In most articles about solderballs found after wave soldering escaping vapors are brought up as the main cause for solderball formation. In general this is true, but it will not explain the small solderballs that can often be found in-between the leads of wave soldered connectors or SO-component leads. These are often positioned with an amazing regularity. In fact the physical mechanism behind the solder separation process is responsible for the formation of this specific solderball pattern.
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