The mechanical aspects of a product's design now directly and profoundly influence the electronic design by determining the board shape, size and positioning of its components. Complex board shapes and flexible board materials are physical evidence of the intimate ties between the mechanical case design and the board assembly it houses.

Traditionally PCB design has been seen as a singular task that a board designer can get stuck into while surfacing periodically for coffee and new design information. In essence, PCB design has been done in isolation to the other design disciplines that have surrounded it.

Traditionally PCB design has been seen as a singular task that a board designer can get stuck into while surfacing periodically for coffee and new design information. In essence, PCB design has been done in isolation to the other design disciplines that have surrounded it.

Today board design is often inextricably linked to the mechanical and 'soft' embedded parts of the design, so all design disciplines need to work together in a collaborative way in order to produce a working and manufacturable product. The hard facts are that design information, and perhaps even your coffee, need to be shared in a cooperative product design environment.

The drivers of change

From a business standpoint globalization has produced an obvious shift in the electronics industry. The move to a single, highly-competitive world marketplace has created an environment where commodity products pour onto the world market from the most cost-effective manufacturing regions.

This change has challenged the fundamental thinking on what makes a product unique, desirable and ultimately successful. Today, being first to market or leading on price give only a temporary competitive advantage since others will quickly follow to dissolve that differentiator.

Ultimately, real and sustainable product differentiation lies in the combined effects of the way a product looks, feels and functions. Today's competitive products - those that exhibit a differentiating edge amongst competitors - are, more than ever, defined by factors such as aesthetics, ergonomics and functional behaviour, which are in turn established predominantly by the mechanical and software interfaces to the product.

The mechanical aspects of a product design now directly and profoundly influence the electronic design by determining the board shape, size and positioning of its components, and in many cases by also defining the type of components used and how the software should behave. Complex board shapes and flexible board materials are physical evidence of the intimate ties between the mechanical case design and the board assembly it houses. This trend makes the interaction between the design domains more important than ever, since the competitive success of a product can now hinge on the effectiveness of that electrical and mechanical design cooperation.

You are no longer alone!

A conventional product design system that exists as a disparate group of design tools tends to create a 'siloed' and sequential approach to design where data is simply 'thrown over the wall' to the next group in the chain. This is true both within the electronics design process itself, and between electronics and other design disciplines.

Bringing the mechanical (MCAD) and electrical (ECAD) design worlds together has been hampered by the very different nature of the two design disciplines. Mechanical design traditionally exists in a very different head-space to electronic design, and this is reflected in the vastly different design data exchange formats that exist in each realm.

Creating the next generation of electronics products, however, dictates that electronics and mechanical designers no longer work in isolation. The challenge for tool providers is creating common ground where they can meet.

Information paths

The need for ECAD and MCAD design data transfer has been addressed at a very simple level by the use of common file formats that pass basic dimensional information between the design applications in each domain.

Traditionally this means the dimensional and positioning data from one application are processed and transferred to the other via a range of 2D and 3D file formats as 'milestone' events. For example, basic PCB shape details might pass from MCAD to ECAD, then at a later stage, a simple 3D model file of the board assembly is passed from ECAD to MCAD to check the mechanical fit between the board and enclosure. With each of these steps suitable design modifications are made, and another data exchange is usually instigated to confirm those modifications. This results in a protracted and iterative process that does little to encourage MCAD-ECAD design collaboration.

Third-party design translators can ease file compatibility issues and make the process more flexible. These often provide import/export options in the native format of the ECAD-MCAD applications and, in some cases, connect directly into those programs using object linking (OLEs) or programming interfaces (APIs).

To date both these approaches have fallen short of the ideal. Data translation errors are frequent and both work-arounds add layers of complexity to the overall design process.

Tackling the fundamentals

A core concept in creating real design collaboration between the ECAD and MCAD domains is that product design must be thought of as a single task, rather than a collection of separate processes that are ultimately brought together.

