Hot air soldering...

[ionut_mtb]

I remember how i desolder smd pcbs few years ago. This might be an destructive way for some components.
Take a big, industrial heating gun, hold the pcb with pliers, heat the board completely (don’t remember the temperature) and after that rapidly hit the working table with it. Components will fly )). A lot of melting solder will be there also. But like that you will empty boards in few minutes.

[ivconic]

I remember how i desolder smd pcbs few years ago. This might be an destructive way for some components.
Take a big, industrial heating gun, hold the pcb with pliers, heat the board completely (don?t remember the temperature) and after that rapidly hit the working table with it. Components will fly )). A lot of melting solder will be there also. But like that you will empty boards in few minutes.

I got similar idea, but as you said; some components will be destroyed.
Most fragile would be the capacitors. Elcos may explode like that.
As for chips... we do know about "electron migration" phenomena, when chip is exposed to high temperature.
Higher density chips (more transistors) is more likely to be liable to this.
I remember my few first PC computers, 1989-1994. Those where without fan coolers.
Only "passive" cooling.
Ever since than i see piling up the "active" cooling more and more in PC computers.
Today a "gamers" PC computer is fed up with fans and massive aluminum coolers.
It is so horrible to see how those machines are forced to the end limits of proper functioning.
All that for what? To avoid ... to prolongue "electron migration" in chips.
That's why they last so short after all.
Temperature is the "enemy".

And "mining" rigs are special story!
People who pay $3-5k for a rig... are not too smart, for my account.
Because it is a ticking bomb, it will die hard randomly, sooner or later.
It is not more likely they will return invested money before the rig dies.
And i see bedlam of adverts in second hand and used rigs, over the internet.
Who on Earth is that stupid to invest money in already used rig?
Almost sure 50% of the chips on that rig are about to die soon.

Probably one of the largest scam in history of mankind.
Invest $3-5k and earn barely 50-60% of that back.
In meantime waste huge energy with that crap!

[ivconic]

Everything became so temporary and short lasting.
Consumers society. Buy, use for short time and scrap it.
I am having IPTV sort of, satellite kind one.
The STB is so weak and funny... i am betting each day on its dying.
It lags, freezes and chokes, especially when messing with EPG.
Look up all the house appliances, most of those are made that way.
Hardly to last until warranty expires.
That's todays "electronics".
Though... i have expensive habit to use only brand name computers, mostly Dell and Asus (actually the same source of production).
My Dells usually do not have active cooling and if some do; usually it is over the top of very massive aluminum passive cooling.
I don't hear fans in my computer, they turn very slowly.
But even like that... it is suffering from electron migration too.
Only a slower process at higher quality products.
Lasting bit longer.
Someone complains on the other topic about missing a chips from the markets.
Well... it is just a begining.
The rush for higher density packaging in chips and rush for performances have led to this situation.
Recycling of old chips and making new ones is one of the solutions. More expensive one.
Buying material for making chips was much cheaper solution... until recently.
Until those who have material in ores got smarter and more cunning!
Obviously this story relies on wasting planetary resources with no intention of recycling spent waste.
It can not last forever, that story has its near and sad end.
I'm afraid this is just the beginning.

[ivconic]

I did a crazy experiment and now I'm amazed ... the opinion of more experienced colleagues is welcome here ...
Namely, my friend is a expert for central heating works and he welds copper pipes with some "paste" that reminded him a lot of the look of my liquid tin that I recently got.
We agreed he to bring that "paste" that he uses, me to look at and check.
Because that "paste" costs about 10e for 250 grams. While my liquid tin costs 5e for 35 grams.
He brought it today as well. Indeed, both substances look pretty much the same. The composition is written on the box.
No lead but some copper in the tin.
I took an old PCB, sanded the part where the small chip with 8 pins stood, to take it all the way to the copper surface.
Then I randomly applied that "paste" with a brush, glued the chip on top and started heating with the rework station.
And look ... the process was going just as fast, if not a little faster, and the legs were soldered very properly.
Even after that, there is not much left to clean, as is the case with "Mechanic" liquid tin !?
The solder spots look brighter and "silver-ish". Solders work looks indeed better.
I just wonder if such solder will last and be of good quality.
It turns out that I found several times cheaper soldering material !!!
Opinions?

