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Kit Soldering
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Kit Soldering

by jaggedtoaster on Mon Feb 22, 2010 8:16 pm

So I just got my USBtinyISP today and have been working to put it together. Most of the soldering looks pretty good. I have put a couple of freeduino's together and a wave shield and they are working. However I would like to get better at soldering. I've got some mediocre soldering connections and worry that one could be a cold joint.

What is the best way to go about resolding a connection? Do I use a solder-sucker/wick to remove the existing solder and then redo the work? I've got a 25 watt Hakko iron. I figure that is decent enough as I am able to get mostly good looking connections. Could it be my tip is too dirty? I try to leave the iron in place touching both the pad on the circuit board and the leg of the component to be soldered for a few seconds, then leave the iron in place for about a second after I remove the solder.

Any tips on resoldering and/or possibly preventing poor soldering connections to begin with? Thanks!

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Re: Kit Soldering

by zener on Tue Feb 23, 2010 2:10 am

Your method will work fine. Make sure to clean your tip with the bronze wool or whatever that is, or a wet sponge.

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Re: Kit Soldering

by FazJaxton on Tue Feb 23, 2010 2:51 am

When soldering, I clean the tip to remove oxide, then put just a bit of solder on the iron before heating the joint. The liquid solder helps conduct heat from the iron to the pad and lead. Note that I am not putting a blob of solder on the iron, then trying to use that for the joint. It's just a little bit to conduct heat.

Also, when I learned to solder, I was taught to melt the solder by touching it to the pad and lead, not to the iron. The solder won't melt until the pad and lead are hot enough, ensuring that you get a nice joint.

You might want to look at Ladyada's Soldering Tutorials. I especially like the Curious Inventor one.

After that, it's just practice, practice, practice! :)
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Re: Kit Soldering

by uknative on Tue Feb 23, 2010 12:38 pm

I agree with the previous people. When i was taught to solder it was to put solder on the iron and then touch the pads and components, after many frustrating problems with cold solder joints and burnt up components. I went back and found tutorials, lady ada's is good and so is the one on the NASA site. And had much fewer problems after some practice. I clean the tip with bronze and after a few projects I use some 220 grit of finer sandpaper and gently polish the tip to clean oxidation off. Don't scrub too hard just gently polish it. This seems to let the tip transfer heat much better.

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Re: Kit Soldering

by adafruit on Tue Feb 23, 2010 12:40 pm

good points, we do want to warn that not all tips should be sanded tho. the 'really nice' tips have a coating on them and if you're a little clumsy you can sand it away & they'll be ruined so CHECK the manual for your soldering station before sanding! :mrgreen:

(that said, you should never buy an iron that doesn't have nice replaceable tips that screw on)

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Re: Kit Soldering

by sirket on Tue Feb 23, 2010 2:18 pm

jaggedtoaster wrote:What is the best way to go about resolding a connection? Do I use a solder-sucker/wick to remove the existing solder and then redo the work? I've got a 25 watt Hakko iron. I figure that is decent enough as I am able to get mostly good looking connections. Could it be my tip is too dirty?

FLUX!

FLUX FLUX FLUX FLUX FLUX! LOTS OF FLUX!

Seriously- you pretty much can't use too much flux. Flux is what gets rid of the oxides in the solder joint. Get a good RMA (Rosin Mildly Activated) flux from Kester. Use good solder as well- also preferably Kester.

Don't de-solder the joint, just put flux on top and then re-flow it. The flux will remove the contaminants and produce a good connection.

Cold joints are rarely the result of too little heat- they're usually caused by contamination.

I try to leave the iron in place touching both the pad on the circuit board and the leg of the component to be soldered for a few seconds, then leave the iron in place for about a second after I remove the solder.

As soon as the solder begins to flow- remove both the solder and the iron. Holding the iron there only keeps the joint molten while the flux boils away thus allowing contamination.

Any tips on resoldering and/or possibly preventing poor soldering connections to begin with? Thanks!

