Epoxy encapsulants

Fig. 6. Thermal stability of epoxy-encapsulated poly(pyrrole tosylate) film,, 0.5 Q/sq, and polypyrrole-coated textiles, D, 20 Q/sq, with exposure to...

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

Evolution of Epoxy Encapsulation Compounds for Integrated Circuits A User s Perspective... 

Various testing procedures have been used to determine and ensure that the epoxy encapsulant will meet the device requirements. This testing can be divided into three categories analytical characterization, functional testing and accelerated life tests. The characterization includes the following ... 

Figures 2 and 3 show that the DRAM chip perforMance has been iMproved even though the chip functionality has increased for the accelerated tests used by the seMiconductor industry. The 85 C/85X RH results are better because of a coMbination of iMproveMents in the chip design, the Manufacturing procedures and the epoxy encapsu-lent. The teMperature cycle test results, however, were priMarily improved by converting to a "low stress" epoxy encapsulant. The im-proveMent in the pressure cooker and the 125 C operating life (Figure 3) was also due to a coMbination of iMproveMents, including those in the epoxy encapsulant. These iMproveMents in device reliability are especially reMarkable when it is realized that the chip susceptibility to contaminants and stress has increased tremendously due to the 60-fold increase to functionality.

As the chip size and functionality increased, the "low stress" epoxy encapsulant was no longer adequate and, in the early 1980 s,... 

The addition of various corrosion inhibitors to the epoxy encapsulant formulation to prevent corrosion was also evaluated (8). This procedure basically adds compounds or complexing agents to neutralize or "getter corrosion accelerating impurities or adds hydro-phobic agents to reduce the moisture permeation of the plastic. 

Due to their small feature sizes, microelectronic circuits need protection from environmental hazards such as mechanical damage and adverse chemical influences from moisture and contaminants. Several approaches are currently in use, for example, hermetic encapsulation of the device in sealed metal or ceramic enclosures, application of soft silicone gels as a cover over integrated circuitry, and encapsulation by transfer molding, which is the topic of this report. Both silicone resins and epoxy resins are used for this purpose. As the quality and performance of the epoxy encapsulants improved, the need for the generally more expensive silicone resins diminished. The present work is exclusively devoted to epoxy transfer molding compounds. 

More than 44 million Americans live or work near places that pose risks from the storage or use of dangerous industrial chemicals.154 The cost of accidents may be more than just a monetary one to the company. A fire and explosion occurred on July 4, 1993, in a Sumitomo Chemical plant in Niihama, Japan, that made over half of all the epoxy-encapsulation resin for semiconductor chips used in the entire world. Cutting off the supply would have been a serious inconvenience to the customers. The company took the unusual step of letting other companies use its technology until it could rebuild its own plant, so that a supply crisis never developed. The company still supplied 50% of the world s requirements for that resin in 1999.155... 

Naito CM, Todd M. Effects of Processing Parameters on the Performance of Epoxy Encapsulant Materials. Dexter Technical Paper Dec. 2000. 

Respiration—Respiratory control systems involve a two-channel implantable stimulator with electrodes applied bilaterally to the phrenic nerve. Most of the devices in clinical use were developed by Avery Laboratories (Dobelle Institute) and employed discrete circuitry with epoxy encapsulation of the implant and a nerve cuff electrode. Approximately 1000 of these devices have been implanted in patients with respiratory disorders such as high-level tetraplegia (Glenn et al.. 

Immersion of epoxy-encapsulated materials in polished sections in an anhydrous lightweight oil (preferably odorless) in a wide-mouth glass jar with a screwtop lid effectively minimizes, but does not eliminate, hydration. If the specimen is re-examined microscopically, the oil appearing on the polished surface can be removed with a sonic cleaner containing iso propyl alcohol, followed by a forceful isopropyl alco hoi spray. Dorn and Adams (1983) used Freon in a sonic cleaner to remove residual oil on polished section surfaces. In the writer s experience, oil droplets on a polished section can be removed with a brief application of acetone, followed by an alcohol spray wash, and blow drying. 

The epoxy-resin procedures described here are intended for single polished sections and polished thin sections of selected sieve fractions of whole or fragmented clinkers, rocks, bricks, ceramics, concrete, and many other materials. The desirable properties of an epoxy-encapsulating and -impregnating medium are ... 

Resin-bonded diamond discs placed on a flat table-top function quite well for rapid hand grinding of a saw-cut surface of epoxy-encapsulated clinkers preparatory to polishing (Hoodmaker, personal communication, 1985). Afew drops of propylene glycol are used as the grinding and polishing liquid. The diamond discs are cleaned with soap and water. 

Ultrathin sections for light microscopy and SEM-EDXA or microprobe work can be made by using an epoxy disc that has been polished on both sides instead of a glass microscope slide. An epoxy-encapsulated and polished section of clinker is attached to the disc with epoxy. A wafer is cut, followed by grinding and polishing to a thickness of approximately 10 pm. 

A LOW COEFFICIENT OF THERMAL EXPANSION EPOXY ENCAPSULATING COMPOUND. 

A cross-section of the experimental apparatus is shown in Figure 6. The basic coupler is of the fused type,and is fabricated from two optical fibers with single mode cutoff at about 590 nm. The fused or "active region of the coupler is about 1 cm long,and has an estimated minimum diameter of about 40 microns. At both ends of the active region, at the points of bifurcation, an epoxy encapsulant is used to anchor and seal the coupler. As shown, after encapsulation, only the active region remains available for... 

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