WO2018206594A1 - Component having emv protection for an electronic board - Google Patents

Abstract

The invention relates to a component, at least comprising electronic and/or electric components, which are mounted on one or on a plurality of boards, or are connected thereto, wherein the components, together with the board, are over-molded with a first and a second plastic layer. There is at least one shielding against electromagnetic radiation, wherein the shielding consists of a grid structure (6), and the structures (5) consist of exposed points in the shielding (13). The invention further relates to a method for producing such a component.

Description

 Component with EMC protection for electronic board

The invention relates to a component at least consisting of electronic and / or electrical components which are mounted on or connected to one or more circuit boards, wherein the components are encapsulated with the circuit board having a first and a second plastic layer, and wherein at least one shield against electromagnetic Radiation is present.

Furthermore, the invention relates to a method for producing such a component.

State of the art

Electronics, especially power electronics, cause electromagnetic radiation in different frequency ranges, which can cause interference with other devices. In order to reduce these disturbances and to keep them below the standardized limits, shielding measures should generally be provided. As far as possible, an attempt is made to reduce emissions through a correspondingly optimized board layout. Often this is only partially sufficient and further shielding measures have to be taken.

One measure consists of applying EMC protective coatings directly to the electronic components of the board. However, these protective coatings have the disadvantage that they are not temperature resistant when the board is encapsulated for protection with a thermoplastic.

From DE4016953A1 it is known that an electrically conductive plastic is applied as a shielding on an already overmolded assembly. This conductive particles are embedded in the layer of the plastic. It is therefore an object of the invention to produce a component with a circuit board in which the EMC protection is optimized and the production of the encapsulation is simplified.

The US 5,355,016 A has a component which consists of electronic and / or electrical see components 16 which are mounted on a circuit board.

 However, the components are not encapsulated with their board with a first and a second plastic layer.

JP S62-19 746 U shows a component applied to a substrate. On the substrate switching elements are attached, wherein the substrate with the

Switching elements is surrounded by a first insulating layer and a second insulating layer. Between the two insulation layers, a conductive layer is present. US Pat. No. 9,293,423 B2 shows a component which has three different electrical components on a carrier. The components are not encapsulated with the carrier. Rather, an insulating layer is applied to one side of the board. This insulating layer is completely covered with a conductive layer as a shield. Subsequently, the whole is over-molded with a plastic layer. There are no areas between the plastic layers in which the plastic layers, namely the insulating layer and the covering plastic layer, would have contact.

US 5 166 772 A shows an insulator in a lattice structure. However, here too the electronic component with the substrate is not encapsulated by the two plastic layers.

From EP 2 955 789 A1 an electro-optical window is known that is provided with a lattice structure. The lattice structure is formed by metallic material which is introduced into etched channels. US 2003/0 042 045 A1 discloses a method for providing plastic substrates with an electrical grid. The object is achieved with the features of claim 1 and 8. In detail, the object is achieved with a component at least consisting of electronic and / or electrical components, which are mounted on one or more boards or connected thereto, wherein the components with the board are encapsulated with a first and a second plastic layer, and wherein at least one shield against electromagnetic radiation is present, wherein in the shield structures are present, the contact points of the first plastic layer with the second plastic layer. The shield consists of a grid structure that can be produced by a coating process between the structures. The structures, which represent the contact points between the two plastic layers, allow an optimal connection of the plastic layers with each other. This makes it possible to use different plastics.

It is advantageous that the structures consist of released points in the shield. It is advantageous that the structures are produced by pretreatment of the surface of the first plastic layer.

It is important that the grid structure is connected to a grounding on the board.

It is advantageous that the grid structure has slots in the surface of the first plastic layer in order to optimize the connection of the shielding the layer or the shielding paint. It is particularly advantageous if the slots are dimensioned so that the shield applied as a paint penetrates by capillary action into the slots.

Due to the capillary action of the shielding paint adheres particularly well.

Advantageously, the structures contain imprints. The inventive method for producing a component according to the preceding claims consists of the following steps:

Overmolding the board with the electronics with a first plastic material,

Applying the shield, overmolding the shield with a second plastic layer.

