DE102023210162A1 - Electronic assembly with spacer for an electronic component on a substrate - Google Patents

Abstract

An electronic assembly (10) comprises a substrate (12) designed as a circuit board with a first (16) and a second main surface (18) opposite thereto, wherein at least one first pad (20) for connecting a wired electronic component extends on the second main surface (18), wherein a through hole (22) extends from the first pad (20) through the substrate (12) to the opposite first main surface (16). The electronic assembly (10) further comprises the electronic component (14), which has at least one connecting wire (24) which is inserted into the through hole (22) and extends through the through hole (22) to the opposite second main surface (18). The connecting wire (24) is soldered (26) to the first pad (20). The electronic component (14) extends at a distance from the first main surface (16). Furthermore, the electronic assembly (10) comprises at least one second pad (28) formed on the first main surface (16) and at least one spacer (30) formed on the second pad (28) from a solder or a solder paste, which, together with the underlying second pad (28), has a height that essentially corresponds to the distance between the electronic component (14) and the first main surface (16).

Description

Technical area

Various aspects relate to an electronic assembly with a substrate designed as a printed circuit board on which a wired electronic component is mounted. The wired electronic component can be mounted using a THT design and its distance from the substrate is determined by one or more spacers.

Technical background

When assembling circuit boards, electronic components can be attached to the designated places on the surface of the circuit board in various ways and can thereby be electrically connected to other electronic components. Standard methods for this include surface mounting technology (SMT) or through-hole technology (THT). While surface mounted devices (SMD) are soldered directly onto a circuit board using solderable connection surfaces or pins, THT components are wired radially or axially, etc., with the wires being pushed through pre-formed holes in the circuit board or circuit board and soldered onto the back of the circuit board.

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 can be found 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). When in use, these are then embedded in the solder.

Spacers are also used in the case of THT components. However, these do not specify a distance between two opposing connection surfaces, but rather ensure that the assembled components meet specified vibration requirements, i.e. meet mechanical stability requirements. Such requirements are particularly placed on electronic assemblies that perform electronic control tasks or the operation of functional units in moving vehicles, particularly motor vehicles. Other aspects relate to enabling a certain amount of adhesive between the component and the circuit board surface through a defined distance. This therefore concerns the distance between the actual body of the electronic component and the circuit board surface.

• Beispielsweise kann das Bauteil selbst in integrierter Weise einen Spacer aufweisen. Allerdings besteht hierbei das Problem, dass die verwendeten Bauteile oftmals Standardprodukte (Massenware) darstellen und daher jedenfalls nicht jedes elektronische Bauteil von vornherein eine entsprechende Spacerausbildung aufweist. Oftmals ist daher eine Modifikation am Design solcher Bauteile erforderlich, die mit höherem Aufwand verbunden sein kann.

The corresponding spacers can be made of plastic or metal and are attached by soldering, gluing, screwing or snapping in. There are various known and common ways of maintaining the appropriate distance:

• For example, the component itself can have a spacer integrated. 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. A modification to the design of such components is therefore often necessary, which can involve greater effort.

Another option is to place special spacers directly on the circuit board, as described above by soldering, gluing, screwing or snapping in, etc. However, this can also have disadvantages because a large number of small mechanical components have to be used as spacers, which can be relatively expensive. Furthermore, such spacers have the additional disadvantage that if they are soldered, for example, the associated soldering points can be damaged due to the mechanical stress or thermal stress. In the worst case, the affected spacers can come loose and cause short circuits in the electronic assembly.

Another option is to adjust the distance using special external mounting devices, which are removed after the adhesive has hardened, for example. But this also requires additional effort due to the corresponding devices and additional manufacturing steps, which can also lead to increased costs.

The publication EN 10 2014 218 048 A1 discloses spacers in the form of plastic films or plastic elements, in particular as plastic frames. The publication EP 0 934 687 A1 discloses spacer elements applied by means of solder paste, which serve as spacers between the heat sink and the carrier substrate.

Consequently, there is a need to save costs and reduce the effort required to adjust the specified distances between THT components and the underlying circuit board, while maintaining or even improving product quality in terms of mechanical stability and durability.

