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Solder Graping - What's this?

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#61372

Solder Graping - What's this? | 16 March, 2010

What is solder graping and how do they look like? What are the possible causes of solder graping during reflow soldering?

kind regards,

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#61373

Solder Graping - What's this? | 16 March, 2010

Most often 'solder graping' refers to poor solder wetting, where the solder paste has partially melted, but has not coalesced or flowed. Sometimes this leaves the outline of the partially melted solder balls still visible, giving the appearance, to some, of a bunch of grapes.

Got a picture?

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#61385

Solder Graping - What's this? | 17 March, 2010

thanks dave. what are the possible causes of solder graping?

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#61386

Solder Graping - What's this? | 17 March, 2010

Primary causes to consider are: * Poor thermal recipe during paste reflow * Failed solder paste

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#61395

Solder Graping - What's this? | 19 March, 2010

I've also heard the problem called "Snot-balls". I have a picture:

http://stevezeva.homestead.com/Type_4.JPG

In my case, this happened because of a bad batch of powder was used when the solderpaste was made. It's happened to me a couple of times sad to say...

Steve

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#61403

Solder Graping - What's this? | 19 March, 2010

That's a great picture of a terrible defect. The quality of solder powder is critical to a good paste (as is the performance of the flux of course). As powders get finer then the challenge to make them better and better is more demanding. It's unforgivable for a paste supplier to supply a paste with such a poor powder quality. Another cause of graping is the flux becoming exhausted in the preheat zone due to it being long and at a high temp (200C). The powder re-oxidises before it melts and you get graping. Select paste with high quality powder (get the supplier to give you data on how they measure powder quality) and flux with high thermal stability and you shouldn't get this defect.

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