DE102008039921B4 - Method of manufacturing an electronic device with a discrete component - Google Patents

Abstract

A method for producing an electronic device (1) with a discrete component (3) on a printed circuit board (7) in a housing (17), comprising the following process steps: Production of a housing (17) with a flat heat dissipation area (19) in the housing base ( 10); - Production of a circuit board (7) with through-contact openings for through-contacts (18) of at least one discrete component (3); - Equipping the circuit board (7) with the discrete component (3); characterized in that - before the circuit board (7) is fitted with the discrete component (3), through openings (12) are made through the circuit board (7) in the assembly area of the discrete component; - the flat heat dissipation area (19) with an adhesive compound ( 11) is covered; - the circuit board (7) equipped with the discrete component (3) is pressed with its wiring side (9) into the adhesive compound (11) and - the adhesive compound (11) through the through openings (12) in the area of the discrete Component (3) penetrates and a free space (13) between the discrete component (3) and the component side (8) of the circuit board (7) with the adhesive compound (11) of the wiring side (9) of the circuit board (7) in the area of the openings ( 12) fills up and hardens, and the hardened adhesive mass (11) supports the discrete component (3).

Description

The invention relates to a method for producing an electronic device with at least one discrete component exposed to mechanical loads. The discrete component has external connections and is fixed with these on a component side of a circuit board. The circuit board has a wiring side with which the external connections are mechanically and electrically connected. A flat, heat-dissipating housing base is aligned at least partially parallel to the wiring side and is mechanically and thermally connected to the wiring side of the circuit board via an adhesive compound.

The WO 96/23397 A1 discloses a circuit board with an arrangement for heat dissipation which has bores below a component to be connected to the circuit board through which a thermally conductive, electrically insulating material can be injected in order to produce a thermally conductive connection from the component to the arrangement for heat dissipation. However, the injection of the thermally conductive material represents an additional processing step that also requires a corresponding drilling.

Also the US 7,031,165 B2 discloses bores in a circuit board below a component, by means of which a soldering material can produce a thermally conductive connection between the two surfaces of the circuit board for better heat dissipation.

Finally reveals the DE 10 2004 024 616 A1 a heat dissipation structure that includes a heat generating electronic component on a circuit substrate, a thermally conductive housing, and lubricant. The electronic component and the substrate are accommodated in the housing. The lubricant is provided between the housing and the electronic component and / or the substrate for transferring the heat generated by the electronic component to the housing. The housing has contact surfaces which are in contact with the lubricant. The contact surfaces have a free energy of at least 20 mN / m and a roughness of at least 1.0 µm. The lubricant must be brought to the required places in a separate process step.

Such electronic devices with at least one discrete component are preferably used in vehicles, with such electronic devices being exposed to increased vibration, which in some cases endangers the soldering points of the external connections of the discrete components on the wiring side of the circuit board, up to and including the tearing off of individual external connections of the discrete component the body of the discrete component. Such a tearing off of an external connection can lead to the destruction of the entire electronic device.

In addition, such electronic devices for motor vehicles often develop a high heat loss that has to be dissipated. This is from the publication DE 10210041 A1 a heat dissipation device for dissipating heat generated by an electronic component is known. This heat dissipation device has at least one electrical component, a circuit board and a cooling element. A cavity is arranged underneath an electronic component that has a high level of heat loss. This cavity is filled with a filler with good thermal conductivity. In the areas of the circuit board where waste heat is generated due to the power dissipation of the component, a thermally highly conductive connection to the cooling element is ensured.

In this known heat dissipation device, however, no solution is disclosed for the occurrence of high vibrations, so that there is still the risk that external connections of the individual components are exposed to the risk of tearing off the circuit board.

The object of the invention is to improve the vibration protection, in particular of discrete components on a printed circuit board in an electronic device, and to specify a method with which discrete components in the electronic device are better protected from vibrations.

This object is achieved with the subject matter of the independent claim. Advantageous developments result from the dependent claims.

According to the invention, a method for producing an electronic device with at least one discrete component exposed to mechanical loads is created.

The method for producing an electronic device with a discrete component on a printed circuit board in a housing has the following method steps. First, a housing with a flat heat dissipation area is produced in the housing base. This heat dissipation area can also have cooling fins on the outside. Inside, this heat dissipation area has a thermally conductive adhesive to which the circuit board can be glued with its wiring side.

