Pressed Ceramic Packages
Pressed ceramic packages are usually a three part construction:
base, lid and leadframe. The base and lid are manufactured
in the same manner by pressing ceramic powder into
the desired shape and then firing. Glass is then screened
onto the fired base and lid. The glass paste is then fired. During
package assembly, a separate leadframe is embedded
into the base glass. The hermetic seal is then formed by
melting the lid glass over the base and leadframe combination.
This seal method is referred to as a frit seal, and therefore
this package is often called a glass frit seal package.
The pressed ceramic packages are typically lower in cost
than the multilayer packages. However, the simple construction
does not allow for many electrical enhancements.
Metal Can Packages
Metal can packages consist of a metal base with leads exiting
through a glass seal. This glass seal can be a compression
seal or a matched seal. After device assembly in the
package, a metal lid (or can) is resistance welded to the
metal base forming the hermetic seal. The metal can packages
are usually low leadcount, less than 24 leads, and low
in cost. Certain outlines, such as the TO-3, have very low
thermal resistance. These packages are used in many linear
and hybrid applications.
Hermetic Package Configuration
National offers DIP configurations in the pressed ceramic
(Cerdip) package style as well as the multilayer ceramic
sidebrazed (SB) package. Other through hole package
styles are the metal can packages (TO) and the ceramic pin
grid array (CPGA) packages.
Many ceramic surface mount packages are offered by National.
Dual in line packages such as the pressed ceramic
Cerpack, and the multilayer ceramic flatpack are available in
the lower leadcounts. These packages typically have a lead
pitch of 50 mils. Applications requiring higher lead density
use quad packages such as the multilayer ceramic quad flatpack
(CQFP) and the pressed ceramic Cerquad. Lead pitch
of 25 or 20 mils (or the metric equivalent 0.65 mm and
0.50 mm) are most common for the quad packages.
The following table provides configuration and characteristic
data regarding each of the ceramic and metal can packages
offered by National.
August 1999
Hermetic Packages
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