DE102017212902A1 - Method for producing a sintered connection electronic assembly and sintered connection electronic assembly - Google Patents

Abstract

The invention relates to a method for producing an electronic assembly and an electronic assembly, which can be generated by such a method. In the method, a circuit carrier (11, 12) equipped with components (15) and z. B. connected via solder joints with these. In addition, a construction component, such. B. a cooler (19), by a sintered connection (18) to the circuit carrier (11, 12). According to the invention, a holding device, in particular a screw connection (20), is applied to the circuit carrier (11, 12) and the structural component (19), which forms a contact pressure for the sintered connection (18) at at least two separate locations. This holding device is therefore very simple and compact, but reliably transmits a contact pressure on the sintered connection (18). The sintered connection can therefore be produced in a simple manner without special tools. Preferably, the sintered connection (18) can be produced simultaneously with the solder joints of the electronic components.

Description

The invention relates to a method for producing an electronic module, in which a circuit carrier is equipped with an electronic component and this component is firmly connected to the circuit carrier (for example, by gluing, soldering or bonding). When the electronic module is produced, a further component is additionally fixed to the circuit carrier in a specific positioning, and the component is subsequently connected firmly to the circuit carrier by sintering via a sintered layer. Moreover, the invention relates to an electronic assembly having a circuit carrier. On this circuit board, an electronic component is attached. In addition, a further structural component is attached to the circuit carrier via a sintered layer.

An electronic assembly and a method for their preparation is for example from DE 10 2014 013 036 A1 known. The electronic module is a power module, wherein an electronic component is mounted on the upper side of a circuit carrier. With the underside of the circuit carrier is connected via a sintered connection with a structural component in the form of a cooling plate. The sintering takes place in that the cooling plate and the printed circuit board are pressed together, for example under increased pressure and elevated temperature. In this way, a silver paste located therebetween can be compressed and form a sintered layer connecting the two components.

The use of silver sintered materials as contact material is common because of the high thermal conductivity of silver. To produce a large-area sintered connection, as required, for example, between a circuit carrier and a cooling plate, however, increased demands are placed on the process control (temperature, time and pressure), so that an error-free sintered connection is formed. This is a prerequisite for good heat conduction, as defects in the sintered layer, such as air pockets, would reduce the thermal conductivity.

Sintered connections are therefore often produced using adapted special tools, which make it possible to insert the components to be sintered in a sintering press. However, the production of such sintering tools only pays off in the case of large quantities that are not always to be found in electronics assembly.

In order to increase the load capacity and reliability of power modules, semiconductor devices are increasingly used as electronic components. These chips are connected without housing directly to the circuit board, which in particular simplifies a dissipation of heat loss. However, this can only be done reliably if the thermal connection between the semiconductor component and the circuit carrier and between the circuit carrier and the heat sink have a high quality. The semiconductor device can be connected, for example, by a sintered connection to the circuit carrier.

The object is therefore to provide a method for producing an electronic assembly with sintered connection, which is easy to carry out and with which can produce high-quality sintered connections. Moreover, it is an object of the invention to provide an electronic assembly with a sintered connection, which can be easily manufactured and has a high quality.

This object is achieved with the method described above according to the invention in that a holding device is attached to the circuit carrier and the component, with the circuit carrier and the component are held in the positioning, wherein the holding device locally at least two separate and spaced locations of Building component generates a contact pressure between the component and the circuit substrate. Thereafter, the electronic assembly is exposed to an elevated temperature for sintering. The holding device according to the invention can advantageously be made very compact and simple, as this attacks at two points of the building component and so a total of symmetrical force introduction into the building component is possible. The fact that the holding device can be made compact, this can be pre-assembled during the process for producing the electronic assembly and the thus provided with a bias sintered connection during the manufacturing process are carried out at a convenient time for the production. In particular, it is not necessary to use a sintering press with a consuming adapted to the components to be sintered recording. Instead, the sintered compound can be produced, for example, in an oven, whereby both a batch oven and a reflow oven come into question. This allows the cost-effective production of electronic assemblies, especially for small planned quantities or custom-made.

