Let's Make Robots!

Can't solder anymore -> solder doesn't melt and stick on the board

Hi all. I've got this cool digital soldering station this morning and boy was I exited! At last I could solder my 1 robot kit! Well after soldering 30 or so contacts + soldering in the axis I couldnt solder anymore! Here's what happend:

1. Since I thought any solder would do (lame huh?) I bought the cheapest Sn99.3Cu0.7 solder. And since I thought it has the same melting temp. as Sn60Pb40  I soldered at 360 C / 680 F.

2. It went all good but after a while the solder wouldnt melt. So I raised the temperature to 450 C / 842 F :)

3. It helped only for a while and after that the solder wouldnt melt even if applied directly to the tip!

4. So I took my sandpaper and cleaned the tip. It helped only a little bit.

5. After all that torture here is what happens: If you apply solder to the tip the solder melts but doesnt stick to the tip! The "ball" of melted solder remains on the solder wire! Of course you cant solder any contacts because you cant heat up the contacts to the melting temperature!

I'd say total fail. I already ordered new iron tip and Sn60Pb40 solder but Iam not sure it will help? And I always cleaned my iron in a wet sponge before and after the soldering. I shouldnt done it after, right? 

Main questions would be:

a) What should I do to be able to tin the iron tip again? I cant do that even after using the sandpaper!

b) Can I use my lead free Sn99.3Cu0.7 solder with some solid rosin I have? I how do I do it? What temperature do I use and how do I apply the rosin?

 

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I'm using solder with flux inside of it so it flows better. maybe thats the problem?

or maybe you have solder without lead instead a tin/lead mix? that requires a higher temperature and different soldering iron

edit: google says Sn99.3Cu0.7 solder = without lead. THATS the problem.

You dont need google to see that the formula doesnt contain Pb in it = no lead :D And yeah, it a SMD solder that kinda weird, it contains flux though. In general you can solder without lead, moreover solder containing lead will be banned in Europe soon :( 

What I dont understand though is how I destroyed 2 iron tips to the point that they didnt melt solder properly in a matter of hours.

Ok so first wrong thing is my solder wich is SMD solder which supposed to melt at 225C but it takes too long so I work with 300-350C. I somehow managed to repair the tip with a sandpaper (was a "broken" tip anyway) so Iam waiting for proper Sn60Pb40 solder while solderig with SMD solder =)

Thx for all the reply. But Iam doing something wrong, I dont know what it is and its pissing me off. So yesterday I got a new tip and it "died" in a 1 or 2 hours! Here are exactly the steppes I did:

1. Turned the station on and set it on ~360C/680F.

2. Tinned the tip with a Sn99.3Cu0.7 solder. Cleaned the tip with a brass wool which I found at home.

3. Soldered like normal and it went like it should. After soldering I always tinned the tip. Before soldering I always cleaned the tip in a brass wool.

4. After 1-2h heat transfer would sink so I raise the temperature to about 400-430C wich helps for not too long.

5. After 30 min or so you cant tin the soldering iron because the solder woudnt stick to the iron.

 

As mentioned, don't ever sand or file a soldering tip. 

You just got it today? If the new tip doesn't fix it send it back, something's wrong. One day's worth of crud and oxidation shouldn't have been that noticable that quickly.

once in a while, I simply turn or rotate the tip in steel wool a few times each way, and the tip stays tinned and I never have any problems, other than it loosening once in a while, as oddbot mentioned.

don't use sandpaper, you don't want to take the tin off and expose the copper.  You can try to go to radio shack and get some tinning compound and try that to get it back.  But you are going to need a new tip after that sanding.  Also go to the kitchen shop and get a brass scrubber as merser suggests and use that to clean the oxidation off your tip from now on.

Ok, thanks, will do. So you suggest to dont use the sponge at all? And I still dont understand what caused the tip to stop to transfer heat even before sanding. A absolutely new tip stopped to transfer heat after an hour or so. Even the solder on the tip wouldnt melt. 

oxidized crap on the tip creates a barrier.  you need to remove the oxidation.  

So how do I remove the oxidation layer? Do I sandpaper it and then apply some rosin? I have some solid rosin at home wich "melds" at hot temp.