One of the interesting things about using a colored flux, is that most of the time the residue is clearly visible – even as it is being cleaned. One thing that grabbed my attention was the way the post-reflow residue from WS3622 lifted off a substrate that was sitting in a glass of room temperature water. After about 60 seconds, the layer of residue pealed upward and floated to the surface of the glass without agitation.
So what does this mean in a real world cleaning application? Essentially I had performed a “worst case” cleaning test without even knowing it. In a typical flip chip cleaning operation the water jets cause turbulence, which helps remove the flux residue.