Abstract:
An arrangement for contact-connecting at least one electronic component mounted in a housing with connection wires to a cooling surface and a spring element that can be fixed in the housing and has at least one spring arm which presses the component against the cooling surface in a contact-pressure position of the spring element is presented. The arrangement is characterized in that the spring element can be inserted into the housing without touching the component, and the housing is provided with retaining means for the spring element adapted in a manner so that no shear forces are produced in the longitudinal direction of the connection wires when the spring element is mounted.

Description:
FIELD 
     The present invention relates generally to an arrangement for contact-connecting at least one electronic component. More