Die attachment and encapsulation

The acoustic microscopy s primary application to date has been for failure analysis in the multibillion-dollar microelectronics industry. The technique is especially sensitive to variations in the elastic properties of semiconductor materials, such as air gaps. SAM enables nondestructive internal inspection of plastic integrated-circuit (IC) packages, and, more recently, it has provided a tool for characterizing packaging processes such as die attachment and encapsulation. Even as ICs continue to shrink, their die size becomes larger because of added functionality in fact, devices measuring as much as 1 cm across are now common. And as die sizes increase, cracks and delaminations become more likely at the various interfaces. 

The general area of adhesion and adhesion science has been one of the most important application areas identified thus far in a variety of applications for the subject imide-siloxane copolymers [74-82]. Many references in the patent literature [83-90] have been found that relate to the utilization of the copolymers in various important applications such as die attach adhesives, encapsulants, interphase agents, etc. It would appear that the combination of very good thermal stability, coupled with the adhesive bonding capabilities provided by the siloxane mobile segment, has attracted a great deal of attention and will be the... 

Avatrel Dielectric Polymers (low-k dielectric applications such as interlayer dielectrics, passivation layers, die attach adhesives, chip encapsulants (both molding and adhesive) and underfill materials). 

The assembled stacks are then attached to a leadframe or substrate again with conductive epoxy or wire bonds, and encapsulated with epoxy. Alternately, they may be packaged in thin, small-outline packages (TSOP) or EGA packages. If multiple die are used on each layer, as many as 64 die may be incorporated in one stacked module." ... 

Moisture absorption in uncured and cured adhesives is important for reliable adhesive bonding. Absorbed moisture in adhesives, particularly those used in surface-mounted parts, may result in voids in the bond hne due to moisture desorption or entrapment. Absorption of moisture after cure also affects reliability. Popcoming, the cracking of plastic parts during solder reflow, is due to the rapid vaporization and expulsion of moisture retained by the die-attach adhesive or the plastic encapsulant. 

These new type of resins contain minimum amount of chloride and other mobile ions, such as sodium and potassium, and have become widely used in device encapsulation and molding compounds. The incorporation of fused silica as filler in the epoxy system has drastically reduced the thermal coefficient of expansion of these materials which make them more comparable with the IC die attached substrate materials. The incorporation of a small amount of the elastomeric material (such as, silicone elastomer) to the rigid epoxy has drastically reduced the modulus of the material and reduced the thermal stress of the epoxy material This new type of low stress epoxy encapsu-... 

Die bond and wire-bond attach suffer from the problem that this method of chip attach is difficult to repair, particularly if the chip is encapsulated. 

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