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Post by mulmany on Jun 9, 2014 22:34:23 GMT -6
I have been soldering for a while now, but every now and then I have issues. I want to see if this is normal or if I need to change what I am doing.
Tonight I am assembling the JLM power station and everything is flowing nice and quick, running just over 300 C°, I get to the electrolytic and it just comes to a stand still. I stop clean the tip really well, recoat with solder, still having the same problem. I have good contact with both the leg and the trace but the solder does not want to flow into the trace/through hole, it's just collecting on the component leg. I tried a little extra flux, that did not work, raised the temp, that helped a little... I did get them to flow it just seemed like it was taking way longer then it should, does not look very good, and I was risking burning everything up.
It seems that this happens to me on almost every project to some extent. It's not always caps either.
I am using a hakko 936 station and the solder that is recommended for the gar2520's.
Maybe I am crazy. I should record it next time it happens.
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Post by svart on Jun 9, 2014 22:56:31 GMT -6
That's called a cold solder joint and it happens because the amount of copper you are trying to heat is wicking away an equal amount of heat that your iron is producing.
Let me give you a tip, turn your iron up in temp. You aren't going to burn anything up. It's actually better to use very high heat for short periods, than using lower heat for longer periods. It's a common wives tale that you need to use as low heat as possible, and it's just plain wrong.
Heat soak is what kills parts, not short temp increases.
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Deleted Member
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Post by Deleted on Jun 10, 2014 6:15:25 GMT -6
svart is totally right with this one. I had this with a Weller iron in the past...
Perfect with some digital electronics, but unusable for some analog pcbs, whereever i came to holes in grounding planes. Turns out it had only 25 Watt electrical power and was too cold...
Nowadays i use irons at high temperature with only short contact to the lead and pcb. Works perfect.
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Post by svart on Jun 10, 2014 6:54:39 GMT -6
In 20 years of soldering, I've never once burnt up a PCB, and I've done some crazy shit to them! I commonly solder large BGA devices (processors, FPGAs, etc) using rosin, aluminum foil and a heat gun like you'd use to strip paint from something! My irons are set to the hottest they can go (around 900F) too.
The most common PCB material these days is called FR4. Fire Resistant #4. That should tell you something. Maybe 20 years ago the boards were phenolic plastic and could burn fairly easily, but now they are made from fiberglass which is very hard to burn.
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Post by mulmany on Jun 10, 2014 6:56:29 GMT -6
Well, it does not look like a cold joint, I am probably being a little OCD about how it looks. I had a feeling that it's always on the ground plane that gives me problems. The heat sinking makes sense.
Isn't there an issue with running too
hot and the flux cooking off before it can actually clean the joint?
Thanks.
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Post by svart on Jun 10, 2014 7:57:18 GMT -6
On the grounds is usually where it happens most since the ground is the lowest impedance electrically, which means it will be the lowest resistance for heat transfer.
Cold joints don't need to look like anything. Cold joints just mean that the solder hasn't bonded fully. Some types of solder can look grainy or otherwise strange, while others will look almost normal but be structurally flawed. Again, a common misconception in the soldering world.
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Post by mulmany on Jun 10, 2014 11:53:59 GMT -6
svart, what about the flux issue I mentioned. Any thoughts on that?
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Post by svart on Jun 10, 2014 12:33:50 GMT -6
Is it "no-clean" flux? I've always hated that stuff. it won't work for heavily corroded junctions. It works marginally well for very clean and new pads and parts.
I've always used rosin cored solder and/or rosin flux with my soldering. It takes more effort to clean but the junctions it helps make are much better.
Anyway, flux is not totally meant to clean the metal. It's main purpose is as a surfactant, which helps the solder stick to the metal through changing it's wetting ability. Some of the fluxes are good at dissolving some amount of corrosion, but they are also corrosive to the metals and these aren't used very often for electronics. If you are not using a standard lead based, rosin-cored solder, then I'd suggest that you get some and try it. I'd bet your problems go away.
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Post by mulmany on Jun 10, 2014 18:08:50 GMT -6
Thanks.... no I am using rosin core lead solder. I had read in a few different places that if you run real hot that the flux cooks off before it can do its job. I had always heard it was for preparing the contacts and cleaning them so the solder sticks.
Well I guess I will not worry about it and just run my iron hot.
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Post by ppa on Jun 14, 2014 13:26:38 GMT -6
In 20 years of soldering, I've never once burnt up a PCB, and I've done some crazy shit to them! I commonly solder large BGA devices (processors, FPGAs, etc) using rosin, aluminum foil and a heat gun like you'd use to strip paint from something! My irons are set to the hottest they can go (around 900F) too. The most common PCB material these days is called FR4. Fire Resistant #4. That should tell you something. Maybe 20 years ago the boards were phenolic plastic and could burn fairly easily, but now they are made from fiberglass which is very hard to burn. I agree with you, I have used often high temp for short time (often 350°C) without problems. I use weller WSD and WSL soldering stations with 80W irons so the temp is very costant. For soldering IC's I have used 280-310°C often. |
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Post by mulmany on Jul 28, 2014 22:50:18 GMT -6
Just wanted to thank you guys. I up ' ed my operating temp on my iron and have been getting great results.
Working on the 51x rack and psu build and everything flowed so nice, even on the big caps.
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