Heat sink diamond

Unlike metals, which are good electrical and heat conductors, crystalline solids such as diamond and seinicoriductors such as silicon are good heat conductors but poor electrical conductors. As a result, such materials find widespread use in the electronics industry. Despite their higher price, diamond heat sinks are used in the cooling of sensitive electronic components because of the... 

Low-pressure processed diamond heat-sinks for ultrafast semiconductors... 

Because of its high thermal conductivity, diamond is an excellent heatsink material, mostly for hIgh-density electronic circuits. Athin slice, in size up to 3 X 3 X1 mm, is cut from a natural crystal, metallized by sputtering a gold alloy and soldered to a copper base. A typical diamond heat-sink configuration is shown in Fig. 12.12. ... 

The drawbacks of these single-crystal diamond heat sinks are the presence of metallic impurities and size limitations. CVD diamond, which does not have these drawbacks, is a competitor which may eventually replace the single-crystal material (see Ch. 13). 

Figure 12.12. Typical design of laser diode on natural-diamond heat-sink.

Diamond Heat Sinks, Technical Brochure from Drukker Zn. NV, 1001 MC. Amsterdam, The Netherland (1989)... 

Diamond, an electrical Insulator with the highest thermal conductivity at room temperature, provides a solution. It compares favorably with conventional heat-sink materials such as aluminum, copper, or ceramics such as beryllia and aluminum nitride as shown in Table 13.8.f H lP3) these two ceramic materials, diamond is an excellent electrical insulator and no electrical insulation between the 1C board and the heat-sink is required. A diamond heat-sink should allow clock speeds greater than 100 GHz compared to the current speeds of less than 40 GHz. 

Thermal Conductivity. The value of 2000 W/(m-K) at room temperature for Type Ila natural stones is about five times that of Cu, and recent data on 99.9% isotopicaHy pure Type Ila synthesized crystals ate in the range of 3300—3500 W/(m-K) (35). This property combined with the high electrical resistance makes diamond an attractive material for heat sinks for electronic devices. 

Electronic. Diamonds have been used as thermistors and radiation detectors, but inhomogeneities within the crystals have seriously limited these appHcations where diamond is an active device. This situation is rapidly changing with the availabiHty of mote perfect stones of controUed chemistry from modem synthesis methods. The defect stmcture also affects thermal conductivity, but cost and size are more serious limitations on the use of diamond as a heat sink material for electronic devices. 

By beginning with methane, the diamonds formed have only in them. These tiny diamonds may then be used as the carbon source to form large (5 mm) single crystals by growth from molten catalyst metal in a temperature gradient. The resulting nearly pure crystals have outstanding thermal conductivities suitable for special appHcations as windows and heat sinks (24). 

CVD plays an increasingly important part in the design and processing of advanced electronic conductors and insulators as well as related structures, such as diffusion barriers and high thermal-conductivity substrates (heat-sinks). In these areas, materials such as titanium nitride, silicon nitride, silicon oxide, diamond, and aluminum nitride are of particular importance. These compounds are all produced by CVD. 1 1 PI... 

Heat sinks, in the form of thin slices prepared from single-crystal natural diamond, are already used commercially but are limited in size to approximately 3x3x1 mm. These single-crystal diamonds are gradually being replaced by CVD diamond, which is now available in shapes up to 15 cm in diameter. P6]-[28] gQg - gf cVD diamond may remain a... 

Some of the present industrial uses of diamond coatings include cutting tools, optical windows, heat spreaders, acoustic wave filters, flat-panel displays, photomultiplier and microwave power tubes, night vision devices, and sensors. Because its thermal conductivity and electrical insulation qualities are high, diamond is used for heat sinks in x- ray windows, circuit packaging, and high-power electroific devices. Moreover, the high chemical stability and inertness of diamond make it ideal for use in corrosive environments and in prosthetic devices that require biocompatibility. 

Diamond has the highest thermal conductivity when compared to other substances. For type la natural diamond the thermal conductivity is about 2000-4000W/m/K. For type Ila it is up to 17500W/m/K. A major problem in heat transfer is an effective heat sink that depends on the effective contact area, forces between both the materials, and the gap interface. Diamond exhibits the best characteristics for a heat spreader, which is the interface material that transfers heat between heat source and heat sink. 

Diamond-like carbon since its inception in 1962 has found applications in some very important areas. These applications include coatings used in scratch-resistant optics, razor blades, prosthesis in medical applications electron emission surfaces in electronics as an insulator material for copper heat sinks in semiconductors such as solar cells and sensors for visible to infrared radiations and as structural materials such as deuterated DLC film used for neutron storage in advanced research instrumentation. As technology matures the unique properties of DLC will find new and important applications. 

One of the major markets for wide band-gap materials is in electronics. Specifically, they are suitable for and have been used for heat sinks (diamond), short wavelength optoelectronic devices (GaP, GaN, SiC), high-temperature electronics (SiC, GaN), radiation resistant devices, and high-power/high-frequency electronic devices (diamond, GaN, SiC). " Recent research showed that Mn-doped GaN can be used for spintro-nic applications.f" Atomically flat technology developed by NASA for SiC and GaN WBG material can introduce a new dimension of application for WBG materials. 

Because of diamond s exceptional heat conductivity (about five times that of copper), it has been used as a heat sink for large-scale integrated circuits. " ... 

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