DE102008048977B4 - Electronic compact module - Google Patents

Abstract

Electronic compact assembly (1) for mounting on a printed circuit board (8), with a housing (6) in which a transformer (2) and next to the transformer (2) a transistor (3) and encapsulated with a potting compound (4) in which the transformer (2) and the transistor (3) have electrical connections (5) which protrude from the potting compound (4), characterized in that the transistor (3) has a metallic cooling surface (101) directed towards the transformer (2) ), with which it is in heat-conducting connection with an iron core of the transformer (2), wherein it is in direct contact with the cooling surface (101) on the iron core, or between the cooling surface (10) and the iron core a heat conducting disk (7) is arranged, which is directly adjacent to the iron core and the cooling surface (10).

Description

The present invention relates to a compact electronic assembly for mounting on a printed circuit board, comprising a housing in which a transformer is arranged and sealed.

It is known to shed transformers in a housing, so that the transformer together with the housing can be mounted on a printed circuit board. The assembly is independent of the assembly of the circuit board with other electronic components. Frequently, electronic power transistors are used on the circuit board, which must be mounted separately from the transformer. In addition to this separate assembly step, a measure for the cooling of the same is still to be made for power transistors. Connecting the Leistungshalbeiters with a corresponding heat sink, which takes place for example by screwing or jamming of the transistor to the heat sink, is carried out manually and therefore requires a separate assembly step. It should also be noted that the heat sink on the PCB requires additional space.

From the German patent application DE 2227876 A an arrangement of circuit parts is known as a closed, pluggable module, in which the majority of the components of a horizontal deflection power amplifier is housed within a modular housing, wherein transformer (s), power transistor (s) and other heat generating or cooling components and -element groups are mechanically mounted on the inside of the existing at least partially made of thermally conductive material housing housing and are in good thermally conductive contact with this.

The German utility model DE 1892269 U discloses a power plug housing having a bottom of metal and a top of plastic, wherein in the housing, a transformer and a transistor are arranged and the lower part acts as a heat dissipation for the transistor.

Furthermore, from the U.S. Patent 2,862,992A an electrical network arrangement with a plurality of electrical components known which are cast together in a housing.

It is an object of the present invention to provide an electronic compact module that simplifies and accelerates the assembly of transformer and transistor on a printed circuit board and at the same time ensures high installation and reliability while maintaining good cooling of the transistor.

This is solved by the features of independent claim 1. Advantageous developments of the invention are given in the dependent claims.

According to the invention, an electronic compact assembly for mounting on a printed circuit board, with a housing in which a transformer is potted, is provided, wherein in the housing additionally a transistor is arranged next to the transformer and molded together with this, and the electrical connections of the transformer and the Protruding transistor from the potting compound.

By connecting transistor and transformer in one housing, i. H. the integration of a transistor together with a transformer in a housing, an assembly is formed, the assembly in one step replaces the originally required steps for the respective assembly of transformer, transistor and heat sink. An additional heat sink can be saved by this measure, since the heat generated by the transistor, can be absorbed by the potting compound. By saving the heat sink can be saved on the one hand costs, on the other hand, space on the circuit board. In addition to the additional installation step for the placement of the transistor and the connection of the same with the heat sink deleted, so that the process for mounting the circuit board can be considerably simplified and accelerated.

Preferably, the entire surface of the transistor can be encapsulated with the potting compound, so that there is a perfect heat transfer between the transistor and the potting compound, since there is no air gap between the transistor and the potting compound, which represents a thermal resistance.

Preferably, the electrical connections of transformer and transistor may be formed by contact pins which are arranged parallel to one another. This ensures that the electrical connections aligned parallel to each other protrude from the potting compound, so that a circuit board assembly can be made easily. The pins can then be plugged through existing on the circuit board holes in the printed circuit, the holes and the pins can then be connected to each other automatically by wave soldering with a corresponding application of solder with each other automatically.

It is particularly advantageous if the potting compound completely fills the housing. The electronic compact module thus offers a particularly high heat capacity for absorbing the waste heat generated by the transistor.

According to the invention, the transistor can be designed in a stationary design. In this design, which is also referred to as THT design (through hole technology), which include, for example, the housing types TO247, TO220 or ISOWATT, extending three pins parallel to each other in a plane lying away from the flat housing. This transistor design is particularly suitable for integration in the housing, since the transformer is essentially formed almost cube-shaped and a flat housing shape only a small extension of the housing of the compact assembly relative to the length or the width of the transformer dimension conditional. A stationary design of the transistor therefore leads to small and space-saving dimensions of the electronic compact module.

According to the invention, the transistor has a metallic, directed to the transformer cooling surface, with which it is in heat-conducting connection with the iron core of the transformer. As a heat-conducting compound is understood in the context of the invention, such a compound which has a better thermal conductivity than air. Via the metallic cooling surface, the waste heat generated by the transistor can be dissipated particularly well from the electronically active parts of the transistor. In a particularly advantageous manner results in the present invention that when the transistor is arranged next to the transformer within the housing of the electronic compact assembly, the waste heat of the transistor from the iron core of the transformer can be accommodated.