It is particularly advantageous that in the second production step, the surface of the first plastic layer is prepared by activating structures in which the coating of the shield does not adhere, and wherein the coating with shielding material then by a dipping process or by a selective application is applied.

Furthermore, it is advantageous that the first or the second production step includes the production of slots, wherein the slots and the surface between the slots with the shielding paint are felt or covered. Furthermore, it is advantageous if, in the first production step, the surface is prestructured by means of an embossing step, wherein the slots become partially or completely closed towards the surface and the surface is prestructured in the region. DESCRIPTION OF THE INVENTION The invention will now be described by way of example with reference to the accompanying drawings.

Fig. 1 and 2 show a schematic representation of a first exemplary

 embodiment,

FIG. 3 shows a second embodiment,

 FIG. 4 shows a non-inventive embodiment.

Fig. 1 and 2 show an embodiment of a component in which the electronics used 4, that is, all the electrical and electronic components, is overmolded on the board 3 with two plastic layers. About a connector 1, the board is electrically connected.

At the edge area of the circuit board 3, areas with grounding signals 2 which are connected to the conductive EMV layer are kept free in this exemplary embodiment. It is only important that surfaces with grounding signals 2 are kept free on the board.

The first plastic layer 1 1 protects the components and the circuit board 3 and should provide the best possible thermal connection, so as to be able to derive also resulting waste heat.

The second plastic layer 12 consists for example of a cheaper plastic which provides the strength and media tightness and can already be used as a housing of the entire component. Alternatively, the second plastic layer is made of the same material as the first plastic layer. In the example of FIGS. 1 and 2, a shielding layer 13 is used between the two plastic layers 11 and 12. In the prior art, the surface of the first plastic layer is coated with an EMC coating or, if the adhesion between the EMC coating and the second plastic layer is sufficient, the entire surface of the first plastic layer is used by dip coating.

Since it has been shown that the adhesion is a major problem, the shielding layer and the EMC coating is only partially applied in the inventive solution. The surface 21 of the first plastic layer 1 1 has a structure 5, which allows a better connection with the second plastic layer 12. The structure 5 is selectively kept free during painting, for example as shown in FIG. This results in grating structures 6 on the surface of the first plastic layer 1 1, which consist of EMC paint. These structures can be applied by screen printing or ink jet processes. Between the applied grid structures of the EMC coating, the surface is rough enough to allow the connection with the second plastic layer 12.

Alternatively, the surface 21 of the first plastic layer is prepared by activation along the structure so that the EMC coating adheres only in the region of the lattice structure 6. Due to the partial surface treatment of the first plastic layer, the adhesion for the EMC varnish is increased so that it is not washed away during the second encapsulation. For this purpose plasma activations or chemical processes can be used.

At the released surfaces, the structure 5, the second plastic layer adheres to the first plastic layer. The grid structure 6 is an embodiment of the geometric arrangement of the EMC paint strips and surfaces, the person skilled in the art may also choose other surface shapes and arrangements.

However, the EMC layer or the EMV layer structure is not protected if the second plastic layer 12 is applied in a second injection molding process.

An improved solution is therefore the embodiment shown in Figure 3, in which slots 7 are used to produce the structure 6 for the EMC paint.

When using slots, the bonding force of the EMC varnish increases because the varnish, assisted by the capillary effect, can be introduced into the slits. Furthermore, results from the slot an enlarged surface for connecting paint plastic. The slots prevent the paint from being washed away from the surface 21 of the first plastic layer 11 in the subsequent encapsulation process. The slots are connected to ground 2 on the boards.

 In the enlarged detail of Figure 3 is shown how the slots 7 are closed in an embossing step and in the structure 5 of the surface 21 of the first plastic layer, a roughness in the form of indentations 15 is pressed. This step takes place before the encapsulation with the second plastic layer and can take place in the injection molding tool. In this case, an embossing tool 14 is indicated, which structures the shield 13, the EMC layer.

