Weaving A Digital Thread For Design And Manufacture Of Additive Electronics

Additive manufacturing has been around electronics since thick-film, screened hybrids came on the scene more than 30 years ago. And while those never quite went away, they never gained the prominence we all expected alongside the more traditional laminated, subtractive-etched PCBs.

Today, emerging technologies are bringing a resurgence in additive manufacturing, also known as printed electronics, thanks to a host of new materials, processes, and 3D printing technologies.

The goal for additive manufacturing is to enable optimizations and ensure a continuous digital thread so that there is absolutely no redesign as a design passes through various design and verification tools and on through to manufacturing.

Whereas electronics have historically been discrete structures encapsulated in some mechanical package, the drive now is to integrate electronics more seamlessly into the end-product’s form factor, requiring circuits that are flexible and/or conformal to the contours of any product surface. In addition to reduced size and weight, other drivers include customization with localized manufacturing, reduction in part count, new 3D structures, and a reimagined supply chain.

There are a number of applications for this new technology, including radar systems and other sensors molded to the surface of an airplane, smart textiles with integrated sensors to measure human performance and provide identification, and medical bandages that sense infection and accelerate healing. Cars are rife with sensors across both the exterior and interior surfaces, conforming to the design of the car, not the other way around. Even product packaging includes sensors that track conditions during shipment to ensure quality.

The plethora of these manufacturing technologies and materials makes it difficult to focus on optimizing a moving target. This article will discuss some of the resulting challenges and solutions.

Design for additive manufacturing

From the designer’s perspective, these technologies can be broken into planar and non-planar categories.

Planar electronics are designed with processes similar to those used for traditional, flat PCB-like layered structures. The manufacturing may be very different (e.g., using an additive printer), but it’s still creating the structure one planar layer at a time. Post-production, they can be flexed or molded into the final form. Advanced technologies that fit the planar design model today include flexible hybrid electronics (everything’s flexible, including the ICs and batteries), molded interconnects, and 3D conformal “wraps” (e.g., 2D designs converted to fit a 3D structure, then printed).

PCB design tool advances made over the years to support rigid-flex, localized dielectrics, HDI, wire bonding, and embedded actives/passives can aid in the design of planar structures (i.e., make the digital twin more intelligent, rather than creating workarounds that must be explained or converted for manufacturing). Certainly, design for manufacturability takes on new meaning when you must ensure things like interconnect and impedance continuity in the final flexed/conformal structure. In this design chain, MCAD tools become more critical, but there can still be a separation between the electronics and mechanical design domains.

Non-planar electronics can have interconnects and components placed at any angle, in any location in a given space. There’s no functional reason to separate electronics from a mechanical enclosure. They’re one and the same—the ultimate in electro-mechanical structures. Given the geometrical challenges, current prototypes of these structures are often designed in MCAD as non-electrically intelligent structures, forgoing much of the automation and verification technologies built up over decades in ECAD. These structures are still relatively simple, so the trade-off is acceptable, but as complexity increases, the need to maintain electrical intelligence and model performance will increase.

Optimizing the tool chain

Over the last 50 plus years of PCB design and manufacturing, the tool chain from design through manufacturing has become largely optimized (there are still areas for improvement). As noted in the introduction, the goal for additive manufacturing is to achieve the same optimizations, ensuring a continuous digital thread so that there is absolutely no redesign as the design passes through various design and verification tools and on through to manufacturing (see figure 1). Part of the challenge today is that there are so many manufacturing technologies and materials in research that it’s hard to focus on optimizing a moving target.

Fig. 1: Tool chain for 3D printed electro-mechanical structures.

At first glance, the process chart in figure 1 could easily represent traditional PCB flows, but a closer look reveals many new challenges:

• The delineation between ECAD and MCAD is blurring so much that electro-mechanical design may have to be done in one tool.
• Design constraints will have to consider the variability of the materials used.
• Given the operating conditions of these new structures, a host of multi-physics analysis will be required to ensure performance (e.g., signal, power, thermal, EMI, stress, vibration, stretch, moisture, impact, deformation, and manufacturability).
• The product model transferred to manufacturing will need to maintain design intent to eliminate redesign. Planar electronics could leverage existing PCB models (e.g., ODB++, IPC-2581), but they will likely need to be extended to support additional design elements. Non-planar electronics will likely require a completely new model. In both cases, the path from design may flow through MCAD, rather than the traditional ECAD outputs.
• In manufacturing, the process preparation stage has to apply multi-material “slicing” and “tool-pathing” algorithms to ensure that the structure is printed as designed.
• In manufacturing, a host of new machines need to be integrated (e.g., 6-axis robotic printers, reel-to-reel processing, and assembly of bare, flexible dies). In addition, the traditional PCB fabricate-then-assemble process could be upended, with the ability to integrate active and passive components during the “substrate build.”

The net result is multiple tool chains in various states of optimization.

To address these challenges, Siemens is leveraging its multi-domain portfolio of ECAD, MCAD, and simulation technologies. We are partnering with NextFlex and its consortium members to refine these tool chains, build a materials database, create process development kits, and optimize the digital thread from concept through manufacturing.

NextFlex is a consortium of electronics companies, academic institutions, non-profits, state, local and federal government partners with the shared goals of advancing U.S. manufacturing of printed flexible electronics (also known as flexible hybrid electronics or FHE), promoting the requisite, sustainable electronics manufacturing ecosystems, and delivering education and workforce development programs to accelerate the growth of the workforce of tomorrow.

Fig. 2: Additively manufactured flexible circuit. (Source: NextFlex)

By taking advantage of FHE’s ability to conform to organic shapes, electronic capability can now be incorporated into new and emerging consumer, medical, and industrial products that, when combined with rapid advancements in data analytics and artificial intelligence, enable real-time decisions and analysis. Additive manufacturing is ideally suited for FHE design and manufacture.

NextFlex uses Siemens tools on all its designs. It has used Xpedition, HyperLynx, and Valor for years and has recently added NX to its tool flow. Through its collaboration with NextFlex and others, Siemens is gaining a deep understanding into how the materials, processes, tool chain, and all aspects of additive manufacturing are evolving over time, so we can target where to invest our research and development.

Additive manufacturing is a reality today, but we recognize that there are many areas that can be improved. Siemens’ collaboration with industry partners like NextFlex is driving these technologies to productization in order to move additive manufacturing forward and deliver a continuous digital thread that weaves the entire design to manufacturing process together.