Maintaining Design Intent Throughout PCBA Development

Two of the most important objectives in business are continuity and growth. To laypersons, this concept may seem to be comprised of ideas at odds with each other. However, the relationship is actually the opposite, continuity and growth are in fact dependent upon each other and are hallmarks of any sustaining enterprise. This can be understood by examining the Shewhart cycle. This cycle consists of four actions: plan, check, act, and do (PCDA). The PCDA cycle, which should be repeated continuously for essential business processes or operations, forces the organization to continually improve itself internally, which should translate into greater profitability, increased market share and other measurable growth factors.

This same principle can be applied to PCBA development that has the objective of maintaining the developer’s design intent throughout the entire process. By incorporating the iterative design⇒build⇒test (DBT) strategy that is foundational to prototyping and akin to the PCDA cycle to the circuit board development process, the highest quality design that most closely is aligned with the design intent can be realized. Let’s see how to best achieve this result after first defining what maintaining design intent means from both the developer and manufacturer perspectives.

What Does Maintaining Design Intent Mean?

Prior to defining maintaining design intent in the context of PCBA development, it is necessary to be able to clarify what design intent means. This can only be done effectively by understanding this essential aspect of board building from the perspective of the developer, as well as the contract manufacturer (CM), as explained below.

Developer Perspective	Design intent is the planned or estimated performance of a circuit board built to the specifications that define the physical parameters for its construction. This includes all components to be used; such that the assembled PCBA will operate and perform its intended functionality.
Manufacturer Perspective	Design intent is encapsulated in the data and information provided in the design package and BOM, which are necessary to fabricate and assemble the PCBA.

 

As the perspectives above indicate, the design intent is not an abstract idea or concept. On the contrary, the design intent is explicitly defined by the data and information contained within the manufacturing file(s) or design package and BOM generated by the developer and sent to the CM.

In order for design intent to be maintained throughout the DBT cycles, the perspectives above must be synchronized such that the objectives of both design (i.e. performance and functionality) and manufacturing (i.e. manufacturability) are achieved. This means the design package must be accurate and complete such that the CM can extract all necessary data and information in order to execute the board’s fabrication, procure the necessary components and assemble the PCBA within the constraints of their equipment capabilities. In the next section, a method for achieving this is discussed.

How to Best Maintain Intent from Design to the Final PCBA

As defined above, maintaining design intent requires that the developer’s specifications be followed explicitly during board fabrication and assembly; however, these specifications must be within CM equipment capabilities. Otherwise, the board is not manufacturable and will require redesign. This is far different from the modifications that normally are done during DBT cycling to improve design quality.

Ensuring manufacturability, especially for more complex custom designs, requires an effective PCBA development process. And a collaborative, symbiotic relationship with your CM is the key to effectiveness. With this environment and adherence to the following guidelines, your PCBA development is well-positioned to maintain design fidelity and generate boards that meet your performance objectives.

Guidelines for Maintaining Design Intent

• Acquire and follow CM DFM and DFA rules and guidelines

The first step toward maintaining design fidelity is to ensure that your design specifications are made within the DFM and DFA rules of your CM.

• Leverage PCB tolerances for design specifications

Following your CM’s DFM and DFA will ensure manufacturability. However, these specifications typically have a range of acceptable values. By choosing values that fall well within CM equipment tolerances precision and alignment with performance parameters can be maximized.

• Use a CAD file for design transfer

Although Gerber files are widely used, there are inherent problems that can impact the transfer of design intent to your CM. It has been experimentally shown that native CAD formats; such as IPC-2581 or ODB++, are better alternatives as they precisely convey the design specifications in a usable format for today’s manufacturing systems, as opposed to simply imagery or art.

• Monitor manufacturing process

It is also desirable to be able to monitor the manufacturing process; such that any issues can be identified and addressed quickly. This capability is available for CM’s that employ a process that provides universal data access throughout PCBA development.

• Collaborate with CM on any design changes

If any issues arise that require modification or change, they should not be instituted in isolation by the developer or the CM. Instead, a collaborative approach should be followed such that the design intent and the actual specifications used for board construction remain in agreement.