what type of flux ???

Thread Starter

xtal_01

Joined May 1, 2016
124
Hey!

Realized I ran out of flux ... never gave it much thought, just used a rosin paste.

So, now I am doing the usual repairs on my car ... plus Amphenol connectors .. and even took a shot at repairing a board with surface mounted parts.

What flux do you guys use?

The one I had was MG Chemicals .... don't know why I choose that ... might have been given to me.

I went to their web page ... wow ... rosin (needing cleaning with alcohol), No-clean, halogen free, paste, liquid, .....

There is Kester ... SRM ... and a host of others!

What do you guys recommend????

Thanks ... Mike
 

SamR

Joined Mar 19, 2019
4,492
I use Kester 951 liquid "no clean" leaves a bit of white residue but no rosin. For paste using a syringe of MC chemicals No Clean Flux Paste. Also have some Kester 186 liquid with rosin but don't use it very much at all. Need paste for surface mount and use a couple drops of 951 just to make sure surfaces are deoxidized and clean to solder for everything else. I also use Kester rosin core size 66, 63/37, 0.031 dia. solder.
 

Ya’akov

Joined Jan 27, 2019
6,856
I agree with @SamR about the Kester 951 no clean. I have it in a needle bottle, but also in a pen which is very nice for clean, minimal applications.

1645522894983.png
I also have a pen with Kester 186 mildly activated flux. It's not no clean but it is very handy for hard cases that need a bit more aggressive action.

For surface mount, I use Amtech NC-5559-V2-TF tacky flux. If you haven't used it you'll find it weird at first. It is a sticky gel-paste. This particular formulation targets hand soldering with Sn/Pb solders, so it's perfect for the kind of small assembly and rework I do.

The tacky nature allows you to position the part without it twitching or escaping. You can use it with an iron or reflow. It is technically no clean, but it tends to leave a lot of material that I prefer to remove. It looks much worse under the scope than with the naked eye, but IPA takes it off easily. It's not cheap, and you can get knock-off products cheaper but I trust it so I pay the premium.

1645523247847.png
You didn't mention it, so I won't get into it but—solder, now that's another area that really needs the proper attention...

[EDIT: added link to needle bottle]
 

Thread Starter

xtal_01

Joined May 1, 2016
124
Thanks so very much for all the advice! I will get a couple types on order today.

Solder .. just didn't think much about it. I build a few industrial control panels each year ... but 99% is screw terminal work so I don't get into soldering much.

I just happen to get a job that has 6 Amphenol connectors ... 9 pin solder type, series 97 ... time to break out the magnifying glass.

I was given a Hakko 937 years ago because one of my suppliers needed a job done quick and didn't have a decent iron (I designed a PC board ... got it made online in three days ... mounted a bunch of switches and LED's to it ... worked great).

I am still using the solder he gave me 20 years ago ... thought it is now almost gone ... Phillips ECG SN60 .031 Rosin Core

I will need some probably later this year.

Thanks so very much again !!!!!!!

Mike
 

Ya’akov

Joined Jan 27, 2019
6,856
Thanks so very much for all the advice! I will get a couple types on order today.

Solder .. just didn't think much about it. I build a few industrial control panels each year ... but 99% is screw terminal work so I don't get into soldering much.

I just happen to get a job that has 6 Amphenol connectors ... 9 pin solder type, series 97 ... time to break out the magnifying glass.

I was given a Hakko 937 years ago because one of my suppliers needed a job done quick and didn't have a decent iron (I designed a PC board ... got it made online in three days ... mounted a bunch of switches and LED's to it ... worked great).

I am still using the solder he gave me 20 years ago ... thought it is now almost gone ... Phillips ECG SN60 .031 Rosin Core

I will need some probably later this year.

Thanks so very much again !!!!!!!

Mike
Actually, I would say you need some now. Solder alloys have different properties. 60/40 alloy like the stuff you have has very good wetting properties so it is often seen in bar form for solder pots used to tin leads.

But, it has a major problem for hand soldering, it has a plastic region in its temperature curve. That is, between the liquid and solid states it can be disturbed and lead to cold joints. That's where the solder looks dull and has a broken crystal-like structure.

If you don't move the joint at all until it cools to a temperature below this region, it will be fine. But it is very easy to move it and not notice the problem and cold joints are unreliable and often fail after some time so seem OK at first.

The answer is to use a eutectic alloy. That is an alloy of metals that has the lowest melting point for the combination and goes from liquid to solid directly. In our case, for tin and lead that is 63Sn/37Pb. This alloy is the best for hand soldering. It takes less heat and can't make cold joints.

Kester 24-6337-0027 .031" is a great choice and it is the same size as what you are using. One pound will last you forever, and you will find it much easier to work with and with better reliability.

