Method of detecting defects in semiconductor package leads

• US 6,128,404 A
• Filed: 11/17/1994
• Issued: 10/03/2000
• Est. Priority Date: 08/02/1993
• Status: Expired due to Fees

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: LeBeau, Christopher J.
• Primary Examiner(s): Mancuso, Joseph
• Application Number:
  US08/340,946
• Time in Patent Office: 2,147 Days
• Field of Search: 382/141, 382/144, 382/145, 382/218, 382/221, 382/100, 382/149, 382/151, 382/147, 348/126, 348/129, 356/237
• US Class Current: 382/149
• CPC Class Codes: G01R 31/308 using non-ionising electromagnetic radiation, e.g. optical radiation investigating or analysing materials by the use of optical means G01N21/00; image analysis G06T7/00
• CPC Class Codes: G06T 2207/30141 Printed circuit board [PCB]
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0004 Industrial image inspection

Abstract

A method of detecting defects (14, 16, 17, 44, 47, 49, and 51) in objects is presented. A first grey level image (18) of a first object (10) is formed and a second grey level image (19) of a second object (12) is formed. The first (18) and second (19) grey level images are converted to a first (21) and a second (22) edge feature image, respectively. The first edge feature image is dilated (26) and the second edge feature image is skeletonized (27). The dilated (26) and skeletonized images (27) are compared. An alternate method includes forming a grey level image (40) of an object. A principal axis of the grey level image is identified, and a shifted grey level image is formed by shifting the grey level image a distance along the principal axis. The grey level image (40) is then compared to the shifted grey level image.

Claims

1. A method of detecting a defect in an object comprising:

forming a grey scale image of the object wherein the grey scale image has a major axis;

forming a shifted image of the grey scale image by shifting the grey scale image along the major axis; and

comparing the shifted image to the grey scale image to detect the defect.

2. The method of claim 1 wherein comparing the shifted image to the grey scale image includes forming a binary image of the grey scale image and a binary image of the shifted image, inverting the binary image of shifted image to form an inverted binary image, and performing a logical "and" function using the binary image of the grey scale image and the inverted binary image.

3. The method of claim 1 wherein shifting the grey level image includes shifting the grey level image a distance at least as large as a minimum size of the defect to be detected.

4. The method of claim 1 wherein the object is a metal conductor.