Presentation of various aspects

Aspects of the invention are based on an electronic assembly that comprises a substrate designed as a circuit board and at least one electronic component. It is an axially or radially etc. wired electronic component, in particular a THT component. At least one first pad for connecting a wired electronic component extends on a second of the two main surfaces of the substrate. The pad can be a connection and soldering pad and a flat extension of a conductor track connecting the electronic component, e.g. made of copper or aluminum. The conductor track and the first pad can be surface-treated (OSP, HAL, HASL, chemical tin or silver, ENIG, ENEPIG, PALLATEC etc.).

A through hole extends 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 connecting wire. This is inserted into the through hole and extends through the through hole to an opposite second main surface. The slightly protruding connecting wire is soldered to the first pad there - preferably by flow or wave soldering from the second main surface. This essentially corresponds to the THT design.

The electronic component extends with its body (considered without the wire) at a distance from ("above") the first main surface. If, for example, it is a horizontal cylindrical body, the distance can be essentially constant along its length. If, on the other hand, it is a disk- or spherical body, for example, the distance can also be variable (depending on the position on the surface of the circuit board).

Aspects of the invention now provide that the electronic assembly further comprises at least one second pad formed on the first main surface. This second pad can be formed in the same way as the first pad. In particular, however, it is able to absorb solder paste and to form a secure and reliable connection with the resulting solder in a soldering process. As a result, a spacer formed from a solder or a solder paste is now arranged on the second pad, which, together with the underlying second pad, has a height that essentially corresponds to the above-mentioned distance between the electronic component and the first main surface.

It is therefore a basic idea to use solder paste to form a spacer, namely by creating a raised area on the circuit board. The formation of the spacer can take place in a joint step with the soldering process of other components on the circuit board, namely in particular when, for example, reflow soldering takes place on the same or both main surfaces at the same time to connect SMD components on the same circuit board. The spacers solidified after the SMD process can now be used as such in a subsequent THT soldering or gluing process when assembling the relevant electronic components.

This means that there are practically no additional costs (according to calculations, depending on the design, currently only around 0.2 cents per spacing point for the solder paste), and the additional effort for mounting the previously used spacers is also eliminated because an existing process step is used. Only the layout of the conductor tracks, which are usually formed photolithographically on the substrate, has to be adjusted in advance using additional pads. In any case, this reduces costs and effort.

A further advantage is that the height of the spacer formed from the solder paste can be controlled relatively well by the respective process, as experiments by the inventors have shown. The final height resulting after cooling is determined by the area and geometry of the underlying second pad. The solder paste applied during the process takes on a shape on the second pad that depends on various other, but known, factors (chemical composition, temperature profile, etc.). By appropriately dimensioning and geometry of the second pad in the layout, the height of the spacer can therefore be precisely adjusted. This also makes it possible to put different distances or heights for different spacers on the same circuit board into practice. It should be noted that a step stencil can also be used to influence the amount of solder paste and thus the resulting height of the spacer.

According to a further development, the electronic component is a THT component. This results in the advantages mentioned above.

According to one embodiment, the at least one second pad is made of the same material and with the same thickness on the substrate as the at least one first pad, preferably made of copper, or aluminum, or alloys thereof. This allows uniform processes to be used in the production of the conductor tracks and other structures on the circuit board, which reduces costs.

A further development provides that the at least one second pad is neither connected to the at least one first pad nor to further conductor tracks formed on the first main surface, but rather is designed to be electrically insulated. In other words, the second pad with the spacer on it is essentially functionless from an electrical point of view.

According to a further development of the proposed electronic assembly, the substrate is made of a fire-resistant FR4 material. This material is also commonly used for applications in motor vehicles, but since it does not come from an injection molding tool, it usually causes difficulties when spacers (as finished components) are to be subsequently soldered on. In this case, the formation of the spacers is independent of this, so this is another advantage.

According to embodiments, the spacer supports a surface of the electronic component facing the first main surface, i.e. there is permanent mechanical contact. However, it is also possible that the spacer loses a small amount of height (shrinks) after the process, so that a small gap can remain in the end product.

According to further embodiments of the electronic assembly, the electronic component is a capacitor, a coil, a transformer, a connector or an electronic switch. However, other electronic components can also be supported by a spacer.

Furthermore, it is also possible to provide at least two of the spacers with respect to the electronic component.

As mentioned above, further aspects of the invention relate to electronic assemblies produced using a mixed construction method (SMD, THT). In addition to the wired electronic component, at least one or more SMD components can be formed on the first and/or the second main surface. As described, the advantage here is that the spacer for the THT component can already be produced en passant in a previous SMT process, so to speak, which saves costs and effort to a considerable extent.

