DE102007045418B4 - Manufacturing method for an arrangement for cooling an electrical component - Google Patents

Abstract

Manufacturing method for an arrangement for cooling an electrical component (1), the heat conductively connected to a heat sink (6), in which between the electrical component to be cooled (1) and the heat sink (6) a heat conducting material is arranged and at the electrical component (1) is pressed against the heat sink (6),
in which the heat-conducting material is applied as pasty or liquid material between the component (1) and the heat sink (6),
in which a first pressing force is exerted in a first pressing step and a second pressing force is exerted on the component (1) in a second pressing step,
wherein the value of the second contact force is less than the value of the first contact force,
wherein, during the first pressing step, a mechanical alternating field additionally acts on the applied heat-conducting material in order to reduce air pockets in the area between the component (1) and the cooling body (6) or to fill up microspaces,
where the ...

Description

The invention relates to a manufacturing method for an arrangement for cooling an electrical component.

From the publication Shubauer, B., Hanson, K .: Compressive Modulus of Elasticity for Gap Pad material ^®, application note no. 16, The Berquist Company, in 1999, a thermally conductive viscoelastic material for producing a thermally conductive connection to an arrangement for cooling at least one electrical component known, in which between the component and a heat sink, the heat-conducting material is arranged and wherein a contact force whose value decreases over time from a high contact pressure to a low value acts on the at least one electrical component.

From the US 2003/0 011 997 A1 is the use of alternating fields for making a heat conductive connection between an electrical component and a heat sink known.

From the DE 600 09 646 T2 is a further use of alternating fields for producing a heat-conducting connection between an electrical component and a heat sink known.

From the DE 10 2004 046 475 A1 a cooling arrangement for an electrical component is known, wherein the component is pressed by means of a spring element against a heat sink.

The invention is therefore based on the object to further develop the production of an electrical appliance, in particular to accelerate.

According to the invention the object is achieved in the manufacturing method for an arrangement for cooling an electrical component according to the features specified in claim 1.

Important features of the invention in the manufacturing method for an arrangement for cooling an electrical component, the heat conductively connected to a heat sink, in which between the electrical component to be cooled and the heat sink a heat conducting material is arranged and in which the electrical component to the Heat sink is pressed,
in which the heat-conducting material is applied as pasty or liquid material between the component and the heat sink,
in which a first pressing force is exerted in a first pressing step and a second pressing force is exerted on the component in a second pressing step,
wherein the second contact pressure is less than the value of the first contact force,
wherein, during the first pressing step, a mechanical alternating field additionally acts on the applied heat-conducting material in order to reduce air pockets in the area between the component and the heat sink or to fill up microspaces,
wherein the alternating mechanical field in the area between the heat sink ( 6 ) and the component or in the heat conducting material is introduced,
wherein as a mechanical alternating field acoustic waves are used, whose frequency is in the range of the audible or ultrasonic range.

The advantage here is that are pressed out by means of the greater pressure force at the beginning of air pockets from the intermediate region between the component and heat sink. In addition, microspaces and microwells in the surface of the device and / or the heat sink are better filled by the thermal paste or the thermal adhesive. In this way, the total contact surface is increased and the heat transfer resistance is good. Even if the value of the pressing force then drops below the first value later, the inclusions are pushed out and the microspaces are well filled. Thus, the heat transfer remains good, so the heat transfer resistance is essentially the same.

In particular, a mechanical alternating field is additionally introduced and / or introduced during the first period, in particular in the intermediate region between the heat sink and the component or in the contact region of the heat sink to the component or in the intermediate medium.

Under such an alternating mechanical field, for example, to understand structure-borne noise, the frequency depending on the type of medium, for example, depending on its viscosity and / or the geometric dimensions of the intermediate region, low, such as in the infrasonic range, or highly selectable, such as in the ultrasonic range , In contrast, an alternating thermal field is to be understood, for example, as meaning a fluctuating temperature profile at a location which is at a distance from a heat source and which can be generated by temporally fluctuating heat output of the heat source.

