Today's electronic components such as active and passive components must be interconnected and assembled together in order to form a functional and operating system. The manufacturing and designing of these interconnections have evolved into a separate higher density discipline called electronic packaging. As far as early 1950s, the building block of electronic packaging is the printed circuit board or most of us call it printed wiring board (PWB), and it will always remain the fundamental and support into the foreseeable future.
As we all know that the mobile phone and computer board are getting smaller, and we are seeing the component supplier continuing increase in component performance and lead density, specifically focus on the reduction in package sizes, this has also required that PWB technology to improve and to increase the interconnection density of the substrate. The continuing refinement and introduction packaging techniques such as the chip-scale packaging (CSP) and ball grid array (BGA), the traditional PWB technology has come to a point where more advance or alternative ways of providing high-density interconnection have had to be developed in order to cope for market's needs. This has been called at times high-density interconnects (HDI) which involved higher density with laser via hole, or the industry call it the density revolution, because doing the same things in the same old fashion way, only smaller in size, was no longer sufficient.
How to select a good packaging? In fact, the selection of the packaging is among the various aforementioned elements that dictated not only by the total system function, but is also determine by the component types selected as well as by the operating parameters of the system, for instant the clock speeds, power dissipation and consumption, and heat control management methods, and not forgetting the environment in which the system will operate.
One of the important factors that we need to consider is the speed of the electronic system operates and this is the primary rule and factor in the design of interconnections. A lot of digital and electronic systems operate near to 100 MHz and some are already reaching beyond that level. Obviously the increasing system operating speed is placing great demands on the packaging engineers and on the material properties used for PWB and also packaging substrates.