Electronic assembly and method for manufacturing an electronic assembly

Abstract

According to a first aspect of the invention, an electronic assembly is provided which comprises a substrate, for example, a printed circuit board, and at least one electronic component. A through-hole extends, for example, from this first connection pad, through the substrate to an opposite first main surface of the substrate. An opening of the through-hole to the second main surface can be formed within the pad or adjacent to it. The through-hole can have an internal metallization. The electronic component has at least one contact element, e.g., a connecting wire. This is inserted into the through-hole and extends through the through-hole to an opposite second main surface. The contact element is soldered there.The electronic component extends with its body (excluding the connection elements) at a defined distance from the surface of the substrate, thus forming an air gap whose width is sufficient to dissipate gases generated during soldering and reliably prevent defective solder joints. According to the invention, the first main surface of the substrate has a structure, the structure of which creates the defined distance between the body of the electronic component and the surface of the substrate. The structure comprises depressions and / or protrusions on the first main surface of the substrate.

Description

State of the art

[0001] During the assembly of printed circuit boards, electronic components can be attached to the designated locations on the surface of the circuit board in a variety of ways, and thereby electrically connected to other electronic components if necessary. Standard methods for this include surface mounting technology (SMT) or through-hole or through-hole technology (THT). While surface-mounted components (SMD) are soldered directly onto a circuit board using solderable connection pads or leads, THT components are wired radially or axially, etc., with the wires being inserted through pre-formed holes in the circuit board or printed circuit board and soldered to the back of the circuit board.

[0002] It is common practice to use so-called spacers when assembling these components. In the case of SMD components, such spacers serve, among other things, to ensure a defined soldering gap between a corresponding soldering or connection pad on the circuit board and the opposite connection surface of the SMD component, so that the solder paste provides a reliable, permanent, and electrically resistance-free connection between these surfaces. Examples of the implementation of spacers for surface mounting are disclosed, among others, in the publications DE 19547680 A1, EP 1 496 733 A2, and JP 2007-200997 A. Such spacers are usually designed as small balls made of silver or copper (tinned). In use, they are then embedded in the solder.

[0003] In the case of THT components, a defined distance between the component and the surface of the circuit board or board is particularly desirable if the component, when placed directly on the board, obscures the openings for the connecting wires passing through the board or board. In this case, gases generated during selective soldering on the back of the board or board cannot escape optimally and may lead to defective solder joints. A certain distance between the THT component and the circuit board surface can therefore improve the quality and reliability of the solder joints.

[0004] Even in the case of THT components, spacers are used according to the state of the art. The corresponding spacers can be made of plastic or metal and are attached by soldering, gluing, screwing, or snapping. Various options are known and common practice for maintaining the required distance: For example, the component itself can have an integrated spacer. However, the problem here is that the components used are often standard products (mass-produced goods), and therefore not every electronic component has a corresponding spacer design from the outset. Therefore, a modification to the design of such components is often necessary, which can involve considerable effort.

[0005] Another option is to place special spacers directly on the circuit board, as described above by soldering, gluing, screwing, snapping, etc. However, this can also have disadvantages due to the fact that a large number of small mechanical components must be used as spacers, which can entail comparatively high costs. Furthermore, such separate spacers have the additional disadvantage that, if they are soldered, for example, the connected solder joints can be damaged due to mechanical stress or thermal stress. In the worst case, the affected spacers can become loose and cause short circuits in the electronic assembly.

[0006] Document DE 10 2014 218 048 A1 discloses spacers in the form of plastic films or plastic elements, in particular as plastic frames. Document EP 0 934 687 A1 discloses spacers applied using solder paste, which serve as spacers between the heat sink and the carrier substrate. Disclosure of the invention

[0007] It can therefore be considered an object of the invention to provide an electronic assembly with and an associated manufacturing method in which the reliability of solder joints is ensured.

[0008] According to a first aspect of the invention, an electronic assembly is provided which comprises a substrate, e.g., designed as a printed circuit board, and at least one electronic component. This is, for example, an axially or radially wired electronic component, in particular a THT component. At least one first pad for connecting a wired electronic component can extend on a second of the two main surfaces of the substrate. The pad can be a connection and soldering pad and a planar extension of a conductor track connecting the electronic component, e.g., made of copper or aluminum.

[0009] A through-hole extends, for example, from this first connection pad through the substrate to an opposite first main surface of the substrate. An opening of the through-hole to the second main surface can be formed within the pad or adjacent to it. The through-hole can have an internal metallization.

[0010] The electronic component has at least one contact element, e.g., a lead wire. This is inserted into the through-hole and extends through the through-hole to an opposite second main surface. The contact element is soldered there to the connection pad—for example, by wave or flow soldering from the second main surface. This essentially corresponds to the THT design.

