DE1957034A1 - Process for the production of tin layers or tin alloy layers on wire made of copper or copper alloys by hot-dip tinning - Google Patents

Description

Process for producing tin layers or tin alloy layers on wire made of copper or copper alloys by hot-dip tinning

The invention relates to a method for producing tin layers or tin alloy layers made of copper or copper alloys with a diameter <0.5 mm by hot-dip tin plating with a uniform over the wire circumference Thickness> 3 / µm where the wire is a tin bath or tin alloy bath runs through and is passed through a profiled air knife.

For perfect solderability of thickly tinned copper jumper wires a minimum layer thickness of 3 / µm tin or tin alloy is required at every point on the wire. There are already different thinning processes for the production of Copper jumper wires are known or suggested at which one pursues the goal, firmly adhering, evenly thick., to create solderable tin layers on copper wires. You can do this both before inserting the copper wire into the Treat the tin bath appropriately as well as after leaving the tin bath.

It is known, for example, from the German Offenlegungsschrift 1 521 for producing a tin layer with an average thickness between 3 and 10 μm on wires made of copper or copper alloys by hot-dip tinning one on a wire with circular Cross-section of the tin layer applied when passing through a wiping nozzle with a polygonal cross-section to one over the circumference of the wire fluctuating, but the same in the sectors -

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medium tin layer thickness to distribute and this immediately then deform with a calibration nozzle with a uniform cross-section to a uniform layer thickness. -

In such a process of hot-dip tin plating under When using a profiled wiper nozzle, a suitably profiled nozzle must be provided for each wire diameter. Such profiled nozzles can be used up to a diameter of the copper wire of 0.5 mm without any particular difficulties produce. For copper wire diameters smaller than 0.5 mm, an increased economic outlay is necessary to produce a correspondingly profiled wiper nozzle. In addition, copper retaining wires with a diameter which is smaller than 0.5 mm, there is an increased risk of tearing off with hot-dip tinning, for example due to fluctuations in tension. This leads to greater downtimes and considerably higher demands on the operating personnel, which must still be cited is that the introduction of the wire, especially in the Abstreifdüse with small wire diameterη more difficult than at larger is.

The task is based on a method of Type mentioned at the beginning, wires with diameters even less than 0.5 mm flawlessly and without the manufacturing defects described to tinplate.

According to the invention, this object is achieved in that after the tinning of the copper wire through at least one stretching stage out and the diameter of the copper wire reduced by drawing will.

With the method according to the invention, hot-dip tinned wires Small diameter, for example, diameters between 0.1 and 0.5 mm can be produced in a simple manner. The wire diameter only increases after hot tinning reduced the desired value. There is therefore no risk of the malfunctions described. In addition, let yourself

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Stripping nozzles with standardized bore diameters, for example Stripping nozzles with diameters of 1 mm, 0.8 mm and Use 0.5 mm. Between these Bohrungsdiameterη lying Let wire diameter and smaller wire diameter get by pulling. The production of the wiping nozzles is thus considerably facilitated and the economy of the tinning process improved.

It is known per se to reduce the diameter of wires by drawing them in stretching stages. With tinned wires this procedure has not yet been used and it is for ™ surprising the average professional that by pulling the surface quality of the tin layer, for example by smearing pitted areas, is improved and a more uniform one Tin layer thickness is obtained, it is also surprising that by drawing, much tighter diameter tolerances can be maintained for copper wires that have already been tinned, in comparison to copper wires obtained using conventional technology, in which the wires are subsequently drawn to their final dimensions be hot-dip tinned using one of the known methods. .

The solderability of the copper wires tinned according to the invention and subsequently drawn can be tested according to the solder ball test. As test conditions, a Lotkugelgewicht of 75 mg are, if 40 is used as SnPb solder and set a test temperature of 235 ⁰ C at 0.5 mm wire diameter. The clamped wire is immersed in the liquid solder bead and the time is measured that elapses until the solder drop has enclosed the entire wire. In the case of wires tinned according to the invention, these soldering times are significantly less than one second, even after aging for several days, for example by tempering, which means excellent solderability. Because of these

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The copper wires tinned according to the invention are good solderability as jumper wires also for soldering with automatic Soldering process, e.g. for wave soldering or dip soldering suitable.

