The guts of most durable products today contain a lot of electronics. The external package, whether an iPhone, a TV, or even a washing machine, is usually just the outermost package of multiple layers of packaging. In this article, we will look at innermost package type, the packaging that protects the IC (Integrated Circuit, sometimes called a computer chip.)
Today, silicon chips are made with a very large number of transistors arranged to make digital logic. The transistors are very small, allowing hundreds of thousands, sometimes millions, of transistors, to be made on a thumbnail-sized piece of silicon. A major problem is how to connect signal lines and how to protect the IC from damage. Special electronic packages have been developed to accomplish these tasks.
Advances in chip processing techniques have allowed for larger chips with smaller transistors. As this trend toward higher levels of integration (the inclusion of more circuitry onto a piece of silicon) continues, the number of signal lines has also increased. The package size has grown to accommodate the larger number of signal lines.
The demand for the packages with low pin-count has declined significantly. As the volume falls, the economy of scale goes away. The volume decrease causes the unit cost to increase, putting additional downward pressure on its usage. Then another factor comes into play. The tools to produce any given package type are expensive. A plastic package requires not only a mold and a small piece of metal called a lead frame, it also requires tooling for finishing. As these expensive tools wear out, a choice must be made whether to replace them. The manufacturer must decide if possible future revenue justifies the expenditure for the replacement tooling. Often, it is not practical to continue making some package types.
What do you do if you have a product that has a PCB (Printed Circuit Board) designed for a certain package type? If your PCB has a footprint that exactly matches the placement of connections on a particular package type, how do you proceed if nobody makes a package that fits that footprint? One costly approach is to design a new printed circuit board with a footprint for a similar device in a package that is available. The cost to design the new PCB, debug and test it, and update the documentation can be prohibitive. If the PCB was designed a long time ago, the designers may have moved on leaving incomplete documentation. Often manufacturing does not have a budget for design work. Solutions are even more costly when a new design requires a lot of testing such as for FDA approval.
