Metal fusion bonding – Process – Preplacing solid filler
Patent
1996-06-17
1997-11-25
Heinrich, Samuel M.
Metal fusion bonding
Process
Preplacing solid filler
228224, 148 26, B23K 35363
Patent
active
056902719
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a process for soldering on large-area plates of aluminum or aluminum alloys on to a workpiece comprising an iron-base alloy. The invention also concerns the use of the process and a soldering paste which is suitable for carrying out the process.
Large-area solder joins between an aluminum or aluminum alloy plate and a bottom surface of a cooking pot of Inox--namely, stainless high-quality steel 18/8 Mo--have long been known. In those processes, in most cases the flux-solder powder mixture or the paste consisting thereof is sprinkled, coated or sprayed on to the surface to be soldered, and then introduced into the soldering installation and soldered.
In the case of all flux-solder layers which are applied using those known processes, the degree of stability in regard to abrasion wear and capability of being stored without being affected is very low, whereby the flux-solder layer suffers from damage which results in defects in the soldering, locations which are not properly soldered, or included flux residues.
In consideration of that state of the art, the inventor set himself the aim of eliminating the recognised deficiencies and improving the process of the kind set forth in the opening part of this specification in particular in respect of the soldering operation and the storage or transportation capability.
That object is attained by the teaching set forth in the independent claim. The appendant claims set forth desirable developments.
In accordance with the invention for soldering on the plate, use is made of a soldering paste which on the one hand comprises a flux with approximately half proportions of potassium fluoride (KF) and aluminum fluoride (AlF.sub.3) respectively, and on the other hand a solder powder with about 80 to 90% aluminum and 20 to 10% silicon and also a binder on a polymethacrylate base, wherein the preferred proportions of the flux should be between 40 and 60% by weight, solder powder between 60 and 40% by weight, and binder between 0.2 and 2% by weight, in particular 0.3 to 1.2% by weight.
A further feature of the invention provides for using a binder comprising a monopropylene glycol and 10 to 30% by weight and preferably 20 to 25% by weight of a solution of butyl methacrylate and a mixture of aliphatic and naphthenic hydrocarbons (C.sub.7 to C.sub.9); the proportion of monopropylene glycol is added to the soldering paste, but not the solution.
The bonding of the individual particles to each other and to the surface of the aluminum plate is substantially improved and their storage and despatch capabilities are increased by virtue of the resinlike butyl methacrylate.
The butyl methacrylate is dissolved in various solvents depending on the choice of the kind of spray procedure for application in one or in two working operations.
If the layer is applied to the aluminum plate in two working operations, the paste which is sprayed on first comprises flux, solder and monopropylene glycol. The solution which is sprayed on then--in the second working operation--is sprayed on with 10 to 30% by weight and preferably 20 to 25% by weight of butyl methacrylate, dissolved in aliphatic and naphthenic hydrocarbons. In accordance with the stated object the suitability for storage and the despatch capability are enhanced by virtue of the very thin resin film which is formed in that case.
If the layer is to be applied in one working operation, the butyl methacrylate solution is produced in the same ratio--only with another solvent--and mixed with the paste before the spraying-on operation.
In that case, glycol ethers, glycol esters or ketones and to a very slight degree also glycol ether acetates are used as solvent for the butyl methacrylate, as a mixture or each individually.
When using that paste in one working operation the same properties are achieved for the coating, as in the case of the coating which is produced in two working operations.
In the investigations it was also found that the resin-like additives according to the invention do not have any disturbing influence
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patent: 4981526 (1991-01-01), Kudo et al.
patent: 5226974 (1993-07-01), Conn
patent: 5330090 (1994-07-01), Iwai
Castolin S.A.
Heinrich Samuel M.
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