HERMETIC PACKAGES - National Semiconductor

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

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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DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL

COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein:

1. Life support devices or systems are devices or

systems which, (a) are intended for surgical implant

into the body, or (b) support or sustain life, and

whose failure to perform when properly used in

accordance with instructions for use provided in the

labeling, can be reasonably expected to result in a

significant injury to the user.

2. A critical component is any component of a life

support device or system whose failure to perform

can be reasonably expected to cause the failure of

the life support device or system, or to affect its

safety or effectiveness.

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Hermetic Packages

National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications.