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74 DESIGN007 MAGAZINE I DECEMBER 2020 technology. To provide some context, in this particular application, there was the need for mixed materials, unbalanced copper weights, and no less than 10 different flex areas, with only selective layers going into those different areas. As is often the case, the team working on this had competing needs that were driving this complexity. Thankfully, understanding that this was quickly becoming a more com- plicated design than had been done previ- ously, this team reached out to the fabricator for advice and review before jumping in and working on the PCB layout. Again, communi- cation was key to the success of this highly complex design. There were many conference calls pulling in the full group and the fabricator until the material configuration and layout concept were adjusted to something that was both manufac- turable and met the overall design objectives. It would have been a costly mistake to have completed the design and sent it for fabrica- tion without fabricator input. Fabricators are a significant source of knowledge and are happy to share that knowledge early in the design phase. The Power of Communication I share these two success stories to illustrate the power of communication, particularly con- versations between design and fabrication. During the recent "Just Ask Tara Dunn" series, one of the questions that I was asked was "Why don't flex and rigid fabricators provide more feedback to designers, especially if it's not good design and engineering work?" That is a powerful question that shines a light on the opportunity to improve communication to the benefit of both fabricators and designers. I cannot imagine a scenario where a designer would not want feedback that would improve the overall design and improve manufactur- ability. I also cannot imagine a scenario where a fabricator would not be happy to provide that feedback. What I can easily imagine is the impact this improved communication could have on circuit performance, yields, manufac- turability, and time to market. (30 microns or below), the additive process first removes all the copper from the panel and then adds back the conductive metal to form traces. Consequently, that conductive metal is no longer limited to copper, opening the opportunity to meet this requirement of gold conductors on polyimide. Although the addi- tive process is most often used for fine feature sizes, it can also be applied to larger traces. In this case, the minimum feature size was a 75-micron trace and space. The challenge with this new process is just that—it is new. There are not decades of expe- rience and quality specifications to rely on, at least not yet. I think designers and fabrica- tors are very good at communicating design requirements via the fab drawing for standard technology. But with something new, in my opinion, the way to be successful is to com- municate not only through the fab drawing but with actual conversation. In the recent applica- tions with gold conductors, not only were there discussions before finalizing the design, but there were also conversations throughout the fabrication cycle, bringing all parties together to discuss the progress and results and talk through any recommendations for process and design improvement for future applications. Complex Rigid-Flex Another story I would like to share involved a complex rigid-flex design. To some, com- plex rigid-flex designs are something they are well versed in, but to others, this is a new The challenge with this new process is just that—it is new. There are not decades of experience and quality specifications to rely on, at least not yet.

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