Stock material or miscellaneous articles – Structurally defined web or sheet – Including components having same physical characteristic in...
Patent
1990-02-02
1992-03-31
Van Balen, William J.
Stock material or miscellaneous articles
Structurally defined web or sheet
Including components having same physical characteristic in...
428422, 428697, 428698, 428699, B32B 900, B32B 1500, B32B 1800
Patent
active
051007010
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a solder-repelling coating for tools, especially for gripping, insertion and/or bending tools in automatic insertion machines for electric components which have at least one nitride layer as the layer base.
In the automatic insertion of circuit boards with radial, axial components or also DIP components, the tinned connecting leads or connecting lugs are bent into the insertion position after the components are inserted. At the gripping, insertion and/or bending tools, accumulations of solder occur here which have an adverse effect on the operation of the automatic insertion machines and can lead to disturbances in the course of production. Depending on the kind of components and the solder used for tinning the terminals, insertion disturbances are found, according to experience, already after 1.times.10.sup.4 to 5.times.10.sup.4 components.
Up to now, in the event of insertion trouble the tools are freed of the accumulated solder, which must be done by scraping out or also reworking the insertion tools. With such maintenance and the down time connected therewith of the automatic insertion machine, goes along a not in considerable operating costs.
It is therefore an object of the invention to improve the tools by a solder-repelling coating in such a manner that larger numbers of insertions can be achieved without additional maintenance.
According to the invention, the problem is solved by a solder-repelling coating with a metal-nitride base, in which, besides the metal-nitride base layer generated by a coating process, at least a second layer is provided as a cover layer with solid-lubricant properties. Preferably, the base layer has a gradual change from high density in the border region to the base material of the tool to a porous structure at the boundary surface to the cover layer. Advantageously, the metal-nitride layer is here the well known titanium nitride.
The invention is based on the fact that the coating of tools, known per se in machine design, of tools with hard material layers, especially of titanium nitride, also ensures better resistance to melted solder. Although experimental examinations showed that such hard material layers were not yet sufficiently usable for the intended purpose, the coating is usable for the intended purpose only if a cover layer with solid lubricant properties is applied on such hard material layers. It is utilized here that the titanium nitride can be produced on the one hand with a structure of high density which adheres well to the base material and on the other hand with a porous structure, where the porous layer and the micro-roughness connected therewith serves for anchoring and as a depot for the solid lubricants.
Organic as well as inorganic substances can be considered as the cover layer with the solid lubricant properties. In particular, a known teflon suspension has been found suitable as an organic substance which can be produced by immersion or spraying-on and subsequent firing as the cover layer. Besides there can be used as an inorganic substance, for instance, the well known solid lubricant molybdenum sulfide in a silver matrix or metal-carbon combinations such as silver graphite, zirconium-carbon, iron-nickel carbon or also iron-nickel-chromium carbon.
The latter substances are known in technology because of their good trilological properties and ar used customarily as solid lubricants. In the invention it is now advantageously utilized that in the cover layer, the softer solid lubricant is sufficiently enough anchored in the hard base layer due to its microroughness. In this combination, surprisingly good and long-lasting solder-repellent properties of such a layer structure are obtained. Even in the event of partial abrasion in the region of the peaks and after leveling the surface, sufficient solid lubricant remains as a depot in the depressions and thus maintains the solid-repellent function.
Further details and advantages of the invention are obtained from the description of examples, reference being made to the figures
REFERENCES:
patent: 2740193 (1956-04-01), Pessel
patent: 4204886 (1980-05-01), Bens
patent: 4420110 (1983-12-01), McCollough et al.
patent: 4603704 (1986-08-01), Mund et al.
patent: 4619865 (1986-10-01), Keem et al.
patent: 4643951 (1987-02-01), Keem et al.
Freller Helmut
Horauf Friedrich
Lorenz Hans P.
Schack Peter
Siemens Aktiengesellschaft
Van Balen William J.
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