Productive Approaches to Creating Prototype PCBs

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Productive Approaches to Creating Prototype PCBs

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So far, for printed circuit board or PCB prototype, designers limited their choice of PCB design tools to high-end, enterprise-level solutions, as these tools were expensive. The early design tools also added the cost of an extended setup time and learning curve, were limited in their capability, and most often, error-prone. Thankfully, modern tools are now affordable and come packed with all the features designers need for complex designs. Moreover, they are easy to use and focus more on ease of adoption.

Typically, a designer takes about two to three iterations for developing a custom PCB prototype for a working product with a high-speed computer-based design tool. However, with decreasing product life cycles, the time-to-market is steadily gaining in importance. Depending on overheads, board iterations can be expensive, because delaying the product’s market launch and the missed opportunity could cost the company several thousand dollars, or even the total loss of market share.

The above is prompting designers to employ simulation in the design cycle before they order PCB prototypes, as this dramatically reduces the cost of development. As the cost of change increases with development time, design changes occurring early in the design process cost substantially lower compared to those introduced during full-scale PCB fabrication. Using virtual prototyping has the advantage of identifying issues early on in the design process, and rectifying them is cheaper and simpler before they become a major problem.

Virtual Prototyping as a Productive Approach

Although entry-level tools did allow quick designs and prototype building, most designers relied on reference designs provided by chip vendors. Increasingly, designers are finding they cannot rely on reference designs to make their products work in operating environments—they need design for reliability and manufacturability for the real world.

Implementation of each new technology introduces multiple fast rise-time signals propagating at increasingly faster speeds. That does not allow the luxury of building prototypes, testing, reviewing, and revising the design approach with each build.

With virtual prototyping, designers can do with fewer PCB prototypes and improve their design efficiency. Virtual prototyping includes simulation of signal and power integrity, design for manufacturability, thermal analysis, and 3-D interference validation.

Earlier, skills of PCB designers and engineers were necessary for the entry-level tools to detect possible issues as they came up during the design process. High efficiency, complex designs, on the other hand, require a more constraint-driven approach, with correct-by-construction methodology. Once the engineers establish the rules, designers with downstream tools will follow them and use various design rule checks (DRCs) to conform their validation.

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Designing for Profitability

Modern PCB tools are able to handle several tasks other than simply laying traces. It is possible to use these design tools at every phase of the project from initial concept to the final assembly documentation. The addition of 3-D rendering engines in most of these design tools and the complete integration of 3-D component bodies in the footprint libraries makes this possible.

This capability allows designers to give shape to concepts very quickly. They can use virtual prototyping along with vendor-supplied 3-D step models to make a preliminary PCB layout. This allows a quick look at the finished product, such as the position of the I/O connectors, without the detailed board design.

This method helps designers handle request for change early in the design, as the visualization tools allows an upfront view of the design process, and everyone involved has a good idea of the direction the design is headed, and they can spot the misconception or conceptual errors early.

Virtual prototyping has an added side benefit. Every step of the process can confirm the mechanical fit of the product. Moreover, designers can now put together the fab drawing first and get quotes on any proposed design, material, and so on. They can pass the mocked-up fabrication drawing to the assembler for a review to uncover any issues. This not only saves time, but also the unnecessary expense of multiple prototypes. Silk-screeners, pick-and-place machines, and reflow ovens require tabs, holes, and other modifications that are not part of the original circuit design, but part of manufacturability. Assemblers reviewing the preliminary fab drawing often make recommendations based on their experience with materials and others.

Keeping a Dynamic Supply Chain Visibility

A major reason for design iterations is the supply chain information not being available to the designers in real time. Many a time designers have to manufacture printed circuit board prototypes only to have to change their design because of the non-availability or a certain component or components, which they have to replace with a suitable alternative and now requires a change in the PCB design. The cost of having to change the design at the prototype stage is much lower compared to that required once the product is in full production. Therefore, it is necessary to have a real-time view of the supply chain from the product management or procurement team.

Additive Manufacturing Rather than Subtractive

Regular PCB prototype making is a subtractive process. The fabricator starts with more material than needed, and removes the unnecessary parts. However, in an additive process, the fabricator starts with a thin substrate and adds the required copper traces with conductive ink.

Although still in its infancy, 3-D printing and additive manufacturing for electronics is a great way to generate less waste than traditional subtractive methods for PCB fabrication, especially for custom PCB prototypes. With additive manufacturing machinery deployed in-house, engineers can make necessary changes in a design without the traditional penalties in cost and time. The designer does not have to wait for the fab house to send the order PCB prototypes back, as he can create the prototype on his or her desktop.

Designers can select from 3-D printing and 2-D printing processes for additive manufacturing. The 3-D printing prints PCBs from scratch, using a variety of gels, inks, and substrates, layer by layer, manufacturing them at the nanoparticle level. This is a very new process and involves material complexity and extrusion requirements.

The 2-D inkjet-style printing matches more readily with the Gerber files designers generate to communicate designs to manufacturing. These machines only have print the conductive traces on a flat horizontal substrate. This is ideal for printing PCB prototypes for quick prototyping.

Conclusion

There are several ways to reduce the iterations involved with designing, PCB prototyping, and cutting down on the time to market factor. While virtual prototyping can actually save on the time required for ordering, testing, and reviewing prototypes, additive manufacturing can cut down the actual time for fabricating prototypes. Additionally, keeping a clear dynamic supply chain visibility precludes the necessity for redesigning the board at a later stage.

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