Patent Application
20130043066
The invention relates to a pane with an electrical connection element and an economical and environmentally friendly method for its production.
The invention further relates to a pane with an electrical connection element for motor vehicles with electrically conductive structures such as, for instance, heating conductors or antenna conductors. The electrically conductive structures are customarily connected to the on-board electrical system via soldered-on electrical connection elements. Due to different coefficients of thermal expansion of the materials used, mechanical stresses occur during production and operation that strain the panes and can cause breakage of the pane.
Lead-containing solders have high ductility that can compensate the mechanical stresses occurring between an electrical connection element and the pane by plastic deformation. However, because of the End of Life Vehicles Directive 2000/53/EC, lead-containing solders have to be replaced by lead-free solders within the EC. The directive is referred to, in summary, by the acronym ELV (End of Life Vehicles). The objective is to ban extremely problematic components from products resulting from the massive increase in disposable electronics. The substances affected are lead, mercury, cadmium, and chromium. This relates, among other things, to the implementation of lead-free soldering materials in electrical applications on glass and the introduction of corresponding replacement products.
EP 1 942 703 A2 discloses an electrical connection element on panes of motor vehicles, wherein the difference in the coefficient of thermal expansion of a pane and an electrical connection element is <5×10−6/° C. In order to enable adequate mechanical stability and processability, it is proposed to use an excess of solder material. The excess of solder material flows out from the intermediate space between the connection element and the electrically conductive structure. The excess of solder material causes high mechanical stresses in the glass pane. These mechanical stresses ultimately result in breakage of the pane.
The object of the present invention is to provide a pane with an electrical connection element and an economical and environmentally friendly method for its production, whereby critical mechanical stresses in the pane are avoided.
The object of the present invention is accomplished by a pane with a connection element that comprises the following characteristics:
An electrically conductive structure is applied on the pane. An electrical connection element is electrically connected to the electrically conductive structure by a soldering material on portions. The solder material flows out with an outflow width of <1 mm from the intermediate space between the connection element and the electrically conductive structure.
In a preferred embodiment, the maximum outflow width is less than 0.5 mm and, in particular, roughly 0 mm. The maximum outflow width can even be negative, i.e., pulled back into the intermediate space formed by an electrical connection element and an electrically conductive structure, preferably in a concave meniscus.
The maximum outflow width is defined as the distance between the outer edges of the connection element and the point of the solder material crossover, at which the solder material drops below a layer thickness of 50 μm.
The advantage resides in the reduction of mechanical stresses in the pane, in particular, in the critical region present with a large solder material crossover.
The first coefficient of thermal expansion is preferably from 8×10−6/° C. to 9×10−6/° C. The substrate is preferably glass that has, preferably, a coefficient of thermal expansion from 8.3×10−6/° C. to 9×10−6/° C. in a temperature range from 0° C. to 300° C.
The second coefficient of thermal expansion is preferably from 8×10−6/° C. to 9×10−6/° C., particularly preferably from 8.3×10−6/° C. to 9×10−6/° C. in a temperature range from 0° C. to 300° C.
The coefficient of thermal expansion of the connection element can be 5 4×10−6/° C.
The electrically conductive structure according to the invention has, preferably, a layer thickness of 8 μm to 15 μm, particularly preferably of 10 μm to 12 μm. The electrically conductive structure according to the invention contains, preferably, silver, particularly preferably, silver particles and glass frits.
The layer thickness of the solder according to the invention is preferably <7.0×10−4 m, particularly preferably <3.0×10−4 m, and, in particular, <0.5×10−4 m. The solder material according to the invention contains, preferably, tin and bismuth, indium, zinc, copper, silver, or compositions thereof. The proportion of tin in the solder composition according to the invention is from 3 wt.-% to 99.5 wt.-%, preferably from 10 wt.-% to 95.5 wt.-%, particularly preferably from 15 wt.-% to 60 wt.-%. The proportion of bismuth, indium, zinc, copper, silver, or compositions thereof in the solder composition according to the invention is from 0.5 wt.-% to 97 wt.-%, preferably 10 wt.-% to 67 wt.-%, whereby the proportion of tin, bismuth, indium, zinc, copper, or silver can be 0 wt.-%. The solder composition according to the invention can contain nickel, germanium, aluminum, or phosphorus at a proportion of 0 wt.-% to 5 wt.-%. The solder composition according to the invention contains, very particularly preferably, Bi57Sn42Ag1, Bi59Sn40Ag1, In97Ag3, Sn95.5Ag3.8Cu0.7, Bi67In33, Bi33In50Sn17, Sn77.2In20Ag2.8, Sn95Ag4Cu1, Sn99Cu1, Sn96.5Ag3.5, or mixtures thereof. The solder material according to the invention is preferably lead free and contains no lead or only production-related admixtures of lead.