For a particularly good heat transfer, the cooling surface of the transistor is applied directly to the iron core. This is to be understood in particular that between the transistor and transformer no physically solid or solidifying material is arranged. However, it may be provided that a thermal paste is arranged to achieve a perfect heat transfer between the cooling surface and the iron core.

In an alternative embodiment variant, a thermally conductive disc is arranged between the transistor and the transformer and bears directly against the iron core and the cooling surface. In this case, the transistor is indirectly applied to the transformer. In the heat transfer between the transistor and the heat-conducting disc and / or between the latter and the transformer core, a thermally conductive paste may be incorporated to reduce the thermal resistance from the transistor to the transformer.

Preferably, the transistor may be formed as a high-power transistor with an operating voltage up to 1500 V. The fixed location of the transistor within the electronic package can ensure for the user that any isolation requirements are met which otherwise he would have to consider when developing the PCB with separate mounting of the high power transistor. The necessary distance between the contacts of the high-power transistor and other electrical contacts can therefore already be taken into account in the manufacture of the electronic compact module, so that a high reliability is ensured by the user in the assembly of the circuit board and its subsequent operation.

When using a high-power transistor within the electronic compact assembly insulation is sufficient to provide a sufficiently large distance between the electrical contacts of the transistor and the transformer. To comply with this distance, a disc can be arranged between the two components. It is particularly advantageous if the disk forms the heat-conducting disk, so that a good heat transfer from the cooling surface of the transistor to the iron core of the transformer is achieved.

Alternatively, a transformer may be used whose electrical connection pins are arranged in two parallel rows which are spaced apart by a distance greater than the width of the transistor. The width of the transistor corresponds to the dimension that covers the plane within which the electrical connections of the transistor are located. In this case, since the electrical connections of the transformer and the transistor are recessed from the housing walls, and therefore the diagonal distance, i. the direct distance between the terminals of the transformer and the transistor from insulation view is always large enough.

It is particularly advantageous if the transformer is a double-E core transformer. This has a two-part iron core, wherein each part is formed in the horizontal cross-section E-shaped and thereby has flat surfaces, to which the transistor can be applied directly or indirectly.

Preferably, within the housing, a temperature sensor may be encapsulated, which rests against the transistor for detecting its temperature. Hereby, the temperature of the electronic compact assembly can be monitored and a deactivation of the same in the case of reaching or Exceeding a maximum temperature limit.

Further advantages of the invention are in the following description of an advantageous embodiment with reference to the 1 and 2 explained.

• 1: Anordnung von Transformator und Transistor nach dem Stand der Technik
• 2: Schematische Darstellung der erfindungsgemäßen Kompaktbaugruppe

Show it:

• 1 : Arrangement of transformer and transistor according to the prior art
• 2 : Schematic representation of the compact module according to the invention

1 shows a circuit board 8th on which a transformer 2 and a power transistor 3 are mounted. The power transistor 3 is with a heat sink 12 connected with cooling fins, wherein the heat sink 12 a biased clip 13 comprising, with which the transistor 3 with his to the circuit board 8th directed cooling surface 101 against the heat sink 12 is pressed. The transistor 3 has a cooling flag 102 on that too with the heat sink 12 communicates. Between the cooling surface 101 or the cooling flag 102 and the heat sink is a thermal paste introduced to obtain a low-resistance heat transfer.

The transistor 3 is designed as a THT high-voltage power semiconductor, wherein the connection contacts 5 of the transistor are bent at a 90 ° angle.

As a power transistor, for example, an IGBT (insulated gate bipolar transistor), for example, the model 5N160, or a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), for example, the model 2SK3746 can be used. These have a metallic cooling surface, so that an efficient heat transfer from the power semiconductor to the heat sink can be achieved via this cooling surface. The models mentioned are available in various stationary designs, for example in a TO247 or TO220 housing.

2 shows an embodiment of the invention of the electronic compact module. According to this is in a housing 6 the transformer 2 and next to it a running in a stationary design transistor 3 arranged, the transformer 2 and the transistor 3 together by a potting compound 4 in the case 6 are shed. As potting compound 4 For example, an epoxy resin can be used. In particular, the potting compound 4 be formed thermally conductive.

The electrical connections of the transformer 2 and the transistor 3 are as contact pins 5 formed, and extend parallel to each other from the potting compound 4 out. The housing is on the circuit board 8th on, causing the potting compound 4 a distance to the PCB 4 comply. The contact pins 5 lie in mounted form of the electronic compact housing 1 in corresponding holes of the circuit board 8th one, leaving it from the bottom of the circuit board 8th provided with solder by a wave soldering process and with the corresponding electrical contact surfaces on the underside of the printed circuit board 8th can be connected.

In 2 is the case 6 completely through the potting compound 4 filled. However, it may be provided that between a housing wall of the housing 6 and one of the components, a spacer is arranged to fix the components within the housing for the casting process.