The risk that the EMV layer and structure is washed away by injection molding of the second plastic layer is significantly reduced by the embossing step. The slots are closed or the openings of the slots at least compressed. The embossings 15 increase the roughness, so that in area 5, the two plastic layers are well connected. FIG. 4 shows a non-inventive embodiment. On the first plastic layer 1 1, a plastic layer is sprayed with shielding properties. The first plastic layer is completely covered. The shielding plastic layer 23 in turn has a grounding 2 with which it is connected to the board 3. The shielding plastic layer 23 also surrounds the connector 1. The shielding plastic layer contains conductive particles or layers and a matrix that optimally facilitates the connection to the first plastic layer.

In the embodiment of Figure 4, the shielding plastic layer 23 is surrounded by a second plastic layer 12. This further encapsulation is only necessary if the shielding plastic layer itself is not stable enough to already have housing properties.

The shielding properties of the shielding plastic layer are adjusted so that an optimal shielding in an encapsulation takes place with a much thicker compared to the EMC coating layer.

The production process according to the invention takes place in several steps. The first step involves overmoulding the circuit board 3 with the electronics 4 with a first plastic material. In a second step, the shield 13 is applied. In a third step, the shield 13 is encapsulated by a second plastic layer.

The second production step has several variants according to the invention. In the second production step, the surface 21 of the first plastic layer is prepared. This preparation takes place on the one hand by an activation of structure 5, in which the coating of the shield does not adhere. The coating is then applied by a dipping process or by a selective application such as printing.

However, the second production step can also include the production of slots 7. The slots and the surface 21 between the slots are filled or covered with the shielding paint.

Subsequently, the surface 21 is prestructured via an embossing step, wherein the slots 7 are closed towards the surface and the surface 21 is prestructured. This increases the roughness of the surface. The second manufacturing step may also contain both variants together.

Reference List Connector

grounding

circuit board

electronics

released structure

lattice structure

Slots First plastic layer

 Second plastic layer

 shielding

 embossing tool

 impressing

 surface

 shielding plastic layer

Claims

claims 1 . Component at least consisting of electronic and / or electrical components (4) which are mounted on or connected to one or more circuit boards (3), wherein the components (4) are connected to the circuit board (3) with a first and a second plastic layer (1 1, 12) are encapsulated, and wherein at least one shield (13) against electromagnetic radiation is present, characterized in that in the shield (13) structures (5) are present, the contact points of the first plastic layer (1 1) with the second Plastic layer (12), wherein the shield consists of a lattice structure (6) and the structures (5) consist of exposed locations in the shield (13). 2. Component according to claim 1, characterized in that the structures (5) by pretreatment of the surface (21) of the first plastic layer (1 1) are generated. 3. Component according to one of the preceding claims, characterized in that the shield (13) of the lattice structure (6), which can be produced by a coating process between the structures (5). 4. Component according to one of the preceding claims, characterized in that the grid structure (6) is connected to a ground (2) on the board (3). 5. Component according to one of the preceding claims, characterized in that the grid structure (6) has slots (7) in the surface (21) of the first plastic layer (1 1). 6. Component according to claim 5, characterized in that the slots (7) are dimensioned so that the shield (13) applied as a paint by capillary action in the slots (7) penetrates. 7. Component according to one of the preceding claims, characterized in that the structures (5) contain impressions (15). 8. A method for producing a component according to the preceding claims characterized by the following steps: Enveloping the circuit board (3) with the electronics (4) with a first plastic material (1 1), Applying the shield (13), Overmolding the shield (13) with a second plastic layer (12). 9. The method of claim 8, wherein in the second manufacturing step, the surface (21) of the first plastic layer is prepared by activating structures (5) to which a coating of the shield (13) does not adhere, and wherein the coating with shielding material subsequently is applied by a dipping process or by a selective application. A method according to claim 8 or 9, wherein the second manufacturing step includes making slots (7), wherein the slots (7) and the surface (21) between the slots (7) are felted with the shielding paint. 1 1. Method according to claim 8, 9 or 10, wherein in the second production step the surface (21) is prestructured by means of an embossing step, wherein the slots (7) are closed towards the surface (21) and the surface (21) in the region of the structures (5) is pre-structured.