DE102017201800A1 - Method for producing an electronic unit and electronic unit - Google Patents

Abstract

In a method according to the invention for producing an electronics unit (1), a circuit board (2) is equipped with an electrical component (3, 4) and electrically conductively connected. Furthermore, a Entwärmungskörper (5) on the board (2) and / or the electrical component (3,4) is placed. In a plastic infusion step, the circuit board (2) and the electrical component (3, 4) are surrounded by a thermosetting plastic to form a jacket (6). The Entwärmungskörper (5) is held by means of the jacket (6) on the board (2) or on the electrical component (3,4).

Description

The invention relates to a method for producing an electronic unit. Furthermore, the invention relates to an electronic unit produced by the aforementioned method.

The term "electronic unit" is understood to mean, here and below, arrangements of a number of electrical components that are interconnected in terms of circuitry. The components are, for example, resistors, diodes, transistors, other switching elements, integrated circuits, microprocessors and the like. By means of such electronic units, for example, control devices (also referred to as "controllers"), sensor units, current and / or voltage transformers and the like are formed.

As is known, the electrical components are often sensitive to moisture, since short circuits can be formed when moisture occurs, which in turn can lead to the destruction of the respective component. However, in many applications of such electronic units, for example in motor vehicles, such electronic units frequently come into contact with different liquids (rainwater, cooling fluid, lubricating fluid, fuel and the like). In addition to the risk of short circuits, the electrical components can also be attacked and damaged by chemical reactions, corrosion or the like, especially in the case of liquids based on chemicals. Therefore, the electrical components of the electronic units are often surrounded by a housing, by means of which an ingress of liquids in the housing interior to the components arranged there is to be prevented.

However, it is often - especially in electronic units that are operated with comparatively high currents, for example, more than 1 ampere - usually due to power loss and / or switching losses to heat at least some of the electrical components. The resulting heat must be removed during operation from the electronics unit to prevent temperature-induced damage to these components. However, such a heat dissipation is possible only with relatively high effort in a housing surrounding all electrical components.

The invention has for its object to provide an improved electronics unit.

This object is achieved by a method for producing an electronic unit with the features of claim 1. Furthermore, this object is achieved by an electronic unit with the features of claim 7. Further advantageous and partly inventive embodiments and further developments of the invention are in set out in the subclaims and the description below.

The inventive method is used to produce an electronic unit. According to the method, a board - d. H. in particular, a circuit board provided with interconnects - equipped with an electrical component and electrically conductive (connected to the electrical component). The electrical component is preferably one in which (normal) loss of heat occurs during normal operation of the electronics unit. According to the method, a Entwärmungskörper is further placed on the board and / or the electrical component. Furthermore, in a plastic infusion step, the circuit board and the electrical component are surrounded by a thermosetting plastic to form a preferably media-tight shell. The respective respective Entwärmungskörper is supported by means of the jacket on the board or on the electrical component.

Preferably, the plastic infusion step in which the circuit board and the electrical component are surrounded by the thermosetting plastic is a (thermoset) injection molding step. The board and the electrical component are molded in this case with the thermosetting plastic. Alternatively, the thermoset plastic is applied in the plastic infusion step according to a resin transfer molding process. In both variants, the board and the electrical component are in particular partially or (at least approximately) completely surrounded by the thermosetting plastic (that is, if necessary, except for recesses required for positioning or holding the board in a molding tool used for the plastic infusion step).

For this purpose, the respective cooling body or bodies is preferably at least partially embedded in the jacket formed by the (preferably overmolded) thermosetting plastic (in particular injected, ie, surrounded by the thermosetting plastic in the injection molding step). Optionally, the Entwärmungskörper thereby only (ie exclusively) supported by the shell. Preferably, the holder of the Entwärmungskörpers means of the jacket takes place in particular by a cohesive connection (eg. "Glueing") of the Entwärmungskörpers with the shell due to the wetting with the thermosetting plastic during introduction (preferably injection) thereof. This adhesion is at least partially due to adhesion of the thermosetting plastic causes the Entwärmungskörper. In particular, thus come to attach the Entwärmungskörpers no mechanical fasteners such. As screws, rivets, snap hooks or the like are used.