In the following, the method according to the invention is described in more detail by way of example with reference to FIGS.

In Fig. 1, a hot-dip tinning plant is shown schematically. The copper wire 1, which can have a diameter of 1 mm, for example, runs in the direction indicated by arrows Direction from an unwinding device 2. To It first passes through two pulleys in an annealing furnace 3 in a steam atmosphere at 800 to 900 C, in which its Surface is cleaned. The annealed wire 1 then runs into a water bath 4. With a dry brush 5 is after the water bath 4 stripped the water from the surface of the wire 1. To remove surface layers passes through the copper wire 1 an HCl pickle 6 and runs in the tin bath 7 a. The HCl pickle consists of one with hydrochloric acid filled drip cup. The drip container is above wipers, which can be made of felt, for example, arranged. The felt strips of the wiper are removed by means of the drip device soaked in hydrochloric acid.

In the tin bath 7, the wire T is deflected with a deflection roller 8 and leaves the tin bath 7 at least approximately vertically. To avoid contamination of the tin bath 7, e.g. also oxidation To avoid the surface, the tin bath 7 is covered with charcoal 9 at least in the area of the inlet parts of the wire 1. In the area of the exit point of the wire 1 from the Tin bath 7 there is an oil layer 10 on the surface of the tin bath 7.

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The copper retaining wire 1 running out of the tin bath 7 is passed through a wiping nozzle 11 that is above the surface of the tin bath 7 is arranged. The excess tin, which is moved along with the wire 1, is passed through the wiping nozzle 11 stripped and after passing through a cooling section 12, the wire is deflected over rollers 13 and H and fed to a pulling device. In the one in Pig. 1, the pulling device consists of two stretching stages, a drawing die 15a and 15b being arranged in each stretching stage. After passing through the drawing dies, the Copper wire 1 wound onto a roll 16. " H

The diameter of the copper jumper wires is known per se Way downsized when going through the drawing dies. For example, the assumed diameter of 1 mm for the copper wire when passing through the drawing dies 15a and 15b the pig. 1 can be reduced to 0.6 mm. Steel or a hard metal is suitable as the material for the drawing dies.

It should be noted that in Pig. 1 the distance between the wiping nozzle 11 and the surface of the tin bath

10 is preferably chosen so that the wiping nozzle 11 is within the solidification range of the tin or the tin alloy J of the bath 7 is located. Regarding the profiling of the Abstreifdüse ™

11 and its influence on the tin layer thickness of the tinned. Wire, reference is made to the later description of the figures.

In Pig. Figure 2 is another embodiment of the thick tinning line drawn schematlsch. In Fig. 2 is the wiping nozzle 11 arranged so that it is with its outlet nozzle located below the surface of the tin bath 7. The Abgtreifdüse 11 is inserted into a tube 17 with which it.

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is printed under the surface of the tin bath 7. With immersed Stripping nozzle 11 prevents impurities, for example oxidation products, which are attached to the Surface of the tin bath 7, the tin layer of the Contaminate wire 1. This can already be done with a wiping nozzle 11 can be achieved, which deviates from Pig. 2 with her The inlet opening is immersed in the tin bath 7. Beyond that is with the Abstreifdüse 11, the outlet opening located below the surface of the tin bath 7, the hydrodynamic and hydrostatic pressure in the tin bath in the area of Inlet opening of the stripping nozzle 11 influenced in a favorable manner.

The drawing device of FIG. 2 again consists of two stretching stages. In the first Reek stage, the wire runs over two rollers 18 and 19. The diameter of the second roller 19 is larger than the diameter of the first roller 18. The two rollers 18 and 19 rotate, the rotational speed of the second roller 19 can be greater than the rotational speed the first roll 18. By the rolls 18 and 19 are different circumferential forces exerted on the copper wire 1, the TJmfangskraft exerted by the roller 19 greater is than that of the roll 18. As a result of the different Circumferential forces, the copper wire 1 is stretched in a very even manner. After the two rolls is the copper wire; 1 guided in a second Reek stage through a drawing die 15, in which the surface of the tinned copper wire 1 is smoothed and the diameter of the copper wire is further reduced will. After the drawing die 15, the wire 1 is as in Pig. 1 fed to a take-up roll. This take-up reel is in Pig. 16 not shown separately.

