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What is the need of "FLUX" when soldering on PCB?

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ahmad_abdulghany

ahmad_abdulghany

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solder flux pcb

What are the advantages/disadvantages of using flux when soldering components on a PCB, also how can it be used?

Thanks for help,
Ahmad,
 

solder stainless steel to copper pcb

from my experience....it just makes soldering easier...soldered lead easily bonds on the copper pads because of that...other than that...i dont know...i hope that helps...
 

cleaning pcb after soldering

Soldering flux has a role to lower surface tension of a melted tin in a process of soldering. This enables good owerflow and good contact.
 
cleaning pcb site:edaboard.com

Borber said:
Soldering flux has a role to lower surface tension of a melted tin in a process of soldering. This enables good owerflow and good contact.
Click to expand...

That's great, and how does it be used?
 

flux solder pcb

The purpose of using flux when soldering is the same as using soap when washing hands.
 
what flux is best for reworking a circuit board

Borber said:
The purpose of using flux when soldering is the same as using soap when washing hands.
Click to expand...

I don't understand, suppose that i am now soldering, how to put flux on pins or soldered points?
 

special flux for circuit boards?

Basically the same way as when you are using soap. Cover element pin and pad on PCB with flux. But soldering tin already contains flux and you usually do not need to add additional flux.
 
do i really need flux for soldering

Soldering flux, as well as acting as a surfactant, cleans the oxide layer off the metal and protects the bare metal during soldering. This is what really makes it useful. Without the flux, you would be trying to solder to copper/tin oxide, and the heat would be making the oxide layer thicker as the metal reacted with oxygen in the air.

As said, electronics solder usually contains flux, unlike plumbing or bar solder.

It is often useful to apply extra flux though, especially if you need to make a joint quickly to lessen the risk of damaging a component. Flux pens are the easiest way to do this. simply wipe the pen across the pads/pins to be joined, then solder quickly. It really does make a difference.

Foxyrick.
 
what kind of flux do i need for a circuit

Note that soldering fine pitch components like TQFP (for example) is really impossible without flux.
Use flux to wet the one or two sides of the TQFP package that you can reach without lifting your other finger. Heat several of the pins on the part to tack it in place. Because of the flux, the existing solder on the PCB pads will wick up on the leads and hold them in place temporarily.
Apply flux the other side of the chip. If it's a quad chip, flux the other three sides. Using a small diameter solder, lay the solder right across all the pins of a side so the solder is on top of the pins parallel to the chip edge. Drag the hot iron across that row, contacting both the solder and the leads (lightly). You have to have the flux on there otherwise it won't work very well. Physics is a wonderful thing - just the right amount of solder will flow around each pin, the flux is the key.

But don't forget to clean your board after your work, because flux can cause a lot of malfunctions... ( i spent a lot of time, trying to find a failure, and it was a "flux-full" board...arggg!!!)
 
solder flux for pcb

Also It clean oxide.
 

how solder flux are made

how do I clean the FLUX from pcb after soldering?
 

using flux to solder pcb

gloobox said:
....
But don't forget to clean your board after your work, because flux can cause a lot of malfunctions... ( i spent a lot of time, trying to find a failure, and it was a "flux-full" board...arggg!!!)
Click to expand...

Can you give some more details about this? What is your experience, and what circuits were involved? (rf, analog...etc.).

/pisoiu
 

when to apply flux to your pcb

how do I clean the FLUX from pcb after soldering?
Click to expand...

you can clean your pcb after soldering with alcohol, and a brush.
after, you can clean it with water, and then blow it with dry presurised air
( the better way to clean boards after manual soldering is to use an ultrasonic machine, with water + special soap )

Can you give some more details about this? What is your experience, and what circuits were involved? (rf, analog...etc.).

/pisoiu
Click to expand...

I had a problem on a resistive measurement system.
there were multiple chanels which were selected by electromecanic relays.
after a FPGA replacement, the board was full of flux, and i didn't washed it....

the functioning of the board was very strange, we had bad measures, and even when all channels were disconected, we had some signal on measuremend front-end...
that was the flux behind the relays which made some resistive links..
the frequency of the measured signals was quite slow: 10kHZ-1V.

I had also problems with flux with integrated oscillators: they sometimes refused to start after a power-on with flux on....
 

make solder flux

That's odd, sometimes when servicing, I leave some flux over some amplifiers and matching networks I use in 2,5GHz band, and they do not seem to be affected. The parameters are identical with those coming out from the production.
This made me curiuos, I will make some tests next days with a VNA.

/pisoiu
 

will alcohol remove dried residual flux

Hi,

You may want to check out more on the do and don'ts when you do your soldering from the following web page. Lead free soldering is the trend these days as ROHS Directive has come out that require every product to contain minimal lead.

https://www.electronics-project-design.com/solderingtips.html
 

do i need to use flux when soldering

That's odd, sometimes when servicing, I leave some flux over some amplifiers and matching networks I use in 2,5GHz band, and they do not seem to be affected. The parameters are identical with those coming out from the production.
This made me curiuos, I will make some tests next days with a VNA.
Click to expand...

Maybe you work with low impedence lines at this frequency (50Ω?)
In my application, the perturbated input were JFET type (OPAMP ) with very high impedance.
i think the problem, and the difference is here.
 

clean pcb trace before soldering

to merge solder between copper track of pcb and component wire
 
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