Production of copper strips for surface modification for laser bonding

Abstract

The invention relates to a method for producing a wire, the method having at least the following steps: (i) providing a wire precursor; (ii) pressing recesses on the wire precursor and optionally reshaping the wire precursor in the process, and (iii) annealing the wire precursor provided with recesses to form the wire; wherein the wire has a copper content of at least 95 wt.-%, based on the total weight of the wire. The invention additionally relates to a wire obtainable according to the above-mentioned method, and to the use of a roll to produce the wire and / or to set the roughness at at least one location of the wire.

Description

[0001] This invention relates to a method for producing wire, the method comprising at least the following steps: (i) providing a wire precursor; (ii) pressing recesses onto the wire precursor and optionally reshaping the wire precursor during the process; and (iii) annealing the wire precursor with the recesses to form a wire; wherein the wire has a copper content of at least 95% by weight, based on the total weight of the wire. The invention also relates to a wire obtainable by the above method, and to the use of rollers for producing the wire and / or for setting a roughness at at least one location on the wire. Background Technology

[0002] Bonding wires are used in the manufacture of semiconductor components to electrically connect integrated circuits and printed circuit boards during the manufacturing process. Additionally, bonding wires are used in power electronic devices to electrically connect transistors, diodes, and other components to contact surfaces (also known as pads or leads) of the housing. Although bonding wires were previously made of gold, more cost-effective materials such as copper are now used. Copper wires have excellent electrical and thermal conductivity. However, copper wires are susceptible to oxidation.

[0003] Regarding wire geometry, bonding wires with circular cross-sections and so-called strips with more or less rectangular cross-sections are the most common. Both types of wire geometry have their advantages, making them suitable for specific applications. Therefore, both types of geometry have their market share. For a given cross-sectional area, strips have a larger contact surface because they can be laid flat on components. However, the flexibility of strips is limited. Furthermore, the orientation of the strip must be considered during bonding to achieve adequate electrical contact between the strip and the component it will be connected to. Bonding wires are more flexible. However, bonding involves welding and / or greater deformation of the wire during the bonding process, which can mean damage or even destruction of the underlying electrical structure of the bonding pads and the components connected to them.

[0004] Laser bonding is of particular interest. This is a method that uses a laser beam to transfer the energy required for bonding to the bonding wire. In this case, a metal ribbon is used instead of a wire because the ribbon provides a larger surface area for coupling in the laser. The advantage of bonding ribbons is that they can be easily brought into place and held there compared to round wires. This significantly increases the reliability of the bond. The larger connections in ribbon bonding mean that higher currents can be conducted through such connections. However, there is a continuous need for further improvements to the technology, both in terms of the bonding wire itself and the bonding process.

[0005] It is known that roughened surfaces exhibit greater electromagnetic radiation absorption due to their increased surface area. Therefore, the increased surface area of ​​the bonding wire should also enable greater absorption of laser radiation during laser bonding. Surface roughening can be achieved through mechanical or chemical methods, such as brushing or etching. However, these methods often result in residues on the wire surface that can negatively impact the bonding connection. In the case of mechanical methods, these residues can be abrasion products from the brush and particles removed from the wire material, which can re-accumulate at other locations on the wire during the brushing process. During bonding, these residues can lead to incomplete melting of the wire, resulting in less reliable bonding connections. Furthermore, overlap of wire material may occur in the aforementioned alternative methods. During laser bonding, this overlap can cause wire material splashing due to intense heating and the sudden expansion of the surrounding air volume. Wire material splashing can lead to unreliable bonding results due to material loss and can also cause harmful contamination of other electronic components. Furthermore, chemical methods have the following drawbacks: the dimensions of the recesses are more difficult to configure in terms of depth and positioning. For example, single-sided etching of strips can only be accomplished using complex masking steps. Additionally, introducing patterns into the recesses can only be achieved by increasing the applied force.

[0006] Purpose of the invention

[0007] The object of this invention is to overcome, at least in part, one or more of the disadvantages caused by the prior art.

[0008] Specifically, the object of the present invention is to describe in detail a method by which wire surfaces optimized for laser bonding methods can be produced.

[0009] Another object of the present invention is to describe in detail a method by which a wire can be produced, wherein at least one surface of the wire has a defined roughness.

[0010] Another object of the present invention is to describe in detail a wire having a roughness free of impurities, residues and cavities.

[0011] Another object of the present invention is a method for producing wires in which the surface of the wire absorbs as much of the incident laser radiation as possible during laser bonding.

[0012] Another object of the present invention is a method for producing wires, wherein the wires are heated more strongly under the same intensity of incident laser compared to other bonded wires.

[0013] Another object of the present invention is a method for producing materials in which no impurities or residues are formed during laser bonding.

[0014] Another objective is to simplify the manufacturing process for producing the bonding wires according to the invention, for example, by reducing the number of required steps. Therefore, in addition to the technical advantages of the method according to the invention, cost and time savings can be achieved in the production of the wires according to the invention.