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In the embodiments of the Pig. 1 and 2 will be the copper wire 1 is introduced into the drawing machine immediately after tinning and the wire is heated in the tin bath 7 for drawing exploited. Additional heating may be necessary during drawing, for example by Resistance heating can be achieved. There are sliding contacts for this to put on the copper wire 1. These contacts are not shown in FIGS. 1 and 2. If necessary, can however, the drawing device can be separated from the tinning line. The tinned wire can then after complete cooling possibly only inserted into the pulling device, heated and stretched after a long period of storage. The quality the tinned copper wire, stretched to its final size, is not affected by the interruption in production.

As a result of the drawing in the stretching stages of both FIG. 1 and FIG. 2, the thickness of the tin layer increases with the wire diameter scaled down. Since, after completion, the copper wire should have a tin layer that should not fall below 3 / µm and which should not be larger than 10 / um if possible, otherwise the tin consumption will be uneconomical, the tin layer must, which is applied to the copper wire in the thick tinning plant, to the final dimension of the drawn, tinned Be adapted to the wire. This adjustment can be done with the help of the relationship

perform in a simple manner. In this regard, r .. the original wire radius r ^ is the radius of the copper wire after drawing and S ₁ or S2 is the thickness of the tin layer before

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or after pulling. The given relationship can be obtained with simple considerations, which assume that both the Volume of the copper wire as well as the volume of the up. applied tin layer must be the same before and after drawing. The problem with pulling the tinned copper wire is a Even tin layer of a defined thickness on your copper wire can be traced back to the problem of adding a tin layer of a defined thickness when tinning create. This is achieved with the help of the profiled wiper nozzle, where the bore diameter of the nozzle and the profiling of the nozzle to both the radius of the copper wire and to the desired layer thickness must be adapted.

To adjust the layer thickness, it has proven to be particularly advantageous to use a wiping nozzle 11, the bore of which has a corrugated profile. In Pig. 3 shows such a wiping nozzle 11 in section, a copper wire 1 also being shown in section in the bore -.20 of the wiping nozzle 11 and the bore 20 having a corrugated profile. Two concentric circles 21 and 22 with the radii R ₁ and Rp are shown in the figure. The wave train 23 runs between these concentric circles and 22. The wave train 23 has between 3 and 15 »preferably 5 to 8 half waves per millimeter of the circumference of the inner circle 21. In the pig. 3 shows a nozzle for a wire radius r .. of 0.25 mm. A closed wave train with 8 half-waves is provided, this corresponds to about 5 half-waves, based on the length unit. The radii R ₁ and R ₂ and thus the depth (R ₁ - R _? ). of the half-waves of the wave train 23 are adapted to the radius T _{1 of} the wire. The tolerance limits for the wire radius r ₁ and the desired layer thickness for the tinning are decisive for this adaptation. The tolerance limits for the wire diameter T ₁ essentially go into the radius R _{1 of} the inner concentric

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tric circle 16 a. This radius must be chosen to be at least so large that the wave profile does not dig into the wire surface when the wire 1 passes through it. It is beneficial if R-. is between 1 and 20 / µm larger than the upper tolerance limit for the wire radius r ₁ . The layer thickness is essentially determined by the depth R ₁ - Rp of the individual waves and by the distance between the wave maxima and minima, äii. determined by the number of half waves per millimeter of the circumference.

