Circuit board

Abstract

The present invention relates to a printed circuit board (2) with at least two contact receptacles (15, 16, 17) for receiving electrical contacts (10, 12, 14), wherein a cutout (20) is formed in the printed circuit board (2) between two contact receptacles (15, 16, 17) for electrical contacts (10, 12, 14) that can be energized with different electrical polarities. Preferably, the cutout (20) is an insulating body (22). The cutout (20) with the insulating body (22) passing through it increases the air and creepage distance between the contact receptacles (15, 16, 17). This is particularly advantageous when a circuit breaker (8) is connected to the printed circuit board (2) via the contact receptacles (15, 16, 17). Here, the breakthrough (20) is preferably formed between the contact receptacle (16) to which the emitter of the power switch (8) is connected, on the one hand, and the contact receptacles (15, 17) to which the collector and gate of the power switch (8) are connected.

Description

[0001] The present invention relates to a printed circuit board with a modified creepage distance between two contact receptacles for electrical contacts that can be energized with different polarities. This is preferably used in electrical heating devices comprising at least one PTC heating device.

[0002] Particularly when large potential differences are present on printed circuit boards, for example, when switching large power currents at large potential differences, the requirements for breakdown protection lead to large distances between the contacts and contact receptacles that are at the corresponding potentials during operation. This is particularly disadvantageous when space is limited.

[0003] The present invention is based on the problem of providing a solution that enables a compact design of a printed circuit board.

[0004] To solve this problem, a printed circuit board with at least two contact receptacles for receiving electrical contacts is proposed, which is characterized in that an opening is formed in the printed circuit board between two contact receptacles for electrical contacts that can be energized with different electrical polarity.

[0005] The term "printed circuit board" refers to both populated and unpopulated circuit boards. The term "current-carrying capability" refers to two contacts with different polarities that are not directly connected to each other via a conductive path. A "cutout" is an opening that extends through the thickness of the circuit board, so that no circuit board material remains in the cutout. Preferably, the cutout is an opening whose edge is closed in the circuit board.

[0006] By forming a breakthrough between two contacts that can be energized with different electrical polarity, the creepage distance between the contacts is extended. Compared to a circuit board without a breakthrough, this allows the distances between the contacts to be reduced while maintaining the same dielectric strength. This allows for a more compact circuit board design. This is particularly advantageous when contacting power switches, for example, those designed as bipolar transistors with insulated gate electrodes, on the circuit board, as these regularly switch high voltages and currents. These are used in a wide variety of applications, for example in switched-mode power supplies, and in particular in electrical heating devices that include at least one PTC heating device.In such electrical heating devices, the present invention can preferably be used for a circuit board populated with semiconductor components, which is usually part of a control device of the electrical heating device. Alternatively or additionally, the present invention can also be used with so-called wiring modules. These are circuit boards that are not populated with semiconductor components and that have contact receptacles for the electrical contacting of PTC heating devices. The wiring module is then in turn electrically connected to the aforementioned circuit board of a control device. Such a design is often advantageous because the heat loss generated at the electrical contact between the PTC heating device and the wiring module only heats the wiring module, which, however, is unpopulated, thus preventing thermal damage to semiconductor components.The size and shape of the opening in the circuit board is preferably designed so that a specified creepage distance extension can be achieved.

[0007] According to a preferred embodiment, the contact receptacles are designed for contacting a component, wherein the component comprises a semiconductor component, in particular a transistor, preferably a field-effect transistor, a metal-oxide-semiconductor field-effect transistor or a bipolar transistor with an insulated gate electrode, a capacitor, a diode and / or a resistor.

[0008] The component is preferably connected to the contact receptacles via electrical contacts, so the circuit board is preferably equipped with at least one component, preferably a semiconductor device. The breakout extends the creepage distance between the electrical contacts of the component.

[0009] According to a preferred embodiment, an insulating body extends through the aperture. The insulating body is made of an electrically insulating material, in particular a plastic. The insulating body extending through the aperture extends the air gap between the contact receptacles, so that the distance between two contact receptacles that can be supplied with current of different polarity can be reduced while maintaining the same dielectric strength. This enables a more compact circuit board design while maintaining the same dielectric strength. By combining the aperture with the insulating body extending through the aperture, the air and creepage distances between the contact receptacles separated by the aperture are extended.