The connection element according to the invention contains preferably at least 50 wt.-% to 75 wt.-% iron, 25 wt.-% to 50 wt.-% nickel, 0 wt.-% to 20 wt.-% cobalt, 0 wt.-% to 1.5 wt.-% magnesium, 0 wt.-% to 1 wt.-% silicon, 0 wt.-% to 1 wt.-% carbon, or 0 wt.-% to 1 wt.-% manganese.
The connection element according to the invention contains preferably chromium, niobium, aluminum, vanadium, tungsten, and titanium at a proportion of 0 wt.-% to 1 wt.-%, molybdenum at a proportion of 0 wt.-% to 5 wt.-%, as well as production-related admixtures.
The connection element according to the invention contains preferably at least 55 wt.-% to 70 wt.-% iron, 30 wt.-% to 45 wt.-% nickel, 0 wt.-% to 5 wt.-% cobalt, 0 wt.-% to 1 wt.-% magnesium, 0 wt.-% to 1 wt.-% silicon, or 0 wt.-% to 1 wt.-% carbon.
The connection element according to the invention further contains preferably at least 50 wt.-% to 60 wt.-% iron, 25 wt.-% to 35 wt.-% nickel, 15 wt.-% to 20 wt.-% cobalt, 0 wt.-% to 0.5 wt.-% silicon, 0 wt.-% to 0.1 wt.-% carbon, or 0 wt.-% to 0.5 wt.-% manganese.
The connection element according to the invention is, particularly preferably, partially coated, with nickel, tin, copper, and/or silver. The connection element according to the invention is, very particularly preferably, coated with 0.1 μm to 0.3 μm nickel and/or 3 μm to 10 μm silver. The connection element can be plated with nickel, tin, copper, and/or silver. Ni and Ag improve the current carrying capacity and corrosion stability of the connection element and the wetting with the solder material.
The connection element according to the invention contains preferably kovar (FeCoNi) and/or invar (FeNi) with a coefficient of thermal expansion of invar of 0.1×10−6PC to 4×10−6PC or a maximum difference of kovar of 5×10−6PC to the coefficient of expansion of the pane.
Kovar is an iron-nickel-cobalt alloy that has a coefficient of thermal expansion of usually roughly 5×10−6PC, which is thus less than the coefficient of typical metals. The composition contains, for example, 54 wt.-% iron, 29 wt.-% nickel, and 17 wt.-% cobalt. In the area of microelectronics and microsystem technology, kovar is, consequently, used as a housing material or as a submount. Submounts lie, according to the sandwich principle, between the actual carrier material and the material with, for the most part, a clearly greater coefficient of expansion. Kovar thus serves as a compensating element which absorbs and reduces the thermo-mechanical stresses caused by the different coefficients of thermal expansion of the other materials. Similarly, kovar is used for metal-glass implementations of electronic components and material transitions in vacuum chambers.
Invar is an iron-nickel alloy with a content of, for example, 36 wt.-% nickel (FeNi36). There is a group of alloys and compounds that have the property of having abnormally small or sometimes negative coefficients of thermal expansion in certain temperature ranges. Fe65Ni35 invar contains 65 wt.-% iron and 35 wt.-% nickel. Up to 1 wt.-% magnesium, silicon, and carbon are usually alloyed to change the mechanical properties. By alloying 5 wt.-% cobalt, the coefficient of thermal expansion a can be further reduced. One name for the alloy is Inovco, FeNi33Cu4.5 with an coefficient of expansion a (20° C. to 100° C.) of 0.55×10−6/° C.
If an alloy such as invar with a very low absolute coefficient of thermal expansion of <4×106/° C. is used, overcompensation of mechanical stresses occurs through noncritical pressure stresses in the glass or through noncritical tensile stresses in the alloy.
The connection element according to the invention contains preferably iron-nickel alloys and/or iron-nickel-cobalt-alloys post-treated thermally by annealing.