[0015] For so-called laser bonding, it is known to use bonding wires with roughened surfaces on the side facing away from the electrical contact surface. In this case, it is observed that under the same emitted laser radiation, more energy is transferred to the bonding wire compared to the case of smooth bonding wire. Without being bound by theory, it is assumed that due to the roughened side, the incident laser radiation is absorbed by the bonding wire to a greater extent or less laser radiation is reflected. However, further improvements are still needed to further increase the quality and reliability of the bonding connections.

[0016] It has been found that the quality of bonded connections relative to impurities / yield can be improved by roughening the bonding wire, rather than by removing material (i.e. by brushing or milling), by introducing recesses (e.g., by embossing).

[0017] Preferred embodiments of the present invention

[0018] The independent claim enables at least partially satisfying at least one of the foregoing objectives. The dependent claims provide preferred embodiments that enable at least partially satisfying at least one of these objectives.

[0019] |1|A method for producing materials, the method comprising at least the following steps:

[0020] (i) Provide wire precursors;

[0021] (ii) pressing a recessed portion onto the wire front body; and

[0022] (iii) Anneal the wire precursor with the recessed portion to obtain the wire;

[0023] The wire has a copper content of at least 95% by weight, based on the total weight of the wire.

[0024] |2|The method according to implementation scheme|1|, wherein the pressing is selected from the group consisting of: stamping marks, notches, embossing, stamping, grooves and slots or a combination of two or more of them.

[0025] |3|The method according to any one of the foregoing embodiments, wherein the pressing is performed by a roller, preferably by an embossing roller.

[0026] |4|The method according to embodiment|3|, wherein rolling is performed by at least one roll having a cylindrical surface including ridges, wherein the ridges are formed by a height difference (D) of the cylindrical surface.

[0027] |5|The method described in implementation scheme|4|, wherein the height difference (D) is in the range of 3 μm to 9 μm.

[0028] |6|The method according to any one of the foregoing embodiments, wherein the recess on the wire is pressed by the method to form a pattern.

[0029] |7|The method according to any one of the foregoing embodiments, wherein the method presses the recess only at a first position of the wire, and the wire used includes multiple positions.

[0030] |8|The method according to any one of the foregoing embodiments, wherein the wire has a roughness R in the range of 3 μm to 9 μm at at least one location. z .

[0031] |9|The method according to embodiment 7, wherein at least one other position of the wire is smooth, wherein the at least one other position is located on the wire away from the first position.

[0032] |10|The method according to any one of the foregoing embodiments, wherein the wire is a bonding wire, preferably a strip.

[0033] |11| The method according to any one of the foregoing embodiments, wherein the element selected from the group consisting of the wire and the wire precursor has a diameter of 25,000 μm. 2 Up to 900,000 μm 2 Cross-sectional area Q within the range A The cross-sectional area Q A The component is arranged perpendicular to its longitudinal direction (L).

[0034] |12| The method according to any one of the foregoing embodiments, wherein the cross-sectional plane Q E The elements are laid through the group consisting of the selected wire precursor and the wire.

[0035] Wherein the cross-sectional plane Q E Arranged perpendicular to the longitudinal direction L of the component.

[0036] Wherein the cross-sectional plane Q E This element forms a cross-sectional area Q A ,

[0037] Where the cross-sectional area Q AIt includes two perpendicularly intersecting lines, L1 and L2.

[0038] Among them, the shortest possible segment A of line L1 L1 By Q A The intersection of the edges defines the boundary, and

[0039] The longest possible segment A of line L2 is... L2 By Q A The intersection of the edges defines the boundary.

[0040] Where A L2 and A L1 The quotient is 2 or a larger number.

[0041] |13| A wire that can be obtained by means of at least one of the methods described in embodiments |1| to |12|.

[0042] |14| An apparatus comprising at least:

[0043] (1) First contact surface;

[0044] (2) The wire according to at least one of the embodiments |13| or the wire that can be obtained by the method according to any one of the embodiments |1| to |12|;

[0045] The wire is electrically connected to the first contact surface.

[0046] |15| A roller with raised grooves is used for producing wire, wherein the raised grooves are characterized by a height difference (D) in the range of 3 μm to 9 μm, wherein a recess is introduced at at least one location on the wire by means of the roller.

[0047] |16| A roller including a textured surface is used to reduce the roughness R at at least one location on the wire. z Applications are defined in the range of 3μm to 9μm, wherein the ridge is characterized by a height difference (D).

[0048] |17| A method for producing an apparatus including at least one conductive connection, wherein the method includes the following steps:

[0049] (I) Provide a substrate having at least a first contact surface and a wire;

[0050] (II) Position the wire to be mechanically connected to the first contact surface;

[0051] (III) The first position of the wire is heated by electromagnetic radiation with a wavelength range of 700 nm to 1,100 nm.

[0052] To obtain a conductive connection between the first contact surface of the substrate and the wire.