In particular, the one or more SMD components can be connected to corresponding third pads by solder, and the at least one spacer for the wired electronic component and the solder connections of the SMD components are formed in a common reflow soldering process. Instead of reflow soldering, other soft soldering processes can also be useful.

Various aspects also provide that the electrical circuit arrangement implemented in the electronic assembly is designed to control or operate a functional unit of a motor vehicle, in particular an electric sunroof or window lifter or an electric heater. In these areas of application, there are special requirements for mechanical stability and reliability, so that the advantages are particularly evident here.

Further advantages, features and details of the various aspects emerge from the claims, the following description of preferred embodiments and from the drawings. In the figures, the same reference numerals designate the same features and functions.

Short description of the drawings

• 1 in schematischer Darstellung einen ausschnittweisen Querschnitt durch eine Leiterplatte mit THT- und SMD-Bauteilen einer elektronischen Baugruppe gemäß einem Ausführungsbeispiel;

Show it:

• 1 in a schematic representation of a partial cross-section through a printed circuit board with THT and SMD components of an electronic assembly according to an embodiment;

Preferred embodiment(s) of the invention

In the following description of preferred embodiments, it is to be understood that the present disclosure of the various aspects is not limited to the details of the construction and arrangement of the components as shown in the following description and in the figures. The embodiments can be practiced or carried out in a variety of ways. It is further to be understood that the phraseology and terminology used herein is for the purpose of specific description only and should not be interpreted as limiting by one skilled in the art. Furthermore, in the following description, the same reference numerals in the various embodiments or figures designate the same or similar features or objects, so that in some cases a repeated detailed description of the same is omitted in order to maintain the compactness and clarity of the illustration.

In 1 is a schematic representation of a partial cross-section through a circuit board (substrate 12) with THT and SMD components 14, 34 of an electronic assembly 10 according to an embodiment. It should be noted that the drawing is not to scale.

The substrate 12 can be a plate made of FR4 material, for example. The substrate 12 has a first main surface 16 and an opposite second main surface 18. An electronic component 14 is provided in THC construction. Two connecting wires 24 extend in an axial direction and then bent towards the first main surface 16 and then through a through hole 22 to the opposite second main surface 18, where they protrude slightly. First pads 20 are formed on the second main surface 18 at a corresponding location. The through holes 22 can have an internal metallization. The through hole 22 extends with the connecting wires 24 through the pads 20. The connecting wires 24 are each electrically connected to the corresponding pads 20 by a solder connection 26. The pads 20 can be connected to conductor tracks formed on the second main surface 18, for example from copper, in order to enable an electrical connection of the component.

On the first main surface 16, two pads 28 are formed on the surface directly below the electronic component 14. More precisely, they face the body of the electronic component 14 directly. Spacers 30 produced from solder paste in an SMD process (e.g. reflow soldering or other soft soldering process) are formed on the pads 28. They contact the inherently electrically insulating outer surface of the body of the electronic component 14. They therefore form a stop during THT assembly of the electronic component 14 to establish a defined distance between the surface of the body of the electronic component 14 and the first main surface 16. The height of the spacers 30 can be 0.2 mm, for example. Smaller or larger values for the height, e.g. from 0.2 mm up to and including 0.4 mm or even more, are also possible. The defined distance can be determined from experience and/or tests in vibration tests of the assembly, which reflect the requirements of the intended use. When considering the values given, it should be noted that a varnish may be regularly applied to the circuit board and that the height is measured from the surface of this varnish.

The second pads 28 can, but do not have to, be connected to any conductor tracks 32 on the first main surface 16 or the second main surface 18. No electrical function is provided in this regard. The advantage arises from the fact that the second pads 28 can be produced in the same step as the other pads 20, 40 using photolithographic means when structuring the wiring of the circuit board. No additional step is required for creating the spacers. Likewise, the spacers 30 can be produced after the circuit board has been provided with conductor tracks etc. in the same process step for assembling SMD components as the solder connections of such SMD components. The conductor tracks formed on the main surfaces 16, 18 can, purely by way of example, have a thickness of, for example, 35 µm.

The 1 shows an example of such an SMD component 34 on the right. It has connection surfaces 42 that are positioned opposite third pads 40. Conventional spacers 38 in the form of small tinned copper balls are inserted between the connection surfaces 42 and the third pads 40. In the SMD process, solder paste is applied to the third pads 40 and between these spacers 38 and subjected to a soft soldering process. This creates solder connections 36 for the SMD component 34, in which the conventional spacers 38 are embedded. In the same soldering process, the spacers 30 are also produced from the solder paste applied to the second pads 28. This means that no additional process step is required here either.

