How Do You Solder without Flux?

Hi Paul - Normal soldering is done with what is called rosin core solder. The solder comes with rosin built right into it and the rosin acts as a flux. Make certain that you are using rosin core electrical solder and not what is called solid core or plumbing solder. This should make things work better for you.

John

Paul, in addition to what john says, you want to make sure the surfaces being joined are clean. Isopropyl alcohol does nicely. Temperature of the iron and time with the iron are important, as well as stability. Too little temp or time and you can get a cold solder joint. Too much and it can be overheated. If the items being soldered move while cooling, such as a shaky surface or being moved by the iron, you can get a disturbed joint. One more thing to note is that if you are using lead free solder, the joint may not be shiny, even if it is a proper, well-wetted joint/fillet.

Thanks to both of you for your help.  I am using an 800 degree iron with appropriate tip for the job and am using rosin-core leaded solder.  I'm wondering if the rosin in the solder ages and becomes less effective.  I've had the roll of solder for several years.  I'm also wondering if there is enough rosin inside the solder.  I've heard that you can get different ratios of solder:rosin.

Any ideas?

Hi Paul,  Jbix was corect to point out the need for clean metal. I often will wire brush or use fine sand paper if the wires or traces to be soldered look dull. Your solder iron heat, if it is indeed 800 degrees is too hot. At this temperature the rosin will boil away and the solder will oxidize quickly. Do you get a puff of smoke when you apply the solder to the iron? If you do it is probably too hot. A more appropriate temperature is between 600 F and 700F. According to the solder manufacturers there is a shelf life to solder though I have used rosin core solder 20 years old without too much problem.

John

I just looked at the date on the spool of solder - 2005.  Too old?  Hmmmm.....

I don't think it is too old, the roll of solder I am using right now has a date of 02/12/87 on it and the price tag reads $1.98. Back in the early 90's some one was out at the sidewalk sale with a case of 1lb #66/44 solder rolls by Kester and I bought 10 of them. I am down to the last roll and have not had a single issue with them. So I don't think it is age, I would lean towards the iron begin too hot.

Could you take a video of you soldering so I can see your technique? If your joints are cloudy, you may not be holding the iron on the joint long enough to burn all the rosin.

http://www.seas.ucla.edu/ethinfilm/Pb-freeWorkshop/pdf/lee.pdf

Thanks so much.  So I've learned that, even though the manufacturer shows a shelf life of 2 years, that may not be a big concern.  Also, that for leaded solder, my iron temperature should be between 600F and 700F.  I do see smoke when I solder which substantiates that 800F is too darn hot. I learned from the Kester website that there are variety of cored solder with a variety of types of chemical.

I think I will lower my iron to 700F and see what happens.

Thanks again.

I'm interested to see if the reduction in temperature solves your problem.