Soldering materials

Engineering rework is possible with eutectic and solder materials, but impossible with silver—glass. This constraint severely limits the usefulness of the material. Tables 4 and 5 give the electrical, mechanical, and thermal properties for various adhesives. 

Table 8. Mechanical and Electrical Properties of Solder Materials ...

Nonconventiona.1 Solder Systems. Nonconventional solder systems are developed for use with newer alloys, especially base metal alloys. They are few in number and will probably remain the exception rather than the rule. Some new solder systems consist of metallic particles either pressed to form a rod or suspended in a paste flux. The metallic composition is close to that of the alloy to be joined. If the particles are nonhomogeneous, the solder has particles with melting points lower and higher than that of the alloy. For nonhomogeneous solders, once the flame has been placed on the parts to be joined and the soldering material, it should not be removed until the flow process is completed. 

Soldering materials are alloys that are composed primarily of tin and lead (qv), and have low melting temperatures relative to the conductor metals which are being soldered (see Lead alloys Tin and tin alloys). Welding requires sufficientiy high temperatures for the fusion of metals. 

Gas Atomization 50-300 Standard deviation 1.9-2.5 <10-50 at high gas pressures with close-coupled atomizer Solder materials. Precious metals, Cu, Fe, Al, Mg, Co, Ti, Zn, Al-6Cr-3Fe-2Zr alloy. Low-alloy steels. High speed steels. Stainless steels, Specialty alloys, Ni-base superalloys, Alumina, Intermetallics io3-.o5 1-70 Spherical smooth particles. Cleanliness, Rapidly-solidified structures, Acceptable production rates High cost, Low 1 volume, Low energy efficiency (EE), Gas-filled porosity in particles H... 

Ultrasonic Atomization 30-50 USWA >100 Medium size distribution Solder materials, Welding electrodes, Ag-, Cu-base alloys, Dispersion-hardened allovs USWA 107 0.02-0.8 Low Spherical high quality particles, Low cost, Small unit, High EE Low volume productivity... 

For low melting-point metals (for example, solder materials), the liquid metal and the atomization gas may be mixed internally inside the atomizer for both low and high melting point materials, the two fluids can be mixed externally outside the atomizer in the nearnozzle region. 

Table 2.11. Thermophysical Properties of Precious Metals and Solder Materials in Atomization Processes...

Tin is a soft, white, silvery metal that is insoluble in water. Tin metal is used to make cans for food, beverages, and aerosols. It is present in brass, bronze, pewter, and some soldering materials. 

The four forms of lead are pure lead, also known as corroding lead (99.94%), common lead (99.94%), chemical lead (99.99) and acid-copper lead (99.99%). The resistance of lead to sulfuric acid enables its use in batteries. It is also used as sheet and pipe in buildings. The main use is as a solder material in the electronics industry. 

Lead-tin alloys are the most commonly used solder materials for microelectronic packaging. Pb and Pb-rich alloys have one of the most desirable characteristics of C4 solders in that they are soft and compliant. The compliant nature of these alloys act a cushion for absorbing thermal and mechanical stresses and transfer minimum stresses to the die during microprocessor assembly processes. On the other hand, the melting... 

Here / is the cycle frequency, Nf the number of cycles to failure, and AT the temperature difference. The Coffin-Manson model is widely accepted for describing material degradation (e.g., solder materials), fatigue fracture, and crack propagation. 

There are many such structures in the world around us. They are omnipresent in the natural landscape and appear implicitly in the complex phenomena of chaos, turbulence, avalanches, climatic fluctuations and the spreading of epidemics. Less evidently, because of their microscopic nature, they can help us to understand polymer structures, glue or cement hardening, metal soldering, material fracture, chemical reaction rates, rubber strengthening, and petroleum migration. 

Replace steel contacts with solder material (see table 11 for properties). Selecting the solder material satisfies two of the recommendations that a) softer contact material be used, and b) reduce CTE mismatch between the contact and TE materials. 

However, conductive adhesive technology is still in its infancy, and concerns and limitations do exist. The main limitations of commercial ICAs include lower conductivity than that of solder materials, an unstable contact resistance with nonnoble metal finished components, and poor impact performance. The electrical conductivity ( 10 S2 cm ) of an ICA is lower than Sn-Pb solders ( 10 cm ). Although generally adequate for most electronics applications,... 

H. H. Manko, Solders and Soldering, Materials, Design, Production, and Analysis for Reliable Bonding, 2nd ed., McGraw-Hill, New York, 1979. 

K. Solder, Material Safely Data Sheet for Water Soluble Soldering Flux. MSDS Number 1452, Des Plaines, IL, USA 1996, p. 1. 

The second cost aspect addresses the manner in which a Pb-free capabihty is to be implemented on the factory floor. Specifically, the decision must be made whether to have separate Sn-Pb and Pb-free solder assembly lines or to mix the two technologies using the same assembly equipment. Critical factors include capital costs, factory floor space, infrastructure required to prevent inadvertent mixing of technologies, and projected product volumes. It is preferred to separate the two assembly capabilities physically. This separation is not limited to the actual machines, but also includes support functions such as solder material storage and component inventory control in order to prevent the use of the wrong solder or components and circuit boards with incorrect finishes. The extent of this separation of capabUities wiU determine the... 

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