Hermetic Packages
National Semiconductor offers a wide variety of ceramic and
metal can packages for through-hole and surface mount ap-
plications. These ceramic and metal can packages are of-
fered as solutions for high reliability and often high perfor-
mance applications, and are extensively used in military/
aerospace and commercial applications. By design, a
hermetic seal prevents gases and liquids from entering the
package cavity where the die is mounted. Because of the
package materials, hermetic packages are able to withstand
higher temperatures than the equivalent plastic packages.
The construction of hermetic packages can be divided into
three main categories: multilayer ceramic packages,
pressed ceramic packages, and metal can packages.
Multilayer Ceramic Packages
For multilayer packages, ceramic tape layers are metallized,
laminated and then fired to create the package body. Leads
are then brazed to the package body. The metallized areas
of the package are then electroplated (usually nickel fol-
lowed by gold).After assembly, the hermetic seal is achieved
by soldering a metal lid onto the metallized and plated seal
ring. These packages therefore are often referred to as sol-
der seal packages.
The multilayer construction allows the package designer to
incorporate electrical enhancements within the package
body. For example, power and ground planes to reduce in-
ductance, shield planes to reduce cross talk, and controlled
characteristic impedance of signal lines have been incorpo-
rated into multilayer ceramic packages.
Pressed Ceramic Packages
Pressed ceramic packages are usually a three part construc-
tion: base, lid and leadframe. The base and lid are manufac-
tured 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. Dur-
ing 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 combina-
tion. This seal method is referred to as a frit seal, and there-
fore 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 construc-
tion does not allow for many electrical enhancements.
Metal Can Packages
Metal can packages consist of a metal base with leads exit-
ing through a glass seal. This glass seal can be a compres-
sion 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 pack-
ages 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 Na-
tional. 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 flat-
pack (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
© 2000 National Semiconductor Corporation MS011794 www.national.com
Package Configuration Package Characteristics
Ceramic Sidebrazed Dual-In-line Package (SB) Through Hole Package
Brazed Straight Leads to Pads on Package Side
Gold Plate or Solder Dip Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with Cerdip and MDIP
Ceramic Leadless Chip Carrier (LCC)
Surface/Socket Mount Package
Terminal Pads Instead of Leads
Gold Plate or Solder Dip Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with CQJB and PLCC
Ceramic Quad J-Bend (CQJB) Surface Mount Package
J-Bend Lead Configuration
Gold Plate Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with LCC and PLCC
Ceramic Quad Flatpack (CQFP) Surface Mount Package
Straight Lead Configuration
Gold Plate Lead Finish
Multilayer Ceramic Package
Solder Seal
Hermetic Packages
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Package Configuration Package Characteristics
Ceramic Flatpack Surface Mount or Through Hole Package
Straight Lead Configuration
Gold Plate Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with Cerpack
Ceramic Dual-In-Line Package (Cerdip) Through Hole Package
Straight Lead Configuration
Solder Dip Lead Finish
Pressed Ceramic Package
Glass Seal
Footprint Compatible with SB and MDIP
Ceramic Small Outline Package Surface Mount Package
Gull Wing Lead Configuration
Gold Plate Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with Wide Body Plastic SOP
Ceramic Pin Grid Array (CPGA) Through Hole Package
Straight Lead Configuration
Gold Plate Lead Finish
Multilayer Ceramic Package
Solder Seal
Footprint Compatible with PPGA
Hermetic Packages
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Package Configuration Package Characteristics
Cerpack Surface Mount or Through Hole Package
Straight Lead Configuration
Solder Dip Lead Finish
Pressed Ceramic Package
Glass Seal
Footprint Compatible with Flatpak
Cerquad Surface Mount Package
Straight Lead Configuration
Solder DIP or Tin Plate Lead Finish
Pressed Ceramic Package
Glass Seal
Footprint Compatible with PQFP
Can be Electrically and/or Thermally Enhanced
Cerquad EIAJ Surface Mount Package
Gull Wing Lead Configuration
Solder DIP or Tin Plate Lead Finish
Pressed Ceramic Package
Glass Seal
Footprint Compatible with PQFP
Can be Electrically and/or Thermally Enhanced
TO-3
Metal Can Through Hole Package
Solder Dip Lead Finish
Steel or Aluminum Base
Compression Glass Seal
Hermetic Packages
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Package Configuration Package Characteristics
TO-5 and TO-39
Metal Can Through Hole Package
Solder Dip or Gold Plate Lead Finish TO-5
Kovar Base
Matched Glass Seal TO-39
Kovar or Steel Base
Matched or Compression Glass Seal
TO-18
Metal Can Through Hole Package
Solder DIP or Gold Plate Lead Finish
Kovar Base
Matched Glass Seal
TO-46, TO-52 and TO-72
Metal Can Through Hole Package
Solder Dip or Gold Plate Lead Finish
Kovar or Steel Base
Matched or Compression Glass Seal
Hermetic Packages
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can be reasonably expected to cause the failure of
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Hermetic Packages
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