Patent ID: 6298149
Filing Date: 2001-10-02
Classification: G01N

Abstract:
A machine vision method for inspecting a semiconductor device, including either a semiconductor die lead frame or a semiconductor surface, comprising the steps of:illuminating the semiconductor device with an illumination source selected from a group of illumination sources including a direct on-axis light source and a diffuse off-axis light source, wherein the on-axis and off-axis sources are each selected and positioned to provide an image of the semiconductor device having a defect-to-background contrast polarity which is opposite to that of the other source;generating a first on-axis image of the semiconductor device with an image capture device while it is so illuminated;illuminating the semiconductor device with another illumination source selected from the aforesaid group;generating a second on-axis image of the semiconductor device with the image capture device while it is so illuminated; andsubtracting the second image from the first image to form a third image that emphasizes any defect on the semiconductor device.