another soldering quesition - perhaps incorrect use of flux?

Hello, While I was soldering 2mm pin headers to a wireless module, I ran into some issues. I'm a newbie, so any tips would be appreciated.

I used 62/38/2 solder from radio shack. I used a flux pen to wipe across the pins and pads. The flux is not a "no clean" flux. I put the tip of the weller soldering iron (40W) on the pad and pin. Let it sizzle for a 3 seconds there and then poke the solder into the base of the pad where the pin sticks out. It worked great 80% of the time.

The problem is sometime the solder doesn't flow into the spot. I thought it was hot enough, but when I poke it into the base it doesn't melt and instead I bend the length of solder I was holding. Once that happens, it was hell to try to get it to work.

When I sizzle the flux, does that leave a film on the pads? Should I have wiped off the flux before heating it up? From the tutorials I watched, people just apply flux, then heat the pads and solder.

After soldering, the module was pretty hot. There are a couple spots where I ran into the issue and the PCB got a little brown. Is that bad?

I also would like to solicit advice on how to wire the pin headers to an Arduino Uno now that I have the wireless module soldered onto it. The spacing is 2.0mm instead of the standard bread board spacing. Should I just solder male-male dupont wires onto the pin header? I couldn't find 2.0mm F-M dupont cables.

The wireless module looks like this:

With the headers on, it looks kind of like this:

arusr: Hello, While I was soldering 2mm pin headers to a wireless module, I ran into some issues. I'm a newbie, so any tips would be appreciated.

Place the end of the rosin-cored solder between the iron and the pad/pin, then as the solder and rosin melt they flow immediately onto the fresh copper/tin surface before it has time to oxidize. Heating the pad first just risks forming an oxide film and causing heat damage.

Normally before soldering you would tin both contacts first ("tin" means coat in solder), but this isn't normally needed on clean tin or gold plated surfaces. Copper surfaces always need tinning, copper forms an oxide layer very readily.

Normally before soldering you would tin both contacts first ("tin" means coat in solder),

Yes! Nothing sticks to solder like solder.

MarkT: Place the end of the rosin-cored solder between the iron and the pad/pin, then as the solder and rosin melt they flow immediately onto the fresh copper/tin surface before it has time to oxidize. Heating the pad first just risks forming an oxide film and causing heat damage.

Maybe that's what was happening. The difference between when it worked and when it didn't was so stark. I knew something was going on, but I couldn't figure out what.

In the soldering tutorials, they say to heat the pads...something about hot pad forming chemical reaction with hot solder to form a joint. Will melted solder flowing on a cool/not-so-hot pad form a good joint?

I usually do the following to fairly good success: 1) Position two parts to be soldered together with a good mechanical connection (Tweezers or a little bit of pressure for through hole parts 2) Clean the tip of my iron and drop just a little bit of solder onto the end to get some fresh tinning/solder blob on it. The size of this blob is dependent upon the size of the solder joint. 3) Apply the tip to a joint between both parts using the tinned part of the iron. You want good contact between both. Solder should flow relatively quickly onto both, or the temperature is probably wrong. 4) Without lifting the iron, add more rosin core solder into where the solder has already melted. This should spread the solder out and the flux in the solder will help it flow out to cover the pad and lead. Take away the iron and the solder.

If you are doing a part with a lot of pins, I'll tack down 2 pins by doing 1-3, then fill in all of the other pins, then do step 4 on the first 2 pins. This has worked for me pretty effectively for both through-hole and relatively large pad parts (Down to 0603 but I try to avoid those) The only difference is for SMD parts, I use 0.015" diameter solder instead of the more normal 0.032" diameter solder.

mirith:
2) Clean the tip of my iron and drop just a little bit of solder onto the end to get some fresh tinning/solder blob on it.

I’ve tried this, but haven’t gotten it to work yet. I’ve cleaned the tip with flux, and I clean it with the sponge. I let the iron get hot. When I apply the solder to the tip, the solder doesn’t flow onto the tip. It just bunches up into a ball at the end of the length of solder in my hand.

My soldering iron seems to repel solder.

See this for instructions on tinning your soldering iron tip. http://www.instructables.com/id/Soldering-101%3A-Lesson-1%3A-Tin-the-Tip/

arusr:

mirith: 2) Clean the tip of my iron and drop just a little bit of solder onto the end to get some fresh tinning/solder blob on it.

I've tried this, but haven't gotten it to work yet. I've cleaned the tip with flux, and I clean it with the sponge. I let the iron get hot. When I apply the solder to the tip, the solder doesn't flow onto the tip. It just bunches up into a ball at the end of the length of solder in my hand.

My soldering iron seems to repel solder.

Look at LarryD's video. Something is wrong if you aren't able to tin the tip, as that is how you get the best heat transfer. You might need to buy some tip tinner/cleaner from Radioshack as well.

Tip cleaner, ok, I've seen those.

Can I use a fresh dishwasher sponge instead of a special soldering iron sponge?

The tip of your soldering iron might need replacing. I think the tips have a normally easy to tin coating, but eventually it wears away. I use a 15w pencil tip iron, and the sharp tip starts disappearing after some amount of usage.

arusr:

mirith: 2) Clean the tip of my iron and drop just a little bit of solder onto the end to get some fresh tinning/solder blob on it.

I've tried this, but haven't gotten it to work yet. I've cleaned the tip with flux, and I clean it with the sponge. I let the iron get hot. When I apply the solder to the tip, the solder doesn't flow onto the tip. It just bunches up into a ball at the end of the length of solder in my hand.

