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40 The PCB Magazine • October 2017 FEATURE by Happy Holden I-CONNECT007 Introducing the Benefits of Microvias The increasingly widespread use of fine- pitch ball-grid array (BGA), chip scale pack- aging (CSP), and other evolving technolo- gy form-factors means that new fabrication techniques must be used to create printed cir- cuit boards (PCBs). In addition, extremely fast clock speeds and high signal bandwidths chal- lenge systems designers to find better ways to over come the negative effects of noise, radio frequency interference (RFI) and electro-mag - netic interference (EMI) have on their prod- uct's performance. Finally, increasingly restric- tive cost targets are compounding problems associated with today' s smaller, denser, lighter, and faster systems. Staying competitive and delivering the products people want means seeking out and embracing the best available technologies and design methodologies. The use of PCBs incor- porating microvia circuit interconnects is cur- rently one of the most viable solutions on the market (Figure 1). Adopting microvia technol- ogy means that products can use the newest, smallest, and fastest devices, meet stringent RFI/ EMI requirements, and keep pace with down- ward-spiraling cost targets. What are Microvia Technologies? Microvias are vias of 6-mils (150 microns) diameter or less. Their most typical use today is in blind and buried vias used to create inter- connections through one dielectric layer with- in a PCB. Microvias are commonly used in blind via constructions where the outer layers of a multilayer PCB are connected to the next adja- cent signal layer. Used in all forms of electron- ic products, they effectively allow for the cost effective fabrication of high-density assemblies. The IPC has selected high-density interconnec- tion structures (HDIS) as the term to refer to these various microvia technologies. This defi- nition is by no means universal. The Japanese refer to any via drilled by lasers in a thin dielec- tric as a microvia.

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