[0010] Preferably, the aperture is formed in the shape of a circular segment. This allows for a particularly efficient creepage distance extension and, in the case of an insulating body passing through the aperture, an extension of the clearance distance.

[0011] The semiconductor component is preferably a power switch with at least three contacts. Preferably, an insulated-gate bipolar transistor (IGBT), a field-effect transistor (FET), or a metal-oxide-semiconductor field-effect transistor (MOSFET) is used as the semiconductor component or power switch. In this context, it is particularly preferred for the breakdown to be formed between one contact receptacle and the two remaining contacts. This allows for an extension of the clearance and creepage distances between the emitter of the semiconductor component, in particular the IGBT, on the one hand, and the collector and the gate on the other.

[0012] Since circuit breakers switch high voltages and / or currents, they carry a comparatively high risk of breakdown. By creating a breakdown between the contact receptacles for the circuit breaker's electrical contacts, which can be energized with different polarities, a more compact design of a circuit board with a circuit breaker can be achieved while maintaining a given dielectric strength.

[0013] Furthermore, an electric heating device comprising at least one PTC heating device is proposed, wherein at least one circuit board is designed according to the present invention.

[0014] The electric heating device preferably comprises a connection chamber and a heating chamber, which are separated by a partition wall for dissipating heat to a medium to be heated, and a housing part which delimits the heating chamber. At least one PTC heating device is formed, which is thermally conductively connected to the heating chamber and which is electrically connected in the connection chamber, wherein a control device with at least one printed circuit board populated with at least one semiconductor component is formed in the connection chamber. Preferably, a further, unpopulated printed circuit board is designed as a wiring module, to which the at least one PTC heating device is electrically connected and which in turn is electrically connected to the populated printed circuit board of the control device.Preferably, at least one heating device housing projects from the partition wall in the direction of the heating chamber, forming a receiving pocket in which at least one PTC heating device is supported in an insulated manner.

[0015] The electric heating device according to the present invention is preferably used in a motor vehicle, preferably a partially or fully electrically powered motor vehicle. The PTC heating device comprises at least one PTC element, which has conductor tracks electrically connected to it and electrically connected in a connection chamber. The conductor tracks serve to supply current to the PTC element with different polarities. Thus, the power current for operating the PTC element is fed to the PTC element via the connection chamber. The at least one PTC element and the conductor tracks are preferably supported in an insulated manner in the receiving pocket. The insulating support can be provided, for example, by insulating plates that lie flat against the outer surface of the conductor tracks. The conductor tracks are preferably designed as contact plates.

[0016] For the PTC heating device to operate efficiently, it is necessary to dissipate the heat generated by the PTC element as effectively as possible to both sides of the main side surfaces of the PTC element. The PTC element is preferably cuboid-shaped. The main side surfaces are those side surfaces of the cuboid with the largest areal extent. These main side surfaces are preferably connected to one another by a peripheral edge of the PTC element, which usually has edge surfaces extending at right angles to the main side surfaces. The area of ​​each main side surface is preferably at least a factor of 5 larger than the area of ​​one of the edge surfaces. The heating device housing preferably forms a type of heating fin that projects into the heating chamber.

[0017] The PTC elements are preferably sintered ceramic blocks, which are usually metallized on their main side surfaces to conduct the power current into the PTC element. These ceramic components are brittle and prone to breakage. The same applies to the insulating layer, provided it is made of a ceramic plate. The use of an aluminum oxide plate is quite common for insulating the PTC element against the inner surface of the heater housing. To increase electrical safety, corresponding insulating layers are typically provided on both sides. There are suggestions to additionally provide these ceramic plates with an electrically insulating foil to maintain a certain degree of electrical insulation from the metallic heater housing in the event of a breakage of the ceramic plate.

[0018] Due to electromobility, electric heaters are increasingly operated at higher voltages of 48 volts and above. Sometimes these electric heaters operate at a power current of 100 amps or more. Electrical safety and dielectric strength measures must be adapted accordingly.

[0019] The design of a printed circuit board according to the present invention enables a more compact design of the control unit and thus also of the electrical heating device while at the same time maintaining dielectric strength.