According to an advantageous embodiment of the invention, it is provided that the electronic component is firmly connected by generating a solder joint with the circuit carrier, wherein the generating of the solder joint simultaneously with the Sintering is performed. This advantageously makes it possible to save a production step when the electronic assembly is produced. This is possible because the sintered connection with the compact holding device can be subjected to further manufacturing steps, for example, can be equipped with components. The soldering and the sintering can then be carried out, for example, in a reflow oven, during which time the holding device provides the necessary contact pressure to form the sintered connection.

The solder material and the material of the sintered layer are matched in this embodiment of the method according to the invention to one another such that overlap the required process window for soldering and sintering. In other words, process parameters which are suitable both for forming the solder connection and for forming the sintered connection can be found in the overlapping area of these process windows.

For example, as a sintered material, a silver sintered material can be selected. Pressure sintering sintered sintered materials are typically sintered at 200-250 ° C within 1-3 minutes, depending on the manufacturer. Suitable soldering materials include, for example, lead-free solder alloys based on tin-silver-copper. Peak temperatures during soldering are around 245 ° C, whereby the time above 200 ° C is around 100s. Thus, both a remelting of the solder and a sintering of the silver sintered material in one and the same manufacturing step is possible.

According to another embodiment of the invention, the holding device of at least two brackets, which are plugged from the side on the edge of the circuit substrate and the structural component and generate the contact pressure. Advantageously, the mounting of the brackets is particularly easy. This can be done for example by a placement and thus automated. The contact pressure can be generated by the elasticity of the staple material. The clamps can be removed again after the sintering treatment and thus used several times.

According to another embodiment of the invention it is provided that the holding device consists of at least two screw, wherein the contact pressure is generated by tightening the screw. Advantageously, the tightening torque can be calculated for a specific contact pressure, this being a conventional method for screw connections and therefore not explained in detail here. Thus, it is also possible to build up the contact pressure regardless of tolerances occurring to be connected via the sintered connection components, since the thread of the screw simultaneously allows axial tolerance compensation in the direction of the screw axis. In addition, the components of a screw, so screws, nuts and washers for distributing the force to standard components, which are inexpensive to procure. The screw connection (as well as a clamp) can be left after the sintering treatment on the electronic assembly or removed again.

It is particularly advantageous if the screw connection is guided through a hole which runs through the structural component and / or through the circuit carrier. The hole advantageously allows easy placement of the screw at exactly the point of the component, where the contact pressure is to be generated. The hole also prevents the screw connection from shifting during tightening. The hole may but need not be formed in both connection partners. The hole can also be a threaded hole into which the screw is screwed.

According to a particular embodiment of the invention, it is provided that the circuit carrier has a substrate plate for receiving the component and a bottom plate for receiving the component. The substrate plate may, for example, have the conductor track for generating the electronic circuit. The bottom plate may be metallic, for example, to promote heat dissipation. At the same time, the bottom plate stabilizes the circuit carrier, which makes it possible to better distribute the contact pressure generated by the holding device on the entire surface of the sintered connection, since the force is applied at spaced locations of the structural component.

Preferably, the component may consist of a heat sink or an electrical load terminal or a semiconductor device. If a heat sink is connected to the circuit carrier as a structural component, the heat dissipation into the heat sink is advantageously improved by the high-quality sintered connection. If an electrical load connection is mounted, it preferably benefits from a better electrical transmission. The lower contact resistance between the load connection and the circuit carrier advantageously leads to less power loss. If a semiconductor component is processed as a component, the sintered connection can be used for improved heat dissipation due to its higher quality. As with the load connection leads an improved sintered connection also to reduced contact resistance in the sintered connection, if this is to be used for electrical contact.

It is also advantageous if the sintered layer is applied to the circuit carrier or the component before the fixing of circuit carrier and component. This simplifies the subsequent assembly, because the sintered layer then does not have to be handled as a separate component. The sintered layer can be applied to the component or to the circuit carrier, for example, in a stencil printing process.