The term "mechanical alternating field" also means a periodic change in distance between the component and the heat sink imposed, for example, by a tool.

It is advantageous in this coupling of an alternating field that said pushing out and the enlargement of the total contact surface is faster and even improved reachable, in particular in a shortened first period of time, and thus an acceleration of the production can be achieved.

Alternatively, important features of the invention are that, in the method of manufacturing a device,
which comprises at least one heat-generating component and a heat sink, the component is pressed onto the heat sink with a pressing force, in particular for achieving a low heat transfer resistance,
wherein a mechanical alternating field is introduced and / or introduced during a first period of time, in particular in the intermediate region between the heat sink and the component or in the contact region of the heat sink to the component or in the intermediate medium. The advantage here is that a particularly rapid production of a good heat transfer can be achieved. A long-lasting application of a high pressure force is therefore dispensable and the production of the cooling arrangement or this comprehensive device, such as electrical appliance, electric drive, is particularly fast executable. When using the mechanical waves mentioned a particularly pronounced shortening of the period of application of the necessary initial high pressure force can be achieved.

In the embodiment according to the invention during the first period of time, the amount of the pressing force is greater than a first value and then smaller than the first value. The advantage here is that a decrease in the pressing force after the first period of time does not deteriorate the heat transfer. Advantageously, therefore, in a first embodiment during the manufacture of the electrical appliance, a pressing force by means of a special tool can be introduced into the component. In another embodiment, the pressing force of an aging spring element can be applied. For example, for this purpose, a plastic part is used, which has a decreasing elastic modulus under the action of heat or due to the aging during the operating time, in particular after the expiry of the first time period.

According to the invention, a medium, such as heat-conducting paste, heat-conducting adhesive or a thermally conductive, electrically insulating liquid medium, is provided between the component and the cooling body. The advantage here is that the microspaces are easy to fill and the effect of high pressure forces or mechanical alternating fields, the filling of the microspaces or the squeezing out of the air bubbles is particularly easy to carry out. In particular, an anisotropic force distribution is advantageous here.

In a further advantageous embodiment, the pressing force is mechanically generated by the device comprising spring elements, in particular with holding means of the device connected spring means. The advantage here is that no special additional funds are necessary.

In an advantageous embodiment, the pressing force is mechanically generated by additional only during manufacture during the first time period connected to the device or these touching means. The advantage here is that high amounts of force are applicable and the device is still compact executable.

According to the invention, the mechanical alternating field comprises acoustic waves, in particular infrasound, ultrasound or audible sound waves. The advantage here is that depending on the viscosity of the medium in the intermediate range infrasound, ultrasonic or audible sound waves are applicable and thus an optimized fast squeezing out the air bubbles or filling the micro rooms is executable.

In a further advantageous embodiment, the mechanical alternating field is provided as structure-borne sound. The advantage here is that the alternating field is also on the Kuhlkörper towards the intermediate region between the component and Kuhlkörper be conducted.

In an advantageous embodiment, the mechanical alternating field is coupled into the cooling body, in the medium and / or in the power semiconductor or generated therein. The advantage here is that, especially in the direct coupling little energy is lost or even the entire energy of the alternating field is brought into effect in the intermediate area. Likewise, generating or passing through the alternating field in or through the power semiconductor can also be carried out, and thus a location-proximate and thus efficiency-optimal use of the alternating field can be carried out.

In a further advantageous embodiment, the mechanical alternating field also includes alternating pressure and tensile stress components in the direction of the normal of the contact plane between the cooling body and the component. The advantage here is that air pockets are herausquetschbar.

In a further advantageous embodiment, the heat-generating component is a power semiconductor, in particular the inverter output stage of an inverter. Alternatively, instead of the power semiconductor, a module is used as a heat-generating Component providable, comprising the at least one power semiconductor and a piezoelectric transducer for generating a mechanical alternating field according to the invention.

