Granulates & Preforms

Product Description

Most sealing and solder glass powders can be further processed into ready-to-press granulates and sintered preforms of various customized shapes. Such preforms are, for example, used in glass-to-metal seals and other electronic applications.

Ready-to-press granulates are agglomerates of glass powder particles held in shape by an organic binder. While glass powders do not easily “flow” due to their irregular shape, granulates do. They are the basis for the production of sintered preforms.

Preforms are pressed and sintered glass “pearls,” rods or spacers in various shapes which are typically used in assemblies such as hermetic glass-to-metal components.

SCHOTT offers ready-to-press granulates as well as customized preforms for further processing by the customer.


  • Supply of a large variety of different sealing and solder glasses to match the diverse needs of sealing partners and application specific requirements
  • Availability of standard as well as customized preform designs are available
  • Tightly controlled tolerances in terms of weight and shape


Sintered preforms are used for the fast and convenient assembly into glass-to-metal components. Other applications include sintered discs or rods which are, for example, used as spacers.

Technical Details


Several technologies can be used to manufacture granulates, with spray drying being the most popular. After mixing the glass powder with an organic binder and water, the slurry is sprayed into a heated tower. During this process, the droplets dry and agglomerate into the typical granulate shape. To manufacture granulates and preforms in different colors, pigments can be added to the slurry.

Preforms are manufactured by automatically pressing granulate into the desired shape. This is followed by a two-step furnace operation. First, the pressed granulate is heated up until the organic binder evaporates. The second step is the so-called “sintering process” itself: the pressed powder is brought up to an even higher temperature causing the boundaries of the individual glass powder grains to soften and to attach to each other. The resulting preform becomes solid after cooling. During the whole operation the pressed glass material shrinks considerably to reach it’s final shape.

Features / Specifications

Most sealing and solder glasses can be supplied in the form of granulates and preforms. For details about the technical glass characteristics, please refer to our sealing and solder glass product pages.

Typical granulate grain size distributions vary between 100 – 300 µm. Smaller distributions for special applications are available upon request.

Preforms are available in customized geometric shapes and diameters ranging from less than 1 millimeter to several centimeters.

Forms of Supply and Product Packaging

Preforms are mostly shipped in bulk. Tray packaging is available upon request.


Please refer to our quality assurance processes pages for more information on our various quality assurance programs.
Exhibitions & Events
Exhibition CIOE - China International Optoelectronic Exposition, Shenzhen, China, 09-01 to 09-03-2021
Exhibition Gastech, Singapore, Singapore, 09-13 to 09-16-2021
Electronic Packaging
SCHOTT North America, Inc.

15 Wells Street
Southbridge, MA 01550
E-Mail to SCHOTT+1 (508) 765-7450
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