12 research outputs found
Computer aided design of printed wiring boards
A method is described for the computer-aided layout of
printed wiring boards. The type of board considered is a single
sided board containing discrete components. The required input for
the layout algorithm is coded from the relevant circuit diagram,
together with a description of the component dimensions. This
information is then stored within the computer in a data structure.
The circuit components and their interconnections are represented
by a set of nodes and branches.
The principles of graph theory are used to construct an
abstract model of the layout. A number of the nodes and branches
of the circuit are first used in the construction of a planar graph.
A method is then described for inserting the remaining branches into
the graph to form a "pseudo planar graph". This represents a set of
components and conductor paths which can be laid out on a single
sided board without intersections. The number of conductor
crossings is thus minimised before the actual layout commences.
An algorithm is then described for automatically constructing
a board layout from the pseudo planar graph. The relative interconnections
are already known so the placement of components and
routing of conductor paths can proceed simultaneously. The layout
is therefore constructed in a series of logical steps working across
from one edge of the board to the other. This approach contrasts
with the more usual methods of layout in which components are
placed first, followed by a search for conductor routes.
The layout algorithm is also provided with facilities for
man-machine interaction by means of a graphical display and light
pen. Interaction allows the user to alter the positions of components during the construction of the layout. Thus the skill
and experience of the user can be combined with the speed and
accuracy of the automatic algorithm. Interaction also enables
special conditions to be incorporated into the layout which would
otherwise entail considerable programming effort.
Three different circuits are used to test the layout
algorithm. The results are shown for layouts constructed both
automatically and by the use of interaction. One layout is also
compared with a manually-produced layout of the same circuit. The
results show that a feasible method has been developed for the
layout of printed wiring boards by computer. Comparable results
are produced in considerably less time than normal layout methods
A selective list of acronyms and abbreviations
A glossary of acronyms, abbreviations, initials, code words, and phrases used at the John F. Kennedy Space Center is presented. The revision contains more than 12,100 entries