In a further step, the circuit board is produced with through-contact openings for through-contacts of at least one discrete component, with through-openings being made through the circuit board in the placement area of the discrete component before the circuit board is fitted with the discrete component. The printed circuit board can then be fitted with integrated circuits and discrete components. In preparation for the assembly of the housing base with the circuit board, the flat heat dissipation area is covered with an adhesive compound, the amount of adhesive compound being larger than would be required for a thermal coupling in the heat dissipation area between the underside of the circuit board and the housing base.

The wiring side of the printed circuit board equipped with the discrete component is then pressed into the adhesive mass and, due to the excess of adhesive mass, this adhesive mass penetrates through the openings in the area of the discrete component and fills a space between the discrete component and the component side of the printed circuit board with the adhesive mass the wiring side of the circuit board in the area of the openings and can then be cured. The cured adhesive compound finally supports the discrete component and protects it from mechanical loads, preferably from vibrations. In order to achieve not only mechanical fixation, but also good heat dissipation, a thermally conductive, insulating adhesive material is preferably used as the adhesive mass.

The adhesive material can have embedded thermally conductive particles. It is thus possible to use a two-component adhesive as the adhesive material, which has a gel with embedded thermally conductive particles made of carbon. The thermally conductive particles in the insulating adhesive mass can certainly be metal particles, but their external dimensions are smaller than the conductor track distances on the wiring side of the circuit board, so that no short circuits can occur when using this thermally highly conductive adhesive. For this purpose, spherical metal particles are preferably used, the outer diameter of which is also smaller than the conductor track spacings of the circuit board.

In a further preferred implementation of the method, before a housing cover is applied, at least partially adhesive mass is applied to an upper side of the discrete component, the adhesive mass filling and hardening a free space between the housing cover and the upper side of the discrete component when the housing cover is assembled with the housing base to form a housing thus providing further support for the discrete component.

The discrete component has external connections and is fixed with these on a component side of a circuit board. The circuit board has a wiring side with which the external connections are mechanically and electrically connected. A flat, heat-dissipating housing base is at least partially aligned parallel to the wiring side and is mechanically and thermally connected to the wiring side of the circuit board via an adhesive compound. The circuit board has openings below the discrete component, the openings and a space between the discrete component and the component side of the circuit board being filled with the adhesive compound of the wiring side of the circuit board in the area of the openings, the adhesive compound supporting the discrete component.

This electronic device produced by the method according to the invention has the advantage that it does not require any separate carrier or support devices for the discrete components located on the circuit board in order to fix them on the circuit board in such a way that they are exposed to the vibrations to which the electronic device is exposed , can withstand. In addition, it is possible to manufacture this electronic device inexpensively, since previous process steps can be used and no extra support devices for discrete components need to be attached to a vibration-prone circuit board to protect the discrete components.

The openings in the circuit board underneath a discrete component that is endangered by vibrations can be produced at the same time as the usual openings that are required to loop through external connections from the component side to the wiring side. When the openings are made in the form of bores, their position, their diameter and their number are each dependent on the component geometry of the discrete component. The mechanical loads that occur later in the form of vibrations also determine the position, diameter and number of openings.

The amount of adhesive depends on the number of holes, the diameter of the holes and the penetration depth of the holes in order to ensure that when the circuit board is installed, sufficient adhesive can penetrate through the openings to at least partially fill the space between the discrete component and the top of the circuit board with adhesive . In addition to the support, the discrete component is fixed by the adhesive compound with at least two wire connections as external connections on the circuit board. This through External connections endangered by vibrations are protected from mechanical loads by the supporting adhesive mass, so that the soldering points on the rear side of the circuit board are also exposed to a reduced load.

The electronic housing preferably has surface-mountable components as discrete components, the external connections of which are soldered directly to the top or the component side of the circuit board. These soldered connections are not additionally supported by a through contact and are therefore particularly at risk from mechanical stress. With the measure according to the invention, namely filling up the space between the top of the circuit board and the bottom of the discrete semiconductor component, vibrations can now be kept away from these sensitive surface-mountable external connections of a discrete component.

The electronic device preferably has a component from the group of coil, capacitor, resistor, ferrite component, potentiometer, variable capacitor or hybrid component as a discrete component.

In addition to the housing base, the electronic device also has a housing cover, the printed circuit board being fixed between the housing base and the housing cover. By means of an additional measure, the housing cover can also contribute to the fixation of discrete components and to their vibration protection, in that the free space between the housing cover and an upper side of a discrete component is also at least partially filled with adhesive. The component is thus fixed via the adhesive between the housing cover and the component as well as the top of the circuit board and the component in such a way that the discrete component is practically wedged between the housing cover and the circuit board.

