Hello everyone! I am glad to welcome all of you to my Youtube channel "Electronics Manufacturing Technologies". My name is Dmitry, I am a process engineer.
And in this video I want to tell you about fluxes.
Or rather, I want to tell you about what fluxes should be for manual installation, for repair. What should they be?
What characteristics should they have so that they can be used and not worried?
Fluxes for manual installation, for repair - what should they be?
The flux has several characteristics. 1 - it is desirable that the flux be in the form of a gel, because the gel is less fluid.
Any liquid, when exposed to temperatures, begins to spread.
The liquid spreads over the surface and its efficiency decreases.
At the same time, the gel is less fluid and retains as much as possible in the place of application.
It is localized at the place of soldering, on some component. This is very important for us so that the flux does not spread over the entire PCB.
2 characteristic - the flux should not be afraid of temperatures. This is especially important for renovations.
Because the temperatures used during repairs are much higher than when brazing in convection ovens.
The temperature is higher during repairs.
And a very important characteristic of flux for manual work and repair is not to be afraid of high temperatures (high boiling point).
The flux, which I have been using for more than 10 years from Nordson, has always stable performance.
To dismantle the microcircuit, I can put 350 degrees Celsius on a hot air dryer and quickly remove it.
The flux will remain in place. It will not spread across the PCB. And it won't evaporate! This is another key characteristic - it will not evaporate.
This is a problem with almost all cheap soldering fluxes.
You put it on the place of soldering, blew it with a hot air dryer with a high temperature, and the flux evaporated - it disappeared.
And this is also important in those moments when we install a new component.
The heating is very fast and the activation of the flux is faster than in a conveyor oven.
The soldering point heats up with lightning speed, as soon as we apply a high temperature there.
And the component we install heats up almost instantly.
Many people change microcircuits in this way. Let's be honest with ourselves.
And the surface and component temperatures rise very quickly.
And many cheap fluxes have this problem - they evaporate very quickly. Therefore, the flux should not contain fractions that evaporate quickly.
As a rule, these are various alcohols that are added to fluxes.
And after you apply such a flux to the printed circuit board, you bring a thermo dryer and this flux disappears.
Some small residues remain on the printed circuit board and the efficiency of such a flux tends to zero.
The first characteristic is gel. The second characteristic is operation at high temperatures (high boiling point).
The third important characteristic is wettability.
Fluxes that have spread or evaporated stop wetting the compound.
This is a serious problem. You applied the flux and it was gone after the temperature was applied to the soldering point.
Soldering efficiency drops sharply.
The fluidity of the spilled metal drops.
Pores are formed, the surface is not smooth and dull.
It can be seen that the alloy is not wetted and the distribution of the metal over the joint is uneven.
Therefore, it is very important that at high temperatures the flux performs the function of wetting the molten alloy.
It is very difficult to find a flux with good performance.
I don’t advertise anything, I just use it for a long time and I’m confident in it. He meets all the requirements.
In fact, there are a huge number of professional expensive fluxes in the world.
Many of the fluxes are not even shipped to Russia.
We now turn to other fluxes that are used in industry.
But due to ignorance and misunderstanding, many of us who work in production
use fluxes for industrial soldering in manual assembly.
And this is a big mistake. Why?
Example. Here is the soldering flux.
This flux is required for application to PCBs prior to wave soldering or for selective soldering.
This flux is applied through nozzles or spot-on to the PCB before it travels to the waveform with the solder.
Depending on the equipment available.
The equipment is different for everyone - some kind of zoo.
Many people adjust the basic technical processes to the equipment that is available in the enterprise.
For example, we bought one type of flux and use it for selective soldering, for wave soldering.
And also some stir it for manual assembly. Why is this flux bad for manual soldering?
This flux is not suitable for manual soldering because it is liquid like water.
And this flux contains alcohols.
Wave soldering applies this flux. The PCB then goes to the conveyor where the flux is activated. Slow heating occurs.
Alcohols will evaporate while preheating the PCB.
Due to the fact that the flux is very fluid, it rises through the vias for the DIP components.
Thus, the flux fights against oxide films on surfaces.
But this flux will not help us with manual soldering, I
stream that when the tip of the soldering iron is touched or hot air is supplied from the hot air gun, the alcohols instantly evaporate.
In this case, the flux begins to splatter due to the fact that it boils.
Therefore, the effectiveness of liquid flux for hand soldering is very low.
Remember this. You do not need to use materials that are intended for other technical processes.
We are always trying to find a universal material and use it in all our technical processes.
Our technical process is deteriorating. There are many mistakes. There are a lot of misses.
This is all due to the fact that we are using the wrong process technology.
Fluxes are a very important material and should be used for their intended purpose.
For repair, for manual soldering, it is most often gel. They are almost always in syringes for manual application or for installing a dispenser.
There are almost no good fluxes in the liquid fraction for manual work.
Many go further - they mix rosin with alcohol.
High temperatures are out of the question in this case. There is a lot of dirt on the PCB.
Blackness, dark spots. All this is ugly. This is uncivilized.
In any case, everyone decides for himself how to solder. And everyone is responsible for this.
But if we work professionally. If we work for customers, then we must approach work with a different level of responsibility.
There are a huge number of reviews of fluxes on Youtube, of
course, they are all different and their characteristics can differ significantly.
But even they will be better than Soviet fluxes.
I do not in any way condemn old Soviet brands of fluxes, use them if you like,
but I want to ask you not to get hung up on old technologies that were used 50 years ago.
You need to match the time.
If you are repairing a phone or laptop for a person, then use quality materials to get an excellent result.
so that the client does not come back to you in a week.
And this applies to the cleaning of printed circuit boards. Hand soldering fluxes are generally no-clean.
And fluxes for industrial brazing are very different - they are washed with water or not washed with water.
The fluxes have a classification.
It is important not to get confused in this. Especially when you don't understand how they differ from each other.
For repairs, it is better to buy a syringe with a high-quality expensive flux, which will be enough for you for a long time.
You will be satisfied with the quality and ease of use you get.
And once again I want to talk about cleaning fluxes, which are used for repair and manual soldering.
Some of you are not worried about laundering. We soldered it and gave it away.
Is it good or bad? The point is which flux you are using.
If you are confident in the quality of your flux. That he is not some kind of no name.
That it is definitely a ROL0 flux, that it will definitely not have any shrinkage, that it definitely does not need to be washed,
and that if it is not washed, it will not harm the printed circuit board. Such a flux really does not need to be washed off.
And if you are using some kind of incomprehensible flux, of an unknown manufacturer with unknown characteristics, then I would recommend that you wash it.
So that the printed circuit board is not coated with oxide. This is the only difference.
There are also aesthetic aspects.
I, for example, will not give a printed circuit board to a customer in a dirty state.
When a printed circuit board comes in for repair, there is already a lot of dirt on it.
I will gladly clean such a PCB and the client will receive a clean working PCB.
Regarding the flux classifiers - I have an old video about it. I will leave it in the description for the video.
Be sure to take a look. Learn how fluxes are classified according to classifiers. You will understand what and where the flux is used.
And which fluxes need to be washed and with what, and which - not.
Below the video you will find the website of the CHIP EXPO.
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There will also be a link to my Telegram - consultations take place in Telegram.