Our surfaces can be found in many areas of everyday life. Both manufacturers of electrical and electronic components and suppliers to the automotive industry have long relied on the outstanding soldering and anti-corrosion properties of our tin and nickel platings. This section provides additional information on topics to which we attach particular importance.
For even the strictest soldering requirements: nickel/copper insulated and tin plated wires or strips in a single operation. Tested to DIN, Bosch, Siemens and other works standards, with test specimens and works certificates. Tin plating, e.g. for pinning wires: whisker proof, nickel insulated and fused.
- Coating thickness measurements using the coulometric or X-ray spectrometric method
- Optical evaluation of surfaces under a stereo-microscope
- Wrapping, torsion or bending tests to determine adhesion
- Determination of freedom from pores using the polysulphide method or according to Geoffroy de Lore
- Scale of the diameter using the laser measurement method or a digital micrometer calliper
- Tensile tests to determine strength and elongation
- Optical evaluation of solderability, also after ageing in a oven or steam
Unless you have different requirements, our processing and production methods conform to the following standards in the edition indicated:
|DIN 17753||Wires of wrought nickel and nickel alloys – Properties|
|DIN 46431||Round copper wires for electrical purposes|
|DIN 50960-1||Electroplated and chemical coatings, designation in technical documents|
|DIN 51212||Torsion testing of wires|
|DIN ISO 7802||Wire wrapping test|
|DIN EN ISO 2177||Metallic coatings – Measurement of coating thickness – Coulometric method by anodic dissolution|
|DIN EN ISO 3497||Measurement of coating thickness – X-ray spectrometric methods|
|DIN EN ISO 9001||Quality management systems|
|DIN EN 1412||Copper and copper alloys – European numbering system|
|DIN EN 1977||Copper and copper alloys – Copper drawing stock|
|DIN EN 1403||Electroplated coatings; Method of specifying general requirements|
|DIN EN 10016-3||Non-alloy steel wire rod for conversion to wire – Part 3: Specific requirements for rimmed and rimmed substitute, low-carbon steel wire rod|
|DIN EN 10002-1||Tensile testing – Part 1: Method of test at ambient temperature|
|DIN EN 10204||Metallic products – Types of inspection documents|
|DIN EN 10218-2||Steel wire and wire products – Part 2: Wire dimensions and tolerances|
|DIN EN 10270-1||Steel wire for mechanical springs – Part 1: Patented cold drawn unalloyed spring steel wire|
|DIN EN 12166||Copper and copper alloys – Wires for general purposes|
|DIN EN 13601||Copper and copper alloys – Copper rod, bar and wire for general electrical purposes|
|DIN EN 13602||Copper and copper alloys – Drawn, round copper wire for the manufacture of electrical conductors|
|DIN EN 60264-2-1||Packaging of winding wires – Part 2: Cylindrical barrelled delivery spools – Basic dimensions|
|DIN EN 60068-2-20||Tests – Test methods for solderability and resistance to soldering heat of devices with leads|
|DIN EN 60068-2-20
|See above (change in the solder temperature for severity 2)|
|ASTM No.||Title||Issue date|
|B 298||Silver-coated soft or annealed copper wire||2009-02|
|B 355||Nickel-Coated Soft or Annealed Copper Wire||2009-05|
We also have a wide range of works standards for various companies as well as earlier standards at our disposal.
Maximum flexibility formed the basis for our company’s activities from the outset. Continuous materials in every imaginable design have been processed on our machines over the years. Whereas in the fifties, rings – that is, simple, not fixed wire or strip containers – predominated, spools in a variety of materials and with the most diverse geometries are the most popular packaging design today.
Plastics are the number one choice of material. Most of the spools shipped by us conform to DIN EN 60264. The first number designates the spool flange diameter in millimetres. The second number denotes the spool width. It can also be a good idea to indicate the diameter of the hole. The following is a typical example of a plastic spool designation: K 500/350/127 (spool diameter 500 mm, width 350 mm, mounting hole diameter 127 mm).
The table below shows the usual maximum weights per spool for copper materials:
|K 125/16||0,100-1,000 mm||3 kg|
|K 160/22||0,100-1,500 mm||8 kg|
|K 200/22||0,200-1,500 mm||12 kg|
|K 250/22||0,300-2,500 mm||20 kg|
|K 355/36||0,400-3,000 mm||45 kg|
|K 500/127||0,600-4,000 mm||90 kg|
|K 500/350/127||0,600-4,000 mm||150 kg|
(Other types of spool, e.g. SD300K, film spools or K100 are also possible on request)
High-strength wires, for example made from bronze or steel, should preferably be wound on larger spools, so that they can be straightened more easily later on.
We implement a re-use system for most of our plastic spools. You return your spools to us at our expense and the price originally charged for this is credited to your account. This policy avoids unnecessary waste and is good for the environment.
For larger quantities, we mainly use the metallic steel or aluminium spools familiar from wire drawing, sometimes also known as annealing spools. Despite this, we have never forgotten our roots and we still supply material in the form of rings to this day.
Corrosion protection using nickel
The term “corrosion” stems from the Latin “corrodere”, which means “to gnaw away at”. In the German Industry Standard DIN 50900 “Corrosion of Metals” Part 1, corrosion is described as “the reaction of a metallic material to its environment, which effects measurable change in the material and can lead to impairment of the function of a metal component or of an entire system”.
For example, if iron or steel are subject to certain environmental conditions, the well-known process of “rusting” starts, i.e. the oxidation of iron to ferrous oxide.
There are several protective methods for avoiding this chemical process, which generally come under the heading “corrosion protection”.
