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Issues with soldering

Last year I got a soldering iron for Christmas last year and it has been a pain ever since I got it. However I don't know whether it's the solder, soldering iron or me that's at fault. The iron is a very basic one for beginners. It's 40W and has a temperature range of 420 to 460 degrees. So it should be hot enough for the job of soldering electronics components to a board. However when I try to tin the tip the solder melts but runs off the tip instead of sticking. If I hold the soldering iron against the terminal pins then hold the solder against the pin the solder doesn't melt. I don't know why this is but I am guessing that it's because I can't properly tin the tip. I don't know whether the solder I am currently using contains flux, if it doesn't then that might explain why I can't tin the tip with it. Any ideas what the problem might be? Below is a picture of the soldering iron I'm talking about.


solderingIron.png
 

gophert

Well-Known Member
Most Helpful Member
That is a very hot iron. I typically solder at 370 with tin/lead alloy. The solder that came with your kit may be lead-free solder which melts at higher temp and doesn't flow as well as tin/lead alloy. If you can find it in the UK, get the easier-to-work with solder, turn down your temp.
Get a wet (damp) sponge and wipe the tip across the sponge every time you pick it up. The hot metal firms oxides that don't stick to anything and the steam quickly dissolves them and sponge grabs them. Wipe reasonable fast to hear the sear but not scorch the sponge. No standing water - just reasonably damp. Completely wet and squeeze tightly. That's about right. The sponge grabs excess solder as well.
 
Thanks for your reply. I have thought about getting some leaded solder as it might be better. But do you think it's possible that I'm right about the solder not containing any flux? As I've heard it's the flux that removes the oxides and allows the molten solder to stick.
 

gophert

Well-Known Member
Most Helpful Member
Thanks for your reply. I have thought about getting some leaded solder as it might be better. But do you think it's possible that I'm right about the solder not containing any flux? As I've heard it's the flux that removes the oxides and allows the molten solder to stick.
yes, get solder specific for electronics, rosin core solder 63%37% tin/lead.
 

DerStrom8

Super Moderator
Years and years ago when I first started soldering, I had this exact same problem. I started off with a 40W pencil-type iron too, and could never get it to work. solder would just ball up and I could never get good heat transfer between the iron and the joint. I eventually learned what I was doing wrong.

1) The temperature of the iron is much too hot for standard component soldering. You might use a 40W iron for soldering to a chassis or large connector leads. Not for common components like resistors, diodes, and capacitors. You could probably throw it on a variac and run at a lower voltage to get a better temperature. If your iron is too hot, solder will not flow and will simply ball up on the tip.

2) The trick is to apply the solder as the iron is heating up. If you wait to apply solder until it's reached full temperature, the tip will already be oxidized and solder will not stick. Chances are your tip is already black from the oxide. I recommend buying a replacement tip and holding solder (with rosin core flux) to the tip while it is heating up for the first time. The instant it starts melting, try to coat the entire tip with the solder. This will prevent the actual tip from oxidizing and solder will flow much better.
 
Thanks for the replies! I actually have a replacement tip and switched it in the other day. It seems to work, this is to say the solder sticks to it instead of running off the tip. But it still seems to form balls rather than a coating. Even when I apply lots of solder to the tip and press the soldering iron against the terminal pin, I still can't get the solder I'm pressing onto the pin to melt and I don't really know why. The tip of my soldering iron does seem very large compared to the terminal pins, so maybe it's too big for this specific job? The iron was advertised as being suitable for electronics, but given the intense heat and the solder that doesn't melt (which came with it) maybe it's not such a good option and I just need a completely new set up.
 

DerStrom8

Super Moderator
Thanks for the replies! I actually have a replacement tip and switched it in the other day. It seems to work, this is to say the solder sticks to it instead of running off the tip. But it still seems to form balls rather than a coating. Even when I apply lots of solder to the tip and press the soldering iron against the terminal pin, I still can't get the solder I'm pressing onto the pin to melt and I don't really know why. The tip of my soldering iron does seem very large compared to the terminal pins, so maybe it's too big for this specific job? The iron was advertised as being suitable for electronics, but given the intense heat and the solder that doesn't melt (which came with it) maybe it's not such a good option and I just need a completely new set up.
I suspect the solder is low quality and has minimal (if any) flux. That coupled with the extraordinary heat makes for a very difficult (or impossible) soldering experience. Flux cleans the oxides off of the iron tip as well as the joint. Without it, solder will not want to flow because the oxides form an insulating layer against the heat. And, again, I recommend either buying a smaller iron (15W works great for smaller electronics, or even better, get a temperature-controlled iron), or putting your 40W one on a variac to adjust the voltage (and thus, the heat output). Between the use of proper flux and a lower power setting, I think your iron will perform as desired.
 

gophert

Well-Known Member
Most Helpful Member
You can also put a diode (1N4004) in series with the AC line voltage. This will cut the power by 50% to 20 watts.
 

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