How does Aacton test multilayer substrates without a known perfect
substrate or special fixturing?
Each conductor line has a finite capacitance with respect to a
ground plane (workholder). In our case, this capacitance is determined
by the area of the conductor line and the dielectric constant
of the substrate and printed Dielectric between the workholder
and conductor line. By using a spring loaded pogo probe, Each
conductor line is tested on five substrates (assuming random failures)
to establish a good capacitance value. During subsequent testing
an open or short will be indicated by lower or higher capacitance
values respectively. (see drawing)
All Aacton needs is the custmer to supply a drawing showing all
exposed metalization on the finished substrate along with *(2)
sample circuits. The customer must also show all banking points
used during screen printing. To characterize each conductor line,
Aacton will need a minimum of 5 random substrates or a substrate
known to be perfect.
NAMING TEST POINTS
Typically, test points are numbered sequentially. Testing order
and point numbering are determined by Aacton.
Custom identification points or customer specified testing sequence
with alpha-numeric identification up to 6 characters per point
* This is only necessary on new or first time circuits to speed
up the programming process and insure a quick turnaround.