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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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 followed
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 solder
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 inductance,
shield planes to reduce cross talk, and controlled
characteristic impedance of signal lines have been incorporated
into multilayer ceramic packages.

Advanced Ceramic Heaters Improve IC Packaging and System Performance

The continuous increase in the consumption of semiconductor devices and the emergence of new applications in optical components — MEMS, LCD display, flip-chip, chip-onglass, and multichip modules — has created a vast demand for faster throughput and better die-bonding equipment for IC packaging. IC packaging requires a typical ramp rate of 100ºC per second to 400 to 500ºC ±2°C, and a cycle time of 7 to 15 seconds. Similarly, IC chip testing, which stresses chips between -40 to 125ºC while monitoring electrical parameters, also requires a faster cycle rate. To manufacture ICs of all types, a die bonder or die attach equipment is used to attach the die to the die pad or die cavity of the package’s support structure. The two most common processes for attaching the die to the die pad or substrate are adhesive die attach and eutectic die attach. In adhesive die attach, adhesives such as epoxy, polyimide, and Ag-filled glass frit are used to attach the die. Eutectic die attach uses a eutectic alloy. Au-Si eutectic, one commonly used alloy, has a liquidous temperature of 370ºC, while another alloy, Au-Sn, has a liquidous temperature of 280ºC.


Epoxy adhesive has a process temperature of 250ºC. In both processes, the temperature profile of the die attach material must be precisely controlled to ensure complete curing of the adhesive or melting of the eutectic materials. In addition to fast heating, uniformity in temperature over the attaching material is crucial to minimize the defects at the bond line. To meet the demanding requirements in those applications, the heating device must be able to perform reliably with the following characteristics:

* Provide a uniform temperature both during ramp up and steady state;
* Heat up extremely fast;
* Dissipate heat quickly to allow for fast cool-down;
* Have minimum dimension change during temperature cycle;
* Withstand compressive pressure during operation;
* Be highly finished with a smooth and flat surface to enable heat transfer;
* Be constructed with mechanical features such as grooves and holes for vacuum passage and/or curved surfaces;
* Have rapid sensor response time/ short sensor response time for precise control of temperature profile; and
* Operate under high-power density.