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Solder Ball Dispersion Test (String Solder)

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Solder Ball Dispersion Test (String Solder) | 3 May, 2018

Our customer is asking for a solder ball dispersion test on our string solder for rework. The do not provide a test spec, only the attached diagram? has anyone seen this before? It looks like just pushing the solder against the iron and counting the stray solder balls. Without some criteria this could be a pretty subjective test.


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Solder Ball Dispersion Test (String Solder) | 3 May, 2018

Bob Willis (was the first I knew of) that has a splatter test that can be performed over a ceramic hot plate or the like.

The concept is pretty straight forward, using a zoned circle, users can introduce the solder wire at a consistent rate and count the solder balls created within each zone on each pass. This can advise the user of the out-gassing conditions of the solder wire they are using in their processes.

Below is a link to a YouTube video demonstrating this concept:

If you are struggling with solder ball and flux splatter issues in your soldering process, might I recommend researching solder feeding perforation stations. A few of these units can be viewed at the links below:

Stand-alone perforation unit:

Perforate and Re-Spooling Station:

Soldering Station with Perforation Feeder:

Hope this helps! FYI - I was not able to open or download the attached document.

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Solder Ball Dispersion Test (String Solder) | 4 May, 2018

Thanks for your response, I changed the attachment to a PDF. It will be easy enough to set up if we need to do this. I was hoping the test was a little more formal and documented but quick and dirty evaluation have their place as well.

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Solder Ball Dispersion Test (String Solder) | 4 May, 2018

For best / most accurate results, I would imagine you will need some automatic solder wire feeding station. - At least to maintain consistency.

Is this something you have on-site to perform the test with?

- Indeed, a pretty straight forward process. We have done many in our lab testing different brand alloys - however all tests are ideally performed with some sort of automated feed for test to test consistency.

Lastly, (and perhaps I should have mentioned earlier) - Flux is flammable. As such, having the temperature too high you will definitely see an increase solder ball counts. This is because of the out-gassing occurring within the flux cored wire. The gas created from the flux (igniting in this instance) is what is creating the flux splatter and solder ball defects.

To reduce: Try to solder with a temperature closest to the liquidus state of your alloy. (lowest possible - assuming all parts are eutectic) - if the alloy is not eutectic, you will need to target the highest liquidous temp in the composition. (Eg. SAC305 - the 3 part composition (tin, copper, and silver) all have 3 different liquidous temperatures -> meaning its non-eutectic. You would want to stay as close to 350°C as possible or (if a slightly off version of SAC305) target the highest melting point of your chemistry) - assuming your temp controller is properly calibrated that is.

Other options to reduce these defects during production would follow my original suggestion: try implementing a perforation gearing system to the process. - There are 2 main types: V-Score (Like a pizza cutter) and Drilling (actually drills holes into the wire using a serrated gear head). Depending upon alloy and diameter, 1 technology tends to perform better over the other.

Wishing you the best of luck!

PS The PDF Version worked!

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