Method for Eliminating Common Defects from Capacitance Opens Shorts Data
Original Publication Date: 1995-Jun-01
Included in the Prior Art Database: 2005-Mar-30
Boyette, J: AUTHOR [+1]
Disclosed is an invention that, via a unique software algorithm, provides a means for identifying common capacitive defects in circuit boards.
Method for Eliminating Common Defects from Capacitance
an invention that, via a unique software
algorithm, provides a means for identifying common capacitive defects
in circuit boards.
defects in circuit boards can be identified
through the use of capacitive measurements. These measurements are
made on a sampling of products to determine the normal and expected
value and deviation in measurements. A significant deviation in the
expected value will then indicate the presence of a defect.
Typically it is desirable to take readings from several products in
an attempt to Learn empirically what this Mean value should be and to
characterize the deviation. A problem exists when there is a common
defect in the sample data that results in the defect being learned as
a normal reading.
measurements are made on circuit boards, and more
generally interconnect devices, to identify opens and shorts. In the
presence of shorts the capacitance will at least double and in the
presence of an open will at least be reduced by half.
manufacturing process by its very nature is controlled to
minimize process deviation. A determination of characteristic
capacitance of the interconnect for each network is easily
established and is a good indication of the presence of a defect when
desirable to establish the normal capacitance reading by
taking measurements from several products. This is a simple straight
forward way to establish the Mean expected value. A problem arises
when a common short or open establishes a Mean value which is
constant among the products sampled and makes the defect look normal.
An additional procedure or method must be utilized to address this
case during the learn process.
There are two methods proposed that address each of the
1. The way to identify the open condition is to verify that all