My soldering iron seems to repel solder.

This same thing happens to me. I've looked at all the tutorials and they make it sound so easy, just touch the tip to the solder and now on to the next step...

I need a video maybe. Or maybe one of us should make a video of what happens to us and someone can try to explain what we're doing wrong.

Vigorously scratch the hot tip with a stainless steel table knife over oxides areas then try to re-tin it. Don't tell you wife I said to use her table knife.

I wouldn't use solder from Radio Shack on a bet, not even for plumbing. I only use 63/37 alloy for electronics. For fairly new through-hole components, flux is not usually necessary (other than what's already in the solder). I'm a real Kester bigot. This is my favorite solder. I use this flux for SMT projects. If I need something a little more aggressive, I use this flux. I use one of these to keep the tip of the iron clean.

Brown means burned and is bad. Iron may be too hot or was on the board for too long. If the board gets burned the components can't be far behind. It shouldn't take more than a very few seconds to make most solder joints.

LarryD: Vigorously scratch the hot tip with a stainless steel table knife over oxides areas then try to re-tin it. Don't tell you wife I said to use her table knife.

The green (abrasive type) Scotchbrite works too.

Delta_G:
This same thing happens to me. I’ve looked at all the tutorials and they make it sound so easy, just touch the tip to the solder and now on to the next step…

I need a video maybe. Or maybe one of us should make a video of what happens to us and someone can try to explain what we’re doing wrong.

hehe, yeah it’s a little frustrating. The tip of my soldering iron looks…rusty. Even though it’s brand new and I’ve only used it for 20 minutes. I think when I first turn it on some manufacturing oil dripped down from the heating element. I saw something drip down…didn’t think much of it.

I use a 15w pencil tip iron from radio shack mainly because I can get new tips at radio shack (expensive, but less than mail order postage). Worst case, you can try to clean the tip with steel wool then retin with acid flux.

Once you get the tip retinned, never let it run dry again.

Every time after soldering, wipe the tip and immediately add solder to it before putting it back in the holder.

Every time before soldering again, wipe the tip clean and immediately add solder. I don’t just mean every time you turn it on, I mean during a soldering session. If you stop soldering for a few minutes and have cleaned and tinned and put the iron in the holder, when you take it out again, repeat this.

When soldering a lot of joints, you will need to wipe it clean and retin occasionally as oxides build up. Oxides build up in minutes. Seconds.

It sounds like you need to clean and tin the solder tip and the leads. Here is an article I found on tip cleaning, tinning and care that I found very helpful: http://blog.gotopac.com/2013/04/11/solder-tip-tinning-and-care/.

They do make tip cleaners if that interests you: http://www.gotopac.com/599B_02_Tip_Cleaner_p/599b-02-hak.htm. Hope that helps! :)

zoomkat: I use a 15w pencil tip iron from radio shack mainly because I can get new tips at radio shack (expensive, but less than mail order postage). Worst case, you can try to clean the tip with steel wool then retin with acid flux.

Never use acid flux with electronics, it destroys circuit boards.

Rosin flux only.

63% Lead 37% Tin with an active rosin type flux is the Only one I will use… I used Ersin solder for many years but it seems most scarce in the smaller sizes (still in business?)
Second best is Kester where I use .018, for small parts pins like SMT… anything and .032 for general PCB soldering. I use a Kester flux sold at Radio Shack under the Radio Shack name. it is a “Rosin Soldering Flux” in a very useful albeit messy format as the rosin is dissolved in petroleum jelly (R.S. P/N 64-022 I’ve used this flux for years on all my PCB and SMT work.
No/Low clean or water wash type fluxes are aggressive organic chemicals that are removable with water and as a class are perfect for digital work and as a general purpose ‘active’ flux. There is a drawback to most of the water clean, No Clean and Low Clean based on the idea that the flux is both chemically active enough to ionize water and a solid slightly hygroscopic residue on the PCB that can and will cause a conductive film to form on the PCB. This ‘stray’ or leakage current is difficult to detect. and more so to compensate or correct for.
Finally, I use a Hakko 936 that is perhaps one of the absolute best I’ve ever used.The temperature control is fast and really keeps an iron tip at the setpoint.
The Digital Variable Temp device is nice but nearly useless but nice looking. I prefer to keep my iron @ 500 - 550F when using it and when not reducing the temp to 450F as this prevents or helps to prevent that really tough scale from forming on the tip. … Great job for an ATTiny… Add digital display of temperature data and an idle power reduction mode if the iron isn’t used… Although i all fairness a simple MicroSwitch and a piece of small gauge stainless steel wire used as the sensor for the presence of the iron… I have the controller circuit and I think I’ll be using an ATTiny for readout and to start the 5 min wait delay to reset… Just move the iron…
There are many tip cleaners available but remember that the ones like Sal Ammoniac can leave a residue on the tip that gets transferred…
I don’t use any of those things as I have two habits in regard to tip care and cleaning, Never, Never file one unless you are doing an instructable on how to turn a soldering iron into a very expensive wood burning set. Steel Wool if used frequently is almost as bad. in particular when the iron is hot.
I remove that glaze by scraping (blade @ 90 deg to tip) gently with the iron hot… when you chip a piece away immediately tin the spot but also wipe and repeat the process. Scrape, Tin and wipe/re-tin… until the film is gone or nearly so.
I usually get those films from contacting or deliberately melting plastic… Or leaving my iron on for days at a time…

Doc