DE202022106958U1 - Electronic assembly with spacer for an electronic component on a substrate - Google Patents

Abstract

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

Description

technical field

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 leaded electronic component may be THT mounted and is spaced from the substrate by one or more spacers.

Technical background

During the assembly of circuit boards, electronic components can be attached in various ways to the intended locations on the surface of the circuit boards and thereby, if necessary, electrically connected to other electronic components. Standard methods for this are surface mounting (surface mounting technology, SMT) or through-hole or plug-in mounting (through-hole technology, THT). Terminal pads or legs are soldered directly onto a printed circuit board, the THT components are wired radially or axially, etc., with the wires being inserted through pre-formed holes in the printed circuit board or board and soldered to the back of the printed 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 printed circuit board and the opposite connection surface of the SMD component, so that the solder paste forms a reliable, permanent and electrically resistance-free connection between them areas available. Examples of the implementation of spacers for surface mounting are inter alia in the references DE19547680A1 , EP 1 496 733 A2 and JP 2007-200997 A disclosed. Such spacers are usually designed as small beads made of silver or copper (tinned). 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 requirements for mechanical stability. Such requirements are placed in particular on electronic assemblies that perform electronic control tasks or the operation of functional units in moving vehicles, in particular motor vehicles. Other aspects relate to enabling a certain amount of adhesive between the component and the surface of the printed circuit board through a defined distance. It is therefore a question of 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 or spacers can be made of plastic or metal and are attached by soldering, gluing, screwing or snapping. In order to keep the appropriate distance through these, various possibilities are known and common practice:

• For example, the component itself can have a spacer in an integrated manner. However, the problem here is that the components used are often standard products (mass 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 required, which can involve greater effort.

Another possibility is to place special spacers directly on the printed circuit board, as described above by soldering, gluing, screwing or snapping, etc. But here too, disadvantages can arise from the fact that a large number of small mechanical components can be used as spacers is to be used, which can entail comparatively high costs. Furthermore, such spacers also have the disadvantage that if they are soldered, for example, the soldering points connected to them can be damaged due to the mechanical stress or also thermal stress. In the worst case, the affected spacers or spacers can come loose and cause short circuits in the electronic assembly.

Another possibility is to adjust the distance using special external mounting devices, which are removed e.g. after the glue has hardened. But here, too, there is additional effort due to the corresponding devices, and further production steps are required, which can also lead to increased costs.

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

Consequently, there is a need for cost savings and a reduction in the effort involved in setting predetermined distances between THT components and the underlying circuit board, while at the same time maintaining or even improving product quality in terms of mechanical stability and durability.

Presentation of different aspects

Aspects of the invention are based on an electronic assembly that includes a substrate designed as a printed circuit board and at least one electronic component. It is an electronic component that is wired axially or radially, etc., 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 connecting and soldering pad and a flat extension of a conductor track connecting the electronic component, e.g. made of copper or aluminum. The trace and the first pad can be surface treated (OSP, HAL, HASL, immersion 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. In this case, 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 connection 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 area. This essentially corresponds to the THT design.

The electronic component extends with its body (seen without the wire) at a distance from ("above") the first major surface. If, for example, it is a horizontal cylindrical body, the distance can be essentially constant over its length. If, on the other hand, it is a disk-shaped or spherical body, the distance can also be variable (depending on the position on the surface of the printed 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 designed in the same way as the first pad. In particular, however, it is able to absorb solder paste and enter into a safe and reliable connection with the solder that is produced in a soldering process. As a result, a spacer made of solder or solder paste is now set up on the second pad, which together with the underlying second pad has a height which 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 bump on the circuit board with it. The formation of the spacer can take place in a common step with the soldering process of other components on the printed circuit board, namely in particular when reflow soldering for connecting SMD components on the same printed circuit board takes place simultaneously on the same or both main surface(s). . 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 increased costs (according to calculations, currently only around 0.2 cents per spacer point for the soldering paste, depending on the design), and the additional effort for installing the previously used spacers or 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 adapted in advance by means of appropriate 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 show. The height that ultimately results after cooling is determined by the area and geometry of the second pad underneath. The soldering paste applied during the process assumes a shape on the second pad that depends on various other but known factors (chemical composition, temperature profile, etc.). The height of the spacer can therefore be set precisely by appropriate dimensioning and geometry of the second pad in the layout. This also makes it possible to put into practice different distances or heights for different spacers on the same printed circuit board. It should be noted that a step stencil can also be used to influence the amount of solder paste and hence the resulting height of the spacer.

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

According to one exemplary embodiment, the at least one second pad is made of the same material and is formed on the substrate with the same thickness as the at least one first pad, preferably made of copper or aluminum or alloys thereof. This means that uniform processes can be used to manufacture the conductor tracks and other structures on the printed 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 formed in an electrically insulated manner. In other words, the second pad with the spacer thereon is essentially non-functional electrically.

