Active metal brazing process

The process flow for active metal braze substrates usually involves coating the braze alloy on the ceramic substrate of interest in a paste form, or as a metal foil. The copper foil is then placed on top of the braze alloy, and the whole assembly is heated in an inert atmosphere. The braze alloy melts and forms a strong bond with the copper and substrate. In many cases, the braze alloy and copper are patterned before bonding to eliminate the need for... 

Active metal brazing (AMB) is a process to braze metals, such as Kovar , titanium, copper, and molybdenum, to ceramics. The process does not require a metallization on the ceramic. For this chapter, only copper brazing will be addressed. The AMB process is used by some manufacturers as an alternative to DBC as it provides higher adhesive strength while using a less critical furnace profile. It also does not rely on oxide formation as in the DBC process. 

Solid state bonding Metallizing + brazing Active brazing Ceramic frit process... 

Because the AMB process uses copper sheets as the metallization, the electrical and thermal performances are identical to that of DEC. It should be noted that the ceramic interaction with the active metal in the braze material has a high thermal conductivity and can be neglected in most thermal analyses. 

The braze may be applied in the form of a paste, a powder, or a film. The combination is heated to the melting point of the selected braze in a vacuum to minimize oxidation of the copper. The active metal forms a hquidus with the oxygen in the system that acts to bond the metal to the ceramic. After brazing, the copper film may be processed in much the same manner as DBC. 

Titanium Basis of the active metals process. May be used as powder or foil prior to braze alloying. Original work by Kelley and Bondley of General Electric. Titanium-bearing brazes wiU wet and flow over ceramic in vacuum, almost as well as solder over cojjier. Frequently applied as the hydride, which dissociates at <800°C, providing nascent hydrogen which tends to scour the... 

A simpler (one-step) and more economical joining process is direct brazing in a furnace under a vacuum or inert gas atmosphere through the use of active filler metals [Mizuhara Cl al., 1989]. An active element such as the commonly used Ti in the filler metal forms a true alloy with the base metal. The difference in the thermal expansion coefficients between the ceramic membrane and the metal housing can lead to high stress at the... 

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