WO2007068663A1

WO2007068663A1 - Circuit arrangement comprising a mechanical damping element

Info

Publication number: WO2007068663A1
Application number: PCT/EP2006/069493
Authority: WO
Inventors: Wolfgang Mueller-Hirsch
Original assignee: Robert Bosch Gmbh
Priority date: 2005-12-14
Filing date: 2006-12-08
Publication date: 2007-06-21
Also published as: DE102005059584A1

Abstract

Disclosed is a circuit arrangement comprising a component (1, 2) which is connected to a contact wafer (3) by means of at least one conducting terminal wire (7). In order to stabilize said circuit arrangement relative to mechanical vibrations, a mechanical damping element (13, 14, 15, 16, 17, 18, 19) is provided between the component (1, 2) and the circuit board (3).

Description

Circuit arrangement with a mechanical damping element

The invention relates to circuit arrangements which are used in particular in mechanically stressed environments, such as in motor vehicles or other motor-powered vehicles, where permanently distributed in engine operation in frequencies between a few Hz and a few 1000 Hz permanent and intense mechanical vibration excitations.

STATE OF THE ART

The proportion of electronics in systems of automotive technology is constantly increasing, so that manifold circuit arrangements are distributed on circuit boards, for example for injection control, but also other systems in a motor vehicle. The vibration excitations, which are exposed to such a system, on the one hand broadband, on the other hand also typically variable by changing rotational speeds of the engine.

This is associated with an extremely high demand for the reliability of the motor vehicle electronics, since the failure of an aggregate in the best case, the immobility of the motor vehicle and thus the driver, in the worst case, however, greater risks in road traffic result.

In addition, the said systems require high stability even over many years of use and under adverse conditions, such as strongly changing temperatures and humidities.

On the other hand, there is ever-increasing cost pressure, which is forcing down manufacturing and construction costs.

In such circuit arrangements, electronic components are usually connected by means of wires to a circuit board, wherein the wires are usually connected by soldering with tracks of the board. Such a solder connection is relatively stiff, with the electrical connection wire and the connection point in the electronic component representing the stiffer elements of the connection. Components subject to prolonged use under the conditions described occasionally show wire breaks or breaks at the terminals leading to failure of the circuit components. Order. Such an effect can occur especially in the case of larger components such as, for example, electrolytic capacitors, such as those used in particular for controlling modern injection valves. To solve such problems, various measures are known.

For example, from Patent Abstract of Japan Publication No. 2002185872 A, it is known to embed one end of a capacitor in a substance adhered to the circuit board so as to establish a firm connection between the capacitive element and the circuit board.

From DE 199 29 598 A 1, an electrolytic capacitor is known whose vibration resistance is improved on the one hand by the design of its internal wiring, on the other hand by the connection with outer connecting plates, which are arranged on the end faces of the capacitor and soldered to the circuit board.

As further measures for solving the problem there are mentioned a bonding of Elektrolytkondensato- ren with a circuit board and the attachment by means of clamps.

From patent abstract of Japan, publication number: 2000049473 A a clamp for the attachment of capacitors on a circuit board is known, wherein the clamp is secured in holes in the board by a snap connection. It is not clear how the capacitors are contacted there.

Japanese Patent No. 06204668 A discloses a clamp for connecting a duct to a part of a motor vehicle, wherein the clamp is clamped in a bore of a sheet-like member and is intended to reduce the vibration of the assembly.

The solutions described have in common that when connecting an electronic component to a circuit board parallel to the electrical wire connection, they require an additional fixed mechanical connection to cope with the mechanical stresses in vibration excitations.

ADVANTAGES OF THE INVENTION

The present invention, however, the object is to provide a simple and inexpensive connection of a component with a circuit board, which on the circuit board little space claimed, easy to assemble and yet ensures a high resistance to vibration excitations.

The object is achieved according to the present invention with the features of claim 1. Advantageous embodiments of the invention are shown in the subclaims.

The invention is based on the idea that the handling of the known vibration excitations is not guaranteed, as known in the prior art, by a stiffer connection of the component to the board, but by an effective damping. For example, the first harmonic of the natural frequency of an electrolytic capacitor in the vibration mode perpendicular to its cylinder axis (provided that the wire connections are arranged frontally and radially down to the circuit board) depending on the mass of the capacitor and strength of the solder wire connections between 180 and 250 Hz , An additional stiffening with solder sheets can cause a shift of the natural frequency, for example in the range of 600 Hz. However, the brazing plates consume space on the one hand, and on the other hand cause material costs and process costs due to the necessary soldering.

