TABLE OF CONTENTS Here's what you're going to see in this chapter:
Why you need to look at packaging before you start your layout
Rules about putting chips in their little black boxes
Different ways to connect the little wires
Placement considerations for the input/output pads
Three quick ways to know if your chip will fit
How to smoosh the chip smaller by using empty pad space
How to compute finished die size after the saw blade
Packaging considerations should be addressed even before you begin your chip layout. Packaging is really part of the floorplanning process, but it's worthy of having it's own separate chapter. As you will see, the choice of package for the chip drives your options for the floorplan. We will see some unique situations for chip size, block placement, and other issues which all begin with the selection of the final package.
The package you choose for your chip has a particularly large effect on placement of your I/O pads. You cannot just blindly put your input/output pads wherever you feel like it, because they interact with the package. There are some rules and guidelines you will follow in order for these signal connections to be bonded properly in the packaging choice.
There are hundreds of different kinds of packages. The assembly rules will be very different from one package to another, from one package vendor to another, and from one assembly house...