The conjunction "and / or" is to be understood here and below as meaning that the terms or features associated therewith may be realized both as an actual alternative and in combination with one another. For example. Thus, the Entwärmungskörper can be arranged either on the board or on the electrical component. Optionally, the Entwärmungskörper but also be arranged on both, for example. With a correspondingly shaped (eg, stepped) surface.

The forming (in the case of injection molding: encapsulation) of the board and the electrical component with thermosetting plastic, d. H. the jacket formed thereby, allows a simple way of protection, in particular a seal in particular the electrical components of the electronic unit against liquid contact. An (additional) Umhausen the board and the at least one electrical component with a housing that regularly requires a mechanical support at least the board in the interior of the housing, can thus be advantageously eliminated. Furthermore, advantageously also eliminates mounting effort for (captive) attachment of the respective Entwärmungskörpers on the board or the electrical component (in particular by means of the mechanical fastening means described above). Thus, a total manufacturing cost for the formation of the particular media-tight enclosed electronic unit is advantageously reduced. As a result, the production costs can be reduced.

In a suitable variant of the method, in the plastic infusion step at least part of the dissipation body is released to the outside of the electronic unit. This means that this part of the Entwärmungskörpers is not surrounded by the jacket in the intended production end state. Preferably, in this case, the outside surface of the Entwärmungskörpers is released, in particular the Entwärmungskörper overmolded flush with the surface. As a result, in a particularly simple manner, for example by direct connection of the Entwärmungskörpers to a thermally conductive surface of the electronics unit over or subordinate assembly (for example, a motor or gearbox housing or a heat exchanger) allows for heat dissipation from the electronics unit.

In a particularly expedient variant of the method, the cooling body is held in its intended position prior to hardening of the thermosetting plastic by means of a mold used in the plastic infusion step. The term "molding tool" or "injection molding tool" is understood here and below to mean a usable and reusable mold on a processing machine, in particular an injection molding machine, in which at least one cavity (a "negative" of the structure to be formed or injection-molded) is formed. For example, the mold comprises a so-called hold-down, which can optionally be reversibly moved into the cavity in order to keep the Entwärmungskörper in the intended position. Preferably, however, a wall of the cavity (that is to say a surface of the molding tool to be molded off) lies, in particular in the closed state of the molding tool, over the entire area of the surface of the dehumidifying body to be kept clear. This advantageously ensures that when introducing (in particular injection) of the thermosetting plastic this can not get between the surface of the Entwärmungskörpers to be kept clear and the wall of the cavity - thus no "spray skin" is formed.

In a suitable variant of the method, in particular a rubber-elastic filling material is introduced between the heat-dissipation body and the circuit board or the electrical component prior to closing the mold, in particular before positioning the dehydration body on the circuit board or the electrical component. This filler material advantageously serves to compensate for tolerances, in particular the printed circuit board equipped with the component and optionally the Entwärmungskörpers and thereby advantageously allows a particularly good sealing of the mold to the Entwärmungskörper. Furthermore, this filling material allows that when closing the mold, the applied closing force, specifically the locking pressure acting on the Entwärmungskörper and the board is not fully forwarded to the board or the electrical component. In addition, the preferably rubber-elastic filling material also allows a compensation of different thermal expansions of the board, the electrical component and the Entwärmungskörpers during operation of the electronic unit. In addition, the filling material expediently also serves as a positioning aid, specifically for holding the Entwärmungskörpers on the board or the electrical component before closing the mold or at least before wrapping (encapsulation) with the thermosetting plastic (thus "pre-positioning").

In a particularly expedient development of the method, a (rubber-elastic) filling material is in particular a thermally conductive material filled plastic, for example, a silicone, polyurethane, a rubber, an adhesive or the like used. As a result, a particularly good heat transfer from the board or the electrical component into the heat dissipation body is made possible during operation of the electronic unit.

