DE102014216585A1 - Compact multilayer printed circuit board with integrated sensor for use in a vehicle control unit - Google Patents

Abstract

Compact multilayer printed circuit board (L) comprising at least one packaged sensor (3) with connection pins (2, 4) wherein the multilayer printed circuit board (L) has an upper outer layer (7a, 6) and a lower outer layer (7b, 6), each comprising an electrically conductive interconnect layer (7a, 7b) and an insulating circuit board base layer (6), and at least one inner layer (8, 6) between the two outer layers, and wherein the material of the circuit board base layer (6) of the multilayer circuit board (L) is a resin impregnated fiberglass base fabric Sensor (3) between the upper conductor layer (7a) and the lower conductor layer (7b) completely enclosed with material of the printed circuit board base layer (6) is arranged, and with a conductor track structure (7a, 7b, 8, 13, 14) of the multilayer printed circuit board (L ) is electrically connected.

Description

The invention relates to a compact multilayer printed circuit board with at least one integrated sensor according to the preamble of claim 1.

From the prior art, it is well known that in automotive engineering components such as transmission, engine or brake systems are increasingly electronically controlled. For this purpose, there are integrated mechatronic controls, also referred to as on-site electronics, which can be generated by integration of control electronics and associated electronic components such as sensors or valves in the transmission, the engine or the brake system. That is, the control electronics and associated electronic components are not accommodated in a separate protected electronics compartment external to the transmission, engine, or braking system.

Compared to the conventional use of external cropping devices, this arrangement has enormous advantages in terms of quality, cost, weight and functionality. In particular, this results in a significant reduction of possibly error-prone connectors and cables.

The integration of the control unit in the transmission makes high demands on its thermal and mechanical strength. The functionality has to be guaranteed over a wide temperature range (about -40 ° C up to 200 ° C) as well as for mechanical vibrations (up to about 40g). Since the control unit is at least partially surrounded by aggressive media such as transmission oil and transmission oil vapor, it must also have a very high degree of tightness compared to these media.

In motor vehicles such controllers are used with an electronic control unit and associated components such as sensors for different tasks, the control unit usually a circuit carrier, for. B. includes a printed circuit board and located thereon active and passive electronic components. For example, when used in a transmission speeds of waves and positions of gear actuators are sensed by means of sensors. On the basis of this information, the electronic control unit controls, among other things, the switching operations in the transmission. The electronic control unit is usually arranged on a carrier plate and enclosed by a housing body. The sensors are due to the application positioned in the vicinity of the parts to be sensed and electrically connected via electrical conductors, in particular stamped grid with the electronic control unit. The stamped grid are usually encapsulated in plastic and form with the sensor as an electrical component and a sensor cover a component carrier, also called sensor dome.

The WO 2006/108932 A1 shows such a control device with a housing comprising a housing cover for receiving sensor dome and a housing shell for receiving a control unit and a foil conductor for electrically connecting the lead frames of the sensor dome on the housing cover with the control unit.

A disadvantage of the conventional use of sensor dome is that in the production of many materials of different mechanical and thermal properties must be used to achieve a relatively safe protection against environmental influences, especially oils. Despite the use of high-quality, cost-intensive materials, failures have repeatedly been recorded, which are largely due to exposed copper surfaces on the sensor dome.

Another disadvantage of using sensor domes is that the sensors in the sensor dome are inherently susceptible to vibration and that geometric constraints, e.g. Height offset, brackets and the like must be complied with. Furthermore, the production of these domes requires a technically sophisticated process technology and must be integrated into the production lines for the production of the control units, which leads to a higher cost.

There are also applications in which the components to be sensed are located in the immediate vicinity of the control unit and thus can be dispensed with the use of domes as a sensor carrier. The sensor components can be mounted directly on the circuit carrier or the printed circuit board of the control unit.

The circuit boards are usually made of fiber-reinforced plastic or ceramic. Due to the miniaturization of the electronic components and the resulting reduction in the available installation space, the trend is towards so-called multi-layer or multilayer printed circuit boards.

Multilayer printed circuit boards made of fiber-reinforced plastic, in particular glass-fiber reinforced plastic, essentially comprise outer and inner layers. An outer layer usually comprises a copper layer or copper foil as a conductive element and a so-called prepreg layer as an insulating element, wherein the prepreg layer consists of a glass fiber base fabric impregnated with resin, in particular epoxy resin.

