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Author Topic: Soldering Hell  (Read 2081 times)
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the land of sun+snow
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Interesting, I keep hearing about flux and flux pens, but I've never seen any problems
with solder not flowing flow or not adhering, except in a few minor situations, like pins
with oxidation on them [like TO-220 parts seem to have], or the occasional crappy socket
pins. I use rosin-core solder, and 99% of the time it just flows right onto the joints, no
problem. I don't do much smt.

What are you guys doing that needs a flux pen? Could you qualify this? Specific situations
or for every solder joint of every kind?
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Anaheim CA.
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Flux, Flux, Flux... Get rid of the lead free solder, use a good quality solder, Ersin, If they are still around Kester if not. I use leaded solder, a Hakko 936 iron and the brass tip cleaner. I have used water for all my life and I am finally free of the whole water mess.
I use the 'paste' flux from Radio shack for smd parts only. The paste is a petroleum jelly with Rosin in it.
Extremely messy but worth the effort.
FWIW, I learned to solder when i was 13 years old and passed the mil spec soldering requirements test at Gonset... I was the youngest to ever do that at Gonset. Gonset was a mfr of military RF devices, radios... Etc in the 40's and thru the 60's where I lost contact with them.
Soldering is an art, more than a science as with practice after  a while you just know when to apply solder and when to lift the iron from the work piece.
Yes that tin crap does require more flux and No your work with lead solder isn't going to hurt anything ecologically either so use the lead solder and be done with it.
My $0.02 worth...

Bob
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the land of sun+snow
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If all else fails, go for 300W [just kidding],
http://www.aaroncake.net/electronics/300w_soldering_gun.jpg
tutorial:
http://www.aaroncake.net/electronics/solder.htm

One thing that shows your soldering iron tip is too hot .... many years ago I had a
cheapo Radio Shack soldering iron, non-temperature-controlled. After having the iron
turned on for a couple of hours, the tip was already starting to pit and deteriorate.
OTOH, I have been using a temperature-controlled iron for the past 7-8 years, and
the original tip still looks like new.
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I'm wondering if the solder I have is the problem, I have heard some people saying that newer lead free solder can be extremely difficult to work with.

Yep. Lead-free is very troublesome, I imagine that's the problem.

At a hobby level you're not going to save the planet by using lead-free. You might as well use lead.

Lead-free is perfectly usable - but the iron _must_ be a bit hotter than for lead/tin - otherwise you've just back to the cold-iron issues.

I've used lead/tin solder for 20 years, and for the last 10 have used tin/silver and there is very little difference at all if
the iron is hot enough.  lead-free doesn't behave as well if reworking a joint, but you just have to add a little more.
With the iron at a higher temperature you have to switch off when not using to stop iron-oxide building up on the tip
(this prevents wetting of the tip).

One little detail (sort of mentioned above) is that the iron must melt the solder directly onto the part - place the end of the solder wire
between the iron and the part-to-be-soldered and squeeze it gently - once the solder melts (should take 1/2 second or less) it will
spread heat to the part to be soldered - you hold the iron there for 1 to 2 seconds to bring the part upto temperature, feeding in a
little more solder to fully wet the part, then withdraw iron and solder.  Yes you do need three hands!

If it takes longer than 2 or 3 seconds then something is wrong (large areas of copper like ground planes take longer though, 5 to 6 secs).

Always wet the iron tip with solder, then wipe it on the wet sponge immediately before each joint.  Any oxide build-up will
cause problems.  Parts must be clean and bright too.

Temperature-controlled soldering iron is pretty much a requirement.  Something like 300 C for lead/tin, 330 C for lead-free.

[PS lead contaminates your fingers and cannot be removed to any significant degree by normal soap - avoid lead solder!]
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Centennial, CO
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@oric_dan(333) - I use two types of solder, Radio Shack 0.015" silver bearing (95% sure it's not rosin core) and a 0.032" rosin core. The latter I use for big through hole stuff, pin headers.