In a further expedient variant of the method, a thermally conductive thermosetting plastic having low thermal conductivity is used in the plastic infusion step (for example in the injection molding step). "Low thermal conductivity" is understood here and below in particular to the effect that the thermal conductivity is approximately in the range of "pure", d. H. unintentionally thermally conductive modified plastic lies. In the context of the invention, it is conceivable that such a thermally conductive thermosetting plastic material nevertheless contains a filler of thermally conductive material (eg. Metal, ceramic or the like) with a filler content (eg. Vol.% Or wt .-%) which causes only a slight increase in the thermal conductivity over the unfilled plastic. Preferably, however, a thermoset plastic unfilled with respect to thermal conductivity is used (i.e., introduced or injected). The thermoset plastic used is therefore in particular not thermally conductive modified and thus has in particular a particularly low, preferably in the range of "pure" thermoset plastic thermal conductivity. "Unfilled with respect to thermal conductivity" is understood here and below as meaning, in particular, that other fillers which are directed, for example, to a coloring, reinforcement, adjustment of a viscosity and the like, and thus in particular the thermal conductivity, or only in one for one for heat conduction tasks negligible influence (increase), but can still be used within the scope of the invention. Advantageously, such a non-thermally conductive thermoset filled a low compared to (thermally conductive) filled thermosets low price and is also easier to handle, for example because thermally conductive fillers significantly increase the viscosity of the thermosetting plastic and / or increased wear of the conveyor lead the injection molding machine and the injection mold. Epoxy resins, phenolic resins and the like, for example, are used as duroplastic. Alternatively, in the context of the invention, however, a thermally conductive filled thermosetting plastic can be used.

The electronic unit according to the invention comprises the board described above and arranged on the board and electrically conductively connected thereto electrical component. Furthermore, the electronics unit comprises the heat dissipation body placed on the board or on the electrical component and the jacket formed of the thermosetting plastic. This jacket surrounds the board and the electrical component (in particular, in whole or in part). Furthermore, the Entwärmungskörper is supported by means of the jacket on the board or the electrical component. The electronic unit is manufactured according to the method described above. Thus arise for the inventive electronic unit according to the method described above corresponding advantages.

In a preferred embodiment, the Entwärmungskörper is formed in particular of a metal, such as steel, aluminum, copper or the like. Particularly preferably, the Entwärmungskörper is formed by a formed from such a metal sheet or plate. The Entwärmungskörper thus preferably has a particularly simple geometry, so that the Entwärmungskörper example, as a standard component to procure simple and inexpensive or manufacturing technology simple way of a large semi-finished (for example, from a sheet by trimming or punching) can be produced. In the context of the invention, however, it is also conceivable that the Entwärmungskörper is formed by a body provided with a surface structure, for example. To the plant to the electrical component (or possibly several existing electrical components) and to the board and / or with the outside pointing cooling fins.

In a further expedient embodiment, the Entwärmungskörper on a side facing away from the board or the electrical component, d. H. tapered in particular in the direction of the outside of the electronics unit. Rejuvenation here means, in particular, that the heat dissipation body has a chamfer ("chamfer") or step in the thickness direction (that is, from the side facing the circuit board or the electrical component in the direction of the outside), in particular at one edge. This taper thus forms an undercut as seen from the direction of the board or the electrical component, so that the jacket the Entwärmungskörper (especially in addition) by a positive connection (ie by a mechanical meshing) in particular by a grip behind, on the board or the electrical Component stops.

In an expedient embodiment, the board is made of a preferably thermally conductive, ie a comparatively high thermal conductivity, ceramic, z. B. from an alumina ceramic (AL ₂ O ₃ ) with about 24 W / mK. This is expedient in particular for the case that the Entwärmungskörper is disposed on a side opposite the electrical component side of the board, because a particularly good heat transfer from the electrical component through the board is made possible on the Entwärmungskörper. In an alternative embodiment, the board is formed by a particular durplastic laminate, ie in particular in the manner of a FR4 printed circuit board or the like.

In a further expedient embodiment, the electrical component is, in particular, a power semiconductor component. Thus, the electrical component is designed in particular for the control and / or switching of comparatively high electrical currents (that is to say of more than 1 A).

