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Thick Films

While the thickness of a thin film will be in the range of up to few thousand Angstroms, the thickness of the thick film will be in micron meter range and a typical thick is 12.5 micron meters (.0005”). Of course, a thin filming requires a vacuum system and the method how to apply will be screen printing or spraying. Except one for polymer base, all require sintering at high temperature, mostly in air or oxygen rich environment.

Oxide Ceramic or Glass:

Most popular thick film paste contains about 95% or more One or two metallic elements (powders, grains, flakes or a mixture of them) with 5% or less of an inorganic high temperature binder in powder that might be a glass, ceramic or a combination of both). The metallic elements and the inorganic binders will be mixed together in an organic vehicle forming a paste so that the mixture of metal and ceramic (cermet) can be screen printed, brushed or sprayed on. The organic binder shall be decomposed and burned off during the sinter firing at high temperature. The inorganic binder reacts with ceramic substrate at high temperature resulting some chemical reactions for a bonding and the metallic grains, powder, flakes or some combinations will simply situated in the overall matrix of the thick film material providing certain degree of electrical conductivity or resistivity depending on the materials in it. The most common conductive thick films are Ag, Ag/Pd, Au, Ni, Cu, Pt, Au/Pt, etc. In this thick film system, the adhesion of the thick film comes from the binder and not from the metallic element. Therefore, the small amount of binder may not provide hermeticity while it would provide certain electrical conductivity. Its adhesion strength is usually low due to the small amount of the binder content.

A thick film can be applied on: alumina, zirconia, glass-ceramic (Macor, a Corning product), Cordierite, Forsterite, Steatite, Mullite and many other ceramics. While the organic vehicle is decomposed, inorganic binder reacts with substrate.. The sufficient partial pressure of oxygen over the substrate maintains the stoichiometry of the oxide ceramic.

IJ Research uses both in-house developed thick film pastes as well as commercially available pastes that made in the United States. IJ Research has the capability of formulating a new thick film paste that can be cured at as low as 450OC or as high as 1,200OC.or oxide ceramics followed by thin film
(either resistive or conductive).

Thick Film Heater Technology:

IJ Research’s thick film heaters contain the most up-to-date materials. Our resistive elements are metal/ceramic mixtures (cermet). They include Ruthenium Dioxide (RuO2),
Bismuth Ruthenate (Bi2Ru2O7), Bismuth Iridate (Bi2Ir2O7), and Lead Oxide (PbO). Our custom designed heaters are directly printed on glass, ceramic or metal. Heater patterns can be applied on a flat substrate as well as on a tube where OD or ID may need to have patterns. Power density within .002 W/cm2 is routine at IJ Research. We coat as require on a stainless steel substrate with a dielectric layer before we print a heater pattern.

Note: Cu and Ni are fired in an oxygen poor atmosphere in order to avoid an oxidation of the elements. The Cu or Ni metallization processes require that the inorganic binder containing a strong bonding energy. They must not be reduced in an oxygen poor environment.

Non-oxide Ceramics:

IJ Research uses special thick film pastes for non-oxide ceramics such as nitrides, carbides and boride ceramics along with graphite and other similar carbon base materials such as diamond, C-C composites, etc. Many of the commercially available pastes are less than satisfactory for these non-oxides. We formulate suitable mixes for these non-oxides. We also offer hermetically sealable thick film metallization coating on AlN, Si3N4, SiC and other non-oxides. AlN can be hermetically sealed to another ceramic or a metal. Our thick film based patterns are solderable, brazeable or also wire bondable.

For feed through, we thin film metallize ID as well as OD of the insulator and braze with a metal flange. For a window assembly, window cap assembly or opto-electronic

Resistive Patterning:

If the application is for a resistive patterning, the formula of the paste will have a resistive element with the same binder types. A paste will be formulated for your specific applications including: chemical resistance, high temperature, high pressure and thermal shock resistance.

Metallic Substrate:

The above pastes can be applied on a metallic substrate as long as it has a dielectric layer first. One of the most important features of this dielectric layer is its thermal expansion coefficient (CTE). The CTE must be closely matched to the substrate and the thickness should be adequately adjusted to avoid any warping from a CTE mismatch. For example, if the dielectric layer is to be applied to Al, the dielectric layer’s CTE must be closely matched to that of Al. If it is SST 300 series, the CTE of the coating must again match to that of the stainless steel. The melting point, specific heat and others must also be considered for a success with these products.
IJ Research can formulate a binder system to match Cu, Al, SiO2, zirconia,SST 300 series, SST 400 series, Ni alloy,
Steel and many other metals and alloys.

Dielectric layer:

IJ Research has a capability of applying a dielectric layer along with routine conductive and resistive patterns.
Combination of thick and thick films: IJ Research offers the following combinations for certain applications:
• Thick film on ceramic and then multi-layers
of thin film.
• Thin film on ceramic and dielectrically
and hermetically seal to another material
• Thin film on polymer with a thin
film polymer on top.
• Thick film dielectric layers on non-oxide