HDI’s Beneficial Influence on High-Frequency Signal Integrity


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Introducing the Benefits of Microvias

The increasingly widespread use of finepitch ball-grid array (BGA), chip scale packaging (CSP), and other evolving technology form-factors means that new fabrication techniques must be used to create printed circuit boards (PCBs). In addition, extremely fast clock speeds and high signal bandwidths challenge systems designers to find better ways to overcome the negative effects of noise, radio frequency interference (RFI) and electro-magnetic interference (EMI) have on their product’s performance. Finally, increasingly restrictive 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 incorporating microvia circuit interconnects is currently one of the most viable solutions on the market (Figure 1). Adopting microvia technology means that products can use the newest, smallest, and fastest devices, meet stringent RFI/ EMI requirements, and keep pace with downward-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 interconnections through one dielectric layer within a PCB. Microvias are commonly used in blind via constructions where the outer layers of a multilayer PCB are connected to the next adjacent signal layer. Used in all forms of electronic products, they effectively allow for the cost effective fabrication of high-density assemblies.

The IPC has selected high-density interconnection structures (HDIS) as the term to refer to these various microvia technologies. This definition is by no means universal. The Japanese refer to any via drilled by lasers in a thin dielectric as a microvia.

To read the full version of this article which appeared in the October 2017 issue of The PCB Magazine, click here.

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