[0020] The circuit board is preferably equipped with at least one power switch as a component via electrical contacts connected to contact receptacles. The power current for the at least one PTC heating device can be switched via the power switch, preferably a bipolar transistor with an insulated gate electrode. By forming the aperture, through which an insulating body preferably passes, the creepage distance, preferably the clearance and creepage distance, between the electrical contacts of the power switch, which can be energized with different polarities, is extended. This enables a more compact design of the electrical heating device with the power switch.

[0021] Further details and advantages of the present invention will become apparent from the following description of an embodiment in conjunction with the drawings, in which: Fig. 1 a perspective view of an embodiment of the printed circuit board; Fig. 2 a plan view of a printed circuit board according to the embodiment according to Fig. 1; Fig. 3 a side view of a printed circuit board according to the embodiment according to Fig. 1; Fig. 4 a sectional view of an electric heating device with a circuit board according to the embodiment according to Fig. 1 to 3 and Fig. 5 a perspective view of the electric heating device according to Fig. 4.

[0022] The Fig. 1 to 3 show a circuit board 2 which is equipped with a component 4. The Fig. 1 to 3 are described together below, unless explicitly referred to one of the figures.

[0023] In this example, the component 4 is a semiconductor component 6, namely a power switch 8, which is preferably designed as an insulated-gate bipolar transistor (IGBT). The power switch 8 has a first electrical contact 10, a second electrical contact 12, and a third electrical contact 14. The first electrical contact 10 is connected to a first electrical contact receptacle 15, the second electrical contact 12 to a second electrical contact receptacle 16, and the third electrical contact 14 to a third electrical contact receptacle 17. The contact receptacles 15, 16, 17 are connected to the printed circuit board 2. In this example, the contact receptacles 15, 16, 17 are designed as contact springs 18 as surface-mounted components, which are electrically connected to corresponding conductor tracks (not shown) in or on the printed circuit board 2.Preferably, the contact springs 18 are plugged on and then soldered to the conductor track.

[0024] The electrical contacts 10, 12, 14 are inserted into the contact springs 18 on the contact receptacles 15, 16, 17 and are held in place by spring tongues 19 (cf. Fig. 2) Electrically contacted and mechanically secured. Additionally, soldering can be performed between the electrical contact 10, 12, 14 and the corresponding contact receptacle 15, 16, 17 or contact spring 18.

[0025] The circuit board 2 has an opening 20 between the second contact receptacle 16 on the one hand and the first contact receptacle 15 and third contact receptacle 16 on the other. In this example, the opening 20 is shaped like a circular segment. The opening 20, which extends through the entire thickness of the circuit board 2, increases the creepage distance between the first contact receptacle 15 and the third contact receptacle 17 on the one hand and the second contact receptacle 16 on the other hand. The first contact receptacle 15 and the third contact receptacle 17 can be supplied with current with an electrical polarity that differs from the electrical polarity with which the second contact receptacle 16 can be supplied with current. Preferably, the second contact 12 is the emitter of the power switch 8, while the first contact 10 and the second contact 14 form the gate and collector of the power switch 8.During operation, the gate and collector are at a higher potential than the emitter.

[0026] The opening 20 is thus located between contact receptacles 15, 16, and 17, which, depending on the circuit board layout, can be supplied with current with different polarities. The opening 20 allows the circuit board 2 to be made more compact while maintaining the same level of dielectric strength, or to improve dielectric strength with the same spacing between the contact receptacles 15, 16, and 17.

[0027] To further improve the dielectric strength, an insulating body 22 is formed within the opening 20 and extends through the opening 20. The insulating body 22 is made of an electrically insulating material, for example a plastic, and increases the air gap between the first contact receptacle 15 and the third contact receptacle 17, on the one hand, and the second contact receptacle 16, which can be energized with a different polarity, on the other hand.

[0028] The insulating body 22 has a cross-section corresponding to the opening 20, but slightly smaller, which leads to a gap 23 running around the insulating body 22 (cf. Fig. 1) remains between insulating body 22 and opening 20. As in particular Fig. As shown in Figure 3, the insulating body 22 extends from below through the opening 20 of the circuit board 2 and projects beyond it, so that the insulating body 22 and the opening 20 extend the air and creepage distances on both sides of the circuit board 2. The insulating body 22 is fixed to an insulating plate 24, preferably made of the same material as the insulating body 22, and is preferably formed integrally therewith.

