DE102007037365A1 - Surface mounted device electrolytic capacitor for engine control device of motor vehicle, has projecting leads provided with solderable surfaces, where areas are provided with solderable surfaces and project from side over housing - Google Patents

Abstract

The capacitor (2) has housing (4) and a set of areas provided with solderable surfaces and projecting from a side over the housing. Projecting leads (8, 10, 12) serve as electrical connection pins, where the projecting leads are provided with solderable surfaces. The projecting leads withdraw from the housing through a limiting wall (6), where withdrawal points form corners of a triangle. The projecting leads serve for a mechanical attachment and a support.

Description

The The invention relates to an electrolytic capacitor according to the Preamble of claim 1.

State of the art

electrolytic capacitors (Elkos) for mounting on printed circuit boards or other circuit boards, the in the form of SMDs (Surface Mounted Devices), that is to say surface mountable Components are formed, usually contain a serving as a cathode liquid, pasty or solid electrolyte surrounding an anode and in turn of a Housing is enclosed. For connection of the electrolytic capacitors to a printed circuit formed on the circuit carrier Circuit serve two electrical connection pins or contacts in Shape of protruding over the housing legs, one with the anode and the other with the cathode or is connected to the housing. The two parallel out of the Housing leaking legs also serve as a carrier or support for the case to this to keep at a distance above the printed circuit. to Attachment to the circuit carrier and to the connection to the circuit each have a bent free end part with a solderable Connection surface on, with which they are on a corresponding Lötpastefleck on one of the two broad sides of the Circuit carrier can be soldered.

If Such electrolytic capacitors in dynamically stressed circuits be installed, such as circuits of engine control units of motor vehicles, which often have significant vibrations are exposed, have the housing of the electrolytic capacitors a pronounced main axis of oscillation, which is transverse to a connecting line is aligned between the two legs. At a match of this main vibration axis with a vibration axis of the circuit carrier, this can cause the housing worn by the legs in a decoupled from the vibration of the circuit carrier Self-oscillation be offset. Especially in case of resonance leads This leads to a relatively large oscillation amplitude of the housing and thus to a strong alternating bending stress of the legs, which in turn is an early failure of the electrolytic capacitors can result.

When Measures against such vibration excitation are occasionally SMD electrolytic capacitors of the type mentioned above with four legs two of which are used as electrical connection pins or serve as additional mounting pins. The housing These electrolytic capacitors have no pronounced Vibration axis on, so that the lifetime when used in dynamic stressed circuits due to the lower stress the legs can be extended. However, the support is the Housing on four legs statically indeterminate, what with such a construction bears the risk that when mounting on the circuit board only three of the legs in contact with the adjacent surface of the circuit carrier while the fourth leg is not in contact with it the circuit carrier has. When it comes to this leg is one of the two electrical connection pins, leads this already in the course of production to a failure of the circuit.

Next is from the KR-2005114079 A a structure for reducing the vibrations of an arbitrary component mounted on a printed circuit board is known in which the component connected by a connection pin to the circuit board is additionally supported by a vibration-resistant element which is inserted between the component and the circuit board.

outgoing This is the object of the invention, an electrolytic capacitor of the type mentioned above to improve that at a Use of the electrolytic capacitor on a dynamically stressed Circuit carrier decoupled from the vibration of the circuit carrier Oscillation of the housing with a pronounced Vibration axis avoided and at the same time while soldering the legs a secure contact of all legs with the adjacent surface of the circuit substrate can be guaranteed.

Disclosure of the invention

These The object is achieved according to the invention that the number of protruding, with solderable Surface provided legs is three.

The invention is based on the idea that a decoupled oscillation of the housing with a pronounced oscillation axis can be reliably avoided on the one hand by supporting the housing of the electrolytic capacitor on three instead of two with the circuit substrate legs, while on the other hand supported on three legs housing in contrast forms a statically determined system to a four-legged housing, so that during assembly always all the legs with the adjacent surface of the circuit board in contact, even if their end parts are bent due to manufacturing tolerances at slightly different distances from the housing. In addition, by the inventive measure, the additional up wall avoidable for a disposed between the housing and the circuit carrier vibration damping element.

A preferred embodiment of the invention provides that one of three legs only for mechanical attachment. This requires the Solder paste stain used to solder this leg not connected to the circuit on the circuit carrier be. Alternatively, it is also possible, all three Beinchen to use as electrical connection pins and in the Mounting two of the three legs, namely the one with the cathode in the Contacting legs, with a ground conductor of the circuit board connect for redundancy of the ground connection to care.