During production, after the circuit board has been prepared and the SMD assembly process has been carried out, the pads 28 with the spacers 30 are completed before the electronic component 14 is fitted. For the subsequent THT assembly of the electronic component 14, the spacers or spacers 30 can thus serve as a stop when fitting the electronic component 14. The solder connections 26 are then made as part of the THT assembly process.

Details and details as well as modifications which are usual in the manufacture of electronic assemblies with printed circuit boards have been omitted from the above description for the sake of simplicity. It is understandable to the person skilled in the art that such usual measures such as Surface treatments not mentioned above can be carried out additionally.

The information and details provided in the specific embodiments are not to be interpreted as limiting the scope of protection defined in the appended claims. Further modifications are also possible. For example, soldering processes other than those mentioned are also possible in both the SMD process and the THT process.

LIST OF REFERENCE SYMBOLS:

10

Electronic assembly

12

Substrate (circuit board)

14

Electronic component

16

first main area

18

second main area

20

first pad

22

Through hole

24

Connecting wire

26

Solder connection (1st pad)

28

second pad

30

Spacer, spacer (THT)

32

Conductor tracks, wiring circuit board

34

SMD component

36

Solder connection (3rd pad)

38

Spacer, spacer (SMD)

40

third pad

42

Connection area (SMD component)

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 19547680 A1 [0003]
• EP1496733A2 [0003]
• JP 2007200997 A [0003]
• DE 102014218048 A1 [0008]
• EP 0934687 A1 [0008]

Claims (11)

Electronic assembly (10), comprising: a substrate (12) designed as a circuit board with a first (16) and a second main surface (18) opposite thereto, wherein at least one first pad (20) for connecting a wired electronic component extends on its second main surface (18), wherein a through hole (22) extends from the first pad (20) through the substrate (12) to the opposite first main surface (16); the electronic component (14), which has at least one connecting wire (24) which is inserted into the through hole (22) and extends through the through hole (22) to the opposite second main surface (18); wherein the connecting wire (24) is soldered (26) to the first pad (20); wherein the electronic component (14) extends at a distance from the first main surface (16), wherein the electronic assembly (10) further comprises: at least one second pad (28) formed on the first main surface (16); at least one spacer (30) formed on the second pad (28) from a solder or a solder paste, which, together with the underlying second pad (28), has a height that essentially corresponds to the distance between the electronic component (14) and the first main surface (16). Electronic assembly (10) according to Claim 1 , wherein the electronic component (14) is a THT component. Electronic assembly (10) according to Claim 1 or 2 , wherein the at least one second pad (28) is formed from the same material and preferably with the same thickness on the substrate (12) as the at least one first pad (20), preferably from copper, or aluminum, or alloys thereof. Electronic assembly (10) according to Claim 3 , wherein the at least one second pad (28) is neither connected to the at least one first pad (20) nor to further conductor tracks (32) formed on the first main surface (16), but rather is designed to be electrically insulated. Electronic assembly (10) according to one of the Claims 1 until 4 , wherein the substrate (12) is formed from an FR4 material. Electronic assembly (10) according to one of the Claims 1 until 5 , wherein the spacer (30) supports a surface of the electronic component (14) facing the first main surface (16). Electronic assembly (10) according to one of the Claims 1 until 6 , wherein the electronic component (14) is a capacitor, a coil, a transformer, a connector or an electronic switch. Electronic assembly (10) according to one of the Claims 1 until 7 , wherein at least two of the spacers (30) are provided with respect to the electronic component (14). Electronic assembly (10) according to one of the Claims 1 until 8th , wherein in addition to the wired electronic component (14) at least one or more SMD components (34) are formed on the first (16) and/or the second main surface (18). Electronic assembly according to Claim 9 , wherein the one or more SMD components (34) are connected to corresponding third pads (40) by solder (36), and the at least one spacer (30) for the wired electronic component (14) and the solder connections (36) of the SMD components are formed in a common reflow soldering process. Electronic assembly (10) according to one of the Claims 1 until 10 , wherein the electrical circuit arrangement realized in the electronic assembly (10) is designed to control or operate a functional unit of a motor vehicle, in particular an electric sunroof or window lifter or an electric heater.

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