• 1 in einer schematischen Teilschnittansicht eine Elektronikeinheit mit auf einer Platine angeordneten elektrischen Bauteilen, und
• 2 bis 4 jeweils in Ansicht gemäß 1 ein weiteres Ausführungsbeispiel der Elektronikeinheit.

Embodiments of the invention will be explained in more detail with reference to a drawing. Show:

• 1 in a schematic partial sectional view of an electronic unit with arranged on a circuit board electrical components, and
• 2 to 4 each in view according to 1 a further embodiment of the electronic unit.

Corresponding parts are always provided with the same reference numerals in all figures.

In 1 is an electronics unit 1 illustrated, which forms a controller (ie, a control unit) for a transmission of a motor vehicle. The electronics unit 1 includes a circuit board 2 , On in a manner not shown interconnects for electrical contacting different, also from the electronics unit 1 comprehensive electrical components 3 are formed. The electrical components 3 are on a flat side of the board 2 arranged and with the there running traces of the board 2 connected electrically conductive. At least two of the electrical components 3 are each formed by a power semiconductor device 4, which is set up and provided for controlling and switching high electrical currents (ie greater than 1 A). Furthermore, the electronics unit includes 1 two cooling bodies 5 , in the illustrated embodiment according to 1 on one of the electrical components 3 opposite side of the board 2 are arranged. The Entwärmungskörper 5 serve for heat dissipation during operation of the electronics unit 1 on the electrical components 3 , specifically on the power semiconductor components 4 sloping (loss) heat. As a result, a temperature-induced damage to the electrical components 3 and thus the electronics unit 1 be prevented. Because the electronics unit 1 as a controller for a gearbox in the intended operating condition fluids such. B. gear oil is exposed to short circuits and chemical damage to the electrical components 3 can guide the electronics unit 1 Furthermore, the electrical components 3 and the board 2 surrounding mantle 6.

The coat 6 is made of a thermosetting plastic, specifically an epoxy resin formed in a (thermoset) injection molding process in such a way to the board 2, the electrical components 3 and the Entwärmungskörper 5 is injected that the electrical components 3 completely and the board 2 and the Entwärmungskörper 5 at least partially encapsulated (ie surrounded) by the thermosetting plastic. From the board 2 lie only liquid insensitive edges and for contacting the electronics unit 1 with external electrical components (for example, a power source and a servomotor to be controlled) serving contacts free (not shown).

The Entwärmungskörper 5 are formed by approximately cuboidal plates, concrete punched blanks of aluminum. The Entwärmungskörper 5 are flush with the surface in the mantle 6 injected, so that these in the intended use state for dissipating the heat of the electrical components 3 can be applied to a heat dissipation surface, for example to a housing of the transmission. In the manufacture of the electronics unit 1 be the Entwärmungskörper 5 with its respective outer side (specifically, the outside surface) over the entire surface of a cavity wall of an injection mold used, from this when closing the injection mold to the board 2 kept positioned and sealed on the outside against the incoming thermoset material. The Entwärmungskörper 5 be through the sprayed coat 6 captive on the board 2 supported. In the illustrated embodiment according to 1 the holding force is in particular by an adhesive connection (ie a material bond) between the jacket 6 and the respective Entwärmungskörper 5 applied.

To a particularly good thermal connection of the Entwärmungskörper 5 to the board 2 and a compensation of tolerances and different thermal expansions between the board 2 and the heat-dissipation body 5 to allow is between the dehumidifying bodies 5 and the board 2 a rubber-elastic, ie compressible filling material (also referred to as "Gapfilier") introduced. In the embodiment according to 1 each filler material is an adhesive layer 7 , This adhesive layer 7 is filled with thermally conductive particles, so that the respective adhesive layer 7 a negligible thermal resistance to the heat dissipation from the electrical components 3 over the cooling bodies 5 represents.

For the coat 6 The thermosetting plastic used is an epoxy resin which contains no thermally conductive fillers, ie no fillers which have a significantly increased thermal conductivity compared to the "pure" epoxy resin. The epoxy of the jacket 6 is therefore not thermally conductive filled and thus has a comparatively low material price.