Preferably all three legs pass through one and the same boundary wall from the housing, with their exit points the corners of a Triangles form to the vibration resistance of the housing against vibrations along a pronounced To maximize the main axis of oscillation. The vibration resistance is greatest when the triangle is as equilateral Triangle is formed.

Around an unwanted reverse polarity of serving as electrical connection pins To avoid missing legs, the exit points of the legs can but also beneficial at the corners of an isosceles triangle lie, whose base is appropriate from the exit points the serving as electrical connection pins legs is clamped.

Around for a good support of the housing a flat surface of a circuit substrate Advantageously, the free end portions of all three are advantageous Legs at the same distance from the housing to the outside bent, with the solderable surfaces on the side facing away from the housing side of the free end portions are arranged and span a plane. Preferably, the bent end portions of the legs in relation to a longitudinal center axis of the Housing radially outward.

Brief description of the drawings

in the The following is the invention with reference to an illustrated in the drawing Embodiment explained in more detail. Show it:

1 a perspective view of a surface mount SMD electrolytic capacitor;

2 an end view of the SMD electrolytic capacitor 1 ;

3 a perspective view of another surface mount SMD electrolytic capacitor;

4 an end view of the SMD electrolytic capacitor 3 ;

5 a perspective view of yet another surface mount SMD electrolytic capacitor;

6 an end view of the SMD electrolytic capacitor 5 ,

embodiments the invention

The SMD electrolytic capacitor (SMD electrolytic capacitor) shown in the drawing 2 used for surface mounting on a printed circuit board (not shown).

The electrolytic capacitor 2 consists essentially of an inverted pot-shaped housing 4 , which encloses a serving as a cathode liquid, pasty or solid electrolyte, in turn, one inside the housing 4 Enclosed anode (not visible) surrounds. At its the PCB facing bottom is the housing 4 through a deformed housing cover 6 tightly closed.

Over the housing cover 6 stand three metallic legs 8th . 10 . 12 over, used to attach the housing 4 serve on the circuit board and the housing 4 at a distance above the adjacent surface of the circuit board. The legs 8th . 10 . 12 each consist of a narrow elongated strip of sheet metal, occur essentially in parallel alignment of the housing cover 6 off and are each at the same distance from the housing cover 6 at right angles to the outside, ie in the direction of a peripheral wall 14 of the housing 4 bent, with their bent end sections 16 . 18 . 20 with respect to a longitudinal central axis 22 of the housing 4 are radially aligned. The printed circuit board facing lower broad side surfaces of the end portions 16 . 18 . 20 form solderable surfaces during assembly of the electrolytic capacitor 2 placed on corresponding, previously applied to the adjacent surface of the printed circuit board Lötpasteflecken and soldered, for example, in the reflow process with the circuit board.

Of the three legs 8th . 10 . 12 form two ( 8th and 10 ) simultaneously electrical connection pins for connecting the anode or the cathode of the electrolytic capacitor 2 to a printed circuit board of the circuit board, with which the attachment of the legs 8th . 10 serving solder paste spots are electrically connected such that the cathode and the casing 4 in contact with mass. The third leg 12 serves only for mechanical attachment and support of the housing 4 of the electrolytic capacitor 2 ,

In the electrolytic capacitors shown in the drawing 2 is the third leg 12 arranged so that its exit point 28 from the housing cover 6 opposite a connecting line between the exit points 24 . 26 the two serving as connection pins legs 8th . 10 from the housing cover 6 has a lateral offset, so that the exit points 24 . 26 . 28 all three legs 8th . 10 . 12 forming the vertices of a triangle. This will form the legs 8th . 10 . 12 a statically determined three-point support system for the housing 4 , whereby even in the case of tolerances due to different distances of the end sections 16 . 18 . 20 from the housing cover 6 or in the case of different material thicknesses of the Lötpasteflecken a contact of all legs 8th . 10 . 12 is ensured with the surface of the circuit board or the Lötpasteflecken. In addition, such a system does not have a pronounced oscillation axis, whereby, in particular in the event of dynamic loading of the finished printed circuit board, for example when used in an engine control unit of an internal combustion engine, movement of the housing 4 of the electrolytic capacitor 2 is prevented with a decoupled from the vibration of the circuit board self-oscillation, which latter could lead in particular in the case of resonance due to the relatively large amplitude of vibration to a strong alternating bending stress and thus to an early failure of the legs.

The lower broad side surface of the end section 20 the serving only for mechanical support legs 12 Therefore, it can be soldered to a solder paste patch that does not electrically communicate with the circuitry on the board.