Thus, in the invention, a mechanical alternating field can be used in the manufacture of a device, which comprises at least one heat-generating component and a heat sink, wherein the component is pressed onto the heat sink with a pressing force, wherein the alternating field during a first period of time is effective in an intermediate region between component and heat sink. The advantage here is that instead of the necessary in the initial period, ie in the first period, high pressing force smaller values are sufficient if the additional field acts simultaneously. Alternatively or additionally, a reduction of the initial time period is made possible because the alternating field additionally acts.

Alternatively, a mechanical alternating field can be used, wherein the alternating field is coupled and / or irradiated during a first period of time in a region between the component and the heat sink. The advantage here is that no variable additional pressing force but a constant pressure with, for example, small amount value is sufficient. Thus, additional means for introducing a pressing force are unnecessary.

According to the invention during the first period of time, the amount of a pressing force is greater than a first value and after the first time period smaller than the first value. The advantage here is that aging materials can be used in the device for generating and / or transmitting the pressing force to the component.

The method according to the invention can be used to produce a device which comprises at least one heat-generating component and a heat sink, wherein
a spring element is provided for pressing the component onto the heat sink,
wherein, in particular, at least during a first time period, the heat sink and / or the component are designed such that means for generating an alternating mechanical field can be coupled.

In particular, a mechanical interface for coupling the means can be provided on the component or on the heat sink. The advantage here is that in the manufacture of a tool is approachable and can be brought to the device in contact for coupling the alternating field. In particular, the interface comprises centering means, threading means and / or a finely worked contact surface.

In such a device, the means are provided in the component or in the heat sink. The advantage here is that no additional components are necessary and also the alternating field as close to the intermediate region can be generated and thus a high degree of utilization of the introduced into the alternating field energy is provided.

In such a device, the device comprises an electromechanical transducer as a means. The advantage here is that an electromechanical transducer, such as a piezoelectric element, converts very little electrical energy loss into mechanical energy.

In such a device, a piezoelectric transducer is provided as means. The advantage here is that a very wide range of frequencies can be generated, in particular from the audible sound to the ultrasonic range.

In such a device, the component is designed in such a way and in the component such alternating currents are einprägbar that a mechanical alternating field is radiated from the device, in particular structure-borne sound waves. The advantage here is that the peak amplitudes of the contact force occurring at least briefly reach high values and, in addition, a mechanical time-varying force field with a non-disappearing anisotropic field strength gradient is provided which drives out air inclusions from the intermediate region.

In such a device, the device as a power semiconductor, in particular IGBT, or module, comprising at least two power semiconductors, such as IGBT, diodes or the like, executed. The advantage here is that the control and power supply of this device is provided in any case, thus only the control during the first period must be carried out such that the desired alternating field is formed.

In such a device, the spring element is designed as a plastic part, in which a printed circuit board is provided inserted, which is equipped with the component. The advantage here is that the plastic is so elastically selectable that an elastic deflection of the plastic part generates the pressing force. Advantageously, a later, so after the expiry of the first time period instead of aging process or fatigue process that reduces the spring force, has no effect on the achieved in the first period heat transfer resistance between the component and heat sink.

In such a device, the plastic part to the heat sink with screws is so connected, that it is elastically deflected, wherein the spring force thus generated via retainer, in particular Andrückdome, is transmitted to the circuit board. The advantage here is that the pressing force can be generated in a very simple and cost-effective manner of an anyway necessary component that has a function of positioning the circuit board within the device.

In such a device, the hold-down are made hollow for insertion of a tool, in particular a coupling force and / or a mechanical alternating field tool. The advantage here is that the tool is threaded directly to the point at which the introduction of the pressing force is provided. In addition, the force is not guided along the surface of the holding member having the blank portion but only across the wall of the shell part.

The invention will now be explained in more detail with reference to figures:

In the 1 is a mounted component drawn in sectional view.

