Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2000-05-16
2002-05-28
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000
Reexamination Certificate
active
06397376
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and device for determining an interconnect route in a circuit board from a plurality of virtual interconnect targets to lands which are arranged in a matrix around the virtual interconnect targets, and also relates to an information storage medium.
BACKGROUND OF ART
A bare tip mounting is ideal for pursuing miniaturization of semiconductor devices. However, because bare-chip mounting results in difficulty in assuring quality and in handling, the semiconductor device is processed into a package form to deal with this problem. As a package form meeting the requirements, particularly, for multi-terminal arrangement, a BGA (Ball Grid Array) package has been developed in recent years.
A flexible circuit board is used as one BGA type package. Such a circuit board is provided with a lead group connected to an IC terminal group, and a ball land group are arranged in a matrix around the lead group. Each land is provided with a solder ball, as required. This circuit board mounted with an IC is surface-mounted on a motherboard or the like through the solder balls.
An important subject in using such a circuit board is how to determine interconnect routes between each lead (a virtual interconnect target) in the lead group and each land ball in the land group arranged around the lead group.
In particular, circuit boards recently used have many leads and land balls provided on a circuit board for mounting ICs due to the increased number of terminals of the ICs to be mounted. Accordingly, how efficiently the interconnect routes are designed from each lead to each ball land without intersecting the interconnect route becomes important for shortening the development period and reducing the cost of a circuit board.
However, in a conventional technique, a designer determines interconnect routes between each lead and each land manually on a drawing by trial and error. Because such a design work requires time and labor, it was impossible to design a circuit board in a short time at a low cost.
Specifically, the amount of interconnect which can pass through a space between each of the lands differs depending on various parameters such as spaces between ball lands and widths of interconnect leads used. Therefore, it is necessary that the interconnect route should be determined so that the amount of interconnect between the lands may not exceed the allowable amount and also that the interconnects may not intersect each other.
However, if a land which cannot be interconnected should be found during a design work using a conventional technique in which a designer determines the interconnect routes between each lead and each land manually on a drawing by trial and error, the determination of the interconnect routes has to be repeated from the beginning by changing the parameters. Thus, the design work must be dependent on the experience and intuition of the designer.
The present invention has been made in view of the above-described conventional problems. An object of the present invention is to provide a method, device, and information storage medium for determining interconnect routes in a circuit board between virtual interconnect target group and lands which are arranged in at least one of inside and outside of the column, efficiently in a short period of time.
DISCLOSURE OF THE INVENTION
(1) To achieve the above object, the present invention provides a method of determining interconnect routes in a circuit board, the interconnect routes running from a plurality of virtual interconnect targets to lands arranged in a matrix on at least one of inside and outside of the virtual interconnect target, the virtual interconnect target forming a target group arranged into a substantially rectangular frame, the method comprising:
a first step of assigning an order of priority to each of the lands; and
a second step of performing processing for determining an interconnect route between a next virtual interconnect target adjacent to another virtual interconnect target of which an interconnect route has been determined and a next interconnect land according to the order of priority,
wherein, in the first step, when a rectangle formed by the lands is divided into eight areas by centerlines and diagonals, and when a plurality of oblique lines connecting lands included in the lands which are adjoining each other in a direction parallel to the diagonals are priority order setting lines,
priority of each land included in each of the divided areas is set so that higher priority is assigned to a land on one of the priority order setting lines further from the diagonals, and higher priority is assigned to a land positioned further from the target group, on the same priority order setting line.
The present invention also provides a program for performing the above-mentioned method of determining an interconnect route.
The present invention further provides a computer readable information storage medium which stores information (for example, a program) for determining interconnect routes in a circuit board, the interconnect routes running from a plurality of virtual interconnect targets to lands arranged in a matrix on at least one of inside and outside of the virtual interconnect target, the virtual interconnect target forming a target group arranged into a substantially rectangular frame,
the information comprising:
a first information (for example, a program) for assigning an order of priority to each of the lands; and
a second information (for example, a program) for performing processing for determining an interconnect route between a next virtual interconnect target adjacent to another virtual interconnect target of which an interconnect route has been determined and a next interconnect land according to the order of priority,
wherein the first information comprises information (for example, a program) for setting priority of each land included in each of the divided areas, when a rectangle formed by the lands is divided into eight areas by centerlines and diagonals, and when a plurality of oblique lines connecting lands included in the lands which are adjoining each other in a direction parallel to the diagonals are priority order setting lines,
so that higher priority is assigned to a land on one of the priority order setting lines further from the diagonals, and higher priority is assigned to a land positioned further from the target group, on the same priority order setting line.
According to the present invention, a land which should be the interconnect land can be automatically determined based on the order of priority assigned to each land. Therefore, the interconnect routes can be determined efficiently and certainly.
When there is no other restriction, the order of priority means an order by which a land with a higher priority is selected as the interconnect land.
In the present invention, an interconnect route to lands arranged in a matrix on at least either inside or outside of the target group can be determined.
In the case where the interconnect routes for outer lands positioned outside the target group are determined,
it is preferable that, in the second step, a number of interconnect routes being able to pass through a space between adjoining lands is previously set to a certain value and
when the number of determined interconnect routes has reached the set value in the space between the adjoining lands, the processing for determining an interconnect route is performed to a next interconnect land that is an unconnected land and is one of the lands forming the space in which the number of the interconnects has reached the set value, instead of using the order of priority.
In addition, in the case where the interconnect routes for outer lands positioned outside the target group are determined,
the second information preferably comprise information for:
previously setting a number of interconnect routes being able to pass through a space between adjoining lands to a certain value, and
when the number of determined interconnect routes has reached t
Naitoh Susumu
Sakurai Kazunori
Hogan & Hartson L.L.P.
Seiko Epson Corporation
Smith Matthew
Speight Jibreel
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