Relevance

Modern society pays great attention to issues related to the preservation and protection of the environment. In particular, soldering technology without lead has become widespread. Lead is a material that causes serious harm to humans, but at the same time, abandoning its use in electronics would be premature. Solders that do not contain lead have a high melting point, which makes the soldering process more difficult and less manageable. For example, after switching to lead-free soldering, pure tin was used to cover the contact pads of boards. But when using it, a number of new problems arose due to properties of this material that impairs operability and reliability of equipment under severe conditions. These are, first of all, thread growths of tin and the ability to "get sick" in the cold ("tin plague").

Pure tin plating.

Contact coatings treated with pure tin are used for reliable bonding and corrosion protection of metal. The transition to lead-free soldering technology has led most manufacturers to start using pure tin for plating contact surfaces. However, the introduction of pure tin and the steadily increasing requirements for microminiaturization of parts has led to new negative qualities of this metal, the so called "tin plague" and "tin whiskers", known for a long time.

Tin whiskers.

The formation of "whiskers" is a characteristic phenomenon not only for this metal, cadmium and zinc are also prone to it. Tin mustaches are thin threads growing vertically, spirally, or as fork-shaped or hook-shaped crystals. These whiskers can be up to 150 µm long and cause a serious hazard by shorting out adjacent elements in the conductive pattern on the circuit board. The whiskers, when broken off or bent during manufacture or use, may well form a jumper-conductor between the conducting elements. At higher currents, whiskers may well melt and cause equipment failures.

Tin plague.

This phenomenon is quite rare in the electronics industry. It is possible when pure tin is used, which at low temperatures changes from α-phase white tin to β-phase, a gray amorphous substance. Products soldered with tin simply fall apart. The reason is the increase in the volume of the metal in the cold. Alloys of lead and other metals inhibit this transformation, which once started, has the property of contact creep. The highest rate of spreading of the "plague" is at t° -33 ° C. When bismuth is added to the alloy, plague can be prevented, because the atoms of this element in the crystal lattice of pure tin prevent rearrangement, and the alloy does not turn into a powder even at very low temperatures. The alloying of tin with cobalt, antimony, and other metals also became a good remedy. At the same time it was found that zinc and aluminum, on the contrary, contribute to the spread of plague.

Buy, price

Evek GmbH sells non-ferrous metals at the best price. It is formed taking into account the LME (London metal exchange) rates and depends on the technological features of production without additional costs. We supply semi-finished products of tin and its alloys, tin solders in a wide range. All product batches have quality certificate for compliance with standards requirements. With us you can buy in bulk the most various products for large-scale productions. The wide choice, exhaustive consulting of our managers, reasonable prices and timely delivery determine the face of our company. There is a system of discounts for wholesale purchases.