[0011] The electronic component extends with its body (considered without the connection elements) at a defined distance from the surface of the substrate, so that an air gap is formed whose width is sufficient to dissipate gases formed during soldering and reliably prevent defective solder joints.

[0012] According to the invention, the first main surface of the substrate has a structure, wherein the structure establishes a defined distance between the body of the electronic component and the surface of the substrate. The structure comprises depressions and / or elevations on the first main surface of the substrate.

[0013] In a preferred embodiment, the electronic component is a capacitor, in particular an electrolytic capacitor, with a cylindrical body, and wherein the air gap is formed between a base surface of the cylindrical body and the surface of the first main surface of the substrate. Such a capacitor has, for example, two connecting wires that are guided through two corresponding through-holes in the substrate and are soldered starting from the second main surface of the substrate.

[0014] According to a preferred embodiment of the invention, the structure comprises depressions and / or elevations formed on the first main surface of the substrate.

[0015] More preferably, the structure may comprise one or more regions in which a resist layer (e.g., a solder resist) arranged on the substrate has been removed, thereby forming at least one recess.

[0016] In a particularly preferred embodiment, one or more annular and / or circular-ring-segment-shaped regions are provided in which the lacquer layer arranged on the substrate has been removed. This embodiment is particularly advantageous when the body of the electronic component has a circular base area, as is the case, for example, with a typical, essentially cylindrical capacitor. If the radius of the annular and / or circular-ring-segment-shaped regions is selected to be equal to or smaller than the radius of the base area of ​​the electronic component, a uniform spacing and thus a uniform width of the formed air gap is ensured.

[0017] Alternatively or additionally, in one embodiment of the invention, the structure may comprise one or more elevations formed from a solder material on the first main surface of the substrate. The elevations may, for example, be formed in a hill-like manner from a solder material. This offers the advantage of simple manufacturing combined with high reliability.

[0018] In a particularly preferred embodiment, the elevations extend radially on the first main surface of the substrate, starting from a projection of a center point of the surface of the body of the electronic component onto the first main surface of the substrate. This, in turn, offers the advantage, for electronic components with a body having a substantially circular base area, of ensuring a particularly symmetrical and thus uniform spacing and thus a uniform width of the resulting air gap.

[0019] According to a further aspect of the invention, a method for producing an electronic assembly as described above is proposed. The method comprises the following steps: a. Providing a substrate, wherein at least one first connection pad for connecting the electronic component is formed on a second of the two main surfaces of the substrate, and wherein the substrate has at least one through-hole extending from a first connection pad through the substrate to an opposite first main surface of the substrate, b. Applying a structure to the first main surface of the substrate, c. Placing an electronic component on the first main surface of the substrate, wherein at least one contact element of the electronic component is inserted through the through-hole and wherein the structure of the first main surface of the substrate ensures an air gap of a certain width between a body of the electronic component and the surface of the first main surface of the substrate, d. Soldering the contact element starting from the second main surface of the substrate.

[0020] Preferably, in step b, at least one depression and / or at least one elevation can be formed on the first main surface of the substrate.

[0021] A recess can be formed in particular by selectively removing a solder resist from the first main surface of the substrate.

[0022] A protrusion can be formed in particular by applying a solder material to the first main surface of the substrate. Short description of the characters

[0023] Embodiments of the invention are described in detail with reference to the accompanying figures. Fig. 1 shows the perspective top view of the bottom surface or base area of ​​a substantially cylindrical electrolytic capacitor. Fig. 2 shows a section through a solder joint of a contact element of an electronic component, wherein the contact element is inserted into a through-hole of a substrate. Fig. 3 a) a plan view of a first main surface of a substrate according to the prior art. Fig. 3 b)-d) each show a plan view of a first main surface of a substrate according to various embodiments of the invention. Preferred embodiments of the invention

[0024] In the following description of the exemplary embodiments of the invention, identical elements are designated by identical reference numerals, whereby a repeated description of these elements is omitted where appropriate. The figures only schematically illustrate the subject matter of the invention.

[0025] Fig. Figure 1 illustrates a typical electrolytic capacitor as an electronic component, such as can be used in the invention. The electrolytic capacitor 50 has a substantially cylindrical body 52 with a substantially circular base 54. The base includes a circular, recessed region 56 in which two contact elements 62, 64 are formed or arranged. The contact elements are designed to be inserted through corresponding through-holes in a substrate and soldered from the back of the substrate. Thus, the electrolytic capacitor 50 can be mounted using a THT design.

