My interest was piqued by a recent article from the pen of good friend, Ray Rasmussen. In this piece, Ray reviews a presentation by Phil Plonski of Prismark Partners on a tear down analysis of an Apple iPad. Ray comments on the profoundly dense interconnection, with package-on-package (PoP), flip-chip, etc. The result is a product with super-dense IC packing with a minimum of printed circuit boards (PCBs) needed. The micrograph, from Prismark, shows this impressive packaging design.
Ray goes on to lament that these types of designs require fewer and fewer PCBs. He then states: “It won't be long before they learn how to build the iPad and iPhone without a PCB altogether.”
Whoa, slow down! Let’s think this statement through.
The PCB provides at least two fundamental functions:
1. It provides mechanical support for the electronic components.
2. It interconnects the components to each other and provides input/output connections so that the electronics can interact with the user.
(PCB experts will point out that there are many other functions such as heat transfer, electrical impedance matching, electromagnetic shielding, and a few other things the PCB provides in addition to those mentioned above. Many product designs require all of these functions of the PCB, however, even the most basic designs require 1 and 2.)
It is an imperative in any electrical design to minimize the number of components, PCBs, connectors, etc. in order to minimize cost and increase performance. However, the minimization of PCBs often results in those used becoming more complex and hence having more “value added.”
In looking at the micrograph cross section, one could strongly argue that the PCB has never been so important or so strongly a “partner” in the design. The multilevel, fine feature, high density interconnection provided by this PCB is truly a miracle of modern PCB manufacturing. Any other “PCB-less” design would require these functions and would essentially, by any other name, be a PCB. As an example, let’s say all of these functions were performed by the case of the electronic device. To manufacture this new PCB-less device, the processes that are used to make a PCB would be needed to form these functions in the product’s case. In addition, solder paste printing, component placement and reflow soldering of the case would likely be a challenge!
So expect the PCB to be alive and well for some time to come…..and never more needed.