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38 The PCB Design Magazine • November 2017 modate more and more functions making the design itself much more complex, and all of this on smaller and smaller circuit boards. The onset of these increasingly sophisticated electronic products, has led to more advanced PCBs becoming more commonplace. The specifications here require high-density interconnect (HDI) solutions with greater num- ber of layers, and more connections both on the surface and inside the PCB, utilizing finer conductor widths and narrower spaces between them. This all leads to a design that is based upon smaller, laser-drilled microvias (blind vias), since normal through-hole vias simply wouldn't fit into the space available. Therefore, we are seeing manufacturers producing more boards that also incorporate buried vias. All of which increases the number of interconnec- tions within the board and frees up valuable space on the outer layer for more components to be placed. The increased number of layers, together with the microvia technology, also requires the use of thinner prepegs and cores than in conventionally manufactured boards which also leads to increased demands upon the factories. by Chris Nuttall NCAB GROUP Modern electronic products are expected to offer evermore advanced functions, while the products themselves are becoming increas- ingly smaller. This puts greater demand on the PCB design and the aspects relating to the PCB manufacturing process. There are two key fac- tors for the successful production of HDI PCBs: first, making the right choices at the design stage, and then carefully choosing the factory that can support the specific technical demands of the project. Whether it's consumer electronics, comput- ers, automotive or medical technology, the over- all trend is reduction in size. Not just through a reduction in actual or finished product size, but also as the components themselves are be- coming smaller, so the assemblies must be more densely packed and use smaller features. Consider the way mobile phones have evolved. A modern smartphone is so much thin- ner, lighter and smaller than the mobiles we had 10 years ago, but in terms of what it can do, it is light years more advanced than its predecessors. Therefore, the PCBs inside are having to accom- FEATURE