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

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

According to further exemplary embodiments of the electronic assembly, the electronic component is a capacitor, a coil, a transformer, a plug 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 created in mixed construction (SMD, THT). In addition to the wired electronic component, at least one or more SMD component(s) 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, so to speak, in a preceding SMT process, which saves costs and effort in a considerable way.

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 set up to control or operate a functional unit of a motor vehicle, in particular an electric sunroof or window opener or an electric heater. In these areas of application, there are special requirements for mechanical stability and reliability, so that the advantages have a particular impact here.

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

character list

• 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, a partial cross section through a 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 exemplary embodiments, it must be taken into account that the present disclosure of the various aspects is not limited to the details of the construction and the arrangement of the components, as they are illustrated in the following description and in the figures. The example embodiments may be practiced or carried out in various ways. It is further to be understood that the phraseology and terminology used herein are used for the purpose of specific description only and should not be construed as such in a limiting manner by those skilled in the art. Furthermore, in the following description, the same reference symbols in the various exemplary embodiments or figures designate the same or similar features or objects, so that in some cases a repeated detailed description of the same is dispensed with in order to preserve the compactness and clarity of the illustration.

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

The substrate 12 can be, for example, a plate made of FR4 material. The substrate 12 has a first major surface 16 and an opposing second major surface 18. An electronic component 14 is provided in THC construction. In the axial direction and then bent, two connecting wires 24 extend 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 at a corresponding point on the second main surface 18 . The through holes 22 can have an internal metallization. The through hole 22 extends through the pads 20 with the connection wires 24 . The connecting wires 24 are electrically conductively connected to the corresponding pads 20 by a soldered connection 26 each. The pads 20 can be connected to conductor tracks formed from copper, for example, on the second main surface 18 in order to enable 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. As shown in FIG. More specifically, they face the body of the electronic component 14 directly. Pads 28 are made of solder paste in an SMD process (for example reflow soldering or other soft soldering process). Spacers 30 formed. They contact the intrinsically 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 define 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 may be determined from experience and/or experimentation in vibration testing of the assembly reflecting the requirements in intended use. With the given values it should be noted that a varnish can regularly be applied to the printed 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 else 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 with photolithographic means in the same step as the other pads 20, 40 when structuring the wiring of the printed circuit board. In this case, no additional step for creating the spacer is required. Likewise, the spacers 30 can be produced after the provision of the printed circuit board with conductor tracks etc. in the same process step for the assembly of SMD components as the soldered 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 35 μm, for example.

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

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

Details and details, as well as modifications, which are common in the manufacture of printed circuit board electronic assemblies, have been omitted from the above description for the sake of simplicity. Those skilled in the art understand that such conventional measures as the surface treatment not mentioned above can also be carried out.

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

Reference List

10

electronic assembly

12

substrate (printed circuit board)

14

electronic component

16

first main surface

18

second main surface

20

first pad

22

through hole

24

hookup wire

26

Solder connection (1st pad)

28

second pad

30

spacer, spacer (THT)

32

Conductor tracks, circuit board wiring

34

SMD component

36

Solder connection (3rd pad)

38

Spacers, standoffs (SMD)

40

third pad

42

Landing area (SMD component)

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited 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 assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 19547680 A1 [0003]
• EP 1496733 A2 [0003]
• JP 2007200997 A [0003]
• DE 102014218048 A1 [0008]
• EP 0934687 A1 [0008]

Claims (11)

Electronic assembly (10) comprising: a substrate (12) embodied as a printed circuit board with a first (16) and a second main surface (18) opposite thereto, with at least one first pad (20) for connecting a wired electronic component extending on its second main surface (18), with a through hole (22) extending from the first pad (20) through the substrate (12) to the opposite first major surface (16); the electronic component (14) having at least one lead (24) inserted into the through hole (22) and extending through the through hole (22) to the opposite second main surface (18); wherein the lead wire (24) is soldered (26) to the first pad (20); wherein the electronic component (14) extends at a distance from the first major surface (16), wherein the electronic assembly (10) further comprises: at least one second pad (28) formed on the first major surface (16); at least one spacer (30) formed from a solder or solder paste on the second pad (28), which together with the underlying second pad (28) has a height which essentially corresponds to the distance between the electronic component (14) and the corresponds to 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 made of 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 formed in an electrically insulated manner. Electronic assembly (10) according to one of Claims 1 until 4 wherein the substrate (12) is formed from an FR4 material. Electronic assembly (10) according to one of 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 Claims 1 until 6 , wherein the electronic component (14) is a capacitor, an inductor, a transformer, a plug or an electronic switch. Electronic assembly (10) according to one of 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 Claims 1 until 8th , wherein in addition to the wired electronic component (14) at least one or more SMD component (s) (34) on the first (16) and / or the second main surface (18) is formed. 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 Claims 1 until 10 , wherein the electrical circuit arrangement implemented in the electronic assembly (10) is set up 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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