Determining an optimum wiring pattern and component placement scheme for a printed wiring board

A method for designing a printed wiring board wherein information on electrical components to be mounted on the board, information on connection between the components, and a grade of the board is selected, said method comprising the steps of:

• determining an actual board area;
• determining an unwirable area of said board;
• and
• determining an INDEX value for said board wherein said INDEX value comprises a ratio of a total wirable length for said board based on a wirable area of said board obtained by subtracting said determined unwirable area from said determined actual board area to a wiring length connecting said electrical components mounted/placed on said board.

An apparatus for designing a printed wiring board wherein information on electrical components to be mounted on the board, information on connection between said components, and a grade of the board is selected, said apparatus comprising:

• means for determining an actual board area for said printed wiring board;
• means for determining an unwirable area of said board;
• means for determining an INDEX value for said board wherein said INDEX value comprises a ratio of a total wirable length for said board based on a wirable area of said board obtained by subtracting said determined unwirable area from said determined actual board area to a wiring length connecting said components mounted/placed on said board, and
• wherein said means for determining said unwirable area includes means of estimating a via hole count to be formed on said board on the basis of said grade of said board, a signal count, and a power count, and
• wherein said unwirable area includes a wiring-inhibited area resulting from the formation of at least one via hole and at least one land, and
• wherein said wiring-inhibited area is determined by multiplying a predetermined length parallel to a wiring passing through said at least one via hole and said at least one land by a distance between the wirings of said board which sandwich said at least one via hole and said at least one land.

A method for designing a printed wiring board wherein information on electrical components to be mounted on the board, information on connection between the components, and a grade of the board is selected, said method comprising the steps of:

• determining an actual board area;
• determining an unwirable area of said board;
• and
• determining an INDEX value for said board wherein said INDEX value comprises a ratio of total wirable length for said board based on a wirable area of said board obtained by subtracting said determined unwirable area from said determined actual board area to a wiring length connecting said electrical components mounted/placed on said board, and
• wherein said step of determining said unwirable area includes estimating a via hole count to be formed on said board on the basis of said grade of said board, a signal count, and a power count, and
• wherein said step of determining said unwirable area comprises:
• determining a length between wirings which sandwich said at least one via hole and said at least one land;
• multiplying a predetermined length parallel to a wiring passing through said at least one via hole and said at least one land by said determined length;
• and
• determining a wiring-inhibited area for said board by giving consideration to said at least one via hole and said at least one land.

A method for designing a printed wiring board wherein information on electrical components to be mounted on the board, information on connection between the components, and a grade of the board is selected, said method comprising the steps of:

• determining an actual board area;
• determining an unwirable area of said board;
• determining an INDEX value wherein said INDEX value comprises a ratio of a total wirable length for said board based on a wirable area of said board obtained by subtracting said determined unwirable area from said determined actual board area to a wiring length necessary to connect said electrical components to said board;
• and
• wherein said step of determining said area of said board includes:
• determining a virtual maximum board area on the basis of an outermost edge of the board not used for wiring or having said components thereon;
• determining a ratio of the actual board area to the determined virtual maximum board area;
• and
• multiplying said actual board area by said determined ratio.