The component 1 has connecting feet 2 on, which lie in a plane and on the circuit board 4 rest and there by means of solder joints 5 are soldered.

In the 2 is a mounted component drawn in sectional view.

The component 1 has connecting feet 2 on, which lie in a plane and lie on the circuit board and soldered there. The connection feet 2 have a bead 3 , So an arc-like bending, on, makes the tolerances compensated.

As tolerances are vertical tolerances, ie in the direction of the circuit board level, and horizontal tolerances, ie in the normal direction of the circuit board level, compensated.

The circuit board 4 is installed in such a way in the surrounding housing, that with the housing part 7 the housing connected heatsink 6 in contact with the underside of the component 1 brought is. The contact should be as good as possible, so executable with vanishing tolerance. For this presses a spring, which is also on a housing part 8th supported by the surrounding housing, on the top of the component 1 and causes by means of the pressure force generated by it the best possible contact between the underside of the component 1 and heat sink 6 , However, the spring also causes a shift in the normal direction of the printed circuit board.

By means of the bead compensation of the displacement tolerance can be effected. Without the bead could cause damage to the component and the circuit board.

Thus, even complex circuits, such as converters, which include heat-generating power electronics and less heat-generating signal electronics, can be built on a circuit board and be equipped in a machining operation.

In the 3 is shown as a further embodiment of a device in a schematic sectional view.

The device is designed as an electrical appliance which has at least one printed circuit board 35 that has electronic components 33 is equipped. In addition, heat-generating components, in particular power semiconductors 34 , fitted on the board, their heat to the heat sink 31 is dissipated.

The power semiconductors 34 and components 33 are equipped with SMD mounting technology and thus quickly and easily electrically and mechanically connectable. In this case, the connection feet of the power semiconductors are provided with a bead, in particular for compensation of mechanical or thermally induced voltages.

The circuit board is designed as a multilayer printed circuit board and thus has not only outer but also inner layers. In this way, a high integration density on the circuit board can be achieved. In addition, areas of the layers, in particular the inner layers, are used to spread the heat. For this purpose, in areas where high heat peak currents occur in spatially restricted areas, electrically conductive portions of the outer and / or inner layers are provided in order to achieve a spreading of the heat or to form an increased heat capacity for damping occurring temperature peaks. These layers are provided in particular on the side facing away from the heat sink side of the power semiconductors and thermally conductively connected to each other by means of plated-through holes. In particular, the power semiconductor is made metallic on its side facing the printed circuit board and soldered to the outer layer of the printed circuit board. In this way, a particularly good coupling to these layer areas of the circuit board 35 achieved and the spread of peak heat flows easily allows.

Advantageously, the power semiconductor also has a metallic region for the heat sink, which is preferably made of metal or ceramic, in order to enable a low heat transfer resistance to this end.

The printed circuit board is in a shell part 32 made of plastic, on the one hand correspondingly shaped areas for lateral, ie perpendicular to the normal direction of the circuit board level, limiting the mobility of the circuit board has. These shaped areas are in the 3 as a recording 321 shown. On the other hand, the shell part used as hold-down Andrückdome 322 on, the directed towards the heat sink pressure forces and in touch areas with the circuit board 35 pass on to them. These contact areas are provided offset laterally from the area of the power semiconductors 34 , The pressure forces are thus by means of the slightly elastic deflectable circuit board 35 passed to the power semiconductors, which are thereby pressed onto the radiator body.

The shell part 32 is done by means of screws 36 also laterally offset from the covered area of the power semiconductors 34 are provided, screwed against the heat sink or connected to this housing part. In this way, in this case pressing force can be generated and transferred by means of Andrückdome to the circuit board. Alternatively or additionally, the pressing force or a part thereof can be transferred by means of a tool acting on the shell part or directly on the printed circuit board.

Between power semiconductors 34 and heat sink 31 Thermal paste is provided. The high pressure forces allow a good heat transfer, ie a low heat transfer resistance from the power semiconductor to the heat sink. Because when the high forces are applied over a certain period of time, the microspaces are well filled by the paste and air pockets are reduced.

