Best results with lead free solder

When using lead free (silver) solder for the first time, you are probably much disappointed. The solder joint looks not nice, looks unreliable, and badly done. Well, and that is probably just what it is. Lead-free soldering is not more difficult, but mostly it is ANOTHER process, and you probably don't know that. All you need to do is change the way you are soldering, and you can have very nice results. Lead-free soldering was always done to get solder joints of higher stability. So... what keeps you from doing it? .

Here is a typical problem situation:

What causes this problem?

Here is the difference. With lead solder, the moment it melts, and there is some flux, it will flow nicely. The flux is active from the very moment the solder has melted, and lead solder melts at such a "low" temperature, the flux will not burn away quickly, doing it's job all of the time.

Not so with lead-free solder. The flux is initially not working. You need to understand this. You have to heat up the joint, until the flux starts to burn away, which means really it is quite hot. It is this very moment, where the flux burns away, the solder suddenly flows nice, and after that is nti functional, and you have to remove the solder iron. However, this moment is short, since the burning flux is disappearing quickly. This makes the moment of good solder flow so short, and you can only make small solder joints, like solder two little wires together. The moment you need to do something larger, you simple need to apply extra flux, or even apply it a few times. I have tried everything, but I find this the only way. For best optical results, you can remove the flux residue with alcohol, and it will look very nice.


Ordering code:
610-007-76

This is a liquid flux, of highest possible concentration, so as much as possible will stay on the object. It looks like honey. If for some reason you find it too thick, you can use alcohol to make it thinner.

You can also use it to prepare printed circuit boards before soldering. For this application, mix 1 part of the liquid solder flux with 1 part alcohol. Paint the PCB with this, let is dry on the air for one hour, or dry it with air from a hair dryer. When dry, solder the PCB the normal way. Don't bother how it looks afterwards, you can remove the residue nicely with 100% pure alcohol.

Hint: Resin in a good glue. So keep the bottle clean before you close it. If in any case you glue the lid on, with spoiled residue, you can open it after warming the lid with very hot water, or leave the closed bottle in alcohol a few hours.

How to apply extra flux?

The good old way, to dip the solder iron into some flux is not working with lead free solder. The flux is burning away already on the solder iron. The small residue that is left, will not spread over the solder joint insufficient, and you may just burn the components.

Process for larger solder joints:

  1. Apply liquid flux on all surfaces that you want to solder. Use as much as you can apply on it. Better take too much as too little, any residue can be very easily wiped off afterwards with a cloth and some alcohol.
  2. With litz wires, apply liquid flux solder before you solder them. Then pre solder those very thin, before soldering finally into the solder joint that they are intended for.
  3. Solder the normal way. I you have enough solder, but you feel there is not enough flux, let cool down the joint, paint as much liquid flux on is as you can and re solder.
  4. If that will not help, here is another method. Empty half of the bottle content in some small metal container. (Like the metal lid of some bottles) Let it dry in there until you have a sticky paste, of which you can apply as much as you need then. With this it will always work nice.
  5. Smaller joints will need less attention, the above is for larger, more difficult joints.
  6. Once you have this technique under control, you will not understand why you ever had problems with it :)
  7. Conclusion: You do need to apply extra flux, when soldering lead free. There is no other good way.

Hint: For clean de soldering we sell an excellent, and low cost de soldering iron. (Check under "tools" in the menu)