Chip carriers applications

Recently, the telecommunication industry has undergone rapid expansion, and a strong consumer trend towards smaller and lighter telecommunication devices, such as cellular phones and notebook computers, is indicated. Small connection sockets and chip carriers are micro-injection-molded parts requiring the high flowability, high mechanical properties and dimensional stability of LCPs. These merits are now thought to be another application field for LCPs in the electronics industry. 

Resins are used in electromc/electncal applications (connectors, circuit boards that are vapor and wave solderable, microwave transparent radomes, integrated circuit chip carriers, miniature switches, explosion proof enclosures, lamp reflectors, and high-precision fiber optic components). Polyetherimide is used for medical components (hat require all forms of sterilization. Other uses are found in the transportation field, dual-ovenable cookware, as well as bearings, fasteners, and advanced composites. 

Major polymer applications aerospace, electronics (mostly films and coatings), photosensitive materials for positive imaging, solar cells, hollow fiber membranes, composites. unclear power plants, space shuttle, microprocessor chip carriers, structural adhesives... 

Major polymer applications automotive lighting, ignition and braking systems, carburetor parts, fuel components, chip carriers, phone jacks, IC card connectors, transistor encapsulation, tape recorder head moimts, relay components, motor fans, coil bobbins, sockets, relay units, food choppers, steam hair drier parts, lamp sockets, microwave oven components, pump housings, impeller diffusers, oil well valves, halogen lamp sockets... 

Figure 2. Conventional chip carrier. This example with a lid is for hermetic applications. (Reproduced with permission from Ref. 4. Copyright 1988 BPA [Technology and Management, Ltd.].)...

The requirements for advanced military MLBs are shown in Table I. One of the major problems of using leadless ceramic chip carriers in advanced avionics (VHSIC and VLSI) applications is the mismatch between the CTE of alumina chip carriers (6.4 ppm/°C) or silicon (3 ppm/°C) and conventional glass/epoxy substrates (12 to 17 ppm/°C). This mismatch results in work-hardening and cracking of solder joints which attach the devices to the substrate. 

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. 

Eccobond D125F/Henkel Stencil application for surface-mount devices (capacitors, resistors, small outline ICs, and plastic leadless chip carriers) N/A N/A N/A... 

Applications and uses electrical and electronic parts (connectors, sockets, chip carriers), mechanical parts, food containers, automotive underhood parts, and chemical processing, household cookware for conventional and microwave ovens. 

LCP characteristics, such as high mechanical properties (strength, modulus), ease of processibility, excellent thermal resistance, low water absorption, and low gas permeability, make LCPs attractive for a wide range of applications. The applications of main-chain LCPs can be divided into several areas extrudates (fibers, rods, sheets) used in the chemical and materials industry, and moldings (chip carriers, connectors, switches) used in microelectronics [6]. 

ACA flip chip technology has been employed in many applications where flip chips are bonded to rigid chip carriers (13). This includes bare chip assembly of ASICs in transistor radios, personal digital assistants (PDAs), sensor chip in digital cameras, and memory chip in lap-top computers. In all the applications, the common feature is that ACA flip chip technology is used to assemble bare chips where the pitch is extremely fine, normally less than 120 /rm. For these fine applications, it is apparently the use of ACA flip chip instead of soldering which is more cost effective. 

ACA Bumped Flip Chips for High Frequency Applications. The high frequency behavior of ACA interconnections has attracted much attention in the past several years. Sihlbom and co-workers demonstrated that ACA-bonded flip chips can provide performance equivalent to solder flip chips in the frequency range of 45 MHz to 2 GHz on FR4 chip carriers and 1 to 21 GHz on a high frequency Telfon-based chip carrier (Fig. 5). The different particle sizes and materials in the conductive adhesives gave little difference in high frequency behavior of ACA joints (22,23). 

ACAs have been investigated as replacement for SnPb solder in surface mount (SM) attachment for fine pitch applications. The key attractive advantage is the cost effectiveness of using ACA to bond fine pitch SM components. A limitation of ACAs is the need to cure imder a contact pressin-e. The concept of using an ACA as a solder replacement on rigid chip carriers ntiUzing conventional SMT... 

Because thermotropic wholly aromatic LCPs have characteristics such as high strength, low melt viscosity, low shrinkage, ease of processibility, excellent thermal resistance, low water, and gas absorption, they have wide applications in following areas fibers, rods, sheets, composites used in mechanical and chemical industries chip carriers, connectors, switches used in electronics connectors, couplers, buffers used in fiber optics interior components, brackets in aerospace and so on (3,5,9,16,17,26,30). 

Hermetic packages, such as the older flat pack design or ceramic leadless chip carriers (CLCCs), are used in harsh applications (such as military and space applications) where water vapor and contaminants can shorten the life of the device. Thus they are used in mission critical communication, and navigation and avionic systems. The reliability of CLCC package connections can be further improved by the attachment of leads to the connection pads, to eliminate differences in the thermal coefficient of expansion between the parts and the circuit board material. 

The important feature of LC polyesters is a low coeffident of thermal expansion a < 1 x 10 grad that is comparable with the value for inorganic glasses (5 x 10 grad ) and significantly less in comparison with ordinary polymers (1 x 10 grad" ). These properties have led to the use of Vectra LC polymers in many electronic applications such as sockets, switches, bobbins, connectors, chip carriers, and sensors. Vectra LC polymers have replaced stainless steel in medical applications. The LC polyesters are particularly attractive for miaowave frequency electronics due to low relative dielectric constants, low dissipation factors, and the commerdal availability of laminates. 

Of equal importance for this particular application, however, is the dielectric permittivity, e, which determines the velocity of propagation (Vp) of electric signals. As Vp l/Vi, the dielectric permittivity should be minimized to maximize the speed of signal transmission. Figure 11.14 shows different ceramic substrate materials in a plot. Clearly, a compromise is always required, and target materials suitable for electronic substrate and chip carrier apphcation should be... 

J. W. Stafford, Chip Carriers— Their Application and Euture Direction, Proceedings of the International Microelectronics Con/erence, Anaheim, CA, February 26-28,1980, New York, June 17-19,1980. Also published in Electronics Packaging and Production, vol. 20, no. 7, July 1980. 

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