1645547600233.png
 

Thread Starter

xtal_01

Joined May 1, 2016
124
WOW! And this is why I joined this group ... you guys always educate me!

Question ... I noticed this solder (and most others) is available in both 44 and 66 (2.2 and 3.3 % flux).

Which is better ?

It seems the 2.2% would be less corrosive but 3.3% might clean better?

And in the end, maybe it does not matter?

Thanks!
 

Ya’akov

Joined Jan 27, 2019
6,856
WOW! And this is why I joined this group ... you guys always educate me!

Question ... I noticed this solder (and most others) is available in both 44 and 66 (2.2 and 3.3 % flux).

Which is better ?

It seems the 2.2% would be less corrosive but 3.3% might clean better?

And in the end, maybe it does not matter?

Thanks!
Since the core is activated you want the 2.2%. You can always add no clean flux but the flux in the solder is "mildly corrosive" so cleaning is a good idea. Much less to clean with less flux.

For the record, I have used this particular solder for a long time and have never seen and corrosion on account of the flux.
 

MrChips

Joined Oct 2, 2009
27,695
63/37 #44 rosin-core solder is what is needed for electrical work.
The flux is already in the inner core of the solder wire. Hence you don't need to use additional flux.
 

Ya’akov

Joined Jan 27, 2019
6,856
63/37 rosin-core solder is what is needed for electrical work.
The flux is already in the inner core of the solder wire. Hence you don't need to use additional flux.
This is generally true but applying flus to the joint before soldering can help with wetting reducing heating times and for some sorts of small joints, putting flux on the parts allows "carrying" the solder on the tip. This burns off the core flux but if you've placed flux ahead of time it doesn't matter.

I have definitely seen improvements when using flux in addition to flux core solder but I only need it sometimes. Most of the time just careful application of the solder is enough.
 

sparky 1

Joined Nov 3, 2018
732
Different kinds I prefer these, adequate quality with less cleanup.
specs are no longer as informative as before. Out of 5 that did not work very well.
One of the quality issues was an expensive brand name or so the seller claimed.
The picture below shows the specs, part numbers. I found worked good for the money.

IMG_20220222_104031.jpg
 
Last edited:

Thread Starter

xtal_01

Joined May 1, 2016
124
I just looked at the Kester site.

It seems the 63/37 at .031 is available in what they call series 44 or series 66

This means it as a 2.2 or 3.3 % rosin flux core.

Is one better than the other or ???

I see the one made in China don't even control it that clearly .. it says 1.0 - 3.0%

Thanks!
 

Ya’akov

Joined Jan 27, 2019
6,856
I just looked at the Kester site.

It seems the 63/37 at .031 is available in what they call series 44 or series 66

This means it as a 2.2 or 3.3 % rosin flux core.

Is one better than the other or ???

I see the one made in China don't even control it that clearly .. it says 1.0 - 3.0%

Thanks!
I use the 44, which is what I linked to.
 

Thread Starter

xtal_01

Joined May 1, 2016
124
hmmm ... sorry ... not trying to be a pain but this is why I asked ...

the link you gave takes me to:

Kester 24-6337-0027 Solder Roll, Core Size 66, 63/37 Alloy, 0.031" Diameter

That is a size 66 core ... but you said you use a size 44 ?

Just want to make sure I get the right one.

Thanks !!!!!
 

SamR

Joined Mar 19, 2019
4,492
The really confusing part is that its name is Kester 44 solder. It's what I use but some of my parts are old and oxidized a bit so the little extra flux in the core is a plus. I still also dab it with a bit of liquid flux anyway. Kinda like wearing a belt and suspenders... LOL
 

Thread Starter

xtal_01

Joined May 1, 2016
124
Got it !!!!!!!!

I see on the web site .... it is Flux 44 but with 66 Core (3.3%) ....

I will put it on order right now ... may as well try to make my life a bit easier.

Good job to try it on ... 6 connectors with 9 pins each .... 54 joints to solder.

We will see how steady these 59 year old hands are.

Thanks so very much again for all the advice !!!!
 

SamR

Joined Mar 19, 2019
4,492
I believe there is also a 44 core like Yaakov and Mr. Chips mentioned but, to me at least, it's splitting a fine hair. But then I've been wrong before. ;)
 

Ya’akov

Joined Jan 27, 2019
6,856
hmmm ... sorry ... not trying to be a pain but this is why I asked ...

the link you gave takes me to:

Kester 24-6337-0027 Solder Roll, Core Size 66, 63/37 Alloy, 0.031" Diameter

That is a size 66 core ... but you said you use a size 44 ?

Just want to make sure I get the right one.

Thanks !!!!!
Sorry, I must have picked the wrong one. 44 is the right stuff.
 
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