In the electrolytic capacitor 2 in the 1 and 2 form the exit points 24 . 26 . 28 the three legs 8th . 10 . 12 each corner of an equilateral triangle, from where the end sections 16 . 18 . 20 the legs 8th . 10 . 12 in relation to the longitudinal central axis 22 of the housing 4 at equal angular intervals of 120 degrees radially outward in the direction of the cylindrical outer peripheral wall 14 of the housing 4 extend beyond their free ends slightly.

In contrast, the exit points form 24 . 26 . 28 the three legs 8th . 10 . 12 with the electrolytic capacitors 2 in the 3 and 4 such as 5 and 6 each corner of an isosceles triangle, its base B from the exit points 24 . 26 the two serving as pins or contacts pins 8th . 10 is formed while the apex of the triangle from the exit point 28 of the serving for mechanical support legs 12 is formed. Compared to the arrangement in the 1 and 2 This can ensure a better polarity reversal protection.

Here are the exit points 24 . 26 the serving as connecting pins legs 8th . 10 in the electrolytic capacitor 2 in the 3 and 4 in relation to the longitudinal central axis 22 of the housing 4 diametrically opposite, with their end sections 16 . 18 enclose an angle of 180 degrees while the exit point 28 of the serving for mechanical support legs 12 at the same distance from the longitudinal central axis 22 lies on the bisector of the base B and the end portion 20 this little leg 12 each an angle of 90 degrees with the end sections 16 . 18 the other two legs 8th . 10 includes.

In the electrolytic capacitor 2 in the 5 and 6 in contrast, have the exit points 24 . 26 the legs serving as electrical connection pins 8th . 10 a relatively small distance apart, while their end sections 16 . 18 an acute angle of about 45 degrees. The distance between the exit points 24 . 26 and the exit point 28 of the serving for mechanical support legs 12 There is greater than the mutual distance of the exit points 24 and 26 the legs 8th . 10 , whose end sections 16 . 18 with the end section 20 of the leg 12 each enclose an angle of about 150 degrees.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• - KR 2005114079 A [0005]

Claims (11)

Electrolytic capacitor in the form of a surface-mountable component, comprising a housing and a plurality of legs projecting beyond the housing, provided with solderable surfaces, wherein at least two of the legs serve as electrical connection pins, characterized in that the number of protruding, with solderable surfaces provided legs ( 8th . 10 . 12 ) is three. Electrolytic capacitor according to claim 1, characterized in that a ( 12 ) of the three legs ( 8th . 10 . 12 ) is used only for mechanical attachment or support. Electrolytic capacitor according to claim 1 or 2, characterized in that all three legs ( 8th . 10 . 12 ) by one and the same boundary wall ( 6 ) out of the housing ( 4 ), with their exit points ( 24 . 26 . 28 ) form the corners of a triangle. Electrolytic capacitor according to claim 3, characterized in that the exit points ( 24 . 26 . 28 ) of the legs ( 8th . 10 . 12 ) form the corners of an isosceles triangle. Electrolytic capacitor according to claim 3 or 4, characterized in that the exit points ( 24 . 26 ) serving as electrical connection pins legs ( 8th . 10 ) span a base (B) of the isosceles triangle. Electrolytic capacitor according to one of claims 3 to 5, characterized in that the distance of the exit points ( 24 . 26 ) of the two serving as electrical connection pins legs ( 8th . 10 ) greater than their respective distance from the exit point ( 28 ) of the serving for mechanical fastening Beinchens ( 12 ). Electrolytic capacitor according to one of claims 3 to 6, characterized in that the exit points ( 24 . 26 ) serving as electrical connection pins legs ( 8th . 10 ) with respect to a longitudinal center axis ( 22 ) of the housing ( 4 ) are diametrically opposed. Electrolytic capacitor according to one of claims 3 to 6, characterized in that the distance of the exit points ( 24 . 26 ) serving as electrical connection pins legs ( 8th . 10 ) smaller than their respective distance from the exit point ( 28 ) of the serving for mechanical fastening Beinchens ( 12 ). Electrolytic capacitor according to claim 3, characterized in that the exit points ( 24 . 26 . 28 ) of the legs ( 8th . 10 . 12 ) form the corners of an equilateral triangle. Electrolytic capacitor according to one of the preceding claims, characterized in that free end sections ( 16 . 18 . 20 ) of the three legs ( 8th . 10 . 12 ) each at the same distance from the housing ( 4 ) are bent outwards, wherein the solderable surfaces of the housing ( 4 ) facing away from the free end sections ( 16 . 18 . 20 ) are arranged and span a plane. Electrolytic capacitor according to claim 10, characterized in that the bent end sections ( 16 . 18 . 20 ) of the legs ( 8th . 10 . 12 ) with respect to a longitudinal center axis ( 22 ) of the housing ( 4 ) are radially aligned.