Precision ceramic components (such as optical fibers, optical components, radio frequency components) are composed of various smaller ceramic parts, and the various parts are welded into a component using a brazing process;
Precision ceramic parts can be assembled by brazing process under certain conditions, but compared with traditional brazing between metals, there are significant technical challenges that requireSpecial brazing materials, surface treatment and process control. Here are the detailed instructions:
1. Why can ceramics be brazed?
Although ceramics (such as alumina Al₂O₃, aluminum nitride AlN, zirconia ZrO₂, silicon carbide SiC) themselvesStrong chemical inertness, low surface energy, non-wetting conventional metal solder, but a reliable connection can be achieved by:
✅Key technical paths:
Use active metal solder（Active Metal Brazing, AMB）
Added to Ag-Cu, Ag-Cu-Ti, Cu-Ti and other solders Active elements such as Ti (titanium), Zr (zirconium), Hf (hafnium), etc.；
Active elements react with O and N in ceramics to form Interface compounds such as TiO, TiN, ZrO₂, to achieve "chemical wetting";
Typical solder materials:Ag-Cu-Ti(such as Cusil-ABA®),Cu-Ti、Au-Ni-V wait.
Strictly control the process environment
Surface preparation
The ceramic surface requires ultrasonic cleaning, plasma activation or polishing to ensure no pollution and high cleanliness;
Sometimes a metal layer needs to be pre-deposited (such as the Mo-Mn method), but AMB can eliminate this step.
2. Typical application scenarios (precision ceramics + brazing)
| Application areas | Component example | Brazing purpose |
|---|
| power electronics | AlN ceramic substrate + Cu heat dissipation base | High thermal conductivity, high insulation packaging (IGBT, SiC modules) |
| Aerospace | SiC ceramic component + metal flange | High temperature resistant structural connections |
| Semiconductor equipment | Al₂O₃ electrostatic chuck + stainless steel shell | Vacuum sealed, plasma corrosion resistant |
| medical device | ZrO₂ Bioceramic + Ti Alloy | Heterogeneous integration of implanted devices |
🔧 Advantages: Compared with adhesive (organic adhesive is temperature resistant)<200°C) or mechanical connection (stress concentration),Brazed joints can withstand temperatures above 500°C, are airtight and highly reliable。
3. Main challenges and countermeasures
| challenge | reason | solution |
|---|
| thermal expansion coefficient（CTE） | Ceramic CTE ≈ 6–8 ppm/°C, Metal ≈ 16–20 ppm/°C | Select CTE-matched metals (such as Kovar alloys) and design flexible transition structures |
| residual stress cracking | Interface stress concentration during cooling | Optimize heating/cooling rates, use gradient solder or intermediate layer (e.g. Mo) |
| Difficult to control interface reaction | Excessive amount of active elements → brittle phase; insufficient → poor wetting | Precise control of Ti content (typically 1–4 wt%) and holding time |
| High cost | Vacuum equipment and active solder are expensive | Only used for high value-added products (such as aerospace, medical, power modules) |
4. Comparison with other ceramic connection methods
| method | temperature | strength | Air tightness | Temperature resistance | Applicable scenarios |
|---|
| Active metal brazing（AMB） | 800–1000°C | high(>100 MPa） | ✅ Excellent | >500°C | High reliability, hermetically sealed packaging |
| Glass solder sealing | 400–600°C | middle | ✅ | <400°C | Optoelectronic devices and sensors |
| Transient liquid phase diffusion welding（TLP） | 900–1200°C | extremely high | ✅ | >800°C | Aero engine parts |
| Epoxy/silicone bonding | Room temperature –150°C | Low | ❌ | <200°C | Temporarily fixed, non-load-bearing parts |
5. Conclusion
Precision ceramic parts can be assembled using the brazing process, which is a mature technology in the field of high-end manufacturing, especially with Active metal brazing(AMB) is the mainstream solution.
But its success depends on:Appropriate active solder selection, strict atmosphere control, CTE matching design and meticulous process window management。