Although the natural frequency in the named mode is hardly changed by means of a damping element provided instead of the soldering plates, effective damping prevents the excitation of the corresponding natural vibration. The vibration energy is removed dissipatively. Such a damping element can be easily and inexpensively manufactured and inserted with very little manufacturing effort between the component and the board.

The damping element can either be connected to the component itself or to a part attached to it and can be present on the circuit board or a support element supported thereon or connected to the circuit board or a support element supported thereon and bear against the component.

It can also simply be clamped between the component and the circuit board and be frictionally held by the connection wire connection of the component to the circuit board. It is conceivable, for example, to clamp an elastomer pad, for example in the form of a foam such as neoprene, between an electrolytic capacitor and the circuit board. The production cost is for example reduced particularly by the fact that a damping element can be clamped onto the component and is supported by means of at least one support element on the printed circuit board.

In the manufacturing process, after the electrical connection of the component with the board, the damping element can be clamped and elastically supported against the board. For this purpose, the support element is advantageously made of an elastically deformable material or has an element which consists of an elastically deformable material. Such an element may also be formed, for example, as a hollow body or hollow profile.

Specifically, the damping element may be formed as a U-shaped plastic clip which can be clamped onto the component and which has deformable body on their free legs, which bear against the printed circuit board.

The deformable bodies may be formed, for example, as hollow profiles and consist of a silicone rubber. They can be attached to the legs of the U-shaped clip by means of an adhesive bond, for example a double-sided adhesive tape.

Such a clip compensates for manufacturing tolerances both in the diameter of the component to which it is clamped and in terms of the distance between the component and the board by its deformability.

The U-shaped bracket may also have on its inner side elastically damping intermediate layer elements in the form of one or more strips, which rest against the component. These can be between the clamp and the component clamped, but also be glued by means of double-sided adhesive tape. By means of the strips on the one hand ensures that the clip adheres to the component by frictional engagement. On the other hand, vibrations are already damped between the component and the clip and tolerance compensation takes place both between the clip and the component and with respect to the positioning of the clip with respect to the printed circuit board. For mounting, the clip is pushed onto the component, for example an electrolytic capacitor, after the component has been fastened to the printed circuit board, thereby expanding elastically. The inner edges of the clamp slide over the surface of the component. The component is supported on the above-mentioned hollow profiles on the circuit board. The tolerance compensation is made both by the intermediate layer elements and by the hollow profiles and leads to a frictional engagement of the clamp on the component on the one hand and on the circuit board on the other. DRAWINGS

In the following the invention will be shown with reference to an embodiment in a drawing and described below.

It shows

Figure 1 shows the typical arrangement of cylindrical electrolytic capacitors in a circuit arrangement;

FIG. 2 schematically shows a cylindrical electrolytic capacitor and the direction of the main oscillation mode; 3 shows a cylindrical electrolytic capacitor on a circuit board with a damping element;

DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows two cylindrical electrolytic capacitors 1, 2 in perspective view, which are soldered onto a circuit board 3. The longitudinal axes of the electrolytic capacitors 1, 2 are perpendicular to each other. The vibration excitation within a motor vehicle may well be anisotropic, so that one of the two capacitors is excited in different vibration modes than the other.

In principle, however, the suggestions are varied and distributed over several directions, so that the attenuation of all vibration modes should be taken care of.

Schematically, conductor tracks on the circuit board 3 are also indicated in FIG. 1, with which the capacitors shown are connected via the connecting wires 4, 5 by means of soldering.

Figure 2 shows schematically in a three-dimensional view of a cylindrical electrolytic capacitor 1, which is connected at its two end faces, of which only one is shown 6, by means of connecting wires 7 with a circuit board 3 by soldering. The most excited vibration mode is the tilting vibration of the capacitor around the attachment points 8 or the axis connecting them, which is indicated by the arrows 9, 10. The frequency of this mode may be, for example, in the order of 200 Hz. Such a vibration claimed the material of the connecting wire 7, so that sooner or later a break can occur, which then preferably occur at the solder joint 8 or at the exit point 11 of the lead wire from the capacitor.

FIG. 3 shows a cylindrical electrolytic capacitor 1 which, as in the figures described above, is contacted to a circuit board 3 by means of a connection wire 7. The lying on the opposite end side connecting wire is not shown.

On the cylindrical surface 12 of the capacitor 1, a U-shaped bracket 13 is pushed and fastened there by clamping. It consists of an elastic plastic material such as a casting resin.

