BGAs are used more commonly now than ever before and are increasing design density and complexity. At the same time, the BGAs, themselves, are shrinking in size and adding greater numbers of pins. This calls for more precise design and manufacturing techniques.
However, size of the traces is shrinking. Currently, trace routing between BGA pads is 2 - 3 mils. This poses difficulties at fabrication and assembly. These thin traces demand tight control of compensation factors to highly precise levels and at different manufacturing stages.
The escape routing technique takes into account such factors as ball pitch, land diameter, number of I/O pins, via type, pad size, decoupling capacitor placement, trace width/spacing, and the number of layers required to escape the BGA.