[0053] The first location of the wire has a roughness R in the range of 3μm to 9μm. z For example, 4μm to 8μm, or 5μm to 7μm, or 4μm to 9μm, or 5μm to 9μm.

[0054] The wire at another location (facing the contact surface) away from the first location has a roughness R in the range of 0.1 μm to 1 μm. z ,

[0055] The roughness R at at least the first location of the wire z It is produced by pressing, wherein the pressing is selected from the group consisting of: stamping marks, serrations, embossing, stamping, grooves and slotting, or a combination of two or more of them.

[0056] |18|The method according to embodiment |17|, wherein the wire is preferably obtainable by any one of embodiments |1| to |12|.

[0057] |19|The method described in implementation scheme|17|, wherein a laser beam is selected as electromagnetic radiation.

[0058] |20|The method according to any one of embodiments|17| to|19|, wherein the wire is a strip. Then, the first position and the other position of the wire are each part of the first side or the other side of the strip, or the first side or the other side of the strip as a whole.

[0059] |21|The method according to any one of the embodiments|17| to|20|, wherein the first position of the wire or the first side of the wire is arranged on the side of the wire facing away from the first contact surface of the substrate.

[0060] |22|The method according to any one of embodiments|17| to|21|, wherein the roughness R of the wire at at least the first location z Produced by rolling (e.g., embossing rolling).

[0061] |23|According to the method of embodiment|22|, for rolling, a textured roller is used to produce wire, wherein the texture is characterized by a height difference (D) in the range of 3 μm to 9 μm, wherein the recess is introduced by the roller at at least one location on the wire.

[0062] General

[0063] In this specification, the range specification also includes values ​​designated as limits. The indication "within the range of X to Y" relative to the type of variable A means that A can assume values ​​of X, Y, and values ​​between X and Y. Therefore, the range "up to Y" defined on one side of the type of variable A correspondingly means Y and values ​​less than Y. Detailed Implementation

[0064] The first subject of this invention relates to a method for producing materials, the method comprising at least the following steps:

[0065] (i) Provide wire precursors;

[0066] (ii) pressing a recessed portion onto the wire front body; and

[0067] (iii) Anneal the wire precursor with the recessed portion to obtain the wire;

[0068] The wire has a copper content of at least 95% by weight, which is based on the total weight of the wire.

[0069] In principle, wire precursors are considered to be all wires and raw wires known to those skilled in the art and deemed suitable for bonding in microelectronic and power electronic devices. Like the resulting wire, the wire precursor is typically a single object. Many forms are known and suitable. Preferred forms are those with circular, elliptical, and rectangular cross-sections. Wires for bonding with approximately rectangular cross-sections are also referred to as ribbon wires.

[0070] According to the present invention, the wire comprises at least 95% by weight of copper, preferably at least 99.95% by weight, or at least 99.9% by weight, or at least 99.99% by weight of copper, wherein the weight percentage is based on the total weight of the wire.

[0071] Therefore, the wire contains up to 5% by weight, for example 4% by weight or 3% by weight, of additional components. In this case, the additional components are considered to be all elements familiar to those skilled in the art and seemingly suitable, particularly metals that can be alloyed with copper, and metals, quasi-metals and non-metals that can form intermetallic phases with copper. Preferably, the following metals are considered as additional components: tin (Sn), iron (Fe), and nickel (Ni). Preferably, the following quasi-metal is considered as an additional component: Si. Preferably, the following non-metal is considered as an additional component: phosphorus (P). Combinations of two or more metals, quasi-metals and non-metals within a class (metal, quasi-metal, non-metal) and components from different classes can also be used. In addition to the targeted addition of additional components, the wire may also contain impurities.

[0072] The wire precursor typically has the same copper content as the wire formed from the wire precursor by the method according to the invention.

[0073] In a preferred embodiment, the wire precursor is a flat strip. It can then be longitudinally cut into multiple strip wires after step (ii) or after step (iii). According to another preferred embodiment, the wire produced according to the invention is a strip.

[0074] In principle, the specification in step (i) can be made in a manner known and seemingly suitable to any person skilled in the art. Preferably, the specification is the alignment of the wire precursor in the apparatus.

[0075] In step (ii), a recess is pressed into the wire precursor. The wire precursor may be reshaped simultaneously or subsequently. Reshaping is preferably performed simultaneously with pressing the recess.

[0076] The term "pressing" is understood to refer to a process on the wire that is essentially performed without material removal. This differs from grinding, in which material removal is caused by the grinding process itself. Examples of grinding include brushing and polishing. Therefore, wire that has been ground is lighter than before the process.

[0077] In principle, pressing can be performed in any manner known and seemingly suitable to any person skilled in the art. Preferably, pressing is performed by means selected from the group consisting of: punching marks, scoring, embossing, stamping, grooves, and slotting. Pressing is particularly preferred by embossing.

