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Lotmaterial, enthaltend ein Metallstearat sowie Verwendung von Metallstearaten in Lotmaterialien

Soldering powder, useful in assembling electronic components, comprises solder material particles coated with flux consisting of stearate of metal with specific oxidation properties
 
: Diehm, R.; Ludeck, W.; Prihodovsky, A.; Schmitt, W.; Trageser, H.; Fix, A.; Hutter, M.; Pape, U.; Zerrer, P.; Meier, H.; Müller, B.; Wittreich, U.; Wormuth, D.

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DE 102008031004 A: 20080630
DE 102008031004 A: 20080630
B23K0035
German
Patent, Electronic Publication
Fraunhofer ZV, Patent Department ()

Abstract
(A1) Die Erfindung betrifft Lotmaterialien, wie z.B. eine Lotpaste (11) und Kontaktflaechen fuer Loetverbindungen, wobei erfindungsgemaess vorgesehen ist, dass als Flussmittel ein Metallstearat zum Einsatz kommt, welches entweder als feste Schicht (14, 15) auf den Lotpartikeln (12) oder Kontaktflaechen (nicht dargestellt) aufgebracht ist oder als Dispersion oder Loesung im Bindemittel vorliegt. Vorteilhaft kann der Einsatz klassischer Flussmittel hierdurch vermieden werden, insbesondere koennen harzfreie Lotmaterialien zur Verfuegung gestellt werden. Dies bewirkt eine vereinfachte Lagerung und Verarbeitbarkeit der Lotmaterialien unter Ausbildung vergleichsweise besserer Loetverbindungen. Die Verwendbarkeit von Metallstearaten als Flussmittel laesst sich erreichen, wenn Metalle verwendet werden, deren erstes Oxid bei einer geringeren Sauerstoffaktivitaet (a?o?) aus reinem Metall gebildet wird, als das erste Chromoxid aus Chrom, bevorzugt als das erste Titanoxid aus Titan und dieses Metallstearat in genuegender Menge vorhanden ist.

 

DE 102008031004 A1 UPAB: 20100115 NOVELTY - In a soldering powder comprising particles (12) of solder material surface-coated with a solid metal stearate layer (14, 15), the metal stearate forms at least 20 (preferably at least 40) wt. % of the layer and is formed from metal(s) for which the first oxide is formed from the pure metal at a lower oxygen activity than that at which the first oxide is formed from chromium (and preferably lower than at which the first oxide is formed from titanium). DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) a soldering paste containing coated solder material particles (12) as above; (2) a soldering paste comprising particles of solder material particles enclosed in a binder (13), where the binder contains (a) metal stearate as defined above in an amount of at least 10 (preferably 20) wt. % based on the binder, (b) a solvent or dispersion medium in an amount of at least 50 wt. % and (c) other metal salts, up to 10 wt. % carboxylic acid and/or activators forming the remainder of the binder; (3) solder material in the form of a semi-finished product (specifically a wire or shaped article), where the semi-finished product is provided with a layer of solid metal stearate as defined above; (4) a support (17) with contact surfaces for electrical components (or electrical component with contact surfaces), where the contact surfaces are provided with a layer of solid metal stearate as defined above; (5) a support or electrical component with contact surfaces for a soldered connection, on which a solder deposit is formed, where the solder deposit is provided with a metal stearate layer, at least 20 (preferably at least 40) wt. % formed from metal stearate as defined above; (6) the use of a metal stearate (not necessarily as defined above) as flux for solders, where a solid layer of the metal stearate is applied to solder particles, semi-finished solder product, solder deposit on a supporting surface or component or solder connection contact surface on a supporting surface or component; and (7) the use of a metal stearate (not necessarily as defined above) as flux for solders, where the solder material consists of solder particles and a binder to which at least fatty acids and the metal stearate are added, the binder also including a dispersion medium or solvent for the metal stearate. USE - The soldering materials, containing metal stearates as flux, are useful e.g. in the assembly of electronic components. ADVANTAGE - The stearates of metals with relatively low thermodynamic activity towards oxygen provide metal ions with the necessary reducing effect to act as fluxes during soldering. Use of the present specific metal stearates (rather than e.g. copper stearate) reduces the amounts of conventional fluxes required, and provides resin-free soldering materials. Storage and processing of the solder materials is facilitated, and superior soldered connections are obtainable. The fluxes are not subject to significant variations in quality. The present metal stearates are generally non-toxic and non-corrosive.

: http://publica.fraunhofer.de/documents/N-118891.html