In 2 is another embodiment of the electronics unit 1 shown. This embodiment differs from the embodiment described above 1 in that the filling material is filled by a thermally conductive silicone layer 8th is formed. This is compared to the adhesive layer 7 thicker.

Due to the elasticity of the filling material, ie the adhesive layer 7 or the silicone layer 8th In addition, there is also an improved seal between the heat dissipation body 5 and the closing of the injection mold to the Entwärmungskörper 5 reached pressed cavity wall. Furthermore, the closing of the injection mold on the Entwärmungskörper 5 applied closing pressure due to the compressibility of the filling material is not fully on the board 2 transfer.

In 3 is another embodiment of the electronics unit 1 shown. In addition to the adhesion of the coat 6 at the respective Entwärmungskörper 5 also a positive connection, ie a mechanical clawing of the shell 6 on the heat-dissipation body 5 and thus an improved holder of the Entwärmungskörpers 5 on the board 2 to allow, has the respective Entwärmungskörper 5 one to the outside of the electronics unit 1 running rejuvenation in the form of a slope 9 (also called "chamfer") on.

In a further embodiment of the electronic unit 1 according to 4 is one of the cooling bodies 5 directly on two electrical components 3 and thus on one of the power semiconductor devices 4 arranged.

The object of the invention is not limited to the embodiments described above. Rather, other embodiments of the invention may be derived by those skilled in the art from the foregoing description. In particular, the individual features of the invention described with reference to the various exemplary embodiments and their design variants can also be combined with one another in a different manner.

LIST OF REFERENCE NUMBERS

1

electronics unit

2

circuit board

3

electrical component

4

Power semiconductor component

5

Entwärmungskörper

6

coat

7

adhesive layer

8th

silicone layer

9

slope

Claims (11)

Method for producing an electronic unit (1), according to the method a printed circuit board (2) is equipped with an electrical component (3, 4) and electrically conductively connected, - A Entwärmungskörper (5) on the board (2) and / or the electrical component (3,4) is placed, and in a plastic infusion step, the circuit board (2) and the electrical component (3, 4) are surrounded by a thermosetting plastic to form a jacket (6), the cooling body (5) being pressed against the circuit board (2) by means of the jacket (6) or on the electrical component (3,4) is supported. Method according to Claim 1 wherein at least part of the dehumidifying body (5) is released to the outside of the electronics unit (1) in the plastic infusion step. Method according to Claim 1 or 2 wherein the Entwärmungskörper (5) is held before curing of the thermosetting plastic by means of a mold used in the Kunststoffinfusionsschritt in its intended position. Method according to one of Claims 1 to 3 , wherein between the Entwärmungskörper (5) and the board (2) or the electrical component (3,4) before closing the mold, in particular a rubber-elastic filling material (7,8) is introduced. Method according to Claim 4 , wherein a thermally conductive filled plastic is used as filling material (7,8). Method according to one of Claims 1 to 5 , wherein in the plastic infusion step, a low thermally conductive thermosetting plastic is used. Electronic unit (1), - with a circuit board (2), - with an electrical component (3, 4) arranged on the circuit board (2) and electrically conductively connected to the circuit board (2), with a heat dissipation body placed on the circuit board (2) and / or on the electrical component (3, 4) (5), and - with a jacket formed of thermosetting plastic (6), which surrounds the circuit board (2) and the electrical component (3,4) and by means of the Entwärmungskörper (5) on the board (2) or electrical component (3,4) is supported, wherein the electronic unit (1) according to the method according to one of Claims 1 to 6 is made. Electronic unit (1) to Claim 7 wherein the Entwärmungskörper (5) is formed of a metal. Electronic unit (1) to Claim 7 or 8th , wherein the Entwärmungskörper (5) is tapered on one of the board (2) or the electrical component (3,4) facing away, so that the jacket (6) the Entwärmungskörper (5) by a positive connection to the board (2) or the electrical component (3,4) stops. Electronic unit (1) according to one of Claims 7 to 9 , wherein the board (2) is formed of a ceramic or a thermosetting laminate. Electronic unit (1) according to one of Claims 7 to 10 wherein the electrical component is formed by a power semiconductor component (4).

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