PCB Library Management

The PCB library forms the back-bone of product development, providing the links between the multiple facets of the process including schematic and physical layout of the CAD world through to mechanical enclosures and ultimately component procurement. Each company may have its own unique requirements but essentially every company needs a well-controlled library that facilitates the easy design, procurement and manufacture of each design element.

The library should be built to support the complete product design process; the crux of the matter, when implementing a new library is, ‘What does this mean exactly?’

We can tackle this by breaking this down into its constituent parts and looking at what the library has to provide.

The basic, core, elements have always been the schematic symbol and its associated footprint; the engineer places a symbol, connects it up and then through a process dependent upon which software tools are being used, creates the layout database which includes the connectivity and footprints and in some cases the rules. When creating these symbol and footprint elements there are standards for the user to follow such as for symbols and IPC-7351B for surface mount devices (SMD) footprints. Using these standards ensures readable schematics and most importantly footprints that can be assembled successfully. Today, although this is the baseline information, the increase in complexity of designs has meant that these elements are seen as a given and the library has do so much more.

Engineers spend a significant amount of their time researching components. They need to be able to easily access parameters about the possible devices so that they can quickly find the right component for their needs. This can eat up a lot of time, especially if an engineer has to do this for every component in their design. With the majority of devices there is a good chance that they have been used by someone else within the same company, obviously this will be true for resistors and capacitors but possibly for power devices such as LDOs etc., while the need for the next generation of the main devices may require extra research and selection. The engineering environment should enable the designer to quickly find and select commonly used components allowing more time to spend researching the new leading-edge devices. Organising the data in an intuitive fashion with relevant categories can take time and effort.

Providing a database or library of the commonly used parts greatly aids the engineer during this phase with the additional benefits of using known good parts, they have already been through the component selection, validation and manufacturing process, ultimately de-risking the design as a whole.

More design processes are merging the mechanical and electrical worlds together and the majority of the CAD software now supports the use of 3D models of components etc. to be incorporated into the layout through the library and then exported to a fully-fledged mechanical design system.

The selection of the component is only one part of the puzzle. The component must support all aspects of the fabrication and manufacturing process ultimately driving the procurement process through the bill of materials (BOM). There are a number of facets to this aspect; company-wide part numbers, alternate parts, sole manufacturer all have to be taken into account when considering the library structure and parameter set.

The PCB design process is a dynamic one, requirements change, component availability, price and lead-time all change. During the design process the engineer needs a system that that can coup with these fluctuations and provide up-to-date information so that the relevant action can be carried out.

Every company today is faced with the same time-to-market pressures, the ability to carry-out design tasks following a parallel rather than a serial approach is one way to reduce the overall design cycle. New components can be created while the design engineer continues to progress the schematic capture phase and as soon as the symbol is available it can be placed in situ with little disruption to overall process. While the design is completed the remainder of the device information can be added to the component. The component development will also go through its own life-cycle, symbol, footprint, meta-data such as part number are added; from a development through checking, release and ultimately obsolescence. During this time there may even be a need for a maintenance stage where details have to be changed or updated – this could be due to manufacturing process changes.

The life-cycle of the component must be carefully controlled to ensure that each part of the design team is made aware of the exact status of the component. Finally when the design is released to the manufacturer it is important to ensure that you are using production ready components; being able to easily confirm that the components are ready to go is paramount.

The unique requirements of each company will mean that not all of these elements have to be considered but there will also be others that have not been touched on in this article, such as PLM integration, that will be; whatever facets are required there is one certainty, as it was stated in the beginning, every company needs a well-controlled library that facilitates the easy design, procurement and manufacture of each design element.

The next instalment with focus on managing the work-in-progress (WIP) aspect of the design cycle.
PCB Design Management
Managing PCB work processes and design updates
Releasing data for PCB production
Round up of managing PCB design