An inner layer, also called PCB core or core, consists of a prepreg layer between two copper layers. The copper layers are formed as conductor track structures.

In order to avoid twisting of the multilayer printed circuit board, the layered structure of copper layer and prepreg layer is particularly symmetrical to the innermost prepreg layer.

The loading of various components, e.g. SOT23 Hall sensors and OT89 speed sensors on the surface of a circuit carrier, in particular a printed circuit board by means of different so-called "Surface Mounted" technologies is state of the art. The sensors mentioned are in particular housed components.

In the process, the components are mounted on the surface of the printed circuit board in the same orientation by the "surface mounted" technology, ie. the connecting legs of the components, also called pins, are aligned on so-called pad surfaces of the conductor track structure, which are provided with solder paste, and then soldered in a reflow soldering process. The pins on the underside of the component housing are thus just connected to the conductor track structure of the circuit board.

This arrangement has the disadvantage, in particular when used in transmission control systems, that the components can come into direct or indirect contact with the transmission oil. The aggressive components contained in the gear oil, in particular sulfur components in different concentrations and different states of aggregation, can adversely affect the functionalities of the respective sensor component, which in individual cases can also lead to failure of the respective component.

The invention has for its object to provide a compact multilayer printed circuit board for a motor vehicle control unit with at least one housing sensor, which is constructed to save space and provides improved protection of the sensor against environmental influences, especially aggressive oils.

This object is achieved by a multilayer printed circuit board with the features of claim 1.

The compact multilayer printed circuit board according to the invention comprises at least one packaged sensor with connection pins. The multilayer printed circuit board has an upper outer layer and a lower outer layer, each having an electrically conductive wiring layer and an insulating circuit board base layer, and at least one inner layer between the two outer layers, wherein in the inner layer, a printed circuit board base layer is disposed between two conductor layers. The material of the circuit board base layer is particularly a resin impregnated fiberglass base fabric. The sensor is advantageously arranged between the upper interconnect layer and the lower interconnect layer and completely enclosed with material of the printed circuit board base layer and electrically connected to a printed conductor structure of the multilayer printed circuit board. The sensor is thus protected against environmental influences, in particular against aggressive oils.

An electrically conductive connection between interconnect layers is produced by means of plated-through holes. The position and number of plated-through holes can be individually adapted to the corresponding application.

Depending on the design or requirement, in particular depending on the distance of the sensor to the part to be sensed, the sensor can be arranged in an outer layer of the multilayer printed circuit board of an electrically conductive conductor layer and an insulating PCB base layer, or in an inner layer, an insulating PCB base layer between two electrically conductive trace layers be.

In particular, at least one additional electrical component, in particular a suppression component, may be arranged in the immediate vicinity of the sensor, wherein the electrical component such as the sensor is completely enclosed by material of the printed circuit board base layer. An advantage of the integration of the suppression in the circuit board are very short and low-impedance cable routes.

The interconnect structure of the multilayer printed circuit board preferably comprises at least one power path and at least one signal path, wherein in particular a sensor is signal-transmitting connected to a signal path. This eliminates subsequent wiring of the sensor after mounting in the multilayer printed circuit board.

Preferably, at least one control unit with at least one processor can be arranged on the multilayer printed circuit board, wherein it can then be used in particular as a compact distributor printed circuit board, for example in a motor vehicle control unit.

In the following description, the features and details of the invention in conjunction with the accompanying drawings with reference to embodiments will be explained in more detail. In this case, features and relationships described in individual variants can in principle be applied to all exemplary embodiments. In the drawings show:

1 a sensor on a circuit board in SMD technology according to the prior art,

2 a known sensor dome according to the prior art,

3 Top view of a compact multilayer printed circuit board with integrated sensors,

4 a section through the multilayer printed circuit board 3 in the level AA, and

5 the integration of a sensor and an additional component into a compact multilayer PCB

1 shows a packaged sensor 3 on a circuit board 6 mounted by known SMD technology.

