Browse Prior Art Database

Optical Inspection of Gold Plated Features

IP.com Disclosure Number: IPCOM000109421D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 2 page(s) / 109K

Publishing Venue

IBM

Related People

Benebo, B: AUTHOR [+6]

Abstract

Application of optical inspection equipment has been limited to inspection of circuit defects. Current visual inspection techniques for gold plated features on printed circuit cards are subject to varying degrees of efficiency due to operator ability and fatigue. The new method uses standard equipment (Orbot PC 1245 inspection system) with specially modified operating parameters to distinguish defects/flaws in gold plating. This method is currently not practiced in the industry and provides IBM with the capability of shipping higher quality products and automates an operation previously done manually.

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Optical Inspection of Gold Plated Features

       Application of optical inspection equipment has been
limited to inspection of circuit defects.  Current visual inspection
techniques for gold plated features on printed circuit cards are
subject to varying degrees of efficiency due to operator ability and
fatigue.  The new method uses standard equipment (Orbot PC 1245
inspection system) with specially modified operating parameters to
distinguish defects/flaws in gold plating.  This method is currently
not practiced in the industry and provides IBM with the capability of
shipping higher quality products and automates an operation
previously done manually.

      The main types of defects that the Orbot PC 1245 optical test
system will detect are: gold voids exposing laminate, copper, and
nickel.  In addition scratches, oxidation, finger prints, and solder
mask deposits on the tabs will be detected.

      The different reflectivity levels between the gold and other
materials (copper, nickel, laminate) is the key factor which makes
this application possible.

      The optical head of the tester scans a "Golden" (defect-free)
set of tabs and creates a "gray" gated image.  The image is created
by assigning to each pixel an analog voltage whose amplitude is
proportional to the light intensity measured at a specific pixel.

      The analog voltage must be converted into a digital image in
which each pixel is assigned a numerical value from 0 - 255.  Zero
being no reflectivity and 255 being saturation.  This "gray level"
image is stored in memory.  Gold-plated tabs are scanned and their
gray levels are compared to those on the golden panel.

      The Orbot PC 1245 detects problems such as voids in tabs in a
couple of different ways.  It may find gross errors in tabs by
comparing the image being tested against the golden reference image.
If there are voids in the tab which extend all the way down to the
laminate, the tester will pick them up as either a pin-hole violation
or a junction call.  The tester is using binar...