[0026] Fig. 2 shows a section through a solder joint of a correspondingly soldered electrolytic capacitor 50 on a substrate 20, which is designed, for example, as a PCB. The electrolytic capacitor 50 is placed with its body 52 on a first main surface 21 of the substrate 20. The substrate 20 has at least one through-hole 26 through which a contact element 62 of the electrolytic capacitor 50 is passed. The through-hole is provided on an inner surface with a metallization layer as a contact region 23, which is contacted, for example, with a contact pad or a conductor track (not shown) of the substrate 20. The contact element 62 is soldered to the metallization layer using a solder material 26. This can preferably be done by selective soldering starting from the second main surface 22 of the substrate 20.

[0027] To allow the gases generated during the soldering process to escape without causing defects in the solder contact, the invention provides for a specified minimum distance to be maintained between the body 52 of the electrolytic capacitor 50 and the first main surface 21 of the substrate 20. This minimum distance must be maintained, in particular, between the edge region of the base surface 54 and the surface of the first main surface 21 of the substrate 20. This results in a larger distance 3 in the region of the recess 56 formed on the base surface 54. This creates an air gap 2 whose width is sufficient to allow any gases generated to escape safely.

[0028] In order to create this air gap, the substrate 20 can be structured in different ways in the region of the air gap 2, wherein the width of the air gap is determined by the structure.

[0029] Fig. 3 b) to d) show different possibilities how the first surface 21 of the substrate 20 can be structured in the region of the air gap 2.

[0030] Fig. 3 a) shows a substrate 20' according to the prior art. In the example shown, the substrate 20 is prepared for a total of six electrolytic capacitors. It has two through-holes 26' and 28' for each electrolytic capacitor, through which the two contact elements of the respective electrolytic capacitor can be passed. The positions of the essentially circular base surfaces of the electrolytic capacitors are indicated by the outline lines 51'. The view shows the first main surface 21' of the substrate 20'. No further structuring of the main surface 21' of the substrate 20' is provided.

[0031] Fig. 3 b) shows a substrate 20 for use in an electronic assembly according to a first possible embodiment of the invention. In the example shown, the substrate 20 is prepared for a total of six electrolytic capacitors. It has two through-holes 26 and 28 for each electrolytic capacitor, through which the two contact elements of the respective electrolytic capacitor can be passed. The view shows the first main surface 21 of the substrate 20. On the main surface 21, four circular ring-segment-shaped depressions 32a, 32b, 32c, 32d are introduced into the surface of the first main surface 21 for each electrolytic capacitor. The outer radius of the depressions 32a, 32b, 32c, 32d can, for example, correspond to the radius of the base area of ​​the respective capacitor.These recesses 32a, 32b, 32c, 32d ensure that the respective capacitors extend with their bodies at a defined distance from the surface of the first main surface 21 of the substrate 20, so that an air gap is formed between the body of the capacitor and the surface of the first main surface 21 of the substrate 20, wherein the width of the air gap is determined by the respective depth of the recesses 32a, 32b, 32c, 32d. The recesses 32a, 32b, 32c, 32d can be formed, for example, by removing a layer of lacquer, in particular a solder resist, from the surface of the first main surface 21 in the regions.

[0032] Fig. 3 c) shows a substrate 20 for use in an electronic assembly according to a second possible embodiment of the invention. In this example, too, the substrate 20 is prepared for a total of six electrolytic capacitors. The positions of the essentially circular base areas of the electrolytic capacitors are indicated by the outline lines 51. The substrate 20 has two through-holes 26 and 28 for each electrolytic capacitor, through which the two contact elements of the respective electrolytic capacitor can be passed. The view shows the first main surface 21 of the substrate 20. On the main surface 21, four web-shaped elevations 34a, 34b, 34c, 34d are formed for each electrolytic capacitor and are radially aligned with respect to the essentially circular base area of ​​the capacitors.These elevations 34a, 34b, 34c, 34d ensure that the respective capacitors extend with their bodies at a defined distance from the surface of the first main surface 21 of the substrate 20, so that an air gap is formed between the body of the capacitor and the surface of the first main surface 21 of the substrate 20. The width of the air gap is determined by the height of the elevations 34a, 34b, 34c, 34d. The elevations 34a, 34b, 34c, 34d can be formed, for example, by applying a solder material.

