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Inorganic reactive aluminum solder
- This type of flux has been patented and documented as early as 924, and it is still used in modern times. It is mainly a mixed salt composed of several salts such as ZnCl2, SnClj. NH4Cl. Because of their low melting temperature (170 – 200^), they are in the soldering temperature range. Some of the tellurides are often added as a breaker to become a solder. The molten salt system commonly used in inorganic reactive aluminum soft injections is shown in Figure 2-18. Because of the heavy metal salt used in the matrix, the flux is very high. When brazing, it will react with aluminum and the surface to precipitate metal to enhance the activity, but at the same time, the by-product A1F3 is also precipitated. The viscous flux is foamy, the surrounding of the solder joint is dirty, and the brazing process is not smooth. In addition, there is also the problem that corrosion is not easy to cause corrosion. And 2-9 list the actual formulation of some reactive aluminum solders.
- Table 2-9 Some reactive fluxes for aluminum soldering
Serial number Code Ingredients (quality 1: score, %) Melting temperature / t Special application 1 ZiiCl2 ( 55 )，SnCl2 (28 ) , NH4 Br( 15 )，NaF( 2) — — 2 QJ203 SnCl2(88),NH4a(10),NaF(2) — — 3 ZnCl2(88),NH4CI( 10)，NaF(2) 一 — 4 — ZnBr2 (50-30)，KBr( 50-70 ) 215 Brazing aluminum smokeless 5 — PbCl2(95-97) ,KC1( 1.5-2.5)，CoCl2(1.5-2.5) — Aluminum coated Pb 6 0)134 KC1(35),UC1(30) ,ZnF2(10) .CdCI2(15) ,ZnCl2(10) 390 — 7 ZnCl2(48.6),SnCl2(32.4),Ka(15.0).KF(2.0)tAgCl(2.0) — KSn-Pb (85) solder, high corrosion resistance
Organic aluminum solder
- In the 1940s, the flux of organic matter  began to appear. In the late 1950s, low-temperature aluminum flux [7*] prepared by dissolving fluoroborate in triethanolamine began to appear, and its superior performance was followed. Scholars flocked to study 17740]. The typical composition of this kind of enamel agent is to dissolve some fluoroborate, such as Zn (BF4>2, Cd(BF4)2, Sn(BF4)2, NH4BF4, or 2-3 in organic hydroxylamine. In solution, the available organic hydroxylamines are: Ethylamine, Diethylamine, Triethanol, Dithtrientrien, N-(2-Aminoethyl)ethanolamine [N-(2-aminoethyl) )ethanolamine], etc., also use 10% ~ 25% (mass fraction) of a mixture of ethanolamine and triethanolamine as a solvent, it is said that a solvent with a large solid solubility and a suitable boiling point can be obtained.  Such a flux starts to be practical. On aluminum lamp holders for brazing incandescent lamps [811, such fluxes have since been formed into commodities such as Alu-Sol from Multicore, UK, Stay- dean from J. W. Harris Co, AluTin51 from Caatolin, Switzerland, and Japanese recruits. W-FX of the club; there are also some small companies, such as Kapp in the US, “Golden Flux” from Alloy mulWirc, and QJ-204 flux from Shanghai Smick in China. These are listed in Table 2-10. In the application of organic solder formulations.
- Unlike aluminum brazing, heavy metal ions in the flux are reduced by aluminum, which precipitates metal on the aluminum surface, but it must be liquid at the Vacuum brazing furnace temperature to maximize activity. In the formulation of Q 〖204, when Zn2+ and Cd2+ are separated from f for eutectic precipitation, the brazing temperature needs to pass through 2661 (the eutectic temperature of the Zn-Cd metal binary system), and the liquid phase may occur, so only this temperature is exceeded. The above may be the greatest activity. At 266 ,, ethanolamine has begun to coke, not to mention the Cd is poisonous, so the formula is not very satisfactory. When brazing with this flux, it is best to heat the base metal to 270 – 300T; good results can be obtained by brazing in the shortest time. As for the 4>61 A and 4>54A with the numbers 2 and 3 in Table 2-10, it is even more unreasonable because each of the two formulations uses only one surfactant. The Zn precipitated in the No. 2 injection can be melted at 4201, and it can be melted even if it forms a eutectic with A1. No. 3 flux only precipitates a kind of Cd, its melting point is 321 弋, and A1 is not miscible, and the wettability is not good. Therefore, these two formulations are unlikely to exhibit maximum activity until the coke is coked. The above refers to the maximum activity, not the lack of activity. In fact K, the above formulation still achieves general application. The 1070X flux of No. 4 is more reasonable. The temperature of the liquid Sn-Zn eutectic precipitated by the flux is 198T. If it is brazed at 250~27 (T-Zn or Sn-Pb solder) When the maximum activity of the flux is exerted, the ruthenium material is already in a molten state. At present, the surfactant used as a composite of Zn2♦ and Sn2′ ions has been commonly used for some domestic and foreign commercial aluminum solders.