When selecting the materials used, it must always be ensured that they have a temperature stability above 125 ° C in order to meet the typical ambient conditions, for example in the engine compartment of a motor vehicle.

In order to save weight and achieve greater elasticity, windows 14 can be excluded in the U-shaped bracket 13. On the inner side of the clamp 13, a plurality of elastic, damping strips made of an elastomer or a continuous layer 20, 21 of a corresponding material may be provided for tolerance compensation and to achieve good frictional engagement between the clamp and the component.

The free legs 15 of the clip end in connecting edges 16, 17, each having a flange for fastening elastic hollow body 18, 19 have. These elastic hollow bodies are formed in the example shown as hollow profiles of a silicone elastomer, which by means of a double-sided

Adhesive tape is attached to the edges 16, 17.

An attachment of the hollow sections 18, 19 to the Leiterp latine 3 need not be provided, since the shape and size of the bracket 13 and the length of the legs 15 in comparison to the length of the connecting wires 7 is designed so that when pushing the Clamp 13 on the electrolytic capacitor 1, the hollow body 18, 19 are pressed under elastic deformation and frictional engagement against the circuit board 3. As a result, no special stiffening of the connection between the electrolytic capacitor 1 and the circuit board takes place, but an effective damping of the tilting oscillation, as shown in Figure 2, and other modes.

The clamp 13 can be placed on the circuit board 3 either before or after the soldering of the capacitor 1 to the capacitor.

On the circuit board 3 no space for stiffening elements must be kept free. Although no components can be provided in the area of support of the hollow sections 18, 19, conductor tracks can run there and components can also be arranged on the underside of the board.

The material of which the clamp 13 is made can likewise have strongly damping properties, so that a support on the circuit board 3 can already produce a sufficient damping even without the hollow profiles 18, 19.

Due to the damping direction according to the invention an effective damping and thus an increase in operational reliability and life extension is achieved with low design and cost and low process cost.

It is understood that the realization of the invention is not limited to the embodiment shown and can also be realized by other combinations of said features.

ROBERT BOSCH GMBH, 70442 STUTTGART

Circuit arrangement with a mechanical damping element

LIST OF REFERENCE NUMBERS

Claims

ROBERT BOSCH GMBH, 70442 STUTTGART circuit arrangement with a mechanical damping element PATENT CLAIMS

1. Circuit arrangement having a component (1, T) which is connected by means of at least one conductive connecting wire (4, 7) to a printed circuit board (3), characterized by a mechanical damping element (13, 14, 15, 16, 17, 18, 19) which is coupled on its one side to the component or a part fixedly connected thereto and on the other side to the printed circuit board (3) or a part fixedly connected thereto.

2. Circuit arrangement according to claim 1, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) on the component (1, 2) is attached.

3. Circuit arrangement according to claim 1, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) is attached to the circuit board (3) or to a connected thereto or supported on this holding element.

4. A circuit arrangement according to claim 1, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) between the component (1, 2) on the one hand and the circuit board (3) or supported on this holding element on the other is trapped.

5. Circuit arrangement according to claim 1 or one of the following, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) has an elastically deformable material.

6. Circuit arrangement according to claim 1 or one of the following, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) has an elastically deformable hollow body (18, 19).

7. Circuit arrangement according to claim 1 or one of the following, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) on the component (1, 2) can be clamped and by means of at least one support element ( 15, 18, 19) is supported on the circuit board.

8. Circuit arrangement according to claim 7, characterized in that the support element (18, 19) consists of an elastically deformable material.

9. Circuit arrangement according to claim 7 or 8, characterized in that the support element (18, 19) has an elastic hollow profile.

10. Circuit arrangement according to claim 1, 2, 4 or one of the following, characterized in that the mechanical damping element (13, 14, 15, 16, 17, 18, 19) has a U-shaped bracket which elastically on the device ( 1, 2) can be clamped and on the free legs elastically deformable body (18, 19), which rest against the circuit board.

11. Circuit arrangement according to claim 10, characterized in that the free legs of the clamp converge towards one another and each carry at their ends an elastically deformable body (18, 19).

12. Circuit arrangement according to claim 10 or 11, characterized in that the elastically deformable body (18, 19) are hollow profiles of a silicone material.

13. Circuit arrangement according to claim 12, characterized in that in that the elastically deformable hollow profiles (18, 19) are fastened to the free legs of the clip by means of double-sided adhesive tape.

14. Circuit arrangement according to claim 10 or one of the following, characterized in that, between the U-shaped bracket and the component (1,2) at least one strip

(20,21) is arranged a damping material.