The electronic device is preferably a guiding device of a vehicle from the group of engine control device, transmission control device, anti-lock device (ABS) or electronic safety control device (ESP). Such guide devices are installed in the above-described housings comprising a housing cover and housing base and can achieve a high level of functionality in terms of functionality through the inventive support of individual components.

• 1 zeigt einen schematischen Querschnitt durch ein elektronisches Gerät gemäß einer ersten Ausführungsform der Erfindung;
• 2 bis 8 zeigen schematische Querschnitte durch Teilbereiche von Komponenten zur Herstellung eines elektronischen Gerätes gemäß 1;
• 2 zeigt einen schematischen Querschnitt durch einen Teilbereich eines Gehäusedeckels des elektronischen Gerätes gemäß 1;
• 3 zeigt einen schematischen Querschnitt durch einen Teilbereich eines Gehäusebodens des elektronischen Gerätes;
• 4 zeigt einen schematischen Querschnitt durch einen Teilbereich einer nicht bestückten Leiterplatte vor dem Bestücken derselben;
• 5 zeigt einen schematischen Querschnitt durch die Leiterplatte gemäß 4 nach Bestücken derselben mit einem diskreten Bauelement;
• 6 zeigt einen schematischen Querschnitt durch den Gehäuseboden nach Aufbringen einer Klebstoffmasse in einem Wärmeableitungsbereich;
• 7 zeigt einen schematischen Querschnitt durch den Gehäuseboden gemäß 6 nach Aufbringen der bestückten Leiterplatte gemäß 5;
• 8 zeigt einen schematischen Querschnitt durch das elektronische Gerät nach Aufbringen des Gehäusedeckels;
• 9 bis 12 zeigen schematische Querschnitte durch ein elektronisches Gerät gemäß einer zweiten Ausführungsform der Erfindung;
• 9 zeigt einen schematischen Querschnitt durch einen Gehäuseboden mit aufgebrachter Klebstoffmasse und darauf aufgebrachter Leiterplatte;
• 10 zeigt einen schematischen Querschnitt durch einen Gehäusedeckel mit aufgebrachter Klebstoffmasse;
• 11 zeigt einen schematischen Querschnitt durch einen Teilbereich eines elektronischen Gerätes gemäß einer zweiten Ausführungsform der Erfindung;
• 12 zeigt einen schematischen Querschnitt durch das elektronische Gerät gemäß der zweiten Ausführungsform der Erfindung;
• 13 zeigt einen schematischen Querschnitt durch ein elektronisches Gerät gemäß einer dritten Ausführungsform der Erfindung.

The invention will now be explained in more detail with reference to the accompanying figures.

• 1 shows a schematic cross section through an electronic device according to a first embodiment of the invention;
• 2 to 8th show schematic cross-sections through subregions of components for the production of an electronic device according to FIG 1 ;
• 2 shows a schematic cross section through a partial area of a housing cover of the electronic device according to FIG 1 ;
• 3rd shows a schematic cross section through a partial area of a housing bottom of the electronic device;
• 4th shows a schematic cross section through a portion of an unequipped printed circuit board prior to equipping the same;
• 5 shows a schematic cross section through the circuit board according to FIG 4th after equipping the same with a discrete component;
• 6th shows a schematic cross section through the housing base after application of an adhesive mass in a heat dissipation area;
• 7th shows a schematic cross section through the housing base according to FIG 6th after applying the assembled circuit board according to 5 ;
• 8th shows a schematic cross section through the electronic device after the housing cover has been attached;
• 9 to 12th show schematic cross sections through an electronic device according to a second embodiment of the invention;
• 9 shows a schematic cross section through a housing base with applied adhesive and printed circuit board applied thereon;
• 10 shows a schematic cross section through a housing cover with applied adhesive mass;
• 11 shows a schematic cross section through a portion of an electronic device according to a second embodiment of the invention;
• 12th shows a schematic cross section through the electronic device according to the second embodiment of the invention;
• 13th shows a schematic cross section through an electronic device according to a third embodiment of the invention.

1 shows a schematic cross section through an electronic device 1 according to a first embodiment of the invention. The electronic device 1 has a housing 17th on with a housing cover 21 and a case back 10 . In the edge areas 26th is between the housing cover 21 and the case back 10 a circuit board 7th fixed that a component side 8th and a wiring side 9 having. The wiring side 9 is with the case back 10 Via a thin layer of electrically insulating and thermally conductive adhesive 11 connected. This adhesive mass 11 can when assembling the electronic device 1 over openings 12th through the circuit board 7th be pressed through and a free space 13th between the underside of discrete components 3rd and the component side 8th the circuit board 7th fill in such a way that the discrete components 3rd additionally be mechanically supported.

