The wafer size back in 1971 was about
2 inches in diameter. Now, wafers as large as
12 inches in diameter are being processed. This
means that ICs are being manufactured in ever increasing batch sizes, and that’s one of the
reasons costs are decreasing. A large wafer will
yield hundreds or thousands of individual chips
(Figure 13-6 on page 390). Some of the individual chips might be defective. Figure 13-7 on
page 390 shows that needle sharp probes are
used to electrically test each chip. The defective
ones are marked with a dot of ink for later
disposal. The wafer is cut apart with a diamond
saw and the good circuits, now called chips, are
mounted onto metal headers as shown in Figure 13-8 on page 390. The chip pads and header
tabs are connected with very fine wire. Ball
bonding, or more likely ultrasonic bonding, is
used to make the connections. The package is then sealed. Plastic packages are most common
and ceramic or metal packages are used for military or other critical applications.