The transistor 3 has a metallic cooling surface 101 on, which is directed to the transformer. In the exemplary embodiment according to 2 is between the high power transistor 3 and the transformer 2 a heat-conducting element 7 arranged in the form of a disk. This will require a space between the high power transistor required for isolation 3 and the transformer 2 respected. The heat-conducting disc 7 allows heat transfer of the waste heat of the high-power transistor 3 over the metallic cooling surface 101 on the iron core of the transformer 2 , The heat-conducting disc 7 may be formed, for example, as a ceramic disk, alternatively from a mica disk or from a heat-conducting rubber, for example from a silicone disk.

The transformer 2 is in the example according to 2 shown only schematically. It is designed in this embodiment as a double E-core transformer and has two in horizontal cross-section E-shaped iron cores, which are arranged in mirror image to each other. The two E cores abut one another such that they form three legs arranged parallel to one another, wherein the middle leg carries a plastic winding carrier on which the transformer coils are wound. The double E-core transformer rests on a plastic base, not shown, the electrical contact pins 5 having. The electrical connections of the transformer windings are with these pins 5 connected. The contact pins are arranged in two parallel rows and face each other at a distance.

The double E-core has flat outer surfaces, of which an outer surface 14 in 2 is specified in more detail. To this outer surface 14 lies the high-power transistor 3 over the Wärmeleitscheibe 7 indirectly. Between the high power transistor 3 and the Wärmeleitscheibe 7 and between the Wärmeleitscheibe 7 and the outer surface 14 can be a thermal grease 9 be provided to the thermal conductance between the transitions of transistor 3 to disc 7 and to the area 14 to maximize.

At the cooling surface 101 or on the cooling flag 102 of the high power transistor 3 is a temperature sensor 11 for detecting the temperature. He is together with the transistor and the transformer in the housing 6 shed.

The necessary distance of the transistor 3 to the transformer 2 can be determined by the insulation class, which in turn is based on the maximum voltage at the transistor 3 directed. Corresponding minimum clearances for clearances and creepage distances on printed circuit boards can be taken from the standard EN61800-5-1. According to this DIN, with a low degree of contamination of the circuit board and a voltage of 1250 V, a minimum distance of 4.2 mm between the pins of the transistor 3 and the contact pins of the transformer 2 provided as air or creepage distance. Therefore, for example, the transistor 3 such in the housing 6 arranged that its electrical contact pins 5 at a distance of more than 5 mm from the contact pins 5 of the transformer 2 are arranged, the prescribed isolation up to an operating voltage of the transistor 3 ensured by 1250V.

By using an electronic contact component 1 in which a transformer 2 and a transistor 3 integrated and encapsulated in a common encapsulation, can be a single manual assembly of the circuit board 8th through the separate components transformer 2 , Transistor 3 and heat sink 12 be avoided. There is only one assembly step necessary so that the assembly process can be simplified and accelerated. By completely enclosing the transistor 3 with the potting compound 4 continues to be a better cooling of the transistor 3 , as between him and the potting compound 4 a perfect heat transfer is achieved. Furthermore, by the arrangement of the transistor 3 inside the housing a safe isolation from the transformer 2 and other electronic components on the circuit board 8th guaranteed. Further, by integrating the transistor 3 inside the case 6 ensures that a reverse polarity of the transistor 3 is avoided, which has been possible in the manual assembly of the prior art. The inventive summary of the electrical components transformer 2 and power semiconductors 3 to a compact module 1 therefore allows a quick and easy installation and ensures an electrically safe operation.

Claims (8)

Electronic compact assembly (1) for mounting on a printed circuit board (8), with a housing (6) in which a transformer (2) and next to the transformer (2) a transistor (3) and encapsulated with a potting compound (4) in which the transformer (2) and the transistor (3) have electrical connections (5) which protrude from the potting compound (4), characterized in that the transistor (3) has a metallic cooling surface (101) directed towards the transformer (2) ), with which it is in heat-conducting connection with an iron core of the transformer (2), wherein it is in direct contact with the cooling surface (101) on the iron core, or between the cooling surface (10) and the iron core a heat conducting disk (7) is arranged, which is directly adjacent to the iron core and the cooling surface (10). Electronic compact module (1) according to Claim 1 , characterized in that the electrical connections (5) are formed by contact pins, which are formed parallel to each other. Electronic compact module (1) according to Claim 1 or 2 , characterized in that the potting compound (4) completely fills the housing (6). Electronic compact module (1) according to one of the preceding claims, characterized in that the transistor (3) is designed in a stationary design. Electronic compact module (1) according to one of the preceding claims, characterized in that the heat-conducting disk (7) is formed from a ceramic disk, mica disk, a heat-conducting rubber or a silicone disk. Electronic compact module (1) according to one of the preceding claims, characterized in that the transistor (3) is a high-voltage transistor. Electronic compact module (1) according to one of the preceding claims, characterized in that the transformer (2) is a double-E-core transformer. Electronic compact module (1) according to one of the preceding claims, characterized in that in the housing (6) a Temperature sensor (11) is arranged, which bears against the transformer (3) and is sealed in the housing (6).

Images