[0078] According to another preferred embodiment, pressing is performed by rolling. Rolling is understood to mean a processing method in which material (in this case, a wire precursor) is processed between two or more rotating tools. According to the invention, the embossing is transferred into the wire precursor by rolling. Preferably, the wire precursor is simultaneously reshaped during rolling. In this case, a strip wire can be obtained. Rolling can be performed as either hot rolling or cold rolling. Rolling is preferably performed as cold rolling. Particularly preferably, pressing is performed by embossing rolls. This means that reshaping and embossing are carried out simultaneously in one step.

[0079] According to another preferred embodiment, rolling is performed using at least one roll. The roll typically has a cylindrical surface, wherein other geometries of the roll are also known to those skilled in the art and may appear suitable. According to another preferred embodiment, the roll is equipped with ridges, wherein the ridges are formed by a height difference of the cylindrical surface. According to another preferred embodiment, the ridges have a pattern.

[0080] According to another preferred embodiment, the height difference (D) of the ridges on the roller is in the range of 3 μm to 9 μm, for example 4 μm to 8 μm, or 5 μm to 7 μm, or 4 μm to 9 μm, or 5 μm to 9 μm.

[0081] According to another preferred embodiment, the recesses are patterned. In the context of this invention, a pattern refers to a repeating image or a repeating design. The pattern formed by the embossing on the roller corresponds to the pattern of the recesses on the wire processed by rolling.

[0082] According to another preferred embodiment, the wire has multiple locations, wherein a recess is introduced only at a first location. The wire, particularly when it is a strip wire, preferably has multiple sides, wherein a recess is introduced only on a first side.

[0083] According to another preferred embodiment, the wire has a roughness R in the range of 3 μm to 9 μm, for example 4 μm to 8 μm, or 5 μm to 7 μm, or 4 μm to 9 μm, or 5 μm to 9 μm at at least one location. z When it is a strip wire, the wire preferably has a roughness R on the first side in the range of 3μm to 9μm, for example 4μm to 8μm, or 5μm to 7μm, or 4μm to 9μm, or 5μm to 9μm. z Roughness is determined according to DIN EN ISO 4287 (2010-07) and DIN EN ISO 4288 (1998-04).

[0084] According to another preferred embodiment, at least one other position of the wire is smooth, wherein the at least one other position is located at a position of the wire away from the first point of the wire.

[0085] In the context of this invention, smoothness is understood to mean a location or plane or a portion thereof, if it has a roughness R. z Within the range of 0.1 μm to 1 μm, for example 0.2 μm to 0.6 μm, or 0.2 μm to 0.4 μm.

[0086] If the wire is a strip, a portion or all of the first side, rather than the first position and another position of the strip, may have the characteristics described herein, and a portion or all of the other side, rather than another position, of the other side of the strip may have the characteristics described herein.

[0087] According to another preferred embodiment, in the case of a strip, at least one other side of the wire is smooth, wherein the at least one other side is located on the side of the wire opposite to the first side of the wire.

[0088] According to another preferred embodiment, the element selected from the group consisting of wire and wire precursor has a diameter of 25,000 μm. 2 Up to 900,000 μm 2The cross-sectional area QA is defined as the area within which the cross-sectional area QA is arranged perpendicular to the longitudinal direction L of the element. If the cross-sectional area of ​​the element is not the same at all locations, the cross-sectional area QA is calculated as the arithmetic mean of several measurements of the cross-sectional area at at least seven different locations of the element.

[0089] According to another preferred embodiment, the element selected from the group consisting of the wire precursor and the wire has a cross-sectional plane QE laid through the element, wherein the cross-sectional plane QE is arranged perpendicular to the longitudinal direction L of the element, wherein the cross-sectional plane QE forms a cross-sectional area QA with the element, wherein the cross-sectional area QA includes two perpendicularly intersecting lines L1 and L2, wherein the shortest possible segment A of line L1 is... L1 Bounded by the intersection with the edge of QA, and the longest possible segment A of its midline L2. L2 Bounded by the intersection with the edge of QA, where A L2 and A L1 The quotient is a number of 2 or greater, for example, in the range of 2 to 30, or 5 to 20, or 5 to 10. Figure 1 and Figure 2 The diagram shows the determination of the cross-sectional plane QE and other features mentioned in this paragraph. If the geometry of the element (whose cross-sectional plane QE and other features are to be determined) differs from... Figure 1 and Figure 2 The shapes shown are schematic, and those skilled in the art will identify and select the closest shape to the shown figure, taking into account different geometries. Wire precursors are likely to have different geometries, for example, A L2 and A L1 The quotient is 1. In this case, the wire precursor is round. It is then reshaped using this method so that the wire has a quotient of 2 or greater than the above.

[0090] If the wire is in strip form, after embossing, it can optionally be divided into multiple strips using a suitable cutting process, such that the longest possible segment A of the strip is... L2 Shortened while maintaining the shortest possible segment A L1 The cutting process can optionally be performed before or after the strip is annealed.

[0091] The pressing is performed using so-called tools. Suitable tools are, in principle, all devices known to those skilled in the art and appearing suitable.