1. Do not sand your tip. It should never be necessary.
2. Use a damp sponge and/or brass wool for wiping the tip.
3. Always put a touch of solder on the iron before bringing it to the joint- but don't wait too long as it can become contaminated.
4. Wipe your iron after _every_ joint or component (if there are several leads right next to each other. Keep it clean!
5. Use a tip tinner to keep the tip in good condition.
6. USE FLUX!
Last edited by sirket on Tue Feb 23, 2010 3:43 pm, edited 1 time in total.
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Re: Kit Soldering

by sirket on Tue Feb 23, 2010 2:21 pm

uknative wrote:I clean the tip with bronze and after a few projects I use some 220 grit of finer sandpaper and gently polish the tip to clean oxidation off. Don't scrub too hard just gently polish it. This seems to let the tip transfer heat much better.

220 grit is _very_ aggressive grit for cleaning a soldering tip- unless you're talking about a copper roofing iron. 600 is probably the harshest you should use to polish a tip- and even then- it should never be necessary.

When you are done soldering: dip your iron in flux, wipe it on a damp sponge and immediately stick it into some tip tinner.
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Re: Kit Soldering

by jaggedtoaster on Tue Feb 23, 2010 3:35 pm

Excellent information, thanks for the replies! I will get some flux and try reflowing the joints that don't look so good. I'll also have to get some tinner.

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Re: Kit Soldering

by sirket on Tue Feb 23, 2010 3:41 pm

jaggedtoaster wrote:Excellent information, thanks for the replies! I will get some flux and try reflowing the joints that don't look so good. I'll also have to get some tinner.

The flux should fix your issue. Tinner is really useful but get a damp sponge first. Damp- not wet. If you can't get tinner just put some solder on the tip right before you turn it off. That will help protect the tip. Wipe it clean next time you use it.
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Re: Kit Soldering

by jaggedtoaster on Thu Mar 04, 2010 10:02 am

So one follow-up question. I used a lot of flux on my last protoboard and the soldering went pretty good. Now that it is finished, what is the best way to clean it up?

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Re: Kit Soldering

by sirket on Thu Mar 04, 2010 11:31 am

jaggedtoaster wrote:So one follow-up question. I used a lot of flux on my last protoboard and the soldering went pretty good. Now that it is finished, what is the best way to clean it up?

That depends on just how much flux, and what type. An RMA or water based flux can generally be left on the board without problems. Anything stronger needs to be cleaned up.

You can purchase special purpose flux removers from companies like TechSpray but they are generally unnecessary. Use soap, water and an old toothbrush to clean the board. Rinse it with water, shake it off and let it dry thoroughly. You can use a hair dryer or low heat gun if you want to speed things up.

Did the flux help, your technique get better or both?
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Re: Kit Soldering

by jaggedtoaster on Thu Mar 04, 2010 4:28 pm

I think the flux tended to help quite a bit. I got the tinning for the iron and it is starting to look better. The flux I used was the stuff that Radio Shack carries. Not a terribly large amount left on the board, but a little sticky in spots. It is a clone of the MintyBoost and I'd like to clean it up to be sure the double-sided tape will stick well to it.

Thanks for the follow-up.

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Re: Kit Soldering

by jaggedtoaster on Thu Mar 04, 2010 8:51 pm

Here are a couple of quick pictures of how it looks. Just a simple MintyBoost protoboard clone.

Also, many thanks to Adafruit for hosting information and schematics about their projects! I've purchased and built the Wave Shield and USBTinyISP. The instructions have always been clear and easy to follow.

Front:
Image

Back:
Image

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Re: Kit Soldering

by Agent24 on Wed May 12, 2010 6:16 am

You need only preheat the joint for about 1 second. Total time for the whole process should be 2-3 seconds usually

If you're using rosin core solder you don't really need extra flux, unless you have seriously dirty components or PCB (which should be cleaned first!)
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Re: Kit Soldering

by adshea on Wed May 12, 2010 5:06 pm

For cleaning tips I've found using fine (0 gauge) steel wool if it's really bad followed by some tip tinning solution. http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SMDTCLF-ND It's like some super flux solder paste that cleans off the tip and tins it nicely.

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Please be positive and constructive with your questions and comments.