It flows good enough without any help from a flux pen. But only just good enough. (I'm not saying its the best rosin core solder).

However, whenever I need to rework a joint, the flux pen has to come out.  Also, with the pen, solder wicks into plated through holes better, so most of the time I just use the flux pen.

I use the thin solder for SMT and flux pen is a must there. The solder just flows so much better with it.

As for leaded solder, do your own research. LIke anything. There are multiple viewpoints on washing and how dangerous it is and such.
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Anyway your jaw will drop the first time you see solder flow after application of flux.
Agreed.  The other jaw-dropping moment for me was when I applied the flux pen directly to solder braid.  The rate at which solder was wicked-up was almost like magic.

I always use flux pens on braid, top tip that! Certainly helps clean up pads and such smiley
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Since we're on the subject of the best soldering techniques, I am getting my hand into fine pitched ICs.  I have a few 2560s that I am trying to solder.  I have a syringe with solder paste and I used my hot air station.  The problem I am having is that no matter what I do, I keep getting solder bridges across the pins.  I use very little paste and still get bridges.  I use so little solder that it barely solders the pin, but I still get bridges.  I have tried not using extra flux and using a ton of it.  Using more paste, still get the same result.  It seems like the solder just isn't reflowing very well.  I have also tried different temps.

Solder paste is from Kester and is 63/37
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//LiNK

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Maybe try an oven? I sometimes find that hot air moves the solder around too much and end up with bridges like you say
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I would disagree with

Quote
1) Always keep your sponge wet

I never use a wet sponge. I prefer this http://dx.com/p/soldering-iron-tip-cleaner-ball-golden-137118 kind of stuff.

You can use both.  I do.
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the land of sun+snow
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The problem I am having is that no matter what I do, I keep getting solder bridges across the pins.  I use very little paste and still get bridges.
This is usual with manual soldering. People just take some solder wick, and wick away
the bridges.
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Since we're on the subject of the best soldering techniques, I am getting my hand into fine pitched ICs.  I have a few 2560s that I am trying to solder.  I have a syringe with solder paste and I used my hot air station.  The problem I am having is that no matter what I do, I keep getting solder bridges across the pins.  I use very little paste and still get bridges.  I use so little solder that it barely solders the pin, but I still get bridges.  I have tried not using extra flux and using a ton of it.  Using more paste, still get the same result.  It seems like the solder just isn't reflowing very well.  I have also tried different temps.

Solder paste is from Kester and is 63/37

Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very *very* thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.) 

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.
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Are you laying the solder paste across the pins? or individually on each pin?
I just lay a very *very* thin bead across all the pins, and on the outer edge.
(I'm using lead free solder paste.) 

Don't have your hot air blowing too hard... because that can push molten solder to places you don't want to (forming a bridge).

Still with this technique, 2 pins out of 16 may form a bridge (SSOP-16)... then just use some flux and wick to fix it.

I am laying across all the pins.  The tutorials I've watched use that method.  The velocity of the air was low. 

This is usual with manual soldering. People just take some solder wick, and wick away
the bridges.

It's funny you say that.  I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick.  The bridges are on the board crossing the pads. 

I will just have to keep practicing.
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//LiNK

the land of sun+snow
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It's funny you say that.  I have tried to use wick to remove the extra solder, but I can't get it suck up into the wick.  The bridges are on the board crossing the pads. 

I don't do a lot of really fine-pitch smt myself. But someone else mentioned that you
might try taking some flux or solder and flow it onto the wick first. It does tend to be
difficult to get the heat transferred enough to get the surface-tension working through
a dry wick, even on non-smt parts.
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I have used flux on the wick, but never thought about tinning it.  I will try that.
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//LiNK

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The bridges are on the board crossing the pads. 

Do your boards have soldermask?

This stuff isn't just for looks, it's actually more "solder-phobic" than bare substrate. When I made my own boards I found they'd bridge quite badly as compared to boards with soldermask.

-j
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