip temperature around 250-260C one could watch a gradual degradation of a MOSFET.
You measure it first - Rgs is out of range (>40MOhm), you touch it once (very shortly) - Rgs drops to MOhms, you touch it twice - Rgs drops to tens of KOhms, you touch it again - Rgs drops to about 1K.

[exe]

With tip temperature around 250-260C one could watch a gradual degradation of a MOSFET.
You measure it first - Rgs is out of range (>40MOhm), you touch it once (very shortly) - Rgs drops to MOhms, you touch it twice - Rgs drops to tens of KOhms, you touch it again - Rgs drops to about 1K.

Did you short the gate to source? If it is floating, it accumulates charge and measurements are completely screwed. I know that from experience

[Unixon]

Did you short the gate to source? If it is floating, it accumulates charge and measurements are completely screwed. I know that from experience

Yes, before measurement. You touch it with a soldering iron, after every touch both Rds(Vgs=0) and Rgs drop down, this thing is starting to conduct while being closed!
Other MOSFETs similar to that BSS138 could be also damaged with high temperature but this degradation speed was outstanding.

[tooki]

Leaded solder: ASAHI with CF10/FC5005 flux 0.5/0.6/0.8mm for through-hole stuff + 0.25mm for small SMDs.

Lead-free solder: FELDER Sn97/Cu3 or Sn95.5/Ag3.8/Cu0.7 (maybe not the best choice but not much worse than leaded ASAHI counterpart)

Are you absolutely sure you mean Sn97Cu3? It’s much more likely you actually have the Sn99.3Cu0.7.

Almost all lead-free solder is high temperature, and as I said, these two I've listed may be not the best choice.

Then this is a very high temperature stuff if you call regular lead free high temperature. If talking about SnCu alloys, for electronics SN99.3Cu07 and Sn99Cu1 are used. Sn97Cu3 is more suitable for soldering pipes rather than electronics.
EDIT:
https://www.felder.de/products/copper-pipes-sanitary-installations/soft-solders-drinking-water-heating/fittingslot-cu-rotin-4-14953020.html

According to DVGW, worksheet GW2, permitted for soft soldering of copper pipes in the cold and hot water installation.

(That’s Sn97Ag3, btw, not the Sn97Cu3 being discussed.)

BTW Sn97Cu3 solder wire is almost guaranteed to come with some nasty corrosive and electrically conductive flux inside it. So your issue might be exactly that, not temperature.

Once I had a bunch of BSS138 that would be dead on the spot if you touch them with a hot tip, I had to go with tip as cool as it can barely melt solder or switch to low temperature solder for them, otherwise they started to conduct through the closed channel and through the gate too.

The Felder catalog actually does list Sn97Cu3 in its rosin electronics solders (ROM1 and ROL1), see pp. 6-7 on https://www.felder.de/products.html?file=files/felder/content/Kataloge/Gesamtlieferprogramm_2012_EN-kl.pdf

Not that it sounds like something I’d want to use on a PCB, with that very high melting point!

[tooki]

Can I ask about Radio Shack solder?  I used it for decades, and am about to run out.  Specifically this one in the 0.032":

https://www.radioshack.com/collections/solder/products/snpb-60-40-rosin-core-solder?variant=31204770021446

 I never really paid any attention to the specifics before, but notice that it has an RA flux, which I understand is more aggressive than something like Kester 44, which is RMA, and in theory needs to be cleaned off afterwards whereas 44 doesn't.  I've never really bothered with doing that, and don't recall having any problems.

Anyway, this is even the right amount to last me for several years, so I thought I would order it.  Is this not a good choice because of the RA flux?  Does anyone else like this solder?

The old RA/RMA system of flux categorization doesn’t tell you as much as the newer IPC system. In that one, Kester 44 and the radio shack RA solder are both type “ROM1”.

I still have a bit of that 60/40 Radio Shack solder left over from my childhood. Has to be 25-30 years old now. But I only use it for tinning, as I prefer using 63/37. (My daily driver solder at home is the Kester 44 63/37 in .031. But I may try the 245 no-clean next time, as I see on its datasheet that it has much better solder spread than the 44!)

[wraper]

(That’s Sn97Ag3, btw, not the Sn97Cu3 being discussed.)