[0092] The preferred tool is a roller. A roller is generally understood to mean a generally cylindrical body. Rollers can, in principle, have any diameter. Preferably, rollers with a diameter of 50mm-150mm are suitable for the intended purpose. Furthermore, the roller should be formed of a material that is harder than the object to be reshaped under operating conditions. Rollers are typically made of forged steel, cemented carbide, or cast steel.

[0093] In a preferred embodiment, the tool is designed to include an arrangement of at least one roller. Arrangements with multiple rollers (e.g., two or more rollers) are also possible. For example, an arrangement in which at least two rollers rotate in opposite directions and the object to be reshaped is guided between the two counter-rotating rollers is suitable. The two counter-rotating rollers are arranged such that a distance is provided between the two rollers. This distance is preferably equal to the thickness of the wire to be reshaped.

[0094] In this configuration, at least one first roller has raised patterns on its surface. In one embodiment, the height difference of the raised patterns on the first roller can form a pattern. As the object to be formed passes through, the raised patterns (also in the form of a pattern) are introduced into the object using a tool. In this case, the depth of the recess introduced into the wire depends on the penetration depth of the raised patterns on the first roller into the object. It is highly likely that the height difference (D) of the raised patterns is greater than the recess introduced into the object. Regarding the recess in the reshaped object, the height difference (D) introduced by the transferred raised patterns is referred to as the roughness R. Z This may also be referred to as embossing depth. The re-forming of an object using rollers is also known as “embossing rolling”, in which at least the first roller has embossing that is transferred onto the object during re-forming. The (first) roller is accordingly referred to as the “embossing roller”.

[0095] In another embodiment, pressing is performed by embossing. The die is a surface with raised textures. The textures have a height difference (D). Suitable materials for the die are, in principle, all materials known to those skilled in the art and seemingly suitable, but particularly the same materials used for the roller. During embossing, the die is lowered onto the object to be processed. In this case, the textures are pressed into the object until the desired depth of the recess is formed. This typically corresponds to the height difference (D) of the textures, but sometimes the depth of the recess is less than the height difference (D) of the textures. Regarding the recesses in the reshaped object, the height difference (D) introduced by the transferred pattern is referred to as the roughness R. Z This is also known as the molding depth. Typically, during the pressing of an object onto the side of the object away from the mold, another tool or plate is provided, specifically to prevent the object to be reshaped from avoiding the mold, for example, by twisting. Instead, the object to be reshaped is held in place relative to the molding direction by another tool.

[0096] In step (iii), the wire precursor with the recessed portion is annealed to form a wire. Annealing is performed at a temperature below the melting point of copper, preferably in the range of 500°C to 900°C, for example, 550°C to 650°C or 750°C to 850°C. G The annealing process is carried out at the following temperature: T. GThis is the temperature the workpiece (in this case, wire) has for a specified time. Annealing the wire takes approximately 10 seconds to 6 minutes.

[0097] Annealing can be performed discontinuously or continuously. Preferably, annealing is performed continuously. A continuous heating furnace is suitable for this purpose. In this case, the intake path in the continuous heating furnace and the temperature T of the continuous heating furnace are selected. O This ensures that the wire passing through the throughput path within the specified time has a temperature T. G In all cases, such as the furnace temperature T of a continuous heating furnace O It can be higher than the annealing temperature T G The throughput path of a continuous heating furnace can also be longer and have temperature gradients at the inlet and outlet. Continuous heating furnaces with multi-zone heaters can also be used. Therefore, certain temperature distributions can be applied to the wire passing through.

[0098] A continuous heating furnace can be heated and maintained at that temperature in a conventional manner by a heating device located within the furnace wall or acting externally on the furnace wall. Electric heating is suitable for this purpose. In another embodiment, the annealing temperature T in the continuous heating furnace... G It can be generated by plasma. Nitrogen plasma can be used for this purpose, for example at a typical power of 750 W and a process gas pressure (N2) of 25 mbar.

[0099] Annealing of the wire is preferably carried out in an atmosphere, such as nitrogen (N2). This is also known as a protective gas atmosphere. In this case, the presence of oxygen (O2) is minimized to avoid surface oxidation of the wire.

[0100] In another embodiment of the invention, the atmosphere has a hydrogen (H2) content of up to 10% by volume, for example, in the range of 2% to 8% by volume, or about 5% by volume. Hydrogen has a reducing effect in the protective gas atmosphere. This has the effect that copper, which may be oxidized on the surface of the wire to form copper oxide (CuO or Cu2O), is reduced to elemental copper.

[0101] The second subject of the invention is a wire that can be obtained by means of a method according to the first subject of the invention or an embodiment of the embodiments described herein or a combination of multiple embodiments described herein.