In Pig. 4 shows an enlarged section of the wiping nozzle according to FIG. 3. The Pig. 4 it can be seen that the half-waves 23a which touch the outer concentric circle 22 are preferably at least approximately semicircular. The radius r of the circle 24 inscribed in a half-wave 23a and the chord c, which is formed by the points of intersection of the circle with the inner concentric circle 21, are, in addition to the difference between the diameters R ₁ and Rp of the concentric circles 21 and 22, for the layer thickness decisive. The radius r or the length of the chord c is determined by the number of half waves of the wave train 18. It has been shown that for a layer thickness of approximately 7 μm, the number of half waves per millimeter of the circumference R _{1 of} the circle 21 must be between 3 and 15, the difference R ₁ - Rg between the radii R ₁ and R ^ of concentric circles 21 and 22 can be varied from 10 to about 100 µm. The tin layer adhering to the wire is profiled with a stripping nozzle 11 of such dimensions. The subsequent smoothing is brought about automatically by the surface tension of the profiled tin sheet, with the shape of the profiling achieving a uniform, mean layer thickness of at least approximately constant size over the entire circumference of the wire.

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Starting from this layer thickness, the drawing process can be used to create a thinner wire, which is also made with a uniform tin layer at least approximately constant layer thickness is provided over the entire wire circumference. It it has already been pointed out that drawing the tinned copper wire increases the surface quality is improved by smearing pitted areas in the tin layer and the tin layer thickness is evened out. Man can therefore use thick tinned copper jumper wires with very tight Establish tolerances in terms of wire diameter and layer thickness that are required for some applications are.

With Pig. 5 and 6, two exemplary embodiments for hot-dip tinned copper jumper wires are explained. In Pig- 5a, a hot-dip tinned copper wire 1 is shown enlarged, the radius of which is r... 0.4 mm. The thickness S _{1 of} the tin layer applied is 6.6 μm. Scars 26a and 26b appear in places in the tin layer 25. Pig. 5b shows the hot-dip tinned copper wire from Pig. 5a after drawing on a radius Γρ of 0.3 mm. The thickness Sp of the tin layer is now 5 μm. As a result of the drawing process, the tin layer is free of pits and what is indicated in the drawing, more even than in Pig. 5a before pulling.

Another example of a copper hookup wire with a diameter T ₁ of 0.25 mm prior to drawing is in Pig. 6a shown. A layer of SnPb 40 is applied to the copper retaining wire 1. The layer thickness S ₂ before drawing is approximately 9 μm. In. Pig. 6b shows the wire according to FIG. 6a after it has been drawn. The copper retaining wire 1 was drawn to a radius r ₂ of 0.15 mm. The layer thickness of the SnPb 40 layer according to

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the pulling is again 5 / um. Fig. 6b also shows that the SnPb layer is more uniform in thickness and free of pits. Another feature of the method according to the invention should be added. When the wire passes through the tin bath, the temperature of which is around 250 ^° C., the hardness of the copper wire is reduced. The subsequent pulling increases the hardness again. If a soft switching dickverzinnter copper wire having a diameter * is required C0,5 mm, the cured shift in drawing copper wire must be subjected to heat treatment at temperatures of 200-220 ⁰ C. This softening of the copper wire can also take place in a continuous process with resistance heating. Electric current is supplied to the copper jumper wire via two contact rollers. With the continuous process, the softening can be achieved in much shorter times, since wire temperatures above 220 C can be used. The wire temperature must not be chosen so high that the tin layer is substantially deformed and that diffusion layers can form in the short time that the wire is exposed to the temperature.

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Claims (4)

YPA 69/1285 - 12 - Claims Process for producing tin layers or tin alloy layers on wire made of copper or copper alloys with a diameter <. 0.5 mm by hot-dip tin plating with a thickness that is uniform over the circumference of the wire -y- 3 / um, in which the wire runs through a tin bath or tin alloy bath and is passed through a profiled stripping nozzle, characterized in that after the third tin the copper wire (1) is passed through at least one stretching stage (15 or 18 and 19) and the diameter of the copper wire is reduced by pulling » 2. The method according to claim 1, characterized in that the Copper retaining wire in at least one stretching stage through a Drawing die (15) is performed. 3. The method according to claim 1 or 2, characterized in that the copper wire (1) in at least one stretching stage is guided over two rollers (18 and 19), the first roller (18) exerting a smaller holding force on the copper wire is exercised than by the second role (19). 4. The method according to any one of claims 1 to 3, characterized ~ shows that the copper wire is introduced into the stretching stage immediately after passing through the zirin bath. 10 9 8 71/16 7 ORIGINAL INSPECTED Blank page