One of these methods is galvanic nickel plating, a passive protection method against corrosion which acts cathodically. The nickel layer forms a cover that prevents corrosive active substances such as water or oxygen from coming into contact with the iron. Nickel is not only corrosion-resistant; it is also resistant to heat and ductile with decorative properties.
At ambient temperature, nickel is resistant to air, water, non-oxidizing acids (e.g. hydrochloric acid), lyes, and most organic substances. Yet the metal itself is not completely immune to corrosion, for instance diluted nitric acid can dissolve nickel. Under certain circumstances, however, a nickel oxide passivation layer is formed which further increases the surface resistance.
When tin plating copper wires and strips, nickel is used as a barrier layer (diffusion barrier) to prevent whiskers. This intermediate layer inhibits the formation of intermetallic phases, which cause whisker formation, at the copper-tin interface. A silver barrier could also be used but would be more costly.
- Over the last 25 years, environmentally sound management has become an increasingly important political, economic and, last but not least, technical necessity. State regulations unquestionably contributes to the responsible management of processed resources taking account of the needs of society. In our opinion, however, the main share of this responsibility must be borne within individual companies, in other words by the people who work there. We accept this responsibility because we want to rather than because we have to.
- It is important to find the right balance: on the one hand, a company’s everyday needs should not conflict with basic environmental protection requirements but on the other, an ecological approach should not call manageable technological processes as a whole into question.
From 0.10 to 4.5 mm
Whisker formation is a potential problem when tin plating copper wires. The term “whisker” describes very fine tin mono-crystals with a diameter as small as 1 micron and a length of up to several millimetres, which are spontaneously formed on the surface. Growth of these mono-crystals is diffusion-controlled and can often be extremely slow, i.e. the crystals are formed over a period of a few years. Even relatively small whiskers can cause a short-circuit – a problem that is aggravated by the increasingly small distances between contacts in electrical engineering.
The topic of whisker formation has already been dealt with in several scientific essays. These have shown that bright, matte and fused tin layers exhibit different rates of whisker growth. Furthermore, the formation of these mono-crystals is influenced by the composition of the electrolytes used for plating. The risk of whisker formation is lowest with pure tin layers that are galvanically plated and then fused, still low with matte, galvanically plated layers and highest with bright layers.
In contrast to these findings, the electronic industry requires abrasion-resistant layers with a low tendency to cold welding. In addition, edge loss in fused connectors is not always acceptable due to possible corrosion problems. Especially in recent years, there has been an increasing demand in this area for bright layers, which is probably also attributable to their decorative aspects.
As a result of their high-quality look, bright pure tin layers are becoming more and more important, notably for connectors. The risk of whisker formation is either accepted or the problem is regarded as controllable.
Whiskers develop under the influence of mechanical forces within the layer and should not be confused with surface phenomena, the consequences of electro-migration or the influence of humidity or ionic contamination.
Whiskers can take a variety of forms. They exist in straight, bent or irregular knot shapes. Since the mechanism of whisker formation is now understood, successful countermeasures can be identified and implemented. Whisker growth is based on various proven assumptions and can be described as follows:
- The driving forces for whisker formation are tensions within the tin layer
- Matte surfaces are only very rarely subject to this kind of tension
- The development of tensions is linked to the irregular formation of intermetallic phases at the copper-tin interface. This also includes the interface between tin and copper alloys such as bronze or brass
Based on these principles, several countermeasures can be taken to effectively prevent whisker formation:
Application of dense barrier layers as a diffusion barrier for the brass or bronze base material
- Tempering the material to form an intermetallic (IMC) barrier layer
- Application of very thick tin layers, which reduce the tensions to an acceptable level
Infineon, for instance, recommends applying a silver barrier layer of at least 2 µm, tempering the material at 150 °C for at least one hour after applying the layer or applying a plating layer of matte tin with a minimum thickness of 7.5 µm.
As a rule, whiskers with a maximum length of 50 µm after two years of storage are considered technically acceptable. The general conclusion based on an extensive series of tests is that neither temperature nor relative humidity during storage influence whisker growth.
Matte pure tin layers are the preferred substitute for coating the contact components of connectors, for press-in pins or for the solder connections of components. Matte tin has several advantages compared to bright tin:
- Reduced risk of whisker formation
- More stable contact resistance after ageing
- Better solderability after ageing
- Better optical detection (contour detection)
Larger process window for easier way of coating
Waste Electrical and Electronic Equipment (WEEE)
The abbreviation WEEE stands for Waste Electrical and Electronic Equipment. This directive deals with the recovery, sorting and processing of electrical and electronic products. In Europe, more than 90% of all waste electrical and electronic devices are disposed of at the end of their life. This adds up to more than seven million tons of scrap materials per year. In future, these scrap materials must be separated, sorted and preferably reused to promote the responsible treatment of limited resources. To ensure that these goals are met, the manufacturers of devices sold in the European Union will be held to account by each member state.
Restriction of Hazardous Substances (RoHS)
The RoHS directive (Restriction of Hazardous Substances) of the European Union additionally governs restrictions on the use of hazardous substances. Since 1 July 2006, the use of certain substances has been banned in electrical and electronic devices. Lead (Pb) is one of several substances banned by the RoHS directive.
Despite the fact that the industry often uses the term “lead-free”, compliance with the RoHS directive is not ensured by the replacement of lead alone. However, lead is the most relevant substance for us as far as RoHS is concerned.
- Solder connections of components
- Contact surfaces of connectors
- Screen covers
- Stamped grids, etc.
For us and our customers, changing over to pure tin (bright or matte) has proven to be the optimum choice of surface when it comes to connecting and soldering processes. To effectively prevent whisker formation, we always recommend prior application of a nickel sub-layer (in individual cases also a copper sub-layer, e.g. for bronzes) to the base material and/or reflow on the tin surface.