Instead of said thermal paste between the power semiconductor and the heat sink, a heat-conducting adhesive can be introduced in all embodiments. Advantageously, this hardens after a certain period of time and thus receives the heat transfer resistance at the low value reached or at least below a critical value.

In the 4 is a central, provided in the adjacent region of the device area of the circuit board from the hold-down 322 applied. In contrast to 3 So there is no lateral pressing by means of hold-down 322 in front.

5 shows an enlarged section 3 and 4 , Here it is clear that the power semiconductor 34 on its connecting legs beading 500 , whereby the solder connection of the legs with printed conductors of the printed circuit board 35 is relieved, especially in thermally induced alternating voltages.

6 shows a hollow embodiment of a hold-down for a further embodiment 322 in section By inserting a tool into the cavity 600 is pressing force can be introduced. The inserted tool then causes a direct transfer of the pressing force in the region of the circuit board, which is covered by the device. The other version with this arrangement corresponds to 3 or 4 ,

In all embodiments according to the 1 to 6 In this first time period after connecting the screws, a high pressure force is provided to achieve a low heat transfer resistance, which presses the respective heat-generating component, in particular power semiconductor, against the heat sink, wherein the thermal paste, heat-conducting adhesive or a similarly good heat-conducting, electrically insulating medium in the intermediate region is arranged between the component and the heat sink.

In the manufacture of the device, the force acting on the power semiconductors pressing force is set to a high value between 10 and 200 N, for example, 50 N. For this purpose, additional force-generating means, such as the tools mentioned, used or the components, such as said shell part, are dimensioned such that when connecting the components of the device, the high pressure force for a first period of time can be ensured.

The first period of time is a few minutes, especially between one and one hundred minutes. Thereafter, the pressing force is reduced by either the tool for power generation is removed or an aging of the force-generating plastic part, such as a flow occurs. The pressing force may be below 10% to 60%, in particular 50% of the value in the first period.

The high contact pressure causes the heat transfer resistance imparted via the thermal paste or the medium to become very low. For this purpose, a displacement of micro-air bubbles and air inclusions contributes and also blends the thermal paste as possible in the micro-rough surface of the power semiconductor and the heat sink as well. Here it is important that the force distribution in the medium is not constant and thus the air bubbles are driven in a respective direction.

According to the invention, this process is accelerated by an additional mechanical voltage change field acts in the thermal paste. For this purpose, ultrasound is supplied from the outside or into a component of the device, such as For example, the heat sink, structure-borne noise coupled. In this way, the necessary first period of time can be shortened and also the high amount of the pressing force can be reduced during the first time span.

A sound field introduced anisotropically within the thermal paste has proved to be particularly advantageous. With a pronounced field strength gradient of the ultrasonic field, a further shortening of the first time span and a reduction of the amount of the pressing force is permissible.

As mentioned above, after the first period of time, for example during the life of the device, ie operating time, a reduced pressing force is sufficient.

The shell part is made of plastic executable because the force applied during assembly high pressing force causes such a good connection of the device to the heat sink, even with reduced during operation operating pressure, for example due to flow of the plastic and thus reducing the spring force generated by the shell part, a very low heat transfer resistance between the component and heat sink is maintained.

According to the embodiment 4 is the hold-down 322 not provided laterally adjacent to but in the area of the heat-generating components. In this way, the elasticity of the shell part is not effective but the - introduced for example by an external tool - pressing force is directly from the hold-down 322 on the circuit board and from this to the device, in particular power semiconductors transferred.

Furthermore, the tool itself can be used for coupling the mechanical alternating field. Thus, at the same time a high pressure force and the mechanical alternating field are coupled in the same area.

