Hi everyone,

I’ve been trying to improve my soldering and desoldering skills with SMD components like adding/removing USB and HDMI ports on PCBs. When watching various tutorials, I noticed a practice that I’d like to understand better. As a self-taught , I want to be sure I'm doing things correctly, not just following along blindly.

In almost every tutorial I’ve watched, whether it's for tinning copper, soldering components, or using a solder wick or hot air station to remove solder, I see people applying flux to the surface first.

For example:

• In one video (0:54), the person applies flux before desoldering with a hot air gun.
• In another video (1:09), someone scrapes off the solder mask from a copper trace, then applies flux before soldering.

What I understand is that, applying flux before soldering helps create stronger solder joints and keeps the solder in place. For desoldering, it helps the solder melt faster and makes the process smoother.

My question is:

1. Should I always apply flux before soldering and desoldering?
2. What are the key points I should retain about using flux so that it becomes second nature, and I fully understand why I'm doing it?

Thanks.

 

Hi everyone,

I’ve been trying to improve my soldering and desoldering skills with SMD components like adding/removing USB and HDMI ports on PCBs. When watching various tutorials, I noticed a practice that I’d like to understand better. As a self-taught , I want to be sure I'm doing things correctly, not just following along blindly.

In almost every tutorial I’ve watched, whether it's for tinning copper, soldering components, or using a solder wick or hot air station to remove solder, I see people applying flux to the surface first.

For example:

• In one video (0:54), the person applies flux before desoldering with a hot air gun.
• In another video (1:09), someone scrapes off the solder mask from a copper trace, then applies flux before soldering.

What I understand is that, applying flux before soldering helps create stronger solder joints and keeps the solder in place. For desoldering, it helps the solder melt faster and makes the process smoother.

My question is:

1. Should I always apply flux before soldering and desoldering?
2. What are the key points I should retain about using flux so that it becomes second nature, and I fully understand why I'm doing it?

Thanks.

Hi D,
I find that using flux achieves better results.
C

 

Answer:
No, you do not have to apply flux when soldering and desoldering, assuming that you are using rosin core solder.

As others will say, adding flux helps.

Desoldering requires different techniques depending on the situation.

 

Soldering to get a good joint is generally faster with flux added first, which can be important when soldering transistors or ICs, which are sensitive to heat.

I see no reason to use flux when desoldering.

 

I always use flux when desoldering through-hole leads with a a desoldering gun, most desoldering braid has embedded flux too for uniform heating. If the lead is on a sizable component, the more even solder heat distribution around the conductor with flux for the melt makes the vacuum pickup much more uniform with older joints.

 

What I understand is that, applying flux before soldering helps create stronger solder joints and keeps the solder in place.

Flux helps with the wetting process; particularly when the surfaces have contaminants (e.g. oil).

For desoldering, it helps the solder melt faster and makes the process smoother.

When desoldering with an iron, flux can help with heat transfer. I don't think that's as effective with hot air because you're just going to boil off the flux.

What are the key points I should retain about using flux so that it becomes second nature, and I fully understand why I'm doing it?

If you use a rosin core solder wire or paste with rosin, you only need additional flux if the surfaces to be soldered have some sort of contaminant on them.

I use liquid flux whenever I'm soldering wires to grabbers because they all seem to have an oily film on them. I also use extra flux when I'm soldering on copper that hasn't been tinned.

 

In almost every tutorial I’ve watched, whether it's for tinning copper, soldering components, or using a solder wick or hot air station to remove solder, I see people applying flux to the surface first.

Yep, you pretty much got the answer already, makes things alot easier to flux first when soldering in components.