Here is the sensor 3 For example, by "Surface Mounted" technology on the surface of the circuit board 6 mounted, ie the connecting legs 2 . 4 of the sensor 3 , also called connecting pins, are on so-called pad surfaces 1 . 5 the conductor track structure on the circuit board 6 aligned and then soldered in a reflow soldering process. The pins 1 . 5 on the underside of the sensor housing are thus just with the conductor track structure of the circuit board 6 connected.

This arrangement has the disadvantage, in particular when used in transmission control systems, that the components, in particular in the region of their connections, can come into direct or indirect contact with the possibly aggressive transmission oil. In individual cases, this can also lead to failure of the component.

2 shows a schematically drawn structure of a known sensor dome. On a sensor 3 , in particular, this is housed, are electrical connection pins 2 usually arranged in the form of lead frames. The punched grid 2 are usually encapsulated in plastic and form the sensor housing 10 , The sensor 3 is in the sensor housing 10 with the sensor dome cap 11 at least spandicht covered. About the electrical contacts 19 are the punched grid 2 electrically contactable, for example with an electronic control unit.

A disadvantage of the use of such sensor domes in particular is that despite the use of high-quality, expensive materials repeatedly comes to failures, which are largely due to exposed copper surfaces on the sensor dome.

3 shows the integration of sensors 3 in a compact multilayer printed circuit board L. The multilayer printed circuit board L can be used mainly as a distributor circuit board, which can be arranged in particular for heat dissipation to a heat sink and / or can be screwed directly to the hydraulics of a transmission. The sensors 3 are in particular in a not explicitly shown here, via laser or mechanically exposed cavity of the multi-layer PCB L equipped and installed in a subsequent PCB manufacturing process with.

The multilayer printed circuit board L preferably comprises at least one power path 13 and at least one signal path 14 , wherein in particular a sensor 3 with a signal path 14 signal transmitting connected. This eliminates subsequent wiring of the sensor 3 after mounting in the multilayer PCB L.

Preferably, on the multilayer printed circuit board L in the recess 12 at least one control unit be arranged with at least one processor. About the performance path 13 the control unit may in particular be connected to a supply voltage source. Such a multilayer printed circuit board L is suitable for use as a compact distributor printed circuit board, for example in a motor vehicle control unit.

4 shows a section through the multi-layer PCB L from 3 in the level AA. 4 shows a packaged sensor 3 with connection pins 2 . 4 in a particular via laser or mechanically exposed cavity of the multilayer printed circuit board L. The multilayer printed circuit board L has an upper outer layer 7a . 6 and a lower outer layer 7b . 6 on, each with an electrically conductive conductor track layer 7a . 7b and an insulating circuit board base layer 6 ,

The multilayer printed circuit board L furthermore has at least one inner layer 6 . 8th between the two outer layers 7a . 6 and 7b . 6 on, with the inner layer 6 . 8th a circuit board base layer 6 between two interconnect layers 8th is arranged. The material of the PCB base layer 6 is in particular a resin impregnated fiberglass base fabric. The sensor 3 is advantageously between the upper wiring layer 7a and the lower wiring layer 7b arranged, here in the outer layer 7a . 6 , and completely with the base board material 6 enclosed. The sensor 3 is thus protected against environmental influences, in particular against aggressive oils. The connection pins 2 . 4 of the sensor 3 are by means of sensor pads 5 with the inner wiring layer 8th electrically connected.

An electrically conductive connection between the interconnect layers 7b . 8th is by means of electrically conductive vias 9 , so-called vias, produced. The location and number of vias 9 In particular, it can be individually adapted to the corresponding application.

Depending on the design or requirement, in particular depending on the distance of the sensor 3 to the part to be sensed, the sensor 3 also in an inner layer 8th . 6 be arranged.

In particular, in the lower wiring layer 7b the multilayer printed circuit board L, not shown here, external connection pads for electrically connecting the sensor 3 formed with electrical components outside of the multilayer printed circuit board L.

5 shows how 4 a housed sensor 3 in a cavity of the multilayer printed circuit board L, being here in the immediate vicinity of the sensor 3 an additional, with the sensor 3 electrically conductively connected electrical component 20 , in particular a suppression component, is arranged.

An advantage in the arrangement of the suppression in the immediate vicinity of the sensor 3 are very short and low-impedance conduction paths, which in turn leads to increase the compactness of the multilayer printed circuit board L.