It is advantageous if the sintered layer is dried in an oven before fixing the circuit carrier and component. As a result, the sintered layer advantageously already obtains greater mechanical stability. Therefore, the contact pressure exerted by the holding device may have a higher amount. This promotes the formation of the sintered bond through the sintered layer in the subsequent sintering process. In particular, it is possible to carry out the sintering at lower temperatures at a higher contact pressure, which advantageously increases the process window for sintering, in particular in the case of a combination of sintering with soldering. In this way, advantageously more solder materials with more sintered materials for a combined assembly process (as described above) can be selected.

The above object is also achieved by the above-mentioned electronic assembly according to the invention that the circuit carrier and the component are enclosed by a holding device, wherein the holding device locally at least two separate and spaced locations of the component a contact pressure between the component and the circuit board generated. The holding device advantageously makes it possible to carry out the method already described above for producing this electronic assembly, wherein the generation of the contact pressure between the component and the circuit carrier by the holding device is advantageously possible reliably and with simple means. Advantageously, the clamping device can be designed by at least two brackets or at least two screw connections. These are simply formed components that can remain on the electronic assembly even after the assembly process. As a result, the associated disassembly effort is saved, which is to weigh whether this advantage over the possibility of multiple use of the clamping device outweighs.

Further details of the invention are described below with reference to the drawing. Identical or corresponding drawing elements are each provided with the same reference numerals and will only be explained several times as far as there are differences between the individual figures.

The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention, which are to be considered independently of one another, which each further develop the invention independently of one another and thus also individually or in a different combination than the one shown as part of the invention. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

• 1 ein Ausführungsbeispiel der erfindungsgemäßen elektronischen Baugruppe von der Seite, teilweise aufgeschnitten, hergestellt nach einem Ausführungsbeispiel des erfindungsgemäßen Verfahrens,
• 2 bis 4 Ausschnitte von Ausführungsbeispielen der erfindungsgemäßen Baugruppe gemäß 1 als Seitenansicht, bei denen alternative Haltevorrichtungen zum Einsatz kommen,
• 5 ein anderes Ausführungsbeispiel der erfindungsgemäßen Baugruppe mit einem Lastanschluss als Seitenansicht, teilweise aufgeschnitten,
• 6 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens, bei dem eine Sinterschicht vorgetrocknet wird, schematisch als Seitenansicht und
• 7 ein Ausführungsbeispiel des erfindungsgemäßen Verfahrens, bei dem die Sinterverbindung in einem Reflow-Ofen erzeugt wird, als schematische Seitenansicht.

Show it:

• 1 an embodiment of the electronic assembly according to the invention from the side, partially cut away, produced according to an embodiment of the method according to the invention,
• 2 to 4 Excerpts of embodiments of the assembly according to the invention according to 1 as a side view, in which alternative holding devices are used,
• 5 another embodiment of the assembly according to the invention with a load connection as a side view, partially cut open,
• 6 an embodiment of the method according to the invention, in which a sintered layer is pre-dried, schematically as a side view and
• 7 an embodiment of the method according to the invention, in which the sintered compound is produced in a reflow oven, as a schematic side view.

In 1 an electronic module is shown, which is mounted on a circuit carrier. The circuit carrier consists of a substrate plate 11 and a bottom plate 12 that are firmly connected. On the substrate plate 11 there is a contact layer from the structuring contact pads 13 for electrical contacts and contact surfaces 14 for receiving electronic components 15 are provided. The electronic components 15 can, for example, by bonding wires 16 or contact structures 17 with the contact pads 13 be contacted electrically. The contact structures 17 are not shown by solder joints with the contact pads 13 electrically contacted.

