Question 1

What is the primary difference between active metal brazing and vacuum brazing for alumina-to-titanium joints?

Accepted Answer

Active metal brazing introduces a reactive element—most commonly titanium, zirconium, vanadium, or niobium—directly into the filler alloy, enabling metallurgical wetting of the alumina surface without prior ceramic metallization. Vacuum brazing with conventional fillers requires a preliminary metallization step, most commonly molybdenum-manganese paste firing followed by nickel electroplating, to render the alumina surface wettable before a conventional silver or gold braze is flowed under high vacuum.

Question 2

Which brazing filler alloys are approved for chronic implantable medical devices?

Accepted Answer

Gold-based fillers dominate where biocompatibility is mandatory. Medtronic established gold-vanadium-yttrium/scandium alloys for pacemaker feedthrough seals. The Commissariat a l'Energie Atomique's 2023 pending US application advances gold-braze-only approaches leveraging in-situ Ti diffusion from the titanium substrate. Zr-Ti-Be-Fe and Ti-Ni systems face regulatory barriers due to beryllium and nickel content respectively.

Question 3

What shear strengths are achievable with sputter-coated Ti brazing filler?

Accepted Answer

Ag-Cu sputter-coated Ti foil brazed at 980°C for 30 minutes in vacuum produces multilayered interfaces with a hard Ti-oxide reaction layer reaching 1,872 HV at the alumina interface. Analogous work on zirconia/Ti6Al4V demonstrates maximum shear strength of 152 ± 4 MPa using the same foil architecture.

Question 4

Does vacuum brazing require different furnace equipment than active metal brazing?

Accepted Answer

No. Both active metal brazing and vacuum brazing with Ti-bearing substrates are performed under high vacuum (less than 10⁻⁵ mbar range) or inert atmosphere. The process infrastructure investment is equivalent; the selection decision therefore turns on filler cost, biocompatibility profile, and joint performance targets rather than capital equipment differences.

Question 5

What is the in-situ Ti diffusion mechanism and when can it replace active filler alloys?

Accepted Answer

When titanium is the metal partner, dissolution of Ti into the braze pool during vacuum heating generates sufficient active species at the ceramic interface to enable wetting without pre-formulated active fillers. This mechanism, documented for both Au and Ag-Cu fillers, fundamentally changes the process decision from which active filler to which vacuum schedule and joint geometry allow adequate Ti diffusion flux. It eliminates the Mo-Mn metallization step and is particularly relevant for high-volume medical device production.

Question 6

Are the Endress + Hauser Zr-Ti-Be-Fe active braze patents still in force?

Accepted Answer

The dominant active braze composition patents from Endress + Hauser (1994–2004) are now expired or inactive across all jurisdictions in this dataset, suggesting relatively open freedom-to-operate for engineers working with Zr-based active braze chemistries for non-implantable applications.

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Vacuum vs Active Metal Brazing Alumina Titanium — PatSnap Eureka

Vacuum Brazing vs. Active Metal Brazing for Alumina-to-Titanium Joints in Medical Devices