[0102] The preferred third theme, which can be obtained by means of the method according to the first theme or as an embodiment of the second theme, is a wire characterized by at least the following features:

[0103] (a) In the case of the first side of the strip, the first position of the wire has a roughness R of 3 μm to 9 μm, for example 4 μm to 8 μm, or 5 μm to 7 μm, or 4 μm to 9 μm, or 5 μm to 9 μm. z;

[0104] (b) The quotient of AL2 and AL1 is 2 or greater, as determined according to the method described in conjunction with the first subject of the present invention;

[0105] (c) A copper content of at least 95% by weight, based on the total weight of the wire (2).

[0106] Preferably, the wire is characterized by at least one of the following additional features:

[0107] (d) At least one other location of the wire is smooth; in the case of a strip, at least one other side of the strip is smooth;

[0108] (e) The wire has a diameter of 25,000 μm. 2 Up to 900,000 μm 2 The cross-sectional area QA within the range.

[0109] More preferably, the wire has features (a) to (c), and at least one of additional features (d) or (e), more preferably two features.

[0110] The fourth topic is a method for producing an apparatus including at least one conductive connection, wherein the method includes the following steps:

[0111] (I) Provide a substrate having at least a first contact surface and a wire;

[0112] (II) Position the wire to be mechanically connected to the first contact surface;

[0113] (III) The first position of the wire is heated by electromagnetic radiation with a wavelength range of 700 nm to 1,100 nm.

[0114] To achieve a conductive connection between the first contact surface and the wire.

[0115] The first location of the wire has a roughness R in the range of 3μm to 9μm, for example, 4μm to 8μm, or 5μm to 7μm, or 4μm to 9μm, or 5μm to 9μm. z ,

[0116] The wire at another location (facing the contact surface) away from the first location has a roughness R in the range of 0.1 μm to 1 μm. z .

[0117] Preferably, a laser beam is selected as the electromagnetic radiation. A laser beam is an electromagnetic wave, typically with a very narrow frequency range and high radiation intensity. Laser beams with wavelengths in the range of 700 nm to 1,100 nm are particularly preferred. For example, as in step (III), a 400 W fiber laser with a focusing diameter of 25 μm is used to heat the wire.

[0118] In another preferred embodiment, the wire is a strip. The first position and the other position of the strip are respective portions of a first side or another side, or the first side or another side as a whole.

[0119] According to another preferred embodiment, the wire mentioned in the fourth subject matter can be produced by the method described in the first subject matter of the invention or is a wire according to the second or third subject matter of the invention. Preferred embodiments of the first, second, and third subject matters of the invention relating to wire are also preferred in the fourth subject matter relating to wire.

[0120] In this context, a conductive connection is understood to mean a contact between two conductive elements, such as a wire having a contact surface (e.g., the contact surface of a power semiconductor) or a substrate surface (e.g., a DCB or lead frame).

[0121] The wire according to the fourth theme of the invention can preferably be obtained by means of an embodiment of the first theme of the invention or an embodiment thereof.

[0122] Roughness R according to the fourth subject of the invention z Preferably, the pressing is performed at at least a first location on the wire. As for the pressing, it is preferably selected from the group consisting of: punching marks, notches, embossing, stamping, grooves, and slotting, or a combination of two or more of these.

[0123] For example, the roughness R at at least the first location of the wire. z It is caused by rolling, such as embossing rolling.

[0124] For rolling, for example, the rolls may include grooves for producing wire. The grooves preferably have a height difference (D) in the range of 3 μm to 9 μm. In this way, recesses can be introduced at at least one location on the wire by the rolls.

[0125] Another subject of the present invention is an apparatus comprising at least:

[0126] (1) First contact surface;

[0127] (2) A wire according to the second or third subject of the invention or a wire that can be obtained by means of the first subject of the invention or by means of one or more embodiments of the embodiments described in this regard in each case;

[0128] The wire is electrically connected to the first contact surface.

[0129] Optionally, the wire can be electrically connected to one or more additional contact surfaces.

[0130] A fifth aspect of the invention relates to the use of a textured roller for producing wire, wherein the roller has a preferably cylindrical surface, and the texture is characterized in that the height difference (D) of the surface is in the range of 3 μm to 9 μm, for example 4 μm to 8 μm, or 5 μm to 7 μm, or 4 μm to 9 μm, or 5 μm to 9 μm, wherein a recess is introduced at at least one location on the wire by the roller. Preferably, when the wire is a strip, the recess is introduced on one side of the wire.

[0131] The sixth subject of the invention relates to a textured roller for reducing the roughness R at at least one location on a wire. z Applications with a diameter ranging from 3μm to 9μm, such as 4μm to 8μm, 5μm to 7μm, 4μm to 9μm, or 5μm to 9μm, wherein the roller has a preferably cylindrical surface, and the ridges are characterized by a height difference (D) on the surface. Preferably, when the wire is a strip, a roughness R is introduced on one side of the wire. z Preferred embodiments of the first subject matter of the invention are also preferred herein, provided they involve rollers and surface roughness R. z The settings and roughness R z And height difference (D).

[0132] Attached Figure

[0133] The invention is further illustrated below with reference to the accompanying drawings and embodiments. The drawings and embodiments are not intended to limit the scope of the claimed subject matter.

