Predictability for PCB Layout Density



Predictability for PCB Layout Density
This paper covers the use of a new tool called a "Predictability Calculator" to predict PCB layout density.
Materials Tech

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Authored By:


Ruth Kastner
Eliahu Moshe,
Adcom Ltd., ISRAEL

Transcript


The trend towards increasingly complex designs with smaller physical sizes has been translated into ever-increasing pressure on system developers to pack more functions and options into a given area. This must all be done while keeping costs down.

To help accomplish this and plan accordingly, a tool known as the Predictability Calculator is now available. This tool provides designers with the necessary trade-off analysis performed at the feasibility stage, given the constraints of the assigned area.

Data analysis is possible given the electrical schematics that are available at an early stage of the PCB layout design. Initial data includes the number of components and their type and characteristics that are known once they have been selected.

This tool has been utilized in the feasibility stage of over 40 complex boards and in post mortem analysis of other boards. This paper will discuss the use of this tool to predict PCB layout density.

Summary


The trend towards increasingly complex designs with smaller physical sizes has been translated into ever-increasing pressure on system developers to pack more functions and options into a given area. In addition, cost needs to be driven down as much as possible. As a result, the design process has become more extensive in terms of resources, complexity, choice of PCB technology and cost reduction. In order to handle this challenge effectively, one would like to predict the efforts involved in the layout design a-priori. This capability is now available in the form of "Predictability Calculator", described below.

The Predictability Calculator is a tool that provides the designer with the necessary trade-off analysis performed at the feasibility stage, given the constraints of the assigned area. It takes advantage of the fact that all designs are done today using CAD systems, hence data analysis is possible given the electrical schematics that is available at an early stage of the PCB layout design. This initial data include the number of components and their type and characteristics that are known once they have been selected. The number of connections is also available based on the interconnections and busses.

Although it is recognized that the PCB technology may be selected independently of the designer, it is nonetheless a part of the tradeoffs supplied by the Predictability Calculator with the objective of providing maximum performance at a minimal cost.

This tool has been utilized so far in the feasibility stage of over 40 complex boards, and also in post mortem analysis of other boards. It has thus demonstrated a proven capability of providing feasibility data for the routing complexity with a high level of confidence. The next step in the tool development will include an in-depth placement feasibility and the trade offs with embedded resistors and capacitors

Conclusions


If the Capacity value is higher than the Demand value, the designer can proceed with the layout with a high confidence that it will be successfully completed, without extra effort and future changes or updates may take place. Nevertheless, cost reduction may be considered already at this stage, by playing "what-if" scenarios with the tool.

If the Capacity value is approximately equal to the Demand value, the designer should review his strategy and design rules. If the board is a new design, changes and add-ons will be very difficult to be implemented in the next phase even if completed successfully at the first stage, or design factors and constrains would be compromised due to the density. The designer should change the parameters to achieve a more relaxed design, where future changes and update may also take place.

If the Capacity value is smaller than the Demand value, the designer needs to change the parameters or the design rules defined by a "what-if" simulation available by the tool, and optimize the parameters to ensure a PCB layout design which will be completed successfully with no constraining compromises, and without extra effort.

Organization that have a PCB data base information center can normalize their boards to a relative board density factor and keep the boards records by comparing the Density Factor data and achieve better electronic performance and PCB cost reduction

Initially Published in the IPC Proceedings

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