MOLYBDENUM COPPER

Molybdenum Copper Properties

Molybdenum and copper’s properties include efficient thermal conductivity and suited coefficient of thermal expansion (CTE) with the CTE of electronic components. In addition, molybdenum copper has excellent hermeticity and machinability. All these properties help moly copper composites to be capable material of heat sinks, heat spreaders, and other baseplates applied in IGBT, LDMOS, and GaN/GaAs-based devices.

Compatible Coefficient Thermal Expansion

Well-matched CTEs are a critical concern when choosing the material of the heat sinks and heat spreaders in high frequency and high power electronic components.
Molybdenum copper materials have a wide range of Mo and Cu ratios from Mo60Cu40 to Mo85Cu15. Each ratio defines a specific CTE ranging from 5.6x 10^-6/K to 11.5×10^-6 K. This range covers the CTEs range, 3×10^-6/K to 10×10^-6/K, of semiconductor and ceramic packaging materials. The common semiconductor materials include Si, GaN, and GaAs. The common ceramic packaging materials are Al₂O₃, BeO, AlN, and SiC. The CTE of molybdenum copper composites can pair with the CTE of these materials. The well-matched CTEs combination can achieve a reduction of thermal stresses. As a result, the reduction improves the operation reliability and the electronic components’ lifespan.

Outstanding Thermal Conductivity

Molybdenum copper has an excellent thermal spreading effect. It is a vital property for heat sinks and heat spreaders in high-power and high-frequency electronics. Take an example of the MoCu composites containing 15% to 18% copper.Mo75Cu25 exhibits outstanding thermal conduction as high as 160 W·m^-1 ·K^-1. While copper tungsten composite materials with comparable copper fractions exhibit relatively high thermal and high electrical conductivity, molybdenum copper has a lower specific density and superior machinability. Both are necessary concerns for weight-sensitive and integrated micro-electronics.

Therefore, molybdenum copper is a well-suited material for heat sinks and heat spreaders by virtue of its superb heat dissipation, electrical transmission, weight sensitivity, and machinability.

Other Impressive Properties

In addition to its superior qualities as detailed above, molybdenum copper possesses other impressive properties. Molybdenum copper composite material yield an outgassing rate of less than 5.0 x ^10-9 Pa.m³/s. It allows MoCu heat sinks and heat spreaders to work well in vacuum environments. In addition, moly copper alloys lend themselves to easy removal of their impurities. The major impurities are Mo and Cu oxides. The other main impurities include N₂, H₂, and C.

Moreover, grain sizes of molybdenum copper range from 6 to 15 µm. The average tolerances of internal pore size are controllable to as small as 0.01 mm. This fine grain size range assures the low porosity of molybdenum copper.

Molybdenum and copper are both non-ferromagnetic metals. Thus, it is also a notable electromagnetic interference (EMI) shielding material. Molybdenum copper is applicable to make components in vacuum electronic devices, requiring high EMI/RFI reduction level and adjustable CTE.
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Infiltration and Solid Sintering Molybdenum Copper

CHEMETAL USA has decades of experience in producing all Mo/Cu composite ratios using either infiltration or solid sintering.
Infiltration sintering involves the molding and sintering of fine molybdenum powders into a porous skeleton structure. Next, capillary forces push the copper particles into the open area of the sintered molybdenum at temperatures exceeding 1100 ^o C. The infiltrated mixture then becomes a further condensed MoCu composite by further sintering, with a Mo volume fraction between 40% and 85%. The infiltration sintering improved microstructure homogeneity and porosity of MoCu composites, thus achieving higher thermal physical performance than possible in the solid sintering process.

Solid sintering is the conventional method for producing MoCu composites. It involves the mixing and compacting of fine powders of pure molybdenum and oxygen-free copper. The composites then go to the isothermal sintering process. The sintering is in an H₂/Ar environment at temperatures rising to 1150 ^o C. This process allows easy control of Mo and Cu weight fractions in the matrix composite. All processing stages have exacting standards and quality control. That ensures unsurpassed purity and precision in copper molybdenum materials.

Our advanced Mo Cu alloy materials can meet specifications as precise as 6-micron grain size, 0.01 mm porosity, and less than 5.0 x 10^-9 Pa.m3 /s outgassing rate. The particle size and purity of these powders, the high temperature of sintering and annealing, and the deforming rates applied at each reduction are all under strict quality control and inspection protocols.

Copper Clad Molybdenum (MoCu Laminates)

Copper clad molybdenum are multiple layers structures comprised of various Mo/MoCu and Cu combinations. One or two Mo/MoCu composites as the core layers. We have the capacity to produce all models of 3 and 5 layers Mo and Cu laminates. The laminates include CMC, CPC, and SCMC, in various Mo: Cu or MoCu:Cu thickness ratios. Laminates have lots of potential in high frequency and high power applications. The superior thermal properties MoCu Laminates have long been known by electrical power engineers.

Multiple layers of Mo and Cu, or MoCu and Cu, in various combinations, are symmetrically roll-bonded to exacting thickness ratios. The bonded layers must not vary in thickness by more than 10% from specifications. All interfaces must be as clear and flat as possible to eliminate deleterious cracks or flakes. The copper outer layer has high thermal conductivity and efficient heat spreading qualities. The molybdenum layer inserted between maintains the overall coefficient of thermal expansion.
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