[0029] The Fig. 4 and Fig. 5 show an example of an electric heating device 26. The Fig. 4 and Fig. 5 are described together below, unless explicit reference is made to one of the figures. The electrical heating device 26 has a connection chamber 28, which is fluid-tightly sealed from a heating chamber 32 by a partition 30. The partition 30 has heating device housings 34 projecting into the heating chamber 32, which form receiving pockets for PTC heating devices 36. The PTC heating devices 36 each have a PTC element (not shown in detail here), which is electrically connected to a wiring module 38 in the connection chamber 28 via conductor tracks and contact tongues. The wiring module 38, in turn, is connected to the conductor track 2 via contacts 40 (cf. Fig. 1). The contacts 40 are electrically and mechanically contacted in contact springs 44 with spring tongues 46 (cf. Fig. 2). The contact springs 44 are designed analogously to the contact springs 18. The heating device housings 34 form flow channels 42 through which a medium, in particular a liquid medium, preferably comprising water, flows during operation to dissipate the heat generated by the PTC heating devices 36.

[0030] The circuit board 2 is as described above in connection with Fig. 1 to 3 is equipped with a component 4. The component 4 is a semiconductor component 6, namely a power switch 8.

[0031] The insulating plate 24 is preferably formed as part of the wiring module 38. The wiring module 38 is preferably an unpopulated printed circuit board in or on which the conductor tracks necessary for electrically contacting the PTC heating devices 36 and the printed circuit board 2 are formed. Other areas, and in particular the area of ​​the insulating plate 24 near the contact receptacles 15, 16, 17, are not provided with conductor tracks.

[0032] The described connection of the component 4 to the circuit board 2 is preferably used in electrical heating devices 26 with at least one PTC heating device 36, since high voltages and currents are present here, which are switched. The extension of the air and creepage distance by the design as in Fig. 1 to 3 increases the breakdown protection and increases the safety of the electrical heating device 26. List of reference symbols 2 circuit board 4 component 6 semiconductor component 8 circuit breakers 10 first electrical contact 12 second electrical contact 14 third electrical contact 15 first contact 16 second contact 17 third contact 18 Contact spring 19 Spring tongue 20 Breakthrough 22 insulating bodies 23 gap 24 Insulation plate 26 electric heater 28 Connection chamber 30 partition wall 32 Heating chamber 34 heater housing 36 PTC heating device 38 Wiring module 40 Contact 42 flow channel 44 Contact spring 46 spring tongue

Claims

[1] Printed circuit board (2) with at least two contact receptacles (15, 16, 17) for receiving electrical contacts (10, 12, 14), characterized by that an opening (20) is formed in the printed circuit board (2) between two contact receptacles (15, 16, 17) for electrical contacts (10, 12, 14) which can be supplied with current with different electrical polarity. [2] Printed circuit board (2) according to claim 1, characterized by that an insulating body (22) passes through the opening (20). [3] Printed circuit board (2) according to one of the preceding claims, characterized by that the contact receptacles (15, 16, 17) are designed for contacting a component (4) which comprises a semiconductor component (6). [4] Printed circuit board (2) according to claim 3, characterized by that the component (4) is connected to the contact receptacles (15, 16, 17) via electrical contacts (10, 12, 14). [5] Printed circuit board (2) according to one of the preceding claims, characterized bythat the opening (20) is circular segment-shaped. [6] Printed circuit board (2) according to one of claims 3 to 5, characterized by that the semiconductor component (6) is a power switch (8) with at least three contacts (10, 12, 14). [7] Printed circuit board (2) according to claim 6, characterized by that the opening (20) is formed between one contact receptacle (16) and the two remaining contact receptacles (15, 17). [8] Electric heating device (26) comprising at least one PTC heating device (36), characterized by that at least one circuit board (2) is designed according to one of the preceding claims. [9] Electric heating device (26) according to claim 8, characterized by that the printed circuit board (2) is equipped with at least one circuit breaker (8) as a component (4) via electrical contacts (10, 12, 14) which are connected to contact receptacles (15, 16, 17).

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