Computer-aided design and analysis of circuits and semiconductor – Nanotechnology related integrated circuit design
Reexamination Certificate
2002-02-12
2004-11-02
Siek, Vuthe (Department: 2825)
Computer-aided design and analysis of circuits and semiconductor
Nanotechnology related integrated circuit design
C716S030000, C716S030000
Reexamination Certificate
active
06813749
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to design analysis of components and, more particularly, to a method, system and computer program product that provide for automated design analysis of components and the component interconnect structure by subjecting a finite element model of the component to various simulated thermo-mechanical environments and enabling modification of the component design and interconnect structure if the component's stress response to the environmental load is outside of pre-selected limits.
Components that are attached to an overall structure, such as an aircraft, automobile, bridge, etc. are subjected to various forces and temperatures over the lifetime of the overall structure. The components may be any type of board or panel-type structures with parts and/or electronic elements mounted thereupon, including printed wiring assemblies, printed wiring boards, chassis containing printed wiring assemblies or boards, transducers, and multifunctional parts with embedded electronics. Typically, the parts and/or electronic elements are attached in some way to the board or panel-type structure, such as by solder or solder balls, which is called the interconnect structure of the component. The forces and temperatures create stresses in the component that can eventually cause wear, damage, and the possible failure of the component interconnect structure, which may adversely affect the operation of the overall structure containing the component. As such, design analysis of the components is important to ensure that a component design does not cause it to have a shorter fatigue life than desired. Design analysis provides component and structural designers with critical information used to determine the likelihood and the causes of fatigue-related failures. Once the component and structural designers have the results of the design analysis, they can design the individual components and the overall structure so as to withstand the anticipated stress and temperature levels over the design lifetime.
The conventional method of design analysis involves initially designing a component using the processes and materials that have been shown, through testing or experience, to create the most durable and effective component. This design may be evaluated using military standards, such as the MIL Handbook 217 for electronics, and if it meets the standards, then a component having this design is built. The component design is tested by subjecting the component to accelerated stresses that are representative of forces or temperatures experienced by the component and the overall structure containing the component. The testing for each type of force and temperature must be performed separately and in separate chambers that simulate the desired testing environment. The testing environments may include, for instance, a thermal testing environment, a vibration testing environment, an acoustic testing environment, and a shock testing environment.
For example, if acoustic testing of the component is desired, then the component must have the exact type of boundary conditions that it will have in operation, i.e., the component must be mounted to the segment of the overall structure that will carry the component with the type of fasteners that will be used in operation. To acoustically test the component, the component and segment of the overall structure are placed in an acoustic chamber where the sonic load spectrum of the acoustic pressures at a typical operating environment are duplicated. The fluctuating acoustic pressure creates vibration base-excitement that acts upon the component. The response of the component is monitored and recorded to determine which parts of the component interconnect structure fail due to the vibration and when they fail, i.e. the failure mode. If the response of the component indicates that an integral part, such as an electronic element, of the component will fail prematurely, then the component interconnect structure must be redesigned to try to mitigate the effect of the vibration on the electronic element at issue. The redesign process may include moving the electronic element to a different portion of the board that is more resilient to vibration, changing the type of material that is used to make the electronic element to a material that is more resilient to vibration, and/or changing the type of material, such as solder, used to attach the electronic element to the board or panel-type structure, in addition to many other ways that the component may be redesigned. The redesigned component is then re-tested using the process described above and this cycle continues until the component design can withstand the acoustic test without any part of the component interconnect structure failing. Typically, it takes two to three cycles of design/redesign and testing before the component design is optimized.
The design/redesign and testing process is similar for the other testing environments and if a subsequent environmental test leads to another redesign of the component, then the component interconnect structure must be re-tested in the prior environment to monitor the response of the further redesigned component in the prior environment. The testing and re-testing continues in the desired environments until the component design is optimized for all of the environments.
Thus, the design/redesign and testing process is a very time consuming and expensive endeavor because of the multiple redesign and testing cycles that may be involved in obtaining an optimal component design and interconnect structure for all of the desired testing environments. In addition, because the testing in the environmental chamber consists of applying accelerated environmental loads to the component, it is not an accurate simulation of the environmental loads that the component will actually experience over the lifetime of the component or the overall structure. As such, accelerated testing generally induces failure mechanisms in the interconnect structure of the component that are different than those experienced by the component in application, which may create misleading failure results and lead to inaccurate redesigns. Furthermore, the military standards that may be used to evaluate the initial design of some components are too broad to assist in determining the impact of detail design changes on the fatigue life of a component. That is, the standards are not helpful for evaluating the design of components in which small design changes may greatly affect the fatigue life of the component interconnect structure in relation to a certain environment because the military standards do not approach the level of detail required for such an evaluation.
Therefore, the conventional design analysis procedure does not accurately identify potential failure points of a component interconnect structure that are associated with the design, manufacture and operation of the component. In addition, the conventional design analysis procedure is extremely expensive and time consuming. As such, there exists a need in the industry for a component design analysis that accurately and efficiently simulates thermo-mechanical environments for testing the component interconnect structure and identifies potential failures within the component interconnect structure when subjected to the environment(s). The need is also for a design analysis that predicts the fatigue life for the component or the part of the component interconnect structure that fails and pinpoints the cause of the failure in order to identify the part or other aspect of the component interconnect structure that must change.
BRIEF SUMMARY OF THE INVENTION
The method, system and computer program product of the present invention provides design analysis of a component that accurately and efficiently simulates thermo-mechanical environments for testing the component and identifies potential failures within the component interconnect structure when subjected to the environment(s). In addition, the method, system and computer pro
Alston & Bird LLP
Levin Naum
Siek Vuthe
The Boeing Company
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