Yeah, wrong link, was posting late at night. Nonetheless Sn97Cu3 usually is referred as "plumbing solder" or for soldering aluminium and steel. Here is a link for Sn97Cu3 which says exactly the same:
https://www.felder.de/products/copper-pipes-sanitary-installations/soft-solders-drinking-water-heating/fittingslot-cu-rotin-3-149727201.html

[tooki]

(That’s Sn97Ag3, btw, not the Sn97Cu3 being discussed.)

Yeah, wrong link, was posting late at night. Nonetheless Sn97Cu3 usually is referred as "plumbing solder" or for soldering aluminium and steel. Here is a link for Sn97Cu3 which says exactly the same:
https://www.felder.de/products/copper-pipes-sanitary-installations/soft-solders-drinking-water-heating/fittingslot-cu-rotin-3-149727201.html

That’s the page for an Sn97Cu3 plumbing solder, so obviously it’s going to describe its use for plumbing. But I already gave you a link to the Felder catalog which lists several Sn97Cu3 electronics solders. It’s weird and I don’t know why anyone would choose it, but they have it. Here’s the product page for one of them: https://www.felder.de/products/electronic-applications/manual-soldering-mechanical-soldering/solder-wire/loetdraht-iso-core-el-20971040.html

[Unixon]

Lead-free solder in question: (updated image)

[tooki]

Lead-free solder in question:

Not that I would trust website pictures (as they often reuse images for similar products), but that clearly says Sn99.3CuNiGe, meaning it’s 99.3% tin, and the remaining 0.7% is a mix of copper, nickel, and germanium. (Of which copper is likely the vast majority.) So... not Sn97Cu3, just as I suspected.

[Unixon]

Not that I would trust website pictures

Sorry, these lazy suckers always put wrong pictures on products and I missed it. Replaced with real photo.

[Unixon]

And for completeness of imagery, leaded solder in question: [picture]
These are really good, maybe even best out there.

[exe]

Other MOSFETs similar to that BSS138 could be also damaged with high temperature but this degradation speed was outstanding.

Yeah, if it's that sensitive, I'd throw it away Do you remember that poor mosfet from the last video? Look what I've done to it: https://youtu.be/g_-7pVNsHrU?t=60 (500C is maximum temperature on my hotair station).

[Unixon]

Yeah, if it's that sensitive, I'd throw it away

I've used up all of that batch with special care during assembly They were very cheap and worked fine if not overheated.
Maybe I still have few of them somewhere... but now these would be 8-10 yrs old not including prior shelf life.

[wizard69]

This thread has been beaten to death but one thing that has not been addressed is that poor soldering isn't always a materials issue.    That is the operator is an element in the process and there practice really does make perfect.   Frankly it is a lot like being a weldor, give two people the same welder and materials, one will produce crap and the other art work.   So practice and working with various supplies, to learn what they can do for you, can help build up the skill level.

Here is the thing there is no one right solder and flux combo for every soldering need in electronics.   I may like 60/40 rosin cored solder while somebody else might go to a different alloy.   The problem is I know that this solder will not work in every soldering task I might run into.   For example liquid fluxes in a flooded manner are at times the right solution.   Sometimes turning up the temperature on the iron is the right solution.

The point I'm trying to get at is that asking questions is good but sometime you best develop skills by experimenting in different situations.  In the end even though soldering a 14 ga wire to a switch is the same thing in concept as soldering a SMT lead to a PCB, the techniques used are a bit different.   As a tech it really pays to develop your soldering skills to support a variety of situations.

[bdunham7]

This thread has been beaten to death but one thing that has not been addressed is that poor soldering isn't always a materials issue.    That is the operator is an element in the process and there practice really does make perfect.   Frankly it is a lot like being a weldor, give two people the same welder and materials, one will produce crap and the other art work.   So practice and working with various supplies, to learn what they can do for you, can help build up the skill level.

Here is the thing there is no one right solder and flux combo for every soldering need in electronics.   I may like 60/40 rosin cored solder while somebody else might go to a different alloy.   The problem is I know that this solder will not work in every soldering task I might run into.   For example liquid fluxes in a flooded manner are at times the right solution.   Sometimes turning up the temperature on the iron is the right solution.

The point I'm trying to get at is that asking questions is good but sometime you best develop skills by experimenting in different situations.  In the end even though soldering a 14 ga wire to a switch is the same thing in concept as soldering a SMT lead to a PCB, the techniques used are a bit different.   As a tech it really pays to develop your soldering skills to support a variety of situations.