Kovar and/or invar can also be welded, crimped, or glued as a compensation plate onto a connection element made, for example, of steel, aluminum, titanium, copper. As a bimetal, favorable expansion behavior of the connection element relative to the glass expansion can be obtained. The compensation plate is preferably hat-shaped.
The electrical connection element contains, on the surface facing the solder material, a coating that contains copper, zinc, tin, silver, gold, or a combination thereof, preferably silver. This prevents a spreading of the solder material out beyond the coating and limits the outflow width.
The electrical connection element is connected over its entire surface to a portion of the electrically conductive structure via a contact surface. Moreover, the contact surface of the connection element has no corners. The contact surface can have an oval, preferably an elliptical, and, in particular, a circular structure. Alternatively, the contact surface can have a convex polygonal shape, preferably a rectangular shape, with rounded corners. The rounded corners have a radius of curvature of r>0.5 mm, preferably of r>1 mm.
The maximum dimensions of the connection elements are, in the plan view, for example, preferably 1 mm to 50 mm long and wide and, particularly preferably 3 mm to 30 mm long and wide and, very particularly preferably 2 mm to 4 mm wide and 12 mm to 24 mm long.
The shape of the electrical connection element can form solder depots in the intermediate space of the connection element and the electrically conductive structure. The solder depots and wetting properties of the solder on the connection element prevent the outflow of the solder material from the intermediate space. Solder depots can be rectangular, rounded, or polygonal in design.
The distribution of the soldering heat and, thus, the distribution of the solder material during the soldering process can be defined by the shape of the connection element. Solder material flows to the warmest point. The introduction of energy during the electrical connecting of an electrical connection and an electrically conductive structure occurs preferably by means of punch soldering, thermode soldering, piston soldering, preferably laser soldering, hot air soldering, induction soldering, resistance soldering, and/or with ultrasound.
The object of the invention is further accomplished through a method for producing a pane with a connection element, wherein
a) solder material is disposed and applied on the connection element as a platelet with a fixed layer thickness, volume, shape, and arrangement,
b) an electrically conductive structure is applied on a substrate,
c) the connection element with the solder material is disposed on the electrically conductive structure, and
d) the connection element is soldered to the electrically conductive structure.
The solder material is preferably applied in advance to the connection elements, preferably as a platelet with a fixed layer thickness, volume, shape, and arrangement on the connection element.
The connection element is welded or crimped to a (partially not shown) sheet, braided wire, mesh. made, for example, of copper and connected to the on-board electrical system (also not shown).
The connection element is preferably used in heated panes or in panes with antennas in buildings, in particular in automobiles, railroads, aircraft, or watercraft. The connection element serves to connect the conducting structures of the pane to electrical systems that are disposed outside the pane. The electrical systems are amplifiers, control units, or voltage sources.
The invention is explained in detail with reference to drawings and exemplary embodiments. They depict:
Fig. E a plan view of another alternative embodiment of the connection element,
The solder material 4 contains 57 wt.-% bismuth, 42 wt.-% tin, and 1 wt.-% silver. The solder material 4 is disposed through a predefined volume and shape completely between the electrical connection element 3 and the electrically conductive structure 2. The solder material 4 has a thickness of 250 μm. An outflow of the solder material 4 from the intermediate space between the electrical connection element 3 and the electrically conductive structure 2, which exceeds a layer thickness t of 50 μm, is observed to a maximum outflow width of b=0.5 mm. The electrical connection element 3 is an alloy that contains 54 wt.-% iron, 29 wt.-% nickel, and 17 wt.-% cobalt. The electrical connection element 3 is designed with an elliptical base surface. The length of the major axis is 12 mm; the length of the minor axis, 5 mm. The material thickness of the connection element 3 is 0.8 mm. No critical mechanical stresses are observed in the pane 1 due to the arrangement of the solder material 4, predefined by the connection element 3 and the electrically conductive structure 2. The connection of the pane 1 to the electrical connection element 3 via the electrically conductive structure 2 is durably stable.