3D data transfer protocols have moved up a level with the relatively new STEP format, which is a data-rich and extremely robust protocol for 3D design and manufacturing processes. STEP is now supported by most MCAD systems, so an ECAD solution that supports bi-directional STEP transfer will significantly reduce 3D data translation problems through this feature alone.

Beyond design data exchange, the ECAD-MCAD workflow needs to be considered from a productivity standpoint. For example, introducing separate third-party translation and processing applications adds more sequential stages to the process, leading to increased workflow complexity and the likelihood of errors. In short, any solution that introduces multiple file formats and sequential data translations must, by definition, slow and complicate the product development process.

Another point to consider is how the 3D data models are created and applied for viewing in the MCAD space. Performing accurate judgments of how the electro-mechanical parts fit together - in practice, object clearance and interference checking - relies on the availability of accurate 3D object models. At a practical level this means that assembly information passed from ECAD to MCAD must include accurate component models, or those electrical models must be available within the MCAD application where they can be inserted as required.

In terms of data integrity and workflow efficiency, MCAD-ECAD connectivity at its basic level is best served by a straightforward approach of sharing common STEP models directly between the two domains. While this seems simple enough, it relies on an ECAD system that includes STEP import/export and display capabilities, comprehensive 3D modelling data, and filter options to control the 3D content of exported files.

The next level

In terms of data flow and file complexity, the MCAD models passed to the ECAD domain are relatively simple (say, an enclosure) while those passed from ECAD to MCAD are usually complex (such as a complete PCB assembly, including components). Board assemblies are object-rich and create complex 3D data files which must be loaded then rendered in the MCAD space for clearance checking purposes. Any corrections for the board layout or shape are passed back to the ECAD space, where revisions are made and data exchange processes repeated.

The point of note here is that checking and revising the board assembly to fit the mechanical housing constraints is largely an ECAD problem, but much of the process occurs in the MCAD space using complex 3D board assembly data. When you consider the fundamental needs of that workflow, it becomes clear that ideally, a significant part of the mechanical fit problem needs to be solved in the ECAD domain.

To make ECAD clearance checking a possibility what's needed are real-time 3D capabilities within the PCB editor, plus the ability to import MCAD assemblies into that space. Using the STEP format to bring, say, an enclosure model into the ECAD domain, practical interference checking would then be a reality in the 3D PCB design environment. If the system is then coupled to user-defined clearance rules and 3D object transparency options, a large part of the mechanical fit task can be resolved in real time within the ECAD domain.

With a linked setup the ECAD application would simply load data from an external 3D STEP file that has been generated by the MCAD application. The PCB editor can then alert the user when that external file changes, in response to an update from the MCAD domain, then refresh the object in the PCB work space and ECAD design files. This would occur in a real time 3D design environment, allowing mechanical clearance errors to be resolved on the fly rather than through a protracted series of MCAD-ECAD design iterations.

Such an approach would significantly reduce the complexity and number of MCAD-ECAD design iterations that are required by traditional systems.

Unity of purpose

Ultimately, the increasing importance of the physical properties of today's designs means that the interdependency of the ECAD and MCAD design environments needs to be catered for by systems that deal with the core problem directly. Most existing systems that attempt to provide an MCAD-ECAD solution take a piecemeal or add-on approach, and in the process fall short of the mark or at worst, create counterproductive and error-prone workflow. As a result, intermittent design concurrency between the domains is the best possible result.

What's needed is a more unified view of the overall product development process where the entire design is treated as a single entity, with a single design data model. In this way the solutions to the growing need for imitate MCAD-ECAD connectivity come from a higher level view that considers the final aim, rather that a closely focused approach of dealing with the file exchange systems alone.

By implementing the groundwork of a robust 3D data exchange format and direct data transfer, the process is simplified and can even be transferred to the ECAD domain where it needs to be solved. In this way designers from both domains can interact in a highly-connected product development environment that promotes concurrent MCAD-ECAD design.

As the electronics design industry continues to evolve and design disciplines converge, it's now crucial that all of the design domains interconnect to a level where cooperative, concurrent design is a reality. When previously disconnected worlds join and work together the benefits are invariably profound and far reaching - the world of electronics design is no exception.