How is silver soldering and sintered contacts done?

For soldering silver and metal-ceramic contacts, it is necessary to have a contact apparatus with a heating transformer and clips or tweezers.

Soldering made from refractory solders types PSr-45 and PMF. A technical drill is used as a stream. Contaminated silver contacts must be cleaned. Sintered contacts must not be chemically treated.

Before soldering contacts, live parts made of copper, brass, bronze and steel must be cleaned of dirt and oxides; use chemical etching, metal brushes and sandpaper for this purpose. It is also necessary to carefully adjust the contact electrodes, ensuring strict parallelism between the working surfaces. It is recommended that the solder be cut in the form of plates so that the area of ​​the solder is equal to the contact area. Borax is used as a fine powder.

When soldering, a thin layer of flux is poured over the part to which the contact is soldered, and a plate of solder and contact is applied on top.The part with the contact is placed on the lower electrode and pressed by the upper electrode of the welding machine. After closing the electrical circuit, the solder is heated until it melts and fills the gap between the workpiece and the contact.

To avoid damage to the contact surface, the welded contact should not be heated above 800 ° C, therefore, while soldering, it is necessary to periodically interrupt the current. After soldering, the contact node of the device is cooled in water. Soldering quality is determined by visual inspection of the seams and a random strength test. The shear force must be at least 2, 2.5, 4 and 6.5 mN (200, 250, 400 and 650 kgf) for contacts with a diameter of 6, 8, 16 and 20 mm.