Molybdenum Copper Alloy

Molybdenum copper (MoCu) alloy combines the high thermal conducting property of copper and the low thermal expansion of molybdenum together. It is an excellent thermal management material for heat spreaders and electronic packing components in a wide range of high-power density electronic devices, including rectifier tubes, thyristors, power modules, laser diodes, microwave tubes, etc. Moly copper composites comprise pure molybdenum and oxygen-free copper. The most typical molybdenum copper composites ratios are 70/30 and 80/20. Other ratios include MoCu 50/50, 60/40, and 85/15. Our molybdenum copper materials include molybdenum copper plate, sheet, foil, rod, tube, and machined parts.

Moly Copper Alloys

Mo85Cu15Mo 85% Cu 15% wt
Mo80Cu20Mo 80% Cu 20% wt
Mo75Cu25Mo 75% Cu 25% wt
Mo70Cu30Mo 70% Cu 30% wt
Mo60Cu40Mo 60% Cu 40% wt
Thermal Conductivity170-300 W/m·K
Electrical Conductivity38-66 IACS % Min.
C.T.E‎6.8-12.8 10-6/K
Density9.2-10.0 g/cm3

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    Molybdenum Copper Properties

    Molybdenum copper’s remarkable properties include highly efficient thermal and electrical conductivity, suitable coefficient of thermal expansion (CTE) closely matched with high power and frequency electronic components, excellent hermeticity, and solderability. These properties make moly copper alloys particularly suitable for heat sinks, heat spreaders, and baseplates applied in IGBT, LDMOS, and GaN/GaAs-based devices.

    CompositionDensityElectrical ConductivityCTEThermal ConductivityHardnessElectrical Resistivity
    g/cm³IACS % Min.10-6 K-1W/m · K-1HVμΩ cm

    Compatible Coefficient Thermal Expansion

    Molybdenum copper is an ideal material for heat sinks and heat spreaders in high frequency and high power electronic devices when the compatibility of CTEs is a critical concern. The CTEs of molybdenum copper composites can pair with common semiconductor materials, such as Si; GaN; and GaAs, as well as ceramic packaging materials, including Al2O3; BeO; AlN; and SiC. This is because molybdenum copper materials have a wide range of Mo and Cu ratios from Mo60Cu40 to Mo85Cu15. Each ratio defines a specific CTE ranging from 5.6/10-6 K to 11.5/10-6 K. This range fully covers the CTEs range, 3×10-6 K to 10×10-6 K, of semiconductor and ceramic packaging substrate materials. As a result, the reduction of thermal stresses generated by high-temperature variation can improve operational reliability and the lifespan of electronic components.

    Molybdenum Copper Alloy Thermal expansion curveOutstanding Thermal Conductivity

    The excellent thermal spreading effect makes molybdenum copper ideally suited for heat sinks and heat spreaders in high-power and high-frequency devices. The MoCu composites containing 15% to 18% copper exhibit outstanding thermal conduction as high as 160 W·m-1 ·K-1 and electrical conduction up to 10 While copper tungsten composite materials with comparable copper fractions exhibit relatively high thermal and high electrical conductivity, molybdenum copper is favored for use as a heat spreader. It is because of its lower specific density and superior machinability than copper tungsten. Those are both critical concerns for weight-sensitive and highly integrated electrical devices. Therefore, molybdenum copper is an exceptionally well-suited material for heat sinks and heat spreaders by virtue of its superb heat dissipation, electrical transmission, weight sensitivity, and machinability.


    Other Unique Properties

    In addition to its unsurpassed qualities as detailed above, 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 comparatively well in vacuum environments. Moly copper alloys also lend themselves to easy removal of Mo and Cu oxides and impurities, including N2, H2, and C, during the manufacturing process.

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

    In addition, Mo Cu alloy is an exceptional electromagnetic interference (EMI) shielding material for vacuum electrical devices which demands both a high EMI/RFI reduction level and CTE compatibility. This is because molybdenum and copper are all non-ferromagnetic metals.
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    Infiltration and Solid Sintering Molybdenum Copper

    CHEMETAL USA has decades of experience in manufacturing 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 infiltered mixture then becomes a fully condensed MoCu composite by further sintering, with a Mo volume fraction between 40% and 85%. The infiltration sintering greatly improved microstructure homogeneity and porosity of MoCu composites, thus achieving higher thermal physical performance than possible in the solid sintering process.

    Solid sintering, the conventional method for producing MoCu composites, involves the mixing and compacting of fine powders of pure molybdenum and oxygen-free copper, followed by isothermal sintering in an H2/Ar environment at temperatures gradually rising to 1150 o C. This process allows easy control of Mo and Cu weight fractions in the matrix composite.

    Our exacting standards and quality control at all manufacturing stages ensure unsurpassed purity and precision in our 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 alternately layered structures comprised of various Mo/MoCu and Cu combinations, with one or two Mo or MoCu composites as core layers. We have the capacity to produce all models of 3 and 5 layers Mo and Cu laminates, including CMC, CPC, and SCMC, in various Mo: Cu or MoCu:Cu thickness ratios. The superior, combined thermomechanical properties of molybdenum and copper have long been known by electrical power engineers who saw the potential of Mo and Cu laminates in many high frequency and high power applications.

    Multiple layers of Mo and Cu, or MoCu and Cu, in various combinations, are symmetrically roll-bonded to exacting thickness ratios. The firmly 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 cracking or flaking. The copper outer layer has high thermal conductivity and efficient heat spreading qualities. The molybdenum layer inserted between copper layers maintains the overall coefficient of thermal expansion of the laminate in an appropriate range for the intended application.
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