Over a sintered layer 18 is the bottom plate 12 the circuit substrate having a structural component in the form of a heat sink 19 connected thermally conductive. To before a sintering treatment, the heat sink 19 and the bottom plate 12 to fix each other, two holding devices in the form of screw 20 used. The screw connections 20 each consist of a screw 21 passing through a hole 22 is plugged, with the hole 22 through the heat sink 19 , the sintered layer 18 and the bottom plate 12 leads. At the end of the screw 21 is a mother 23 provided that a by the tightening torque defined contact pressure on the dressing of base plate 12 , Sintered layer 18 and heat sink 19 exercises. This contact pressure is via washers 24 evenly around the edge of the hole 22 distributed.

Because the heat sink 19 and the bottom plate 12 are executed rectangular, are the screw 20 attached at diagonally opposite corners to a uniform pressure distribution in the sintered layer by a symmetrical introduction of the contact pressure 18 to be able to produce. This effect is improved when the bottom plate 12 is made relatively stiff, for example, consists of a metal. The heat sink is also metallic, for example made of aluminum. So is a good heat dissipation from the substrate plate 11 over the bottom plate 12 and the sintered layer 18 in the heat sink 19 possible. Of course, more than two screw can be used, for example, at each of the four corners of the bottom plate. As a result, advantageously, a higher contact pressure can be generated and / or a contact pressure can be applied more uniformly to the surface of the sintered layer 18 be distributed.

In 2 is an alternative embodiment of the assembly according to 1 shown. The difference is that the sintered layer 18 has a smaller area than the heat sink 19 and the bottom plate 12 so the screw 21 a gap bridged by the thickness of the sintered layer 18 is defined. Because the sintered layer 18 in this way has a smaller area, by means of the screw connection 20 a higher contact pressure can be generated when the tightening torque compared to 1 is equal to.

According to 3 is shown that also the bottom plate 12 can be made smaller so that the hole 22 (shown in pencil) according to 1 located outside the bottom plate. The screw 21 the screw connection 20 then only in the hole 22 of the heat sink 19 guided, with the washer 24 on one side of the screw 21 to a force in the bottom plate 12 is being used. The hole is according to 3 designed as a threaded hole, into which the screw 21 can be screwed directly. Therefore, no nut is necessary to the screw connection 20 according to 3 to secure.

According to 4 is a clip as a holding device 25 intended. This is made by the side on the bandage, consisting of bottom plate 12 , Sintered layer 18 and heat sink 19 postponed. On the side of the heat sink 19 the clamp has a cheek 26 on that under the heatsink 19 attacks. On the side of the bottom plate 12 is a bending spring on the clip 27 formed, located on the top of the bottom plate 12 supported and by the deformation of the contact pressure for the sintered layer 18 is given.

In 5 the circuit carrier consists only of the substrate plate 11 , Of course, as an alternative, not shown, a bottom plate 12 , as in 1 shown, are provided. On the substrate plate 11 is a component 15 with contact structures 17 on the contact pads 13 intended. Other components are not shown, but may also be present, for example, a device which is contacted with bonding wires (see. 1 ).

Unlike in 1 are shown as building components on contact pads 13 over sintered layers 18 a semiconductor device 28 and a load connection 29 contacted. The semiconductor device 28 may for example be a power electronic switching element, and is by means of the clip 25 held (as in 4 explained). A second bracket is behind the bracket shown 25 and is therefore in 5 not recognizable.

The load connection 29 is about two screw connections 20 on the contact pad 13 fixed, with one of the screw connections 20 before the load connection 29 and the other of the screw connections 20 is arranged behind the load connection. This results in a symmetrical force transmission into the load connection 29 possible, so that on the sintered layer 18 a uniform contact pressure is applied. The end of the load terminal is used for contacting with an electrical wiring, not shown.

In 6 is shown as a structural component in the form of the heat sink 19 with the sintered layer 18 can be provided. For this purpose, a template 30 hung up, in the with a dosing device 31 the sintered layer 18 is produced. Subsequently, the sintered layer is in a reflow oven 32a dried. The process is continuous, which is why the individual production steps can be seen in one figure. The heat sinks 19 lie on a conveyor belt 33a and are through this through the individual manufacturing stations including the reflow oven 32a guided.