In this embodiment, a coil is used in the electronic device 14th , a capacitor 15th and a potentiometer 16 with the help of such openings filled with plastic compound 12th and partially filled spaces 13th under the components 3rd protected from vibrations. In addition to the discrete components 3rd instructs the electronic device 1 also integrated circuits with their external connections to the wiring side 9 are electrically connected and because of their large number of external electrical connections and their discrete components 3rd low mass are less at risk of soldering connections and / or external connections of these integrated circuit components being damaged by vibrations.

While the coil 14th only two external connections 4th and 5 like the capacitor component 15th is the potentiometer 16 with three external connections 4th , 5 and 6th via vias 18th through the circuit board 7th with the wiring side of 9 of the circuit board 7th electrically connected. This small number of external connections 4th to 6th of the discrete components 3rd is without the adhesive composition according to the invention, which has openings 12th in the circuit board 7th the free space under the discrete components 3rd fills up, heavily burdened by vibrations, what by the plastic mass 11 is mitigated.

2 to 8th show schematic cross-sections through partial areas of components for the production of an electronic device 1 according to 1 . To do this shows 2 a schematic cross section through a portion of a housing cover 21 of the electrical device 1 on the right side of the 1 . This cup-shaped housing cover 21 points in its edge area 26th a flange 27 and protects a cavity 28 from contamination. Such a housing cover 21 belongs to the three main components of the electronic device 1 and is produced in preparation.

3rd shows a schematic cross section through a partial area of a housing base 10 of the electronic device 1 . This case back 10 points in its edge area 26th also a flange 29 on, but with a recess 31 is provided so that between the housing cover 21 and the case back 10 a field plate in the recess 31 can be fixed. Furthermore, the housing base 10 a depression 32 in a heat conduction area 19th on, which can be filled with an adhesive mass.

4th shows a schematic cross section through a portion of an unassembled printed circuit board 7th before loading the same. In the heat conduction area 19th has the circuit board next to the via opening 18th Additional openings for attaching external connections 12th in the form of bores which are arranged in the area of a discrete component.

5 shows a schematic cross section through the circuit board 7th according to 4th after equipping the same with a discrete component 3rd . An external connection is required for this 5 of the discrete component 3rd into a through opening 12th introduced and on the wiring side 9 soldered to the connecting lines located there.

Before assembling the housing, the recess 32 of the case back 10 , how 6th shows with an adhesive mass 11 filled, with a larger amount of adhesive mass 11 is filled into the recess than it is for the mere gluing of the connection side 9 the circuit board 7th would be required. This additional adhesive mass 11 is used to like it 7th shows adhesive mass through the openings 12th to press when the circuit board 7th , as in 5 shown in the direction of arrow A as it 6th shows on the adhesive mass 11 pressing takes place while adjusting the edge area at the same time 26th the circuit board 7th into the recess 31 of the flange 29 of the case back 10 .

During this fitting, the adhesive mass penetrates 11 through the openings 12th on the component side 8th the circuit board 7th below the discrete component 3rd and fills part of the space 13th between the discrete component 3rd and the component side 8th the circuit board 7th on. After the plastic compound has hardened 11 is thus a support and a fixation for the discrete component 3rd created.

Finally, the flange is used 29 of the case back 10 at the edge 26th the flange 27 of the housing cover 21 fixed and thus the housing 24 , like it 8th shows, gas- and liquid-tight. Ultimately, it also becomes the circuit board 7th in their edge area 26th between the housing cover 21 and case back 10 trapped. Thus, in conventional electronic devices 1 by simply adding openings 12th in the circuit board 7th an improved form-fitting and material-fitting fixation of discrete components without additional process steps 3rd and the vibration protection can be improved.

9 to 12th show schematic cross-sections through an electronic device 2 according to a second embodiment of the invention. Components with the same functions as in the previous figures are given the same reference symbols in FIG 9 to 12th marked and not specifically discussed.

9 shows a schematic cross section through a housing base 10 with applied adhesive mass 11 and printed circuit board attached to it 7th so that about the openings 12th in the form of holes adhesive mass 11 on the component side 8th . the circuit board 7th penetrates and a free space 13th between the component 3rd and the component side 8th the circuit board 7th with plastic compound 11 at least partially fills up. This procedural stage corresponds to that in 7th Process stage shown for the production of the electronic device 1 according to the first embodiment of the invention.

