Figure 1-22.Enlarged flat pack exploded view.
After the external leads are sealed to the mounting base, the rectangular area on the inside bottom of
the base is treated with metal slurry to provide a surface suitable for bonding the monolithic die to the
base. The lead and the metalized area in the bottom of the package are plated with gold. The die is then
attached by gold-silicon bonding.
The die-bonding step is followed by bonding gold or aluminum wires between the bonding islands
on the IC die and on the inner portions of the package leads. Next, a glass-soldered preformed frame is
placed on top of the mounting base. One surface of the ceramic cover is coated with Pyroceram glass, and
the cover is placed on top of the mounting base. The entire assembly is placed in an oven at 450 degrees
Celsius. This causes the glass solder and Pyroceram to fuse and seal the cover to the mounting base. A
ceramic flat pack is shown in figure 1-23. It has been opened so that you can see the chip and bonding
Figure 1-23.Typical flat pack.