Tungsten Slurry

Tungsten Powder Picture

What Is Tungsten Slurry

Tungsten slurry consists of tungsten powder, inorganic binder phase and organic carrier, tungsten powder is the functional phase, it provides fine thermal and electrical conductivity with small co-efficient of thermal expansion, it can easy match with aluminum oxide ceramic and prevent stress during metallization process for the convenient of later sealing-in.

Inorganic binder phase facilitates calcination, tungsten conductive film under low calcinating temperature has fine property, it is the basic principle of active metallization. Inorganic binder phase also stimulates sealing-in. As tungsten slurry needs calcination under reducing atmosphere, tungsten layer deposited directly on Al2O3 ceramic has no adhesive force, but the binder phase can bonding with ceramic with fine sealing-in strength.

Organic carrier consists of resin (ethocel), solvent (terpineol) and additive (surfactant, flatting agent, defoamer).

circuit picture

Tungsten Slurry Preparation

1)Preparation of Organic Carrier
Put the container with solvent into constant temperature water box under 80℃, weigh resin and additive, add into container and mix with homogenizer, rotate speed is controlled under (300-800)r/min, after resin completely dissolving, keep the temperature for 1 hour, filter and seal for standby application.

2)Preapration of Tungsten Slurry
Ingredient organic carrier and tungsten metallization formula with W content 70%~85% and mix it uniformly, then roll by three-roll mill. The fineness is measured by a scraper fineness meter, filtered to be finished and do the solid content and viscosity test. Adjust until get final slurry product.

3)Following Process
Print 96% alumina substrate with screen printing equipment. After drying, thickness is 10~15um and is sintered at 1300℃ in reducing atmosphere. To protect metallization layer, enhance weldability and electroplate nickel layer, control the thickness within 3~5um.

Tungsten Slurry Application

Conductor slurry is the thickest film hybrid integrated circuit which is most widely used. It is used to separate active components and passive components, also interconnect between the components and thick-film capacitor up and down. The conductive phase of the conductive paste is generally Ag, Pd, Au, Pt and other precious metals, the lower melting point of such metals decides them unsuitable for high temperature co-firing technology. Tungsten has high melting point of 3410℃ and well electrical and thermal conductivity, not only is suitable for aluminum oxide substrate, but also can match to aluminum nitrate substrate. Tungsten slurry in high temperature co-firing technology is being studies and paid much attention to.

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