Package crack, prevention

Increasing the adhesion strength of a molding encapsulant and Si-chip interface is another method to prevent the package cracking at the chip edge. 

Figure 8. Prevention of package crack by forming PI layer on the back side of die pad.

PI chip coat is effective for the prevention of passivation crack, A1 slide and package crack of semiconductor devices. Low thermal eiqpansion PI can be regarded as the most suitable material for this application. 

The reaction mechanism by the EDC cracking in industrial conditions is extremely complex. Ranzi et al. [13, 14] proposed a scheme involving more than 200 elementary reactions as well as 40 molecular and radical species. The software SPYRO is available for the detailed design of the reaction system, including the reaction coil and the furnace (www.spyro.com). The package can also be used for monitoring the performance in operation and prevent problems, such as fouling of tubes by coke formation. 

The consistency of ointment sticks has to be high enough to prevent deformation while being used, but it should enable for active substances to be abraded. A suitable base is made from equal amounts of cocoa butter, white wax, wool fat and cetyl palmitate (synthetic spermaceti) or cocoa butter only. Ointment sticks with cacao butter only are used for cracked lips or to prevent lips cracking. Ointment sticks are packaged in aluminium foil and dispensed in a glass or synthetic jar. They can also be placed in lipstick holders. 

Thermal stress in encapsulation materials should be intrinsically small in order to prevent occurrence of cracks in packages or passivations layras, dis 4acetr t of aluminum wirings, short circuits between layers, or changes in device performance, caused by the pile-up of thmnal stress in the package. This bectnnes particularly acute with itKreases in packagir daisity. 

As we discussed above, spills of mercury are extremely hazardous. All possible precautions must be taken to avoid using elemental mercury in a manner such that an uncontrolled spill can occur. Always handle mercury over nonporous, seamless trays lipped at the edges, which can prevent spills from spreading. Note that the plastic containers that some suppliers use to package mercury can become brittle and break. Use a secondary container, such as a beaker, to store these containers in and contain the mercury should the plastic bottle break. If a spill occurs and mercury falls to the floor, the composition of the floor covering becomes important. Floors that have seamless, nonporous coverings are easiest to clean of spilled mercury. The metal can get into the cracks between asphalt tile, into scratches in the tile surface, or under the floor covering itself, where it will be able to release vapors to the atmosphere unimpeded. 

Role of PI chip coat film can be explained as follows. In a case of PSG passivation alone, cracks are generated in the PSG film by the mold stress because of the brittleness of PSG film, and A1 electrode corrodes by the moisture penetrating through these cracks. On the other hand, for a package with PI chip coat, mold stress is absorbed by this PI film and the passivation crack is prevented. 

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