[0134] Figure 1 A schematic diagram of a wire or wire precursor is shown.

[0135] Figure 2 It shows Figure 1 The cross-sectional area Q of the object shown A The view.

[0136] Figure 3 The method for introducing a recess into a wire is illustrated schematically.

[0137] Figure 4 shows a) a strip with raised texture and b) a strip with brush coating.

[0138] Figure 5 The device, which has wires and contact surfaces, is shown schematically. Attached Figure Description

[0139] Figure 1 It is shown that it is characterized by its length L and cross-sectional plane Q E A schematic diagram of wire 2 or wire precursor 1.

[0140] Figure 2 It was shown as Figure 1 The cross-sectional plane Q shown E A portion of the cross-sectional area Q A The view. Two perpendicular lines, L1 and L2, are laid across the cross-sectional area Q. A They have a cross-sectional area Q in the edge of wire 2 or wire precursor 1. A They intersect. Therefore, segment A forms lines L1 and L2. L1 and A L2 .

[0141] Figure 3 A method for introducing the recess 3 into the wire 2 by means of a ribbed roller (upper roller, not denoted by reference numerals) is schematically shown. The lower roller is optional and can be replaced by another opposing surface.

[0142] Figure 4 shows a) the surface morphology of the strip 2, which has an introduced pattern 6 made of recesses 3; and b) the surface morphology of the brushed strip.

[0143] Figure 5 The device 10, which includes a wire 2 connecting a first contact surface 12 to a second contact surface 13, is shown schematically.

[0144] Test methods

[0145] a. Determine the rib height and surface roughness

[0146] The rib height D and roughness R of the wire z The determination is based on standards DIN EN ISO 4287 (2010-07) (definitions and parameters) and DIN EN ISO 4288 (1998-04) (rules and procedures), where the riveting height of the roll and the roughness of the wire are determined transversely to the rolling direction. Unlike standard DIN EN ISO 4288, due to geometric conditions, the strip is measured over both a short sampling length and the entire measurement length. A sufficiently long sampling length is defined as at least one-third of the width of the strip or the effectively usable roll. A Mahr Perthometer PCV with a 2 μm diamond tip is used. Measurements are taken at at least two distinct locations on the wire or roll. The measured data are based on DIN EN ISO 4287 and evaluated using the MahrSurface XCR20 V1.20-4 procedure.

[0147] b. Determine the cross-sectional area of ​​the wire or strip.

[0148] To determine the cross-sectional area, metallographic sections were prepared and measured using an optical microscope.

[0149] Example

[0150] The invention is further illustrated below by way of example. The invention is not limited to the embodiments and combinations of features or parameters shown therein.

[0151] 1. Production of copper strip

[0152] Copper round wire with a diameter of 0.78 mm and a copper purity of 99.98% by weight was used as the starting material. Figure 3 In the arrangement outlined in the figure, the wire is guided by a reforming system with two rollers made of hard metal. Roller 1 (located at the bottom in the figure) is a smooth cylinder with a diameter of 96 mm. Roller 2 (located at the top in the figure) also has a basic cylindrical shape with a diameter of 96 mm. In the case of the reformed wires (1)-(3), the surface of roller 2 has a raised texture with a height of D (D 最大 The surface of roll 2 is smooth and without any raised texture in the case of reformed wires (A) and (B). The wire is guided between rolls 1 and 2, rotating in opposite directions but in the direction of wire transport. There is a roll gap S between rolls 1 and 2. It is set and determined as the shortest distance between the surface of roll 1 and the surface of roll 2 which is basically cylindrical, i.e., at the position without raised texture. The output speed of the wire in the transport direction is the same as the rotational speed v of the roll on the contact surface with the wire. The rolling oil used is the fast-evaporating rolling oil B-Clean62S. After the rolling step, the reformed wires (1)-(3) and (A) and (B) are annealed in a 2.5m long continuous heating furnace at a throughput of 10m / min and an annealing temperature T of 650°C. G Annealing was performed in a hydrogen atmosphere. After annealing, the reshaped wires were cooled to ambient temperature. Following the annealing process, the reshaped comparative wires (A) and (B) were brush-coated according to the properties in Table 2. The properties of the reshaped wires (1)-(3) are given in Table 1.

[0153] Table 1

[0154]

[0155]

[0156] Table 2

[0157]

[0158] 2. Evaluate the quality of the reshaped wire.

[0159] Example number (1) (2) (3) (A) (B) Residues on the surface of reshaped wire + + + - -- Sputtering during laser bonding + + -- - --

[0160] First, scanning electron microscopy images were used to visually assess the quality of the reshaped wire regarding unwanted residues on the surface:

[0161] +: No residue, -: Small residue, --: Large residue

[0162] In the next step, the behavior of the reshaped wire during laser bonding is investigated in terms of potential spattering. To this end, the reshaped wire is bonded to an electronic component of the same construction using the same laser bonder setup. The spattering that occurs is counted using an optical microscope.

