Let's Talk About Flux

All of the solder work I have ever done was without flux (pen). When desoldering, I think it could be useful to make the solder flow better. Desoldering braid has flux already in it. You can always reflow a little to make a part easier to remove. Now having said all that, one of my recent orders had a flux pen in it. I figured if it makes it easier, it's worth it.

extra flux is not necessary for most things.  It helps when you have heavy ground planes, I do use some there when I don't quite get the flow I want....but then I usually crank the heat to about 375C as well.

I use solder with flux already, a rosin core solder.  If you use a brick, then sure.

For desoldering, it helps to get more flow.  For stubborn solder in a through hole, add flux, fill up the solder and then add more flux and hit it with the wick....or get a proper desoldering/reflow station with vacuum.

I use paste, when I need it.  Clean up is a bitch, but, you do what you gotta do.

I don't use much flux on TTH work. For SMD work. I have found it easier to use a paste with flux in it and place it with a tooth pick or a sewing needle.

The most useful thing I have found for soldering is this stuff.

http://www.radioshack.com/product/index.jsp?productId=2062721

i use it on every joint i make, makes for smoother shinier joints no matter the type of soldering. i use cardas quad and it has flux, but a little extra cardas flux paste is excellent for making joints quickly for sensitive components and making for a nice neat joint. i do heaps of smd work and wouldnt live without it

Be careful with flux, excessive amounts can make a bad joint.

I did a theater for Georgetown University a few years back, we had a subcontractor soldering whirlwind mass connectors (between 48 and 120 pins per connector), he kept bragging about being a "mil spec" solderer, and told us that you HAD to add flux to make a proper connection, even when using flux core solder.  After soldering all of the connectors on site (around 60 of them), we began testing the system, at which point we found that around 95% of his solder joints were over fluxed and would not pass signal.

Quote:

Originally Posted by samsquanch 

Be careful with flux, excessive amounts can make a bad joint.

 

I did a theater for Georgetown University a few years back, we had a subcontractor soldering whirlwind mass connectors (between 48 and 120 pins per connector), he kept bragging about being a "mil spec" solderer, and told us that you HAD to add flux to make a proper connection, even when using flux core solder.  After soldering all of the connectors on site (around 60 of them), we began testing the system, at which point we found that around 95% of his solder joints were over fluxed and would not pass signal.

yikes, he must use craploads, because i have never once found this to be a problem and i would make about a thousand joints a week at the moment with several builds plus work. i use cardas organic flux added with a resistor lead or small old screwdriver to cardas solder; only a small amount, but some with each joint. with wire i just wipe a small amount on the end before i tin it and then ove forward and solder it without adding more, there is usually enough there.

if its safe to use high heat and heat the joint really well before applying solder i dont always use extra and just rely on the core, but for smd where i need a quick good joint i use it every time and can only think this guy of yours was also incompetent

Quote:

Originally Posted by qusp 


...can only think this guy of yours was also incompetent

 

Subcontractors usually are.

I don't necessarily know how the excess flux caused the connections to fail (chemically/mechanically), but I've personally taken it as a lesson to not go crazy with flux, adding it all willy-nilly like a mad man.

Flux is very handy for one handed soldering. If you need to hold something in place with one hand and hold the solder, and hold the iron, hmm.. one hand too many! Hold on with one hand, place a dab or drop of flux on the joint and then touch the tip of the iron to the solder to get a little solder on it and then touch the solder to the joint. Your good to go!  This is an indispensable technique I am sure you will find many uses for it. I use it on those fine little tabs on the ipod connectors works swell.

I don't use additional flux too much. Flux in solder core is enough most of the time if you are quick. When I need to hold a part in place, just a touch of solder helps.

I like using paste flux for SMD chips. When I was building a Gamma2 I found that the paste helped hold the chip in place till I got one leg tacked down. It helped make my GurbDac and Mini3 builds go much smoother. However, cleaning up flux sux