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28 SMT007 MAGAZINE I FEBRUARY 2020 Feature Interview by I-Connect007 Editorial Team The I-Connect007 editorial team speaks with Ray Prasad to get his take on the drivers behind smaller component sizes and what he sees in the industry. He also talks about the need to focus on the front end, the printing and imaging area, and why that's a limiting factor currently. Nolan Johnson: We're exploring the trend toward smaller component and feature sizes on boards. The dynamics cause stress on the capability of our manufacturing supply chain. The questions we pose are, "What's driving this trend right now? Are the components driv- ing the features on the boards, or are the fea- tures on the boards driving components?" Ray Prasad: If you look at the big picture, the driver is Moore's Law. In the '60s, Dr. Gordon Moore said that the performance of the silicon would double every 18 months or two years, etc. The silicon has to be put in some kind of housing—the package. The package has to get onto the circuit board, and there are a lot of these packages that will be on the circuit board. The Big Picture on Small Components One electron goes from one place to the other through the wire bond, through the lead, through the vias on the board, through a circuit line on the board to another wire bond of the next package, and then to the lead and back finally to the silicon. This is like com- muting for an electron through rush hour traf- fic at a slow speed. In the process, you have the parasitic loss. The silicon designer talks in picoseconds in terms of performance, but the board designer talks about nanoseconds when they do their timing budget. The electron is slowed by the inductance, capacitance, and resistance of the wire bond, the circuit line, and so on. To make the performance better, you have to reduce the pitches, lead sizes, wire bonds, etc. These are examples of package features that improve the electron's speed. Going from through-hole to SMT, then to fine-pitch to BGA to BTC to flip-chip also improves package per- formance. Similar progress—in terms of lines and spaces on the substrate level—hasn't hap- pened as much. In the '80s, we were at 10-mil lines and spaces, and now, we are probably at five-mil lines and spaces in high-volume pro- duction, and some people can push it to four- mil lines and spaces. This is one of the exam- ples of why the circuit board's performance is Ray Prasad

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