10 shows a schematic cross section through a housing cover 21 with applied adhesive mass 11 in an adhesive area 20th which corresponds to the positions of the discrete components.

11 shows a schematic cross section through a portion of the electronic device 2 according to a second embodiment of the invention. The housing cover 21 is now with its flange 27 at the edge 26th on the flange 29 of the case back 10 Pressed on and fixed in a gas- and moisture-tight manner. This is where the adhesive mass 11 as in 10 on the housing cover 21 is shown on the top 23 of the discrete component 3rd pressed, with the clearance 22nd between the top 23 and the housing cover is at least partially filled. The component is after the adhesive mass has cured 11 wedged between the housing cover and the printed circuit board and protected from vibrations.

12th shows a schematic cross section through the electronic device 2 according to the second embodiment of the invention. As can be seen in this cross-section, there are now the discrete components 3rd like the coil 14th , the capacitor 15th and the potentiometer 16 Not only fixed on their underside by an adhesive mass, but also on their upper sides 23 in appropriate adhesive masses 11 arranged. It is also possible to use these plastic compounds 11 first on the tops 23 of the discrete components 14th , 15th and 16 to apply and then the housing cover 21 on this plastic compound 11 to press in order to create a material connection with the housing cover 21 establish and free space 22nd between top of the discrete components 3rd and the housing cover 21 to fill up.

13th shows a schematic cross section through an electronic device 30th according to a third embodiment of the invention. Components with the same functions as in the previous figures are identified with the same reference symbols and are not discussed separately. The third embodiment of the invention according to 13th differs from the previous embodiments in that the housing base 25th a heat dissipation area 19th with cooling fins 35 has and another area 33 has a cavity 34 between circuit board 7th and case back 25th having.

In this area 33 are just integrated circuits 36 , 37 and 38 arranged with low heat loss, the prior to heating by appropriate discrete components 3rd or power semiconductor components are protected by the fact that they are on the wider area 33 are arranged at a distance from the heat conduction area in which high temperatures can occur on the circuit board.

Claims (9)

A method for producing an electronic device (1) with a discrete component (3) on a printed circuit board (7) in a housing (17), comprising the following process steps: Production of a housing (17) with a flat heat dissipation area (19) in the housing base ( 10); - Production of a circuit board (7) with through-contact openings for through-contacts (18) of at least one discrete component (3); - Equipping the circuit board (7) with the discrete component (3); characterized in that - prior to the assembly of the circuit board (7) with the discrete component (3), through openings (12) are produced through the circuit board (7) in the assembly area of the discrete component; - The flat heat dissipation area (19) is covered with an adhesive mass (11); - the circuit board (7) equipped with the discrete component (3) is pressed with its wiring side (9) into the adhesive mass (11) and - the adhesive compound (11) penetrates through the through openings (12) in the area of the discrete component (3) and a free space (13) between the discrete component (3) and the component side (8) of the circuit board (7) with the adhesive compound (11) the wiring side (9) of the printed circuit board (7) fills and hardens in the area of the openings (12), and - the hardened adhesive mass (11) supports the discrete component (3). Procedure according to Claim 1 , characterized in that a thermally conductive, electrically insulating adhesive material is used as the adhesive mass (11). Procedure according to Claim 1 or Claim 2 , characterized in that a vibration-damping adhesive material is used as the adhesive mass (11). Method according to one of the Claims 1 to 3rd , characterized in that an electrically insulating adhesive material with embedded thermally conductive particles is used as the adhesive mass (11). Method according to one of the Claims 1 to 4th , characterized in that a two-component adhesive is used as the adhesive mass (11). Method according to one of the Claims 1 to 5 , characterized in that a gel with embedded thermally conductive particles of carbon is used as the adhesive mass (11). Method according to one of the Claims 4 to 6th , characterized in that metal particles are used as thermally conductive particles in the adhesive compound (11), the outer dimensions of which are smaller than the conductor track spacings on the wiring side of the circuit board (7). Method according to one of the Claims 4 to 7th , characterized in that spherical metal particles are used as thermally conductive particles, the outer diameter of which is smaller than the conductor track spacings of the circuit board (7). Method according to one of the Claims 4 to 8th , characterized in that prior to the application of a housing cover (21) at least partially adhesive compound (11) is applied to an upper side (23) of the discrete component (3), the adhesive compound (23) when assembling the housing cover (21) with the housing base (10) to a housing (24) fills a free space (22) between the housing cover (21) and the top (23) of the discrete component (3).

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