Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2002-02-28
2003-12-09
Smith, Matthew (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C700S095000, C700S096000, C700S056000, C705S400000
Reexamination Certificate
active
06662353
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a system for estimating person-hours and days necessary to prepare a pattern film for a printed circuit board, and a program used therewith.
2. Description of the Related Art
When an electronic device such as a printed circuit board is manufactured, a client first designs a circuit having desired functions. A design engineer then receives a circuit diagram from the client and prepares a pattern film for the printed circuit board with a CAD (Computer Aided Design) technique on the basis of the circuit diagram.
During the pattern film preparation procedure, the design engineer checks design conditions (requirements), i.e., the number of wiring layers to be included in a product (printed circuit board), the number of parts to be integrated on the product, the types of the parts, the number of pins extending from the parts, the number of wiring (connections) to connect the parts, etc. The design engineer then determines the layout of major parts. Subsequently the design engineer performs a “preset” process to create fundamental wiring.
After the preset, automatic arrangement and automatic wiring are performed on the basis of the circuit design data. The design engineer tests the resulting wiring pattern on the pattern film, and corrects it if necessary. An artwork is then applied to the pattern film to create marks (indicia) on the pattern film. The preparation of the pattern film for the printed circuit board is thus complete.
In the above described preparation procedure for the pattern film of the printed circuit board, the design engineer activities are standardized and a computer fabricates (prepares) most of the detailed arrangement and wiring. Therefore, the person-hours of the design engineer can be easily estimated from the number of wiring layers on the printed circuit board (or the pattern film) and an estimation table. The estimation table provides the relationship between the number of the wiring layers and a total number of the pins extending from all the parts arranged on the printed circuit board.
In recent times, however, high-speed circuits adapted to operate with, for instance, a clock signal of several hundred MHz are marketed. Devices, such as BGA (Ball Grid Array) packages, having high-density wiring are also developed. The high-speed circuits and BGA packages impose a great amount of limitations on the arrangement and wiring on the printed circuit board.
For example, the length of wiring is limited (specified) in order to restrict a delay time of a signal, and the lengths of all the wiring should be the same in order to phase a plurality of signals. The width of the wiring pattern is also limited such that an impedance of the wiring has a particular value. Moreover, the arranging order of the pins connected to each signal line is limited.
The conventional CAD cannot automatically create a pattern film that meet the above described requirements. As a result, the automatic arrangement and automatic wiring are hardly possible to the pattern film of the high-speed, high-density printed circuit board. The design engineer must determine locations of the parts while paying a careful attention to the wiring in order to satisfy the design conditions when the design engineer prepares the pattern film. The design engineer thus creates a substantial part of the wiring pattern by a manual process. Only about 10% of the pattern film can be prepared by the automatic wiring process in a certain product. Consequently the estimation of the person-hours by the conventional approach, which determines the person-hours from the estimation table providing the relationship between the number of the signal layers and the total number of the pins to be made on the pattern film, significantly deviates from the actual person-hours. One example revealed that there is about 50% deviation between the estimated person-hours and the actual person-hours.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an estimation system that presents estimation with higher reliability, and to provide an estimation program suitable for such estimation system.
According to one aspect of the present invention, there is provided an estimation system for estimating person-hours required to prepare a pattern film for a circuit to be printed on a board upon receiving a design condition, the system comprising: a reference pin calculation unit for calculating a number of reference pins on the basis of a total number of pins extending from parts to be integrated on a printed circuit board and a special specification requirement to be applied to a printed circuit; an additional pin calculation unit for calculating a number of additional pins on the basis of a signal line wiring method used in preparing the pattern film for the printed circuit; a total estimated pin calculation unit for correcting a sum of the number of the reference pins and the number of the additional pins on the basis of design difficulty to calculate a total estimated number of pins; and a person-hour calculation unit for calculating person-hours required to prepare the pattern film by dividing the total estimated number of the pins by an average number of pins handleable by a design engineer per a unit time. The design difficulty may be determined from a number of signal layers to be made in the printed circuit, a number of signal lines arrangeable between adjacent pins and a pin density. Since the total estimated number of the pins is corrected and obtained in consideration of various design factors, it is possible to estimate the person-hours at high accuracy.
According to a second aspect of the present invention, there is provided an estimation system for estimating person-hours required to prepare a pattern film for a circuit to be printed on a board based on a design condition, the system comprising: a correction table for setting a correction coefficient in accordance with a total number of pins extending from parts to be integrated on a printed circuit board; a specification table for setting a specification coefficient in accordance with a special specification to be applied to the printed circuit board; a wiring method table for setting an increment/decrement coefficient in accordance with a wiring method to be used to make signal lines on the pattern film; a difficulty table for setting a difficulty coefficient in accordance with a number of signal layers to be made on the printed circuit board, a number of signal lines arrangeable between adjacent pins and a pin density; a reference pin calculation unit for referring to the correction table to obtain a correction coefficient on the basis of a total number of pins indicated in the required design condition, referring to the specification table to obtain a specification coefficient on the basis of a special specification indicated in the required design condition, and multiplying the total number of pins indicated in the required design condition, the obtained correction coefficient and the obtained specification coefficient to calculate a number of reference pins; an additional pin calculation unit for referring to the wiring method table to obtain an increment/decrement coefficient on the basis of a signal line wiring method indicated in the required design condition, and calculating a number of additional pins on the basis of the obtained increment/decrement coefficient; a total estimated pin calculation unit for referring to the difficulty table to obtain a difficulty coefficient on the basis of information included in the required design condition, and correcting a sum of the number of the reference pins and the number of the additional pins on the basis of the difficulty coefficient and a reuse rate of a preceding wiring pattern, to calculate a total estimated number of pins; and a person-hour calculation unit for calculating the person-hours required to prepare the pattern film of the printed circuit by dividing the total estimated number of the pins by an average numb
Fujisawa Shigemitsu
Henmi Sachio
Kobayashi Fumio
Sakurai Masanobu
Tajima Kazuyuki
Dimyan Magid
Oki Electric Industry Co. Ltd.
Rabin & Berdo P.C.
Smith Matthew
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