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Surface-mount applications

Adhesives used for screen or stencil printing in surface-mount applications are generally electrically insulative types whose functions are mechanical attachment and thermal dissipation. However, electrically conductive, silver-filled epoxies have been used for many years as ohmic contact adhesives to interconnect bare-chip devices in hybrid microcircuits and are used as solder replacements for surface mounting of components on printed-circuit boards. Regardless of their... [Pg.178]

Numerous geometrical factors of the specific interconnection will also influence anisotropic adhesive formulation and processing, including lead planarity, IC pad metallization, and IC test patterns. The planarity of the leads on the substrate and/or device and the compliance of the conductive particles will determine if anisotropically conductive adhesives can be used in a particular application. For systems with large disparities between lead height, no electrical interconnection will be formed, as shown in Fig. 5. Fine-pitch IC packages for surface-mounted applications, such as the plastic quad flat pack (PQFP), often use gullwing leads that olfer much compliance to the joint. Even if the... [Pg.852]

Surface Mount Applications. Tin-lead solders (Sn-Pb) are the standard materials used to interconnect electronic components on PCBs. The most common reflow soldering process is SMT which uses tin-lead solder pastes (58-61). The pressure to reduce the industrial use of lead is growing, particularly in Europe, since it poses as a hazard to human health (62). [Pg.1791]

There are a few other materials that need to be covered for this discussion. The first is solder paste. This is a mixture of minute solder beads, flux, and other materials to give it specific rheological characteristics for dispensing and chemical agents for metal surface preparation. For surface-mount applications, it is typically stenciled onto PWB bonding pads, and then the electronic component is placed upon the solder paste deposit. The paste holds the component in place during the reflow process.The second is flux, which, as mentioned previously, is a key component of solder paste. The flux is a heat-activated chemical agent used to clean solder-able surfaces. Both paste and flux will be covered in subsequent sections of this chapter. [Pg.1032]

Abtew, M., and Selvaduray, G., Lead Free Solders for Surface Mount Applications, Chip Scale Review, September 1998, pp. 29-38. [Pg.1055]

J.C. Jagt, Rehability of Electrically Conductive Adhesive Joints for Surface Mount Applications A Summary of the State of the Art, IEEE Transactions on Components Packaging and Manufacturing Technology, Part A, Vol 21, 1998, p 215-225... [Pg.274]

R.S. Rorgren and J. Liu, Reliability Assessment of Isotropically Conductive Adhesive Joints in Surface-Mount Applications, IEEE Transactions on Components Packaging and Manufacturing Technology, Part B, Vol 18, 1995,p 305-312... [Pg.275]

The long-term reliability of isotropic and anisotropic conductive adhesives for surface-mount applications has been extensively studied [144-148]. The data accumulated with die attached chips cannot be transposed to the hybrids or surface-mounted wiring boards because of the dissimilar requirements in mechanical and electrical properties [149]. As shown in Figure 41(a) and (b) of Section 6.5.7, the active and passive devices can be attached to thick film... [Pg.454]

For adequate soldering to occur, it is required that the metal surfaces to be joined are free from dirt, oxides, and other contaminates. Intermetallic compounds can only form if the molten solder is able to alloy or react with the exposed metal pad and lead surfaces. To remove metal oxides present on PCB pads, component terminations, and solder balls, requires exposure through the action of a fluxing agent. Wave fluxes are required to perform the same function as fluxes used in surface mount applications with the exception of component retention. In wave applications, SMT components are held onto the PCB by mechanical means, or by the use of an adhesive. Therefore, a lower viscosity, less tacky flux can be used in wave applications compared to surface mount applications. [Pg.542]

FIG. 7 The initial test vehicle used for the evaluation of solders in surface mount applications. It is FR-4,119x162 xO.8 mm. It contains a wide array of component types such as QFPs, at pitches 0.5 and 0.65 mm, 1005, 1608, and 2125 R/C, mini TR/SOT, SOPs, SOJs, crystal/oscUlators, A1 Caps, connectors, and so on. Electrode finishes used were Sn, Sn-Bi, Pd, Sn-Pb, Au, and Ag. (From Ref 15.)... [Pg.600]

The alloy, Sn-3.4Ag. 8Bi, developed and patented by Sandia National Laboratories, was determined in the NCMS Lead-Free Solder Project to exhibit outstanding fatigue properties for surface mount applications under both accelerated thermal cycle test conditions used in the NCMS study. Sandia performed ATC testing of this alloy to 10,000 cycles for 0-100°C with 10°C/min ramp rates and 5-min dwell times [9,10]. There were no electrical failures at end of test (10,000 cycles) for 68 I/O PLCCs, 241/0 SOICs, and 1206 chip capacitors on FR4 boards, no cracks after 5000 cycles, and only minor surface cracks after 10,000 cycles. The Sn-3.4Ag-4.8Bi alloy has demonstrated considerable promise for use in surface mount applications, exhibiting greater fatigue resistance than eutectic Sn-Pb and most other lead-free alloys. It should be... [Pg.685]

TABLE 50 Promising Lead-Free Alloys for Surface Mount Applications... [Pg.726]

Jagt, J.C. Reliability of electrically conductive adhesive joints for surface mount applications a summary of the state of the art. IEEE Trans. Compon. Packag. Manuf. Technol. Part A, 1998, 21 (2), 215-225. [Pg.765]

Nguyen, G. Williams, J. Gibson, F. Winster, T. Electrical rehability of conductive adhesives for surface mount applications. Proceedings of the International Electronic Packaging Conference, San Diego, CA, September 1993 479-486. [Pg.766]

Lu, D. Wong, C.P. Novel conductive adhesives for surface mount applications. J. Appl. Polym. Sci. 1999, 74, 399-406. [Pg.767]

Kristiansen, H. Liu, J. Bjorneklett, A. A comparison of non-conductive and anisotropic conductive adhesive for surface mount application. Proceedings of the 10th European Microelectronics Conference, Naerum, Denmark, 1995 35-43. [Pg.768]


See other pages where Surface-mount applications is mentioned: [Pg.217]    [Pg.217]    [Pg.1097]    [Pg.273]    [Pg.276]    [Pg.277]    [Pg.304]   
See also in sourсe #XX -- [ Pg.217 ]




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