- Raw materials such as Zn(BF4)2, Cd(BF4)2, and Sn(BF,)2, which are prepared as fluxes, are not commercially available, and in particular, Sn(BF4)2 can only obtain a solution thereof. In fact, fluoroborate is not a necessary component of the flux, and good results can be obtained by directly using the fluoride. No. 4 in Table 2-10 lists an effective formulation. Only 5#2 in the raw materials is sometimes not readily available, and can be prepared by reacting SnO with HF.
- 1040W of No. 5 in Table 2-10 is a solid perfluoroaluminum solder with a melting point of about 501: It is a kind of agent that has been put into practical use by the editor. It has high activity and is suitable for injecting Sn-Zn eutectic solder. It is used to manufacture aluminum solder wire. This enamel agent cannot be directly formulated with a reagent and needs to be chemically synthesized. The process is complex and also suitable for mass production. ZnO and SnO can be successively dissolved in an excess amount of hydrogen acid in a polyene-based container, and then neutralized to pH=7 with diethanolamine to obtain a viscous turbid liquid, which is evaporated to 180 t in a stainless steel pot. Dehydration to obtain a clear colloidal solution. When cooled to 70 ~ 80 «C, pack into a suitable container and seal it, continue to cool to room temperature and solidify into a waxy solid. 1040W is actually a waxy crystal of ZnF2 and SnF2 dissolved in (CH2CH20n)2NH•HF with a melting temperature of 501. 1040W in the humid air is easy to absorb water, and the melting temperature will decrease after water absorption.
- Table 2-10 Some organic fluxes for aluminum soldering
Serial number Code Ingredients (the highest score, “» form Melting temperature / 1 QJ204(<I>59A) Triethylene Dilute Amine (82.5),Cd(BF4)2(10.0).Zn(BF4)2(2.5),NH4BF4(5.0) Slaughter is a solution 一 2 4>61A Triethanolamine (82) ,Zn(BF4)2(10) ,NH4BF4(8) Room temperature is the solution — 3 054A Triethanolamine (82) ,Cd(BF4)2(10) .NH4BF4(8) Room temperature is the solution — 4 1070X Diethylene Dilute Amine (82.0) ,ZnF2(1.0) ,SnF2(9.0) ,NK,HF2(8.0) Room temperature turbidity — 5 1040W ZnF2(3.5),SnF2(6.3)，Hydrogen cyanide tt of diethanolamine (90. 2> Waxy solid -50 6 1080W ZnF2(2.5)，SnF2(26.3) , Diethylamine（71.2〉 Waxy carcass —45 7 1140W ZnF2(1.7),SnF2(6.3)，Hydrofluoric acid ammonium hyaluronate 92.0) Blocky solid 175 8 1090X Diethylamine（82.0) ,ZnCl2 (1.1) .Sna2 ( 8. 9 ) .NH4HF2 (8. 0) Descent —
- 1140W, which is numbered 7 in Table 2-10, is a flux synthesized by substituting diethanolamine with ammonium hyaluronate (chemical name: trishydroxymethylaminomethane). The synthesis route is exactly the same as that of 1040W. The 1140W has a relatively low melting temperature (175^0) and is a rosin-like block that is completely non-hygroscopic but soluble in water. With a combination of 1140W and 1040W in different proportions, a series of fluxes with different melting temperatures can be obtained.
- The content of ZnF2 and SnF2 in the above flux was increased to prepare a 1080W flux of No. 6 in Table 2-10. The flux can be used for self-braking or for brazing, and it does not require additional solder when brazing, and has good effects. A practical example can be seen in Figure 2-38 of this chapter. • Figure 2-40.
- A suitable high-quality, room-temperature liquid, non-aqueous aluminum enamel can be obtained by appropriately diluting 1040W with either B2 or 2D.
- Finally, the number 8 in the list lists the easiest and most convenient formulation, but it has sufficient brazing activity. It uses very versatile and easy-to-use ZnCl2 and SnCl2 as the main raw materials, and the strip remover
- NH4HF2 (ammonium hydrogen fluoride) is also an easy-to-purchase common reagent. The SnCl2 which is usually purchased is a dihydrate compound SnCl2 • 2H20 which is melted in its own crystal water to become a yellow solution, heated to IOOT; dehydration begins, and finally a yellow anhydrous SnCl2 (melting point 2461) hard block is formed. The dehydration process should be carried out in a porcelain evaporating dish. Some
- NH4C1 should be added first to prevent the hydrolysis of SnCl2 during dehydration. When formulating the flux, the number 8 in Table 2-10 can be used.
- After the four components are weighed, they can be used in a mortar to form a thin paste. After the flux contains Cl_, the components, including diethanolamine (or triethanolamine), are heavily absorbed. Therefore, the residue after welding must be carefully cleaned to avoid corrosion of the aluminum base material.