Also, the method according to 7 runs continuously. The heat sink 19 is also by a conveyor belt 33b guided through the individual stations. At the heat sink 19 it is a heat sink provided with a sintered layer, wherein the sintered layer, unlike in 6 , For clarity's sake not shown.

In a first process step, the heat sink 19 with a substrate plate 11 brought into contact with the screw connections 20 be attached and a contact pressure between the heat sink 19 and the substrate plate 11 produce.

In a next manufacturing step, the substrate plate 11 with electronic components 15 stocked. The contacting of these components should be done via solder joints not shown.

In a next step, the entire assembly is passed through a reflow oven, with the sintered connection between the heat sink 19 and the substrate plate 11 simultaneously with the solder joints of the electronic components, not shown 15 will be produced. After passing through the reflow oven 32b become the screw connections 20 removed in a manner not shown.

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

• DE 102014013036 A1 [0002]

Claims (12)

Method for producing an electronic module in which • a circuit carrier (11, 12) is equipped with an electronic component (15) and this component (15) is firmly connected to the circuit carrier (11, 12), • the circuit carrier (11, 12) and a structural component (19, 28, 29) are fixed in a positioning to each other and the structural component (19, 28, 29) by sintering via a sintered layer (18) fixed to the circuit carrier (11, 12) is connected, characterized in that • a holder device (20, 25) is attached to the circuit carrier (11, 12) and the component (15) with which the circuit carrier (11, 12) and the component (19, 28, 29) are kept in the position be, wherein the holding device (20, 25) locally at at least two points of the structural component (19, 28, 29) generates a contact pressure between the structural component (19, 28, 29) and the circuit carrier (11, 12), • thereafter the electronic Assembly for Sint is exposed to an elevated temperature. Method according to Claim 1 characterized in that the electronic component (15) is fixedly connected to the circuit carrier (11, 12) by creating a solder connection, wherein the production of the solder connection is performed simultaneously with the sintering. Method according to one of the preceding claims, characterized in that the holding device consists of at least two clamps (25) which are plugged from the side onto the edge of the circuit carrier (11, 12) and the structural component (19, 28, 29) and the Generate contact pressure. Method according to one of Claims 1 or 2 characterized in that the holding device consists of at least two screw connections (20), wherein the contact pressure is generated by tightening the screw connection (20). Method according to Claim 4 , characterized in that the screw connection is guided through a hole (22) which leads through the structural component (19) and / or through the circuit carrier (12). Method according to one of the preceding claims, characterized in that the circuit carrier has a substrate plate (11) for receiving the component (15) and a bottom plate (12) for receiving the structural component (19, 28, 29). Method according to Claim 6 , characterized in that the structural component of a heat sink (19) or an electrical load connection (29) or a semiconductor device (28). Method according to one of the preceding claims, characterized in that the sintered layer (18) prior to the fixing of circuit carrier (11, 12) and component (19, 28, 29) on the circuit carrier (11, 12) or the structural component (19, 28 , 29) is applied. Method according to Claim 8 , characterized in that the sintered layer (18) is dried in an oven before the fixing of circuit carrier (11, 12) and component (19, 28, 29). Method according to one of the preceding claims, characterized in that the sintering takes place in an oven, in particular in a reflow oven (32b). Electronic assembly comprising a circuit carrier (11, 12) on which an electronic component (15) is fixed, and a structural component (19, 28, 29) which is attached via a sintered layer (18) to the circuit carrier (11, 12) , characterized in that the circuit carrier (11, 12) and the structural component (15) by a holder device (20, 25) are enclosed, wherein the holding device (20, 25) locally at at least two points of the structural component (15) a contact pressure between the construction component (15) and the circuit carrier (11, 12) generated. Assembly after Claim 11 , characterized in that the clamping device is formed by at least two brackets (25) or at least two screw connections (20).

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