Direct bond copper

Fig. 23. (CH3CN)2Cu2Ru6C(CO),6, 20 (50). The distorted octahedral Ru6C core is capped by two directly bonded copper atoms [Cu-Cu = 2.693(1) A], one on an Ru3 face, the second on the CuRu2 face so formed. The Ru-Ru distances range from 2.798(1) to 3.072(1) A (mean 2.89 A). Ru-Q.rtjrte distances range from 2.031(4) to 2.073(4) A (mean 2.05 A). There are thirteen terminal carbonyls, and three asymmetrically bridging Ru-Ru edges. No Cu-CO contacts are short enough to imply bonding interactions.

The cooling module, shown in Fig. 22, consists of an aluminum box with internal dimensions of 50 X 50 X 65 mm and wall thickness of 3.175 mm. At the bottom, the box is closed with a 3.175 mm thick stainless steel plate. The orifice plate was installed on a support located above the heat source and could be moved up or down. The heat source consists of a diode used in current controlled mode to avoid high voltages. The diode is mounted on a Direct Bond Copper (DBC) substrate layer, which is in turn glued on top of a GIO insulating base. The diode is 8.68 x 4.97 mm in size. The electrical connections are provided by means of two copper rods, 3.175 mm in diameter. 

The method of deposition is what differentiates the hybrid circuit from other packaging technologies and may be one of two types thick film or thin film. Other methods of metallizing a ceramic substrate, such as direct bond copper, active metal brazing, and plated copper, may also be considered to be in the hybrid family, but do not have a means for directly fabricating resistors and are not considered here. Semiconductor technology provides the active components, such as integrated circuits, transistors, and diodes. The passive components, such as resistors, capacitors, and inductors, may also be fabricated by thick- or thin-film methods or may be added as separate components. 

Direct bond copper (DBC) A method of bonding copper to a substrate, which blends a portion of the copper with a portion of the substrate at the interface. 

Characteristics Thick Film Thin Film Multilayer Ceramic Direct Bonded Copper... 

For many power systems, hundreds of amperes of current may be flowing through a substrate in a relatively small area. To prevent severe losses in the conductors, the metallization must be very thick and low in resistivity. One approach to this problem is direct bond copper (DBC), which was developed by General Electric in the mid-1970s. Unlike thick-film or thin-film conductors, DBC can be purchased with metal thicknesses up to 0.65 mm (25 mil). Combined with the low resistivity of copper (0.12 mD/n) and a high thermal conductivity substrate such as AIN, this approach creates nearly the ideal substrate for this type of application. 

Ceramic technology offers a wide choice of conductor metallizations, and various conductor technologies are used with ceramics. Screen-printed and photo-defined, thick-film, thin-film, electroplating [3], electroplating over thick film, and direct bond copper (DBC) [4] are tfie most prevalent metallizations. 

For the configuration shown in Figure 3.6 [11], which depicts a silicon chip on a direct-bond-copper metallized substrate, the spreading angle in the... 

Silicon chip on direct-bond-copper substrate. (From Krum, A., Course Notes, UCLA Extension, Engineering 881.152, Power Hybrids Design and Processing, April 3-6,1995, Los Angeles, CA. With permission.)... 

A 0.008 in. thick copper conductor with the same length and width as the thick-film conductor described above is fabricated using the direct bond copper (DEC) process. The resistance is calculated using Equation 8.4 and found to be 16.9 mO ... 

Direct bonded copper exhibits high peel strengths — greater than 65 N/cm. Assembly steps, such as reflow soldering, at temperatures under 400 C do not significantly degrade the adhesion of the copper. 

There are three fundamental methods of metallizing ceramic suhstrates thick film, thin film, and copper, which includes direct bond copper (DEC), plated copper, and active metal braze (AMB). Not all of these proeesses are compatible with all suhstrates. The selection of a metallization system depends on both the application and the eompatihility with the substrate material. 

Thick-fihn, thin-film, and copper metallization processes are available for aluminum nitride. Certain of these processes, such as direct bond copper (DEC), require oxidation of the surface to promote adhesion. For maximum thermal conductivity, a metallization process should be selected that bonds directly to AIN to eliminate the relatively high thermal resistance of the oxide layer. 

Direct bond copper may be attached to AIN by forming a layer of oxide over the substrate surface, which may require several hours at temperatures above 900°C. The DEC... 

Figure 1 AIN direct bond copper substrate for IGBT power device.

Y Kurakawa, et al. AIN substrates with high thermal conductivity. IEEE Trans Components Hybrids Manuf Technol 8 247 (1985). W Werdecker, F Aldinger. Aluminum nitride—an alternative ceramic substrate for high power applications in Microcircuits. IEEE Trans, Components, Hybrids, Manuf Technol CHMT-7 3394 (1984). N Iwase, et al. Thick film and direct bond copper forming technologies for aluminum nitride substrate. IEEE Trans Comp HEMT-8 253 (1985). N Iwase, et al. Development of a high thermal conductive AIN ceramic substrate technology. Int J Hybrid Microelectron 7 49 (1984). 

---