Dispensing solder pastes

Conventional printing processes are less useful for applying conductive adhesives or solder paste. Dispensing of single dots in a complex geometric application is therefore necessary. Three-dimensional circuit carriers also decrease the freedom of component placement, which leads to restrictions for placement systems. [Pg.435]

Viscosity controls the dispensing properties of the paste, irrespective of the particular technique (needle, screen printing, etc.). The viscosity and hence the dispensability of the paste change with time, whether slowly in an unopened jar on the shelf or more quickly when the paste is exposed to air while awaiting the dispensing step. Care should be taken to monitor strictly the manufactnrers recommendations for shelf-life and lifetime on the assembly floor. Poor solder paste dispensing accounts for the majority of solder-joint defects observed in surface-mount technology. [Pg.929]

Solder paste consists of solder powder suspended in a flux. The material is dispensed as a slurry, then heated to its reflow temperature, and finally cooled to create a soHd solder joint. The liquid flux serves multiple purposes ... [Pg.193]

These materials are predominantly used in printed circuit board assembly, and the equipment for their dispensing and reflow is well standardized. Solder paste joints provide excellent electrical and thermal conductivity, and create a strong mechanical bond. [Pg.193]

Figure 30 Alternative Principles for Application of Solder Paste, (a) Stencil printing. (i>) Dispensing.

Discrimination, price, 681-682 Diseases, occupational. See also Occupational safety and health definition of, 1168-1170 descriptions of, 1167, 1169-1170 statistics related to, 1157, 1173-1174 Dispatching, 1723-1725 basic rules, 1723-1724 composite rules, 1724-1725 first-come-first-served (FCFS), 1511-1513 major activities of, 1770 notation used in modeling of, 1719-1722 rules, dispatching, 1511, 1513 Dispensing (solder paste), 425, 426 Display systems, virtual environment, 2502 Distance, computer screen viewing, 1197 Distance learning, 940 Distributed commerce model, 271-272 Distributed component object model (DCOM), 721... [Pg.2723]

In surface mounting of components, both solder paste and adhesive need to be dispensed. The solder paste is usually screen printed or stenciled first, followed by selective dispensing of the adhesive between the solder pads. The prime function of... [Pg.173]

Stencil printing is a fast efficient process for long production runs and is widely used in surface mounting of components. In surface mounting, the solder paste is generally dispensed first by stenciling, followed by needle dispensing the adhesive however, these processes may be reversed or both the solder and adhesive can be selectively dispensed by needle. [Pg.174]

As with most processes, numerous variables affect the final product. For solder paste deposition using stencils, Chouta and Heck identified 39 variables relating to materials, 32 variables to processes and equipment, and 10 variables to personnel and environment. Among variables critical for the successful stencil dispensing of adhesives are stencil design, the adhesive material and its rheological properties, and the printing process. [Pg.176]

Although stencil printing is widely used for both adhesives and solder paste, and has many advantages over other dispensing processes, there are several limitations that must be addressed as follows ... [Pg.180]

Surface-mount adhesive, solder paste, solder mask, and RTV dispensing Thermal grease, solder paste, and surface-mount adhesives... [Pg.190]

Dispensing of materials Adhesives, sealants, with a wide range solder pastes, and... [Pg.191]

When using isotropically conductive adhesives, placement of components is performed by the same equipment as used for nonadhesive attachment techniques. Die bonders are similar to those used for eutectic bonding except for the type of adhesive dispenser. Surface-mounted placement machines developed for solder paste assembly can also be... [Pg.855]

Surface mounting. Surface mounting of components onto PWBs is commonly referred to in the industry as SMT or surface-mount technology. It consists of the attachment of electronic components by automated dispensing or screen printing of solder paste and adhesive onto a PWB, placement of the components, then curing the adhesive and reflowing the... [Pg.9]

Jet dispensing (low-viscosity adhesive), True volume positive dispensing wide range of solder paste and adhesives, TmFlow auger valve for medium viscosity adhesives, and time-pressure for low-to-medium viscosity adhesives. NA - Not Available. ... [Pg.234]

Dispensing. In surface-mount technology, three classes of materials must be dispensed on to the circuit board adhesives, fluxes, and solder pastes. Each of these three categories, which utilize very similar equipment options for the actual dispensing action, is discussed in the following subsections. [Pg.926]

Solder Paste. The dispensing of solder paste is the most widely used means of providing flux and solder metal to the joint for the reflow process. The primary components of the solder paste are the solder metal and the flux. The solder metal is typically 80-90 wt. percent of the paste. Aside from the In- and Zn-containing solders, there is very little sensitivity of the paste properties to the solder metal composition for Sn-based alloys. Important properties of the paste with respect to dispensing are the solder powder particle size and weight percent or metal loading of the paste. [Pg.928]

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