[0033] Fig.3 d) shows a substrate 20 for use in an electronic assembly according to a third possible embodiment of the invention. In the example shown, the substrate 20 is prepared for a total of six electrolytic capacitors. It has two through-holes 26 and 28 for each electrolytic capacitor, through which the two contact elements of the respective electrolytic capacitor can be passed. The view shows the first main surface 21 of the substrate 20. On the main surface 21, four circular ring-segment-shaped depressions 32a, 32b, 32c, 32d are introduced into the surface of the first main surface 21 for each electrolytic capacitor. In addition, four elevations 34a, 34b, 34c, 34d are formed between the circular ring-segment-shaped depressions 32a, 32b, 32c, 32d, which are radially aligned with respect to the essentially circular base area of ​​the capacitors.The elevations 34a, 34b, 34c, 34d in combination with the depressions 32a, 32b, 32c, 32d ensure that the respective capacitors extend with their bodies at a defined distance from the surface of the first main surface 21 of the substrate 20, so that an air gap is formed between the body of the capacitor and the surface of the first main surface 21 of the substrate 20, wherein the width of the air gap is determined by the height of the elevations 34a, 34b, 34c, 34d and the depth of the depressions 32a, 32b, 32c, 32d. The depressions 32a, 32b, 32c, 32d can be formed, for example, by removing a layer of resist, in particular a solder resist, from the surface of the first main surface 21 in the regions. The elevations 34a, 34b, 34c, 34d can be formed, for example, by applying a solder material. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 19547680 A1

[0002] EP 1 496 733 A2

[0002] JP 2007-200997 A

[0002] DE 10 2014 218 048 A1

[0006] EP 0 934 687 A1

[0006]

Claims

[1] Electronic assembly comprising a substrate (20) and at least one electronic component (50), in particular a THT component, arranged on a first main surface (21) of the substrate (20), wherein the substrate (20) has at least one through-hole (26, 28) extending from the first main surface (21) of the substrate (20) through the substrate (20) to an opposite second main surface (22) of the substrate (20), and wherein the electronic component (50) has a body (52) and at least one contact element (62, 64), wherein in each case a contact element (62, 64) is inserted into a through-hole (26, 28) and extends through the through-hole (26, 28) to the opposite second main surface (22) of the substrate (20), wherein the contact element (62, 64) is provided in the region of the through-hole (26, 28) with a contact region (23) of the substrate (20) is soldered, characterized bythat the electronic component (50) extends with its body (52) at a defined distance (2) from the surface of the first main surface (21) of the substrate (20), so that an air gap is formed between the body (52) of the electronic component (50) and the surface of the first main surface (21) of the substrate (20), wherein the substrate (20) is structured in the region of the air gap, wherein the width of the air gap is determined by the structure. [2] Electronic assembly according to claim 1, characterized by , the electronic component (50) is a capacitor, in particular an electrolytic capacitor, with a cylindrical body (52), wherein the air gap is formed between a base surface (54) of the cylindrical body and the surface of the first main surface (21) of the substrate (20). [3] Electronic assembly according to one of the preceding claims, characterized bythat the structure comprises depressions (32a, 32b, 32c, 32d) and / or elevations (34a, 34b, 34c, 34d) formed on the first main surface (21) of the substrate. [4] Electronic assembly according to one of the preceding claims, characterized by that the structure comprises one or more regions in which a lacquer layer arranged on the substrate (20) has been removed, whereby at least one recess (32a, 32b, 32c, 32d) is formed. [5] Electronic assembly according to claim 4, characterized by that a plurality of circular ring-segment-shaped regions (32a, 32b, 32c, 32d) are provided in which the lacquer layer arranged on the substrate (20) has been removed. [6] Electronic assembly according to one of the preceding claims, characterized by that the structure comprises one or more elevations (34a, 34b, 34c, 34d) formed from a solder material on the first main surface (21) of the substrate (20). [7] Electronic assembly according to claim 6, characterized by that the elevations (34a, 34b, 34c, 34d) extend radially on the first main surface (21) of the substrate (20) starting from a projection of a center point of a base surface (54) of the body (52) of the electronic component (50) onto the first main surface (21) of the substrate (20). [8] Method for producing an electronic assembly according to one of claims 1 to 7, characterized by the steps a. Providing a substrate (20), wherein the substrate (20) has at least one through-hole (26, 28) extending from the first main surface (21) of the substrate (20) through the substrate (20) to an opposite second main surface (22) of the substrate (20), b. applying a structure to the first main surface (21) of the substrate (20), c. Placing an electronic component (50) on the first main surface of the substrate, wherein at least one contact element (62, 64) of the electronic component (50) is inserted through the through-hole (26, 28) and wherein the structure of the first main surface (21) of the substrate ensures an air gap of a certain width between a body (52) of the electronic component (50) and the surface of the first main surface (21) of the substrate (20), d. Soldering the contact element (62, 64) starting from the second main surface (22) of the substrate (20). [9] Method according to claim 8, characterized by that in step b at least one depression (32a, 32b, 32c, 32d) and / or one elevation (34a, 34b, 34c, 34d) is formed on the first main surface of the substrate. [10] Method according to claim 9, characterized bythat at least one recess (32a, 32b, 32c, 32d) is formed by selectively removing a resist layer from the first main surface (21) of the substrate (20). [11] Method according to claim 9 or 10, characterized by that at least one elevation (34a, 34b, 34c, 34d) is formed by applying a solder material to the first main surface (21) of the substrate (20).

Images