As an alternative to the invention, a thermal alternating field is coupled in addition to the mechanical alternating field. The coupling is carried out directly in the intermediate region between the heat generating component and heat sink or introduced via the heat sink. Alternatively, the thermal alternating field can be introduced via suitable energization of the power semiconductors. The frequency of the thermal alternating field is preferably in the range between 0.01 Hz and 10 Hz. However, other frequencies are also advantageously applicable. Another advantage of the alternating thermal field is that at the same time a heating is carried out, which leads to a hardening of an introduced into the intermediate region Wärmeleitklebstoffes, and on the other hand changing mechanical stresses are introduced into the intermediate region, which lead to an improvement of the heat transfer resistance.

As with the introduction of an alternating mechanical field air inclusions in the thermal paste or thermal adhesive and / or air bubbles between thermal grease or Wärmeleitklebstoff and heat sink on the one hand and component on the other displaced and thus the heat transfer Gesamtoberührfläche between thermal grease or Wärmeleitklebstoff and heat sink on the one hand and between thermal grease or Wärmeleitklebstoff and device on the other increased. This requires a first period of time. Even with a later decrease of the pressing force, this large total area of contact of the medium with the component and the medium with the heat sink then remains. The said heat waves allow a used Wärmeleitklebstoff cured at the end of the first period and thus reducing the pressing force, for example by means of a withdrawal of the tool from the hollow hold-down 322 or a flow of the plastic, does not lead to a deterioration of the heat transfer resistance between the component and heat sink.

In further embodiments, the pressing force is transmitted to the circuit board and from there to the power semiconductor directly to the circuit board or power semiconductors instead of the hold-down and the shell part. For this purpose, recesses in the shell part are providable, through which the tool can be passed and thus directly brought into contact with the circuit board.

In further exemplary embodiments, a periodic change in distance between the component and the heat sink imposed, for example, by a tool is provided as the mechanical alternating field during the first period of time. Preferably, the amplitude of this change in distance is less than 100 .mu.m, in particular in the range of 10 .mu.m to 30 .mu.m. The frequency of this change in distance is preferably in the range between 0.1 Hz and 100 Hz.

LIST OF REFERENCE NUMBERS

1

component

2

terminal legs

3

Beading, so bow-like bending

4

circuit board

5

soldered point

6

heatsink

7

housing part

8th

housing part

9

feather

31

heatsink

32

shell part

33

Electronic Components

34

Power semiconductor

35

circuit board

36

screw

321

admission

322

Downholder, Andrückdom

500

Beading

600

Cavity for insertion of a tool

Claims (4)

Manufacturing method for an arrangement for cooling an electrical component ( 1 ), which conducts heat with a heat sink ( 6 ), in which between the electrical component to be cooled ( 1 ) and the heat sink ( 6 ) a heat-conducting material is arranged and in which the electrical component ( 1 ) to the heat sink ( 6 ) is pressed, in which between the component ( 1 ) and the heat sink ( 6 ) the heat-conducting material is applied as pasty or liquid material, in which in a first pressing step a first contact pressure and in a second contact pressure a second contact force on the component ( 1 ) is applied, wherein the value of the second contact force is less than the value of the first contact pressure, wherein during the first pressing step, an alternating mechanical field additionally acts on the applied heat-conducting material in the area between the component ( 1 ) and the heat sink ( 6 ) To reduce air pockets or fill in microspaces, the alternating mechanical field in the area between the heat sink ( 6 ) and the component ( 1 ) or in the heat-conducting material is introduced, being used as a mechanical alternating field acoustic waves whose frequency is in the range of the audible or ultrasonic range. A method according to claim 1, characterized in that the mechanical alternating field and changing pressure and tensile stress components in the direction of the normal of the contact plane between the heat sink ( 6 ) and component ( 1 ). A method according to claim 1 or 2, characterized in that the contact forces are generated in the first and second pressing step by means of an aging spring element. Method according to one of claims 1 to 3, characterized in that heat-conducting paste, thermal adhesive or a heat-conducting electrically insulating liquid medium is applied as the heat-conducting material.

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