Carrier pads

Fig. 4. Schematic illustration of the formation of electrical interconnects between a bumped chip and a mating carrier using a Bi-filled ACA. (a) The chip is aligned and placed on a chip carrier, (b) The Bi particle is deformed between a chip bump and a carrier pad when a bonding pressure is applied, (c) The Bi particle dissolves into the liquid lentils upon exposure of heat, (d) Bi diffuses into the Sn-Pb matrix and forms fine solid precipitates.

Fig. 13. Schematic illustrating various die attachment assembly processes utilizing ICAs. (a) Chip with cured ICA bumps mated with uncured ICA on carrier pads, (b) Chip with partially cured (B-staged) ICA bumps mated with bare carrier pads, (c) Chip with thermoplastic ICA bumps mated with bare but preheated carrier pads.

Chips with thermoplastic bumps are placed on chip carriers and preheated to approximately 20°C above the melting point of the polymer, causing the bumps to melt onto the matching chip carrier pads. Mechanical and electrical bonds are... 

Pad array carrier (PAD), a surface mount equivalent of the PGA package. This package extends surface mount silicon efficiency from 15 to 40%. A disadvantage of this package is that the solder joints cannot be visually inspected, although X-ray inspection can be used to verify the integrity of the bKnd solder connections (and to check for solder balls and bridging). Individual solder joints, however, cannot be repaired. 

In silicon wafer manufacturing, solvent exposure during silicon wafer preparation can be hazardous if local exhaust ventilation (LEV) is not used. Methanol exposures of up to 931 ppm were reported during the washing of silicon wafers without adequate LEV. Methylene chloride exposures of up to 522 ppm were reported when no local exhaust was used during the stripping of carrier pads from their metal carrier plates, ... 

The formation of CusSns at copper interfaces such as lead frames and chip carrier pads occurs more rapidly in the case of eutectic Sn Ag compared to eutectic Sn Pb. However, the addition of 0.5% to 1.7% Cu to eutectic Sn Ag reduces the IMC formation at interfaces and also lowers the melting point of the alloy [30]. 

FIG. 79 Ceramic column grid array (CCGA) configurations, a) Single melt eutectic Pb-Sn fillet, b) cast column with eutectic Pb-Sn on card pad, c) column last attach solder process (CLASP) with Pd-doped solder on chip-carrier pad and eutectic Pb-Sn fillet on card pad. 

F(ir axial compressors, the journal bearings are of the plain sleeve type for the larger, slower speed compressors. They are of the tilting pad type for the smaller, higher speed machines. The sleeve bearing is normally housed io a spherically seated carrier. The bearings require pressure lubrication as do most of the other compressors. 

Fig. 23—Sketch of CMP tester (a) polish rig, (b) contact area of carrier, slurry, and polish pad.

Metal is then deposited into the opened vias (openings) in the oxide layer and over its surface. During the subsequent photolithography process, it is patterned to form the desired electrical interconnections. These two steps are repeated for each succeeding level to produce additional levels of interconnections. Finally, a protective overcoat of oxide/nitride is applied (passivation), and vias are opened so that the wires eonnectlng the IC chip to its carrier package can be bonded to output pads. 

Although polyester is always brightened with disperse-type products, the methods of application vary. FBAs are marketed for incorporation in the polymer mass, for exhaust application with or without carrier and for use in the pad-thermosol process at a temperature within the range 160-220 °C. Most products are applicable by more than one method, although none can he applied satisfactorily by all methods and cost-effective products introduced in the 1950s still remain important today. 

Fig. 2. The linear planarizer uses and endless polish pad moving at high speed to achieve high relative velocity values. The carrier rotates slowly to ensure uniformity.

Orbital motion offers the capability of achieving high relative velocities without sacrificing tool footprint. This point is especially important as the semiconductor industry prepares to make the transition to 300-mm wafers. Several CMP tool concepts have been developed based on orbital motion. Some orbit the carrier while rotating the platen [13]. Others orbit the polishing pad while rotating the carrier [14]. Another design involves orbital (as well as arbitrary nonrotational) motion on a fixed polish pad [15]. 

With respect to the edge exclusion, orbital tools differ from other CMP tools because during use virtually the entire pad is in compression. In contrast, rotational tools periodically compress and then release the pad as it passes under the carrier and rotates around the tool. Very little data is publicly available regarding the fundamental properties of pads, so the significance of this difference between tool types is not well understood. 

The simplicity of early carrier designs was complicated by their use as part of the robot used to move wafers from the load cassette to the unload cassette. On a so-called gimbaled carrier, the down force was applied to a central point on a plate behind the wafer, and it was assumed that the applied force was transferred through the wafer backing plate to be distributed uniformly across the wafer. Lateral motion of the pad then caused a torque to be applied to the carrier. To compensate for this rotation, a gimbal was built into the carrier at the point where the down force was applied. 

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