There are various processes for making such silver contact bases which, however, are either very laborious in the manipulation of the silver contact base and intermediate layer, the contact plate and the contact bearer and their soldering or are based on strip material of suitable composition, rolling these strips on one another and cutting the edges. In the latter process, noble metal is wasted. To avoid these drawbacks, according to the invention the solder is applied in the form of a platelet (6) before the actual process on the intermediate silver layer (4). Here it is especially advantageous if this application is made by ultrasonic soldering. The invention is applicable to all silver contacts.

Contact with a silver contact base and process for making it

The blank is made into electrical contacts by connecting it to a contact carrier strip, esp. of copper, using resistive heating. The blank is formed as a metal strip (1) with a contact region and a coating of material on its underside which is to be connected to the carrier strip. The coating material essentially consists of silver, whose melting point lies below that of the metal strip. The coating is applied at least at the tip of a strand-like protrusion (5) on the underside (4) of the metal strip. The core (2) of the metal strip is essentially made of nickel. It can be a copper-nickel alloy.

Preform material and manufacturing process of preform material and semi-finished products for electrical contacts

A contact includes a silver contact base, an intermediate silver layer and a solder in the form of a platelet being provisionally fastened or tacked to the intermediate silver layer prior to an actual soldering operation. The silver contact base is soldered onto a contact carrier by the intermediate silver layer and the solder platelet. A method for making a contact includes pressing an intermediate silver layer onto a silver contact base, then provisionally fastening or tacking a solder in the form of a platelet to the intermediate silver layer and subsequently placing a contact carrier on the solder platelet and soldering the contact carrier to the solder platelet.

Process for making contact with a silver contact base

On a observe, notamment dans le cas ou des couches de contact en un materiau a base d'argent-oxyde metallique (AgMeO) sont pourvues sur leur face posterieure de metal d'apport pendant leur brasage fort sur un support de contact, que le metal d'apport peut monter de maniere inopportune jusqu'aux surfaces de contact, ce qui s'explique par l'echauffement produit pendant le brasage fort. It has been observed, especially in the case where contact layers in a silver-base metal oxide material (AgMeO) are provided on their rear face of the filler metal during brazing to a contact carrier, the solder can rise inappropriately to the contact surfaces, which is explained by the heating produced during brazing. Selon l'invention, on reduit la mouillabilite des faces laterales des couches de contact de maniere a empecher le metal d'apport de monter jusqu'a la surface qui porte les circuits. According to the invention reduces the wettability of the side faces of the contact layers so as to prevent the solder up to the surface which carries the circuit. A cet effet, on insere de preference des oxydes metalliques dans les surfaces des couches de contact. For this purpose, are inserted preferably metal oxides in the surfaces of the contact layers. Dans le cas de couches de contact a base d'argent-oxyde metallique (AgMeO), on utilise de preference des oxydes metalliques deja presents en tant que composants actifs dans le materiau. In the case of contact layers based on silver metal oxide (AgMeO), preferably used metal oxides already present as active components in the material.

Process for bonding contact layers to a contact substrate by hard soldering and semifinished product used to implement this process.

Contact with a silver contact base and process for making the same

Particularly in resistance spot welding or resistance soldering of a contact to a support, e.g. a miniature contact to a contact spring, the process described leads to a minimisation of the contact hardness losses during the process by introducing a short-time energy pulse. Further advantages consist in a reduction in the damage to the surface of the contact material, the increasing of the strength of the joint zone, greater uniformity within the joint zone and the lengthening of the electrode life by three to five times as well as an extremely small transfer of copper from the electrode to the contact surface, the said transfer being at the limit of detectability. In the process, a contact element, e.g. made of silver, is welded to a contact support by means of a welding aid, e.g. composed of Cu Ni 30 Fe or by means of a brazing solder, e.g. composed of L Ag 15 P5, or by means of carrier material and brazing solder, or is connected to the said contact support by flux-free brazing. In order to achieve the abovementioned advantages, the energy pulse used in the process is an extremely steep-flanked controlled energy pulse which at the same time has a high current intensity. This results in rapid introduction into the joint zone of the energy required for joining, unnecessary heating, associated with power loss, of the areas of the material adjacent to the joint zone being eliminated at the same time.

Dederer Guenter Dipl Ing

Papers

Process for joining work pieces by resistance heating with a short-time energy pulse