Original Date: 11/01/2004
Revision Date: 01/18/2007
Best Practice : Manufacturing Cost Modeling
The Center for Advanced Life-Cycle Engineering provides manufacturing cost-modeling tools and methodologies targeted to the electronic fabrication and assembly industries. The Center uses four general approaches to cost modeling and has created several modeling applications and tools to facilitate the process.
During the mid-1990s, engineers designing electronic systems were not concerned about the impact of their designs on manufacturing costs. Consequently, no means existed to determine if the design was cost effective. In today’s competitive environment, all cost impacts associated with the assemblies must be understood to properly assess the assemblies’ market value. This is as true in low-volume avionics applications as it is in the retail electronics field. Engineers are now expected to participate in determining the economic tradeoff for their design decisions. The Center for Advanced Life-Cycle Engineering (CALCE) develops application-specific models that facilitate the tradeoff analyses required within the electronic substrate manufacturing and electronic assembly business areas.
CALCE’s approach is unique because of its ability to make application-specific and application-independent models targeting the electronic substrate and electronic assembly manufacturing. This results in modeling techniques that target conditions of interest to determine if a new technology, material, or process will be cost competitive with existing ones. CALCE also addresses the “performance” requirements that determine the cost effectiveness of that process. The measured performance typically equates to the process throughput or yield. These techniques have been useful for evaluating processes from the component level to the multi-board assembly level.
The approaches most often used by CALCE in modeling the range of electronic systems are: Cost of Ownership: A common basis for costing semiconductor fabrication that is driven by capital machinery-intensive processes. This method can and has been extended to substrate and assembly costing.
Process-Flow-Based Cost Modeling (Technical Cost Modeling): Determines total cost based on labor, material, capital, and tooling factors in continuous processes. The CALCE analysis also includes concurrent generation of material use and waste inventories for Life-Cycle Assessment (LCA).
Test/Rework Economics: Determines the optimum number and placement of test points in a process to assure desired throughput and minimize cost..
Top-down and Bottoms-up: Analysis that yields the total product cost at both a high level of abstraction and at a detailed process-step level.
CALCE has developed several specific noteworthy modeling tools that enhance the costing models: Test/Rework Models highlight the costs associated with various test and rework scenarios inserted along the process flow. These costs facilitate the test/rework optimization models that determine where or where not to test and the amount of fault coverage to buy.
Yielded Cost Metrics provide a rigorous cumulative process cost and means to show the actual effective costs associated with any given step in the process. Using the associated omission methodology provides a rigorous cost impact for any given step in the process.
Ghost Software Tool facilitates the assessment of the design hardware/software co-design tradeoffs. The tool predicts performance, size, yield, and cost for the specified hardware and software combinations needed for a specific design.
Salvage Software Tool provides an application-specific assessment of what components on an assembly are reusable within secondary assemblies and what should be scrapped. This tool provides useful insight into potential life-cycle cost-savings strategies.
Embedded Passives/IPD Tradeoff Analysis Tool (Figure 2-1) provides a means to compare the benefits of embedding certain passive components (resistors and capacitors) in the printed circuit board in lieu of mounting them on the surface. This tool highlights key cost differences that would occur with component embedding, thus providing metrics that are useful for determining if embedding is justified. When used to evaluate the main board layout for a cell phone, one example showed that the assessment tool highlighted a $2.50 per-phone cost savings.
CALCE’s Manufacturing Cost Modeling for electronic systems represents a rigorous approach to process-specific and process-independent modeling, addressing a range of requirements from component fabrication to multi-board assembly. The models enable the assessment of specific cost factors essential for process improvements. CALCE is capable of using the tools to provide the associated assessment or of making the tool available to customers so they have the methodology to perform their own assessment.
Figure 2-1. Embedded Passives/IPD Tradeoff Analysis Tool
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