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New Column: Six Keys to PCB Design Excellence
August 1, 2012 |Estimated reading time: 7 minutes
This article begins a series of six that will discuss a variety of PCB design and manufacturing problems, and possible solutions. I will kick off the series by discussing management of intellectual property.
Typically when we hear the phrase intellectual property (IP), our minds immediately think of two words: “theft” and “protection.” We have in our minds that IP is a valuable resource of an electronics company, second only to its people, and that we must protect it from compromise. What we often forget is that IP, being a valuable asset, is of little value if it cannot be used efficiently: created, controlled, accessed by designers, and leveraged to improve the competitiveness of that company. This all leads to effective management of the IP within the infrastructure and organizations of the company.
This management of IP is especially complex in today’s global environment, where an electronics company may have several locations worldwide that must work together to bring a product to market. These locations may have design teams that specialize in different technologies (analog, digital, RF), or must collaborate to bring together a critical design resource mass, or must design in a “follow-the-sun” methodology to get the product to market on time. For the highest performing, most competitive product, it is essential that these design teams work efficiently with seamless access to the company’s IP.
What Constitutes IP
IP in the electronics design process consists of many elements – some created prior to the start of the process, some created and shared during the process, and some saved and managed for future products. Basically IP falls into two categories: static and dynamic. Static IP is created prior to the design process and accessed by the team. Dynamic IP is created during the design process (work-in-progress). Figure 1 illustrates these two categories and some of the IP associated with each.
Figure 1. IP management is at the hub of the PCB design process and contains both static and dynamic forms of data.
Static IP
Component libraries are IP elements of high value. Companies invest heavily in qualifying parts and then entering them into globally-accessible libraries. A central component library system that enables productive input of part data, control of that data, and global access to the data by various design teams can significantly improve both the time-to-market and the quality of the product. But this data is not just a mass of component information stored in a relational database. It must contain a level of intelligence to be truly valuable.
For example, a company may be in the business of designing both lower-cost consumer products and high-reliability (and high-cost) B2B products. It is important that design groups, although accessing the same central library, have access to only those parts that are appropriate for their class of product. You would not want a designer who is developing a consumer product to choose a very high-cost, high-reliability part that would increase the product cost beyond competitiveness. So the IP management system must be able to effectively filter parts available to the designers by target markets: some parts in common; some unique to target industries.
As well, parts data does not consist of only the information found in the suppliers’ datasheets. These parts will be assembled on a PCB that is fabricated according to specifications of the OEM. So associated with the parts is information that specifically relates to the target PCB such as:
- A reference pad stack that defines how the part leads contact and penetrate the board
- A rule area which might define a different interconnect line width for under the part (in order to escape) than found on the rest of the PCB
- A predefined breakout and fan-out pattern (especially for high pin-count BGAs) to facilitate optimized escape of interconnect under the part
These added characteristics are defined targeting the OEM’s manufacturing, and they also are specific to the PCB design system that will place the components and route the PCB. So again, a lot of unique IP is added to the parts that would not be found on the datasheet or in a company’s PLM or CIS system.
Figure 2. Creating a component library requires data from many sources as well as an understanding of the physical PCB constructs.
Another extremely important element of a library is reusable blocks of schematic, constraint, and physical layout data. Many of today’s designs are in fact upgrades or re-spins of previous designs. A company can save time and resources and improve product quality by reusing part or all of a previous product’s data. These blocks are essentially designs of previous products that have been proven and are now stored, documented, and available for a designer to pick up and drop into a new design. The block elements are stored in the construct of the native PCB system with interdependencies in place. This is a common practice as it saves time, increases productivity, and improves quality. So when a design is complete, saving the design (data), the constraints (intent), etc., in a well organized IP management system can give the next product a jump start.
Dynamic IP
The creation and access to design constraints is another IP element. Manufacturing rules and best practices are created prior to the start of a design, and high-speed rules are created during the design process. Manufacturing engineers create the hard manufacturing failure rules as well as the design-for-high-yield manufacturer-specific best practices. These DFM rules, when applied during the design process, assure that when the data is finally sent to production, it is correct as designed, will not require expensive and time-consuming re-spins, and will enable the manufacturer to quickly reach target volume production levels.
For high-speed constraints, engineers pre-analyze the design and create delay, signal integrity, crosstalk, and EMI rules. These rules are then made accessible to the layout designers as rules for placement and routing. Most state-of-the-art design systems automatically follow these rules and highlight potential violations to the layout designer. As you can imagine, this requires a well-integrated PCB design flow and the constraints have to be defined and used in languages familiar to the multiple disciplines involved. For example, an engineer may think of delays and edge rates in terms of nanoseconds and picoseconds, while a designer must implement them in terms of inches and tolerances of interconnect routing.
The third element is the work-in-progress design data itself. Here is where the process and management gets very complex (Figure 3). Unlike component libraries, which are very static, and constraints, which are dynamic but relatively stable, the work in progress design data is extremely dynamic, especially when multiple-member design teams are involved. Multiple engineers are working on schematics in parallel with multiple layout designers. Design data (e.g., schematics and layout) go in and out of sync. “What-if” sandbox scenarios, looking for a more competitive product, may be defined, with some accepted and many rejected. Snapshot versions of the data may be periodically saved and organized.
Figure 3. Multiple team members’ work-in-progress design data management is a very complex challenge requiring sophisticated design system infrastructure.
It is also important to note here that not only do the designers want access to the design data, but also management. In advanced systems (such as Mentor Graphics’ IP management), analysis functions can enable a manager to look at the data and determine status and progress of the various steps in the design process:
- What percentage of components has been placed?
- High-speed interconnect progress?
- What virtual prototyping has been done?
- Am I ready for manufacturing data generation?
This is all important information for management to better understand the schedule and competitiveness of the product.
Interfacing PCB Design IP with Corporate Infrastructure
Most large companies have existing PLM, ERP, CIS, etc. systems in place. These systems manage huge amounts of data across the company that feed into and archive various functions in the product development and life cycle process, birth to end of life. Yet these systems do not understand the dynamic, complex interrelationships required to manage PCB systems design data especially the “dynamic” IP. That is the function of systems supplied directly from the PCB design tool suppliers. Nonetheless we must eventually store the PCB design into these systems. For this purpose, interface standards are being developed and embraced by the design tools suppliers as well and the corporate infrasucture system suppliers.
Figure 4. Interfacing through standards from PCB IP management systems to corporate infrastructure systems in necessary.
Summary
IP management of PCB design data is complex, dynamic and very specialized to the PCB design system being used. However, if properly supported it can mean the difference between whether or not you get a quality product to market on time with the coordinated efforts of diverse and large design teams.
John Isaac is director of market development for the Systems Design Division of Mentor Graphics. He can be reached at john_isaac@mentor.com.