[0163] +: No splashing, -: Small amount of splashing, --: Large amount of splashing.

[0164] Residues were observed on the surface of the brush-coated reshaped wires (A) and (B). In this case, more residues were identified on the surface when larger depressions were introduced. These residues caused splattering behavior of the brush-coated, reshaped wires (A) and (B) during laser bonding. In contrast, no residues were found on the surface of the reshaped wires (1)-(3).

[0165] It has a roughness R of less than 9 μm z The reshaped wires (1) and (2) did not exhibit any sputtering behavior during laser bonding. Instead, they showed an increased roughness R of 18.6 μm. z The reshaped body (3) exhibits obvious spattering behavior during laser bonding.

[0166] List of reference numerals in the attached figures

[0167] 1. Wire precursor

[0168] 2. Wire

[0169] 3. Depression

[0170] 4 rollers

[0171] Surface of 5 rollers

[0172] 6. Embossed

[0173] 7 First side

[0174] 8. The other side

[0175] 10 devices

[0176] 11 Substrate

[0177] 12 First contact surface

[0178] D Height difference

[0179] Q E cross-section

[0180] Q A Cross-sectional area

[0181] L length

[0182] L1, L2 lines

[0183] A L1 A L2 Section

Claims

1. A method for producing materials (2), the method comprising at least the following steps: (i) Provide wire precursor (1); (ii) A recess (3) is pressed into the wire precursor (1); and (iii) Anneal the wire precursor (1) with the recess (3) to obtain the wire (2). The wire (2) has a copper content of at least 95% by weight, the content being based on the total weight of the wire (2). The wire (2) has multiple locations (7, 8) where the recess (3) is introduced only at the first location (7). The wire (2) has a roughness R in the range of 3µm to 9µm at at least one location. z , At least one other location (8) of the wire (2) is smooth and has a roughness R in the range of 0.1µm to 1µm. z The at least one other position (8) is located on the wire (2) away from the first position (7).

2. The method according to claim 1, wherein the pressing is selected from the group consisting of: punching marks, scoring, embossing, stamping, grooves and slotting.

3. The method according to claim 1 or 2, wherein the pressing is performed by rollers.

4. The method according to claim 3, wherein pressing is performed by rolling, wherein the rolling is performed by at least one roll (4), wherein the roll (4) has a cylindrical surface including a textured surface (6), wherein the textured surface (6) is formed by a height difference (D) of the cylindrical surface.

5. The method of claim 4, wherein the height difference (D) is in the range of 3µm to 9µm.

6. The method according to claim 1 or 2, wherein the recess (3) is patterned.

7. The method according to claim 1 or 2, wherein the wire (2) is a bonding wire or a strip.

8. The method according to claim 1 or 2, wherein the element selected from the group consisting of the wire (2) and the wire precursor (1) has a diameter of 25,000 µm. 2 Up to 900,000µm 2 Cross-sectional area Q within the range A The cross-sectional area Q A The arrangement is perpendicular to the longitudinal direction L of the element.

9. The method according to claim 1 or 2, The cross-sectional plane QE is laid through the element selected from the group consisting of the wire precursor (1) and the wire (2). The cross-sectional plane Q E Arranged perpendicular to the longitudinal direction L of the component. The cross-sectional plane Q E The cross-sectional area Q is formed with the element. A , The cross-sectional area Q A It includes two perpendicularly intersecting lines, L1 and L2. The shortest possible segment A of line L1 L1 By Q A The intersection of the edges defines the boundary, and The longest possible segment A of line L2. L2 By Q A The intersection of the edges defines the boundary. Where A L2 and A L1 The quotient is 2 or a larger number.

10. A method for producing an apparatus including at least one conductive connection, wherein the method comprises the following steps: (I) Providing a substrate and a wire having at least a first contact surface, wherein the wire can optionally be obtained by the method according to at least one of claims 1 to 9; (II) Positioning the wire to be mechanically connected to the first contact surface; (III) Heating the first position of the wire by means of electromagnetic radiation with a wavelength range of 700 nm to 1,100 nm. To obtain a conductive connection between the first contact surface of the substrate and the wire. The first location of the wire has a roughness R in the range of 3µm to 9µm. z , The location of the wire opposite to the first location has a roughness R in the range of 0.1µm to 1µm. z The other position faces the contact surface. The roughness R at at least the first position of the wire z It is produced by pressing selected from the following groups: punching marks, scoring, embossing, stamping, grooves and slotting.

11. The method of claim 10, wherein the first position of the wire or the first side of the wire is arranged on the side of the wire opposite to the first contact surface of the substrate.

12. The method of claim 10 or 11, wherein the roughness R of the wire at least at the first location z Produced by rolling, wherein for rolling, a roll including a groove is used, by means of which a roll recess is introduced at at least one position of the wire to produce the wire, wherein the groove is characterized by a height difference (D) in the range of 3µm to 9µm.

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