Plastic encapsulation

Plastic bags Plastic beads Plastic bearing materials Plastic cements Plastic drums Plastic electronic package Plastic encapsulant... 

Copper wines are used primarily because of thein economy and resistance to sweep, ie, tendency of the wine to move in a plane perpendicular to its length, during plastic encapsulation (11—16). Because copper is harder than gold, more attention is needed during the bonding operation to prevent the chip from cratering. Table 6 fists the various properties for wine materials. 

The binder system of a plastic encapsulant consists of an epoxy resin, a hardener or curing agent, and an accelerating catalyst system. The conversion of epoxies from the Hquid (thermoplastic) state to tough, hard, thermoset soHds is accompHshed by the addition of chemically active compounds known as curing agents. Flame retardants (qv), usually in the form of halogens, are added to the epoxy resin backbone because epoxy resins are inherently flammable. 

M. G. Pecht, L. Nyugen, and E. B. Hakim, Plastic Encapsulated Microelectronics Materials, Processes Quality, Reliability and Applications, John Wiley Sons, Inc., New York, 1995. 

Most UV photodiodes have a sealed metal TO package with an entrance window made of glass or special UV-transmitting glass. A TO housing is extremely reliable but it often counts for a non-negligible part of the sensor costs. Cheaper housings that should be favored for consumer-product applications like in household appliances are hard to find. Full-plastic encapsulation requires a UV-transpar-... 

Plastic encapsulant materials (PEMs), in electronic materials packaging, 17 838-840... 

Hefner, A., et ah, SiC Power Diodes Provide Breakthrough Performance for a Wide Range of Applications, IEEE Trans. Power Electronics, Vol. 16, 2001, pp. 273-280. McCluskey, P., et ah, Reliability of Commercial Plastic Encapsulated Microelectronics at Temperatures from 125°C to 300°C, 2000 IEEE Aerospace Conf. Proc., Vol. 5, March 18-25, 2000, pp. 445-450. 

Higher thermal stability so that the higher Junction temperatures of today s and tomorrow s devices will not be limited by the thermal degradation of the plastic encapsulant. 

Stress Analysis of the Silicon Chip-Plastic Encapsulant Interface... 

M. Isagawa, Y. Iwasaki, and T. Sutoh, Deformation of A1 Metalization in Plastic Encapsulated Semiconductor Devices Caused by Thermal Shock, 18th Annual Proceedings, Reliability Physics, 1980, pp. 171-177. 

K. Miyake et al., Thermal Stress Analysis of Plastic Encapsulated Integrated Circuits by FEM, lECE Proc., Japan, 1984, p. 2833. 

Enhancement of Gold—Aluminum Wirebond Reliability in Plastic Encapsulated Very Large Scale Integration (VLSI) Devices Through C—Br Bond Stabilization... 

Over 95% of all the microcircuits made are packaged in plastic, usually a transfer moulded epoxy resin. Changes in packaging technology will occur away from the familiar PDIP (plastic dual-in-line package) to smaller SOT or chip carrier formats but plastics will continue to be the dominant packaging material for cost reasons. At the same time there is a need to improve the reliability of plastic encapsulated devices (PEDs) as they find further use in professional and certain military applications. 

U.K. Patent Application GB 2087 1S9A. Plastic Encapsulated Electronic Devices. 

Epi-Rez . [Rhone-Poulenc/Perf. Resins Coatings] Epoxy resins or sol ns., sonte bal enat for industrial maintenance coadngs, fUm adhesives, fiberglass-reinforced plastics, encapsulation, castings, filament winding, potting compds., chem. resist pipe, elec, d coatings, varnishes, stdv.-frw fcx-mulations, fiber finishes, textiles. 

Kelly G. The Simulation of Thermomechanically Iruluced Stress in Plastic Encapsulated Packages. Boston Kluwer Academic Puhhshers 1999. 

The number of dots that can be dispensed per unit of time also depends on viscosity. The use of low-viscosity adhesives increases the number of dots that can be dispensed. However, there is a tradeoff between the speed at which the adhesive can be dispensed and the speed of device placement. Most automated component-placement equipment operate faster than adhesive-dispensing equipment. A comparison of the effect of viscosity on dispensing and placement times is shown in Table 4.19 for an 86-lead plastic-encapsulated leadless chip carrier (PLCC). ... 

The decision to rework electronic devices or assemblies depends on the cost of reworking versus the value of the part. Consumer electronics, due to their low cost, are considered throwaways and seldom reworked. For some, such as plastic-encapsulated microcircuits (PEMs) that are produced in high volumes, rework is impractical because of the difficulty in removing the plastic encapsulant without destroying the components. However, for high-value assemblies, such as densely populated PWBs and MCMs, where the final value may be as high as 10,000 or more, the ability to rework is essential. In such cases, rework may be necessary to meet schedules when small numbers of assemblies are produced. 

Adhesives are also tailored to meet specific requirements of the packaging or assembly technology used (Table 5.9). Thus, the requirements for single-chip packaging in hermetically sealed ceramic packages such as CERDIPs will be somewhat different from those of plastic dual-in-line packages (PDIPs) and plastic-encapsulated microcircuits (PEMs). 

Physics of failure for plastic-encapsulated microcircuits (PEMs) 292... 

If package cracks are suspected, a dye penetrant test should be performed. In this test, a fluorescent dye is applied to the package surface and then wiped clean. Examination of the part under UV-light reveals residual dye in package cracks. This test is applicable both to hermetic parts and plastic-encapsulated microcircuits (PEMs). 

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. 

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