Ceramics and glasses · Workhorse
Aluminum nitride and Shapal
AlNvalues describe: high-grade AlN
Why it wins
The insulator that conducts heat: ESC bodies and heaters, laser diode mounts, anywhere alumina would cook.
Why not the alternative
Alumina conducts 25 to 30 W per meter kelvin; AlN runs 170 plus. BeO beats it but carries the toxicity file.
Watch out
Hydrolyzes slowly in hot water chemistry; metallization less mature than alumina.
Properties
The values below are candidate: compiled from the sources named, not yet individually validated. Provisional provenance: Slack, thermal conductivity of AlN, 1973; CoorsTek, CeramTec, Kyocera technical ceramic data.
Wet cleaning
| Recipe | solvent wipe and dry; if aqueous is unavoidable, brief, buffered, and dried immediately |
|---|---|
| Forbidden | water: AlN + 3H₂O → Al(OH)₃ + NH₃; wet machining without an inhibitor |
| Limit | hydrolysis, which makes this the one ceramic where the wet step is the risk |
Vacuum and outgassing
| Outgassing, unbaked (10 h) | 1e-9 mbar·L/s/cm² |
|---|---|
| Outgassing, baked | 1e-12 mbar·L/s/cm² |
| Vapour pressure | none |
Temperature
| Bake, assembled | 450 °C |
|---|---|
| Vacuum degas | 1000 °C |
| Braze / H2 firing | 1200 °C |
| Metallurgical limit | dissociates ~2200 °C; oxidises in air above 800 °C |
Thermal
| CTE | 4.5 ppm/K |
|---|---|
| Thermal conductivity | 170–200 polycrystalline, 285–320 single crystal W/m·K |
| Specific heat | 740 J/kg·K |
| Emissivity | 0.8 |
| Melting / softening | 2200 dec. °C |
Mechanical
| Strength | 300–350 flex MPa |
|---|---|
| Elongation | nil |
| Young's modulus | 330 GPa |
| Hardness | 1100–1200 HV |
| Density | 3.26 g/cm3 |
Electrical and magnetic
| Relative permeability | 1.0 |
|---|---|
| Resistivity | >1e13 Ω·cm |
| Dielectric strength | 14–17 kV/mm |
Engineering
| Corrosion | hydrolyses in humid air |
|---|---|
| Joining | active-alloy brazed or metallised |
| Process notes | Shapal is the machinable grade at lower κ |
| Availability and cost | Maruwa, Tokuyama, Precision Ceramics |
Brazing
Sourced pairings
| With | Filler | Atmosphere | Expansion gap at set |
|---|---|---|---|
| Oxygen-free copper C10100 / C10200 / Kovar (FeNiCo) / Nickel and nickel plating / Austenitic stainless 304L / 316L / 316LN ESR / Titanium Gr 2 / Ti-6Al-4V / refractories (unspecified) | Ticusil | vacuum 1e-5 mm Hg or inert gas | 0.97 % at 780 °C Oxygen-free copper C10100 / C10200 on the outside over budget |
| Oxygen-free copper C10100 / C10200
one built object
microwave absorber module of the Material Plasma Exposure eXperiment: an array of pyramidal AlN tiles brazed onto a water-cooled Glidcop AL-15 baseplate explosion-bonded to a 316SS plate, eight modules and two cooled flanges welded into a stainless cage to make the complete absorber. Two test articles were built and exposed to an electron beam. | Cusin-1 ABA | not stated by the source | 0.97 % at 775 °C Oxygen-free copper C10100 / C10200 on the outside over budget |
| copper, grade not stated by the source
one built object
higher order mode absorber for the 1.3 GHz nine cell superconducting cavity of an energy recovery linac: an AlN cylinder brazed inside a copper cylinder whose inner face carries lattice-like slots, with stainless flanges electron beam welded at both ends. A first prototype was built in 2017 and a second after the tests. | named only in prose: silver, and no more. Table 2 of the paper prints Brazing material Silver, which names a metal and not an alloy of this catalogue. | vacuum | no filler identified, nothing to derive |
Preparation
- none
Chemical affinity
What documents state about a BINARY SYSTEM, one element of a filler metal faced with one element of this material. An affinity is not a verdict on a joint: a joint brings many binaries together at once, some helpful and some harmful, and what follows is the list of those the corpus can name. The count below is not written anywhere. It falls out of the crossing of this material's elements with the composition of every filler the corpus holds, so it grows on its own the day a binary enters the corpus.
Elements of this material: Al N, from the chemical name.
interfacial reaction that wets9 fillersTi against N1 source+1 statement
The two elements react at the interface and the product of that reaction is what the rest of the filler wets. This is the mechanism that makes active metal brazing work, and it is the only one of the six that a joint wants.
9 fillers: 35Au-62Cu-2Ti-1Ni, 48Ti-48Zr-4Be, 49Ti-49Cu-2Be, 56Zr-28V-16Ti, 71.5Ti-28.5Ni, Cusil-ABA, Cusin-1 ABA, Incusil-ABA, Ticusil
Conditions and verbatim
Printed page 862, aluminum nitride section. The article states that sufficient wetting of AlN can be obtained with commercial Ag-Cu brazes that contain a low weight percent of titanium by brazing above 800 C, citing Ref 106 and 107, and that a thin titanium nitride layer is formed at the interface. The temperature carried here is that floor of 800 C and it is stated for AlN with a silver-copper braze, not for the Ti-N system in general. The same paragraph adds that successful copper-titanium braze joints require more than 7 weight percent titanium to achieve enough wetting with aluminum nitride at 1150 C, a second condition the corpus does not carry as a value because it belongs to a filler this corpus does not hold.
Characteristic temperature800 °C, Joining, in Engineered Materials Handbook Desk Edition, M. M. Gauthier editor, ASM International, 1995, pages 846 to 864, DOI 10.31399/asm.hb.emde.a0003056
Source[A] Joining, in Engineered Materials Handbook Desk Edition, M. M. Gauthier editor, ASM International, 1995, pages 846 to 864, DOI 10.31399/asm.hb.emde.a0003056
Source conditionsHandbook article, consulted as a PDF whose printed page numbers run 846 to 864. The article is itself a digest of the Ceramics and Glasses volume 4 of the Engineered Materials Handbook, so its statements are second-hand summaries of the papers it cites by Ref number. The Ref numbers are kept in the conditions of each entry, because a reader who wants the primary measurement needs them.
Grades
| AlN 170 W/mK | standard substrate grade |
|---|---|
| AlN 200 to 230 W/mK | premium thermal grade for ESC and heaters |
| Shapal Hi-M Soft | machinable AlN: prototypes without hard tooling |