Test specimens were produced with the pane 1 (thickness 3 mm, width 150 cm, and height 80 cm), with the electrically conductive structure 2 in the form of a heating conductor structure, the electrical connection element 3, the silver layer on the contact surfaces of the connection element 3, and the solder material 4. The solder material 4 was applied in advance as a platelet with fixed layer thickness, volume, and shape on the contact surface 11 of the connection element 3. The connection element 3 was applied with the solder material 4 applied on the electrically conductive structure 2. The connection element was soldered onto the electrically conductive structure 2 at a temperature of 200° C. and a processing time of 2 seconds. Outflow of the solder material 4 from the intermediate space between the electrical connection element 3 and the electrically conductive structure 2, which exceeded a layer thickness t of 50 μm, was observed only to a maximum outflow width of b=0.5 mm. The dimensions and compositions of the electrically conductive structure 2, the electrical connection element 3, the silver layer on the contact surfaces of the connection element 3, and the solder material 4 are found in Table 1 and
With all specimens, it was possible to observe, with a temperature difference from +80° C. to −30° C., that no glass substrate 1 broke or showed damage. It was possible to demonstrate that, shortly after soldering, these panes 1 with the soldered connection element 3 were stable against a sudden temperature drop.
In addition, test specimens were executed with a second composition of the electrical connection element 3. The dimensions and compositions of the electrically conductive structure 2, the electrical connection element 3, the silver layer on the contact surfaces of the connection element 3, and the solder material 4 detailed values are found in Table 2. Here as well, it was possible to observe that, with a temperature difference from +80° C. to −30° C., no glass substrate 1 broke or had damage. It was possible to demonstrate that, shortly after soldering, these panes 1 with the soldered connection element 3 were stable against a sudden temperature drop.
The comparative example 1 was carried out the same as the example with the following differences: The dimensions and components of the electrically conductive structure 2, the electrical connection element 3, the metal layer on the contact surfaces of the connection element 3, and the solder material 4 are found in Table 3. The solder material 4 was, in accordance with the prior art, not applied in advance as a platelet on the contact surface of the connection element 3. The connection element 3 was soldered to the electrically conductive structure 2 in accordance with the conventional method. With the outflow of the solder material 4 from the intermediate space between the electrical connection element 3 and the electrically conductive structure 2, which exceeded a layer thickness t of 50 μm, an average outflow width b=2 mm to 3 mm was obtained.
With a sudden temperature difference from +80° C. to −30° C., it was observed that the glass substrates 1 had major damage shortly after soldering.
The comparative example 2 was carried out the same as the example with the following differences. The dimensions and components of the electrically conductive structure 2, the electrical connection element 3, the metal layer on the contact surfaces of the connection element 3, and the solder material 4 are found in Table 4. The solder material 4 was, in accordance with the prior art, not applied in advance as a platelet on the contact surface of the connection element 3. The connection element 3 was soldered to the electrically conductive structure 2 in accordance with the conventional method. With the outflow of the solder material 4 from the intermediate space between the electrical connection element 3 and the electrically conductive structure 2, which exceeded a layer thickness t of 50 μm, an average outflow width b=1 mm to 1.5 mm was obtained.
With a sudden temperature difference from +80° C. to −30° C., it was observed that the glass substrates 1 had major damage shortly after soldering.
Usually, higher tensile stresses in the glass result in an increased risk of flaking or shell defects in the glass. Consequently, the influence of the contact surface 11 between the connection element 3 and the portion 12 of the electrically conductive structure 2 was investigated by computer simulations. The tensile stresses during the cooling of panes with connection elements of different geometries were calculated. The various connection elements were bridge-shaped (B) and circular (K).
A kovar alloy with a coefficient of thermal expansion a of 5.2×10−6/° C. and an invar alloy with 1.7×10−6/° C. were assumed as material for the connection elements. The material thickness of the connection elements was, in each case, 0.8 mm. In each case, a glass pane with a material thickness of 2 mm was assumed as the substrate. The material thickness of the solder layer 4 was, in each case, 10 μm.
In the computer simulation, the tensile stresses in the glass pane were calculated with cooling from +20° C. to −40° C. The maximum tensile stresses calculated are listed in Table 5.
The maximum tensile stresses depended strongly on the shape of the connection element. As a result, the maximum tensile stresses in the glass pane with circular connection elements (K) made of kovar or invar were, in each case, 46% less than with bridge-shaped connection elements (B) made of kovar or invar, cf. Table 5.
It was demonstrated that panes according to the invention with glass substrates 1 and electrical connection elements 3 according to the invention have better stability against sudden temperature differences.
This result was unexpected and surprising for the person skilled in the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10169372.9 | Jul 2010 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2011/061195 | 7/4/2011 | WO | 00 | 10/30/2012 |
