Coil

Abstract

Coil formed by a strip (4) of a carrier material of a component used in electronics or electrical engineering, wherein the strip (4) has a surface (8) formed by rolling a base material, characterized by a contact point (6) exposed on the strip (4) at which the surface (8) formed by the base material of the coil is removed, which is surrounded by the surface (8) formed by the rolling.

Description

[0001] The present invention relates to a coil formed by a strip of a carrier material of a component used in electrical engineering or electronics, for which a wire bonding process is provided.

[0002] The reliability and service life of contact systems in switching devices, electromechanical components, and electronic components often depend not only on the contact material used. The choice of the appropriate substrate material also plays a crucial role.

[0003] Copper-based materials are the most important substrate materials. Depending on the application, nickel-based materials or multilayer composite materials, such as thermobimetals, are also used.

[0004] The requirements placed on the substrate materials vary depending on their specific applications. For example, copper materials are required to possess high electrical and thermal conductivity, good strength properties even at elevated temperatures, and sufficiently high corrosion resistance. If the substrate materials are used as contact springs, the material must also exhibit good spring properties. Depending on the manufacturing process, a number of technological properties are also required, such as good hot and cold formability, machinability, punchability, weldability, solderability, and electroplating properties.

[0005] Materials made of copper and copper alloys intended for use in electrical engineering and electronics are generally specified in standards. The DIN-standardized carrier material of the present invention is, in particular, a material in accordance with DIN EN 1758.

[0006] In electronics and electrical engineering, such a substrate is typically used not only for conducting current, especially power current. Sometimes, electronic components such as transistors, light-emitting diodes, or photodiodes are also bonded directly to the substrate.

[0007] Wire bonding is an electrical connection technique in which a thin wire (e.g., AU, Al) with a diameter of 50 to 300 µm is welded to a flat metal surface or a semiconductor element surface using high-frequency mechanical excitation. This joining process is widely used in semiconductor components for the electrical connection between the semiconductor and the system carrier, which is usually made of a copper alloy strip.

[0008] The wire bonding process requires a defect-free surface. During the rolling production of the carrier material, which is supplied in strip form as a wound ring / coil, the surface comes into contact with metallic tools (rollers, straightening rollers) and deflection rollers during many process steps. Imperfections and particles on the tools or rollers can be transferred to the surface of the carrier material. Furthermore, relative movement between the coil turns, e.g., during transport, can cause scratches and other defects in the surface that make it unsuitable for the wire bonding process. To achieve the defect-free surface required for the wire bonding process, extensive measures have been required in the production of the carrier material and in its testing.

[0009] The present invention aims to provide a solution to the problems described above. In particular, the present invention aims to prepare a carrier material for electronics and electrical engineering supplied as a coil in an improved manner for the wire bonding process and to deliver it to the customer in this form.

[0010] To solve this problem, the present invention proposes a coil having the features of claim 1.

[0011] The coil is formed by a strip of carrier material. The strip is formed by rolling a base material and has a surface formed by rolling. According to the present invention, at least one contact point exposed on the strip is formed on the strip-shaped carrier material, at which contact point the surface formed by rolling is removed. The contact point is accordingly deeper than the surface formed by rolling. The contact point is therefore spaced from the surface formed by rolling towards the center of the carrier material. It exposes the base material of the coil and is formed by this base material. The contact point is only formed locally on the strip, which means that the contact point is otherwise completely or partially circumferentially surrounded by the surface formed by rolling.

[0012] The contact point serves to remove impurities and modifications to the base material caused by rolling close to the surface. This base material is free of indentations, scars and disruptive foreign particles at the contact point. This allows the topographical and material requirements of the wire bonding process to be taken into account. Even in the event that the wire bonding process requires a previously applied electroplated coating to the contact point, the conditions for the bonding process are significantly improved compared to those with a rolled surface. Since the contact point is also deeper than the surface formed by rolling, the contact point cannot be affected by the relative movement of adjacent turns during transport. A carrier material with a defined contact point can then be supplied to a processor of the carrier material in the form of a coil with a large number of turns in the electronics or semiconductor industries.Electrical engineering is supplied.

[0013] One of the contact points is usually located on one or possibly two opposing surfaces of the strip, which are formed by rolling. This term is intended to express that the strip has two main side surfaces that extend significantly further than the end faces connecting these main side surfaces. These end faces can also be machined by rolling, but they are not necessarily formed by rolling. At least one contact point is located on the main side surface.

[0014] It is understood that, with a view to mass production and the use of a coil in such a production, the contact points are formed at fixed locations on the strip, usually at cyclical spacing from one another. This allows the respective electrically conductive carriers for use in electronics or electrical engineering to be separated from the coil from lengths of the strip-shaped carrier material. The contact point is usually located between the individual cut edges, through which a length of the strip is insulated from the coil.

[0015] As previously mentioned, the base material is preferably a copper alloy. The strip preferably complies with the specifications of DIN EN ISO 1758.

[0016] As mentioned previously, the contact point is located deeper than the surface formed by the rolling. The contact point is typically between 30 µm and 150 µm from the surface formed by the rolling.

[0017] At the contact point, the material forming the surface formed by rolling is preferably removed by machining.

[0018] This can preferably be done by peeling the surface of the finished rolled strip material.

[0019] Each of the contact points typically has a width of between 2 and 10 mm.

