Solders melting points Table

A detailed study on the wetting characteristics of eutectic Bi-Sn solder has been reported in terms of impurity effects, fluxes, base metals, and soldering temperature [18]. It was determined that eutectic Bi n solder is far less tolerant of impurities than eutectic Plr n [19]. In particular, the presence of impurity elements which form intermetallic compounds with Bi-Sn solder, such as Cu, Ni, Fe, and Pd, is especially critical, while Sb and Pb appear to be beneficial in terms of promoting wetting characteristics. Table 1 compares the solderabihty of several low-melting-point solders on various surface metallizations [20]. Only the Au/Ni-plated metallization is considered acceptable for Bi n solder, while the Cu, Ni, and Au/Ni metallizations are all acceptable for eutectic Sn Pb solder when a rosin-base flux is used. Another study confirmed that Bi Sn solder does not wet Cu-base metallizations as well as eutectic Sn-Pb solder does when a rosin-base flux is used [21]. However, if the Cu surface is pre-tirmed, then Bi-Sn wetting is acceptable even with a rosin-base flux [22]. Based on the wettabihty studies, eutectic Bi-Sn solder can only be considered a viable candidate if a suitable flux system is developed which allows it to be utilized for metallizations other than a Au/Ni overplate. 

Creep behavior of the low-melting point solders has been fully investigated [26,28,29]. Table 6 lists the steady-state creep parameters of several solders, indicating that the steady-state creep rate of Bi-Sn solder joints is smaller than similar Sn Pb solder joints, although eutectic Bi-Sn solder has a significantly lower melting point than eutectic Sn Pb solder, 139°C vs. 183°C, respectively. 

Possible tape materials include polyimide, polyester, polyethersulfone (PES), and polyparabanic acid (PPA) (18). Of these, polyimide is the most widely used material because its high melting point allows it to survive at temperatures up to 365°C. Although polyester is much cheaper than other materials, its use is limited to temperatures less than 160°C. PES and PPA, on the other hand, are half as cosdy as polyimide, and can survive maximum short-term temperatures of 220 and 275°C, respectively. PES has better dimensional stabiUty than polyimide, absorbs less moisture, and does not tear as easily however, it is inflammable and can be attacked by certain common solvents. Table 7 Hsts various plastic tapes and their properties. Common bump materials are gold, copper, and 95% Pb/5% Sn solder (see Tables 6 and 8 for properties see also References 2 and 21). 

When making metal jewelry, the artisan is concerned with the melting point of a chosen metal, especially when he or she must solder together jewelry parts or melt the metal to pour it into a mold. Table 6.3 lists the melting points and approximate composition of various metals and alloys. 

Aluminum fluoride is utilized, in addition to cryolite, as a raw material in the electrolytic manufacture of aluminum (temperature of electrolyte 950°C, composition 80-85% Na AlFft, 5-7% AIF, 5-7% CaF2, 2-6% AFO, 0-7% LiF). No fluorine should actually be consumed in this process, modern plants recovering the fluorine in its entirety. Other uses are as a flux (in welding, soldering, manufacture of casts), and as a melting point depressant in glass and enamel. The aluminum fluoride capacities in Europe are given in the table below. 

Solder powders coated with a thin layer of Parylene exhibit a high degree of resistance to oxidation and to reaction with the flux contained in the solder paste without substantially interfering with the reflow characteristics of the solder. The powders are used as such or as solder paste. The preferred Parylene type is Parylene E, made from 4-ethyl[2.2]paracylophane since it melts below the melting point of the solder, i.e., about 180°C." The formulation of a typical solder pastes are shown in Table 2.4. 

Of those elements that can combine to form solders, several have limitations that restrict their practical implementation for solder use (see Table 45.2). Gallium, gold, indium, platinum, and palladium cannot be mined or refined in sufficient quantity to satisfy the needs of the electronics industry and are prohibitively expensive, blocking their consideration as a major constituent of a worldwide solder supply. The Bismuth (Bi) supply, a by-product of lead refining, would be marginally sufficient. Mercury and antimony are too toxic. Both mercury and Pb are already on the EU s RoHS list of restricted materials. Galhum and mercury possess too low a melting point to be used on their own. This leaves five metals for practical solder alloy consideration bismuth (Bi), copper (Cu), silver (Ag), tin (Sn), and zinc (Zn). Due to... 

Soldering and brazing are methods of joining components together with a lower-melting-point alloy so that the parent metal (the metal or metals to be joined) is not melted (Table 11.12). In the case of soft soldering, the maximum temperature employed is usually of the order of 250 °C and the filler... 

TABLE 14 Some Lead-Free Solder Alloys with a Melting Point or Liquidus Temperature Below 150°C... 

TABLE 7 Viscosities at the Melting Point, Utilized in Solder Alloys... 

The JWES group evaluated various test methods, and tested a range of solder alloys. Measurements of melting point, tensile strength, wettability, and strength of leaded solder joints and chip joints were performed as part of a Pb-free solder evaluation, including the Sn-Ag-Cu, Sn-Ag-Bi, and Sn-Ag-Bi-In alloy systems. The main results for the alloys are summarized in Table 21. 

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