The electrical component 20 is shown here only schematically for the sake of clarity. It can be especially in an outer layer 7a . 6 or 7b . 6 or an inner layer 8th . 6 be arranged. The component 20 is with the sensor 3 by means of inner conductor layers 8th electrically connected (not shown here). The connection of the component 20 with the wiring layer 8th is here via a solder joint 15 realized. In place of the solder connection 15 Any other cohesive type of connection, such as gluing, could also be used.

A significant advantage of integrating a packaged sensor over the integration of bare sensors into a multilayer printed circuit board is that sensor alignment can already be done by the manufacturer. An additional adjustment is therefore not necessary. Furthermore, the sensors are protected against migration of oil by enclosing with Resin or resin and printed circuit board base materials, especially when used in transmission controls and thus in their functionality.

Another advantage of this arrangement is that in the multi-layer printed circuit board, in which the signal and line wiring is already implemented, a further component, in particular a housed sensor between the outer layers is integrated, thus eliminating costly and time-consuming processes for surface mounting and surface wiring of the sensor , The sensors are thus in particular all in the multi-layer printed circuit board on a plane, which can have a positive effect on the measured value determination.

The sensors are advantageously integrated into the multilayer printed circuit board at the anticipated positions. The advantages of oil resistance are given in all variants. Due to the use in a multilayer printed circuit board, complex processes for sealing and encapsulating a sensor are eliminated from the environment. Also, the use of expensive sealants in this embodiment is not necessary.

LIST OF REFERENCE NUMBERS

1, 5

 contact pad

2, 4

 connector pin

3

Sensor, housed

6

PCB base layer, prepreg layer

7a

Upper conductor layer, outer layer

7b

 Lower conductor layer, outer layer

8th

Conductor layer, inside

9

via

10

 Sensordomgehäuse

11

 Sensordomkappe

12

 Recess for control unit

13

 power path

14

 signal path

15

 solder

19

 Electric contact

20

 interference suppression component

L

 Compact multilayer PCB

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• WO 2006/108932 A1 [0006]

Claims (7)

Compact multilayer printed circuit board (L) in a motor vehicle control unit comprising at least one packaged sensor ( 3 ) with connection pins ( 2 . 4 ) wherein the multilayer printed circuit board (L) has an upper outer layer ( 7a . 6 ) and a lower outer layer ( 7b . 6 ), each comprising an electrically conductive wiring layer ( 7a . 7b ) and an insulating circuit board base layer ( 6 ), and at least one inner layer ( 8th . 6 ) between the two outer layers, wherein in the inner layer ( 6 . 8th ) a printed circuit board base layer ( 6 ) between two interconnect layers ( 8th ) is characterized in that the material of the printed circuit board base layer ( 6 ) of the multilayer printed circuit board (L) is a resin-impregnated fiberglass base fabric, the sensor ( 3 ) between the upper wiring layer ( 7a ) and the lower conductor layer ( 7b ) completely with PCB base layer material ( 6 ), is arranged, and with a conductor track structure ( 7a . 7b . 8th . 13 . 14 ) of the multilayer printed circuit board (L) is electrically conductively connected. Compact multilayer printed circuit board (L) according to claim 1, characterized in that an electrically conductive connection between interconnect layers ( 7a . 7b . 8th ) by means of plated-through holes ( 9 ) is made. Compact multilayer printed circuit board (L) according to one of the preceding claims, characterized in that the sensor ( 3 ( 20 ) in an outer layer (( 7a . 6 ) 7b . 6 )) or in an inner layer ( 8th . 6 ) is arranged. Compact multilayer printed circuit board (L) according to claim 3, characterized in that in the immediate vicinity of the sensor ( 3 ) at least one additional, with the sensor ( 3 ) electrically connected electrical component ( 20 ), in particular a suppression component, is arranged. Compact multilayer printed circuit board (L) according to one of the preceding claims, characterized in that the printed conductor structure has at least one power path ( 13 ) and at least one signal path ( 14 ) and that a sensor ( 3 ) with a signal path ( 14 ) is connected signal transmitting. Compact multilayer printed circuit board (L) according to one of the preceding claims, characterized in that on the multi-layer printed circuit board (L) at least one control unit is arranged with at least one processor. Vehicle control unit with a control unit, characterized in that the control unit is arranged on a compact multilayer printed circuit board (L) according to one of claims 1 to 5.

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