Perhaps.  But early on I always wondered why I could solder radiators and copper pipes so well but I just absolutely sucked at electrical soldering.  Then, faced with the need to actually do a good job, I splurged and bought a pro-quality Antex temp-controlled iron and some $$$ silver-bearing rosin core solder from Radio Shack and all of the sudden I was a soldering pro.  There's a certain level of quality for both equipment and solder that if you go below it there's nobody that can do a decent job.  And there's plenty of that crap readily available in the market. 

[tooki]

FWIW, silver-bearing leaded solder is generally a bit harder to work with than 63/37, which is in many ways the optimal alloy for electronics, RoHS notwithstanding.

[bdunham7]

FWIW, silver-bearing leaded solder is generally a bit harder to work with than 63/37, which is in many ways the optimal alloy for electronics, RoHS notwithstanding.

That's sorta part of the point.  My skills weren't the problem, it was the crap I was trying to use because I didn't know how much better non-crap stuff was.  The Radio Shack silver solder made magnificent solder connections and I still have some left 30 years later.  I suspect the iron made more difference than anything else.

[Unixon]

That is the operator is an element in the process and there practice really does make perfect.

I'm afraid that if we start comparing our soldering skills in this thread this would turn out in a weird kind of dick measuring contest instead of initial request for good flux and solder.
Despite of this I must say that I agree with your points and that skills do matter even with good materials.
I know everyone have some tricks in their sleeves and I would encourage to open up another appropriately named thread and share that knowledge there. 

[Unixon]

So please feel free to recommend some decent leaded solder, Lead free solder, Flux.

Where do you buy electronic stuff?

[wizard69]

That is the operator is an element in the process and there practice really does make perfect.

I'm afraid that if we start comparing our soldering skills in this thread this would turn out in a weird kind of dick measuring contest instead of initial request for good flux and solder.
Despite of this I must say that I agree with your points and that skills do matter even with good materials.
I know everyone have some tricks in their sleeves and I would encourage to open up another appropriately named thread and share that knowledge there. 

The point of my post wasn't to start a contest it is just that if somebody is new starting out in this field they need to try different materials and techniques to see what works best in a specific situation.   For example some will discount the value in separately applied fluxes but I've seen first hand how a good flux added to a difficult solder job makes a huge difference.   Asking questions is good but you also have to take answers with a grain of salt and objectively test the suggestions.

As to the other question you posted about buying electronic stuff there are lots of options.   My answers would be more biased to industrial suppliers as that is what I've worked with over the years.   In any event some suggestions:

• Keysight, we don't buy a lot of test equipment but they are the first choice for mainstream bench hardware.
• Fluke, for handheld meters.
• DigiKey, for what I call hard electronic components and materials.   They also have a very good web site compared to many others
• Newark, for things that might be seen as more industrial.   They also have a terrible web site that drives me away.
• Simcona, Especially for cabling
• McMaster-Carr, Actually the world biggest hardware store.   One of the best business oriented web sites going but with one bad characteristic, they make it hard for the user to determine brand names / origins.    Great place for hardware though.
• Mouser, honestly have not dealt with them much.
• Horizon, Industrial electronics and components.
• MSC, Largely a horribly expensive site for industrial machining tech but they do carry some electronic equipment.   Their good point is an uncanny ability to get stuff to you fast.
• CS Automation, probably not stuff you want unless you are building a fancy home CNC system.
• techni-tool, Not a big customer anymore mostly due to not having technicians traveling all over the place.
• Brook Anco, mostly for optics in our case.
• DXP, mostly oriented to the machining industry.
• spectraservices, largely optics.

Occasionally we have to trace down vendors for components that are not easy to fin in the USA.   For example some PCB mounted push buttons for old FANUC controllers.   This is the real trick to fixing things, that is tracing down hard to find components, it is a skill all on its own.   So there have been a lot of one time vendors, where we buy a transistor or whatever and might not see that supplier ever again.

[Teledog]

Whatever you use, just make sure it's big!

Was given this chunk of solder many years ago by a retired hydro generator rewinder (he's passed on now).
They supposedly used massive wooden sledge hammers to pound in the windings/bars back in the day.
Flux?..no idea what they used back then.. perhaps pine saplings? ;-)

[castingflame]

Thank you all for your answers.


The main reason for flux for me is if I want minimal heat build up on a part, to re-flow a joint but Mainly for removing bridged connections on high density SMD parts after being in the oven. I have found solder wick dipped in a flux removes the bridges much much quicker in one go in a very much neater way.

I will take your comments on board and make some choices next time I make a decent order.