Brazing of beryllium copper

Most copper and alloys like beryllium copper material is provided with a ready-made easy soldering, and when a high strength is important, but when the high temperature operation can damage element using soldering ensures that stay on the electrically conductive bonding. The most common joining technology for tin-plated copper in electronic applications. Moreover, it is generally limited to components having a thickness of 3 mm or less. Proper surface preparation techniques, material selection, soldering processes and post-weld cleaning are required. To ensure a dense and reliable welded joint. Soldering has no effect on the performance of beryllium copper.
Surface preparation of surfaces such as oil, grease, dust, rust inhibitors, discoloration and oxidation are all important parts of the problem of soldering. Flux does not replace reasonable surface preparation and does not reliably remove all surface stains. Conventional cleaning methods such as organic solvents, vapor degreasing and alkaline cleaners. Ultra-wave agitation promotes these cleaning effects. After using the cleaning solvent, thoroughly wash the surface.
The surface oxide is formed during the heat treatment of beryllium copper. The composition, thickness and appearance of the oxide are affected by heat treatment conditions such as humidity and heat treatment atmosphere. The inert or reducing atmosphere also has a high vacuum to prevent copper oxidation, which is not completely oxygen-free enough to avoid oxide formation.
When black or light red copper oxide is present, it can be easily removed by conventional techniques. Transparent, highly adherent, refractory and bismuth oxide, even with a thickness of only 500 angstroms, can cause soldering difficulties. The oxide formed during the treatment of beryllium copper can be removed by pickling.
Any heating during the manufacturing process of part stamping should be noted as the cause of oxidative contamination. The factory-reinforced beryllium copper product is heat treated by the supplier and cleaned after treatment without harmful oxidizing pollution. Copper alloys are stored for extended periods of time. Or storage under unprotected conditions will lose luster or discoloration, and bright pickling will remove this discoloration.
Beryllium copper parts should be tinned as soon as possible after cleaning. If it is inevitable to be shelved, the parts should be placed in a clean, dry, away from the workshop, soot and sulphide or ammonia vapor.
Tin-bismuth copper and all kinds of common tin- bismuth tin can be tinned, but the most commonly used tin/ lead . The melting temperature ranges from 183 degrees for 63% SN-37% PB9 (63/37) to 327 degrees for lead and 232 degrees for pure tin. As shown in Figure 1. [next]

The lower tin content (5/95 and 10/90) is cheaper, but only tin is guaranteed to work with copper. Therefore, low tin bismuth is required for the splicing time and higher temperature. Large volume electronic workpieces typically use 50/40 and 63/37 tin. Because of its higher tin content, lower melting point, the curing interval is smaller. 63/37 tin provides higher shear strength and compressive strength, better electrical conductivity, thermal conductivity and lower coefficient of thermal expansion. The 63/37 tin with a high tin content means that the heating temperature and time must be controlled to avoid excessive intermetallic formation at the joint.
There is a wide range of tin options for manual soldering. Because this technology does not have much requirements. A versatile 50/50 tin or special alloy can be used, which contains silver or smoke to improve strength and ductility. Tin/lead tin quickly dissolves the silver-plated layer on the surface of the electronic component, and silver-containing tin reduces this tendency.
Solderability of bare beryllium copper for manual or medium speed automatic welding. However, the wetting speed required for large-capacity soldering may require a pre-plating process. Pre-plating is necessary when the cleaning and soldering process intervals are long. The tin composition generally applied to the beryllium copper is 60/40 or pure tin, and the thickness is at least 0.007 mm. The pre-plating can be accomplished by hot dipping or electroplating. Thin electroplated coatings often have voids that require repeated hot blowing to close the pores. This repeated hot blowing ensures a dense metallurgical bond between the cladding and the base metal. It has the same effect as hot dip preplating. A slight discoloration in the plating is followed by no problem with soldering.
Solder pads, solder pastes and solder powder are often used for beryllium copper to reduce assembly and time, avoid waste and improve product quality.
Solder beryllium copper soldering does not present the problem of selecting a particular flux. The classification of fluxes is: corrosive, neutral or non-corrosive. The general rule is to use the softest flux.