[Carl-NC]

Make sure it rosin flux and not acid flux. Plumbing solder is often acid flux.

[ivconic]

Make sure it rosin flux and not acid flux. Plumbing solder is often acid flux.

That's good point.
How to make sure?
I am reading a label on package, can't find anything else except that it also consist zinc chloride.
And the "rests" can be washed out with water.
There is a warning too, that it is dangerous substance and can irritate skin and eyes.

[David_1]

for water pipes there will be no lead anymore, but can you link to his product there might be a data sheet available !

[ivconic]

for water pipes there will be no lead anymore, but can you link to his product there might be a data sheet available !

https://www.felder.de/products/coppe...229760551.html

[ivconic]

"...The flux residues are corrosive and have to beremoved through wiping from outside and rinsing from inside!..."

As far as i understand; residues can be washed out with water.
Although i noticed there are not much residues on the chip and around it.
I used magnifying glass to chech for particles. Barely spotted few which were easy to remove.

[Altra]

When ever you see the word "chloride" that's a corrosive salt. You can't always clean all the flux under components. Chlorides are also conductive so you could get leakage currents between pins. As you know metal detector circuits are sensitive. I would spend $10 on 10cc of smd flux and another $10 - 20 on 63-37 solder paste. It will save you lots of head aches forward. I have been using the same tube of flux for over three years with many projects.

[ivconic]

When ever you see the word "chloride" that's a corrosive salt. You can't always clean all the flux under components. Chlorides are also conductive so you could get leakage currents between pins. As you know metal detector circuits are sensitive. I would spend $10 on 10cc of smd flux and another $10 - 20 on 63-37 solder paste. It will save you lots of head aches forward. I have been using the same tube of flux for over three years with many projects.

Thanks!
I have this:
https://multi-com.eu/,details,id_pr,...ring-10ml.html
But i do not understant it's role, how to use it with liquid tin, before, after the soldering... details?
It is like gell.

[Altra]

I have a tube of the Amtech flux which I have not tried yet.

I don't know the exact answer to your question. But good solder paste has flux mixed in so when you heat it with hot air or in a oven it cleans and bonds. I don't use flux when using solder paste, assuming a clean pcb and parts. I do use flux when I am doing ICs by hand. Using a small tipped soldering iron and standard wire solder. I take a tooth pick and smear flux across all the pads. Then I position the ic and solder one of the corner pins. This allows you to realign the part. Once aligned you wet the tip with some solder and drag it along the outer edge of the pads/pins its amazing how the solder flows. To clean bridges you can use the iron tip to drag the solder away from the chip. Or better use good solder braid/wick. It takes a little practice but not that difficult. For resistors and caps, I put a dot of solder paste on the pads place the component. Using the hot air tool and a circling motion about a inch over the parts. The parts will self align when the solder is molten. I like to do clusters of four or five parts at a time since the heat is radiating out. These days for quick builds, I tin one pad with the iron and then hold the resistor with tweezers and reheat the tinned pad placing the part. Solder the remaining pad. These methods are ok for protos, but would not use for production. A profiled controlled oven is best.

[ivconic]

Thanks for the explanation, I had roughly similar assumptions that this is how it is done.

[David_1]

yes flux lasts a long time, I have one of those markers like a big sharpie with a thin flux and a syringe of gel flux, both much too old to remember when I got them, I also bought some real rosin to make my own flux, The real stuff I have just works so I have not bothered yet but when the time comes I will report back, you just dissolve it in isopropyl and water !

[bernte_one]

yes flux lasts a long time, I have one of those markers like a big sharpie with a thin flux and a syringe of gel flux, both much too old to remember when I got them, I also bought some real rosin to make my own flux, The real stuff I have just works so I have not bothered yet but when the time comes I will report back, you just dissolve it in isopropyl and water !

add an aspirin