[0020] To produce the coil according to the invention, a process is used in which a strip is first produced by rolling a base material. Material from the carrier material is locally removed from the surface of the strip formed by rolling in order to form the exposed contact point on the strip, preferably in the manner described above. The strip material is then wound to form a coil.

[0021] Prepared in this way, the strip material is either electroplated by the carrier material manufacturer, depending on the requirements, or sent to a puncher, which unwinds the strip from the coil on-site and punches, for example, system carriers for semiconductors, either as cut-to-length sections or wound punched strip. These and subsequent processes are then comparable to those for materials that do not require surface removal during wire bonding and are state-of-the-art.

[0022] Further details and advantages of the present invention will become apparent from the following description of exemplary embodiments of the invention in conjunction with the drawings, in which: Fig. 1 is a perspective cross-sectional view of a length of a band; Fig. 2 a perspective view of a coil with the end of the strip forming this coil; Fig. 3 a side view of a bonded circuit breaker using the tape according to Fig. 1 and Fig. 4 a top view of Fig. 4.

[0023] In Fig. Figure 1 shows an embodiment of a substrate material, specifically using CuSn6 R500 as an example. The embodiment illustrates a sectional view through a length 2 of a strip 4 transverse to the rolling direction, indicated by the arrows at reference symbol W. The strip 4 has a thickness S of approximately 0.8-0.02 mm and a width B of 30-0.02 mm.

[0024] Reference numeral 6 denotes two contact points near the edge of the strip 4, which are formed by machining the surface 8 formed by rolling. The distance A between this contact point 6 and each edge of the length 2 is 10 mm in the application example. The length L and the distance A are each measured transversely to the rolling direction.

[0025] Contact point 6 is beveled at a 45° angle at the transition to surface 8 and has a width b of 5 mm. As the reduced thickness R indicates, strip 4 is only 0.77 mm + / - 0.012 mm thick at contact point 6. This reduced thickness of strip 4 results from machining of surface 8 of strip 4.

[0026] In the illustrated embodiment, contact point 6 was created by a peeling process. This resulted in a surface roughness in the rolling direction of Ra=0.018 µm and Rmax=0.705 µm at contact point 6. The roughness in the transverse direction, i.e., perpendicular to the longitudinal direction, was Ra=0.173 µm and Rmax=1.228 µm.

[0027] Fig. 2 shows an example of a coil 10, which consists of a Fig. 1 modified band 2. As the representation of the free end of band 2 in Fig. 2, this volume 4 has compared to the embodiment according to Fig. 1 only a single contact point 6. For details of this contact point 6, please refer to the previous description. Fig. 1.

[0028] The Fig. 3 and Fig. 4 convey the fastening and connection of a semiconductor switch 12 to the band 4 according to Fig. 1. This is divided into several segments 14 by punching, of which segments 14.1 form busbars for the power current switched by the semiconductor switch 12. These segments 14.1 are each formed by punching the edges of the strip 4. The semiconductor switch 12 is electrically connected to one of the segments 14.1 via its wire bridges / pins 16.

[0029] Segment 14.2 was punched from the center of strip 4. In the illustrated embodiment, it carries the power switch 12 and serves as a busbar for the polarity to be switched by the semiconductor switch 12.

[0030] The extension of segment 14.2 in the rolling direction corresponds to the sum of the extensions of segments 14.1 in the rolling direction on one side of segment 14.2.

[0031] Further essential objects of the invention relate to the process: 1. Method for producing a carrier material of a component used in electronics or electrical engineering, in which a strip (4) is first produced by rolling a base material, material of the carrier material is locally removed from the surface (8) of the strip (4) formed by rolling in order to form a contact point (6) which is exposed on the outside of the strip (4), which contact point is formed by the base material of the coil and which is surrounded by the surface (8) formed by rolling, and winding the strip (4) to form a coil. 2. Method according to 1, characterized in that the material of the carrier material for forming the contact point (6) is removed locally to a depth of between 30 µm and 150 µm from the surface (8) formed by rolling. 3. Method according to 1 or 2, characterized in that the material of the carrier material is removed locally by machining to form the contact point (6). List of reference symbols 2 length pieces 4 volumes 6 Contact point 8 Surface 10 coils 12 semiconductor switches 14.1 Segment 14.2 middle segment 16 wire bridges / pins 16 A distance B Width of the band b Width of the contact point R reduced thickness S Strength

Claims

[1] Coil formed by a strip (4) of a carrier material of a component used in electronics or electrical engineering, wherein the strip (4) has a surface (8) formed by rolling a base material, characterized by a contact point (6) exposed on the strip (4) at which the surface (8) formed by rolling is removed, which is formed by the base material of the coil and which is surrounded by the surface (8) formed by rolling. [2] Coil according to claim 1, characterized by that the base material is a copper alloy. [3] Coil according to claim 1 or 2, characterized by that the band (4) complies with the specifications of DIN ISO 1758. [4] Coil according to one of the preceding claims, characterized by that at the contact point (6) the surface (8) formed by rolling is removed from the surface (8) formed by rolling up to a distance (A) of between 30 µm and 150 µm. [5] Coil according to one of the preceding claims, characterized by that at the contact point (6) a material forming the surface (8) formed by rolling is removed by machining. [6] Coil according to one of the preceding claims, characterized by that the contact point (6) has a width (b) between 2 and 10 mm.

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