Electronic & Technical
Glasses
Product Selection and
Application
Glasses should be selected to provide optimum compatibility with the device requirements and usage, as
well as the application technique used to apply it. The most critical characteristics of a glass are:
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Type of glass
Coefficient of Thermal Expansion at the glass set point (CTE @ Set Pt)
Transformation temperature (Tg)
Particle size distribution (PSD)
Glass flow and wettability at the processing temperature
Compatibility of the glass composition with the application
Glasses are generally of two types, vitreous and devitrifying (crystallizing). Vitreous glasses are
thermoplastic and flow at the same temperature each time they are fired. Devitrifying glasses are
thermosetting and crystallize during firing to form glass-ceramic, which have different properties than the
original glass. The actual crystallization and resultant glass-ceramic can be modified by changing firing
conditions and particle size distribution. They typically have greater strength and allow higher device
operating temperatures than the vitreous form.
Glasses may also be a composite of several different glasses, or glass and ceramic fillers. This is
typically done to meet specific requirements, such as thermal expansion and firing temperature,
that are not possible with a single glass.
The CTE @ Set Pt should be as close as possible to the substrate material to prevent stress within
the glass and/or substrate that can lead to cracking and failure. The largest recommended
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difference between glass and a substrate is ± 5 x 10 /°C; this is generally termed a "matched" fit. In
some special configurations, a "compression fit" can allow the joining of two significantly different
thermal expansion materials by an intermediate glass.
Each glass has a maximum operating temperature, or the temperature a device can be operated
without degrading the glass which can lead to device failure. This is typically somewhat lower than
the Tg of the glass. A devitrifying glass, after firing, will have a maximum operating temperature
dependent on the crystalline phase formed and is higher, sometime significantly, than the original
glass.
The PSD, or powder type, as expressed in maximum (D99) and average (D50) particle sizes, should
only be as small as necessary to achieve the desired fired thickness and line definition using the
application technique chosen. The smaller a powder type is, typically, the more difficult to process
effic iently. In the case of devitrifying glasses (crystallization during firing), changes in the PSD can
affect fired CTE, flow and wetting, densification and strength.
www.ferro.com
DISCLAIMER:
Reasonable care has been taken in the preparation of this information, but FERRO EXTENDS NO WARRANTIES, MAKES NO REPRESENTATIONS AND
ASSUMES NO RESPONSIBILITY AS TO ACCURACY OR SUITABILITY OF THIS INFORMATION OF THIS PRODUCT FOR ANY PURCHASER’S OR USER’S USE OR FOR
ANY CONSEQUENCE OF ITS USE. FERRO DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR WARRANTY OF FITNESS FOR ANY PARTICULAR USE. All
statements, technical information and recommendations contained herein are based on Seller’s or Manufacturer’s test and the test of others, and are believed to be accurate, but no guarantee of
accuracy is made. Judgment as to the suitability of information herein or the user’s purposes are necessarily the user’s responsibility. Users shall determine the suitability of the products for their
own intended application.
Users assume all risk of use or handling whether or not in accordance with any statements or recommendation of the seller or manufacturer, Liability, if any, is and shall be limited to the replacement
of such quantity of material proved not to conform to specifications as set out in product specification. Statements concerning the possible use of these products are not intended as recommendation
to use these products in infringement of any patent. No guarantee is made that any use of the products does not infringe third-party intellectual property or patent rights anywhere in the world.
Page 1 of 1
Rev 01/11
Electronic & Technical
Glasses
Product Selection and
Application
Although some products have unique distributions, our powders have the following typica l
properties:
Typical Range (µm)
Powder Type
D99
D50
VSD
150
> 15
TF
44
10 - 15
VEG, REG
74
6 - 10
MVG
34
4-6
VWG, RWG
20
2-4
SRRG
7
1-2
SMZ
5
<1
www.ferro.com
DISCLAIMER:
Reasonable care has been taken in the preparation of this information, but FERRO EXTENDS NO WARRANTIES, MAKES NO REPRESENTATIONS AND
ASSUMES NO RESPONSIBILITY AS TO ACCURACY OR SUITABILITY OF THIS INFORMATION OF THIS PRODUCT FOR ANY PURCHASER’S OR USER’S USE OR FOR
ANY CONSEQUENCE OF ITS USE. FERRO DISCLAIMS ANY WARRANTY OF MERCHANTABILITY OR WARRANTY OF FITNESS FOR ANY PARTICULAR USE. All
statements, technical information and recommendations contained herein are based on Seller’s or Manufacturer’s test and the test of others, and are believed to be accurate, but no guarantee of
accuracy is made. Judgment as to the suitability of information herein or the user’s purposes are necessarily the user’s responsibility. Users shall determine the suitability of the products for their
own intended application.
Users assume all risk of use or handling whether or not in accordance with any statements or recommendation of the seller or manufacturer, Liability, if any, is and shall be limited to the replacement
of such quantity of material proved not to conform to specifications as set out in product specification. Statements concerning the possible use of these products are not intended as recommendation
to use these products in infringement of any patent. No guarantee is made that any use of the products does not infringe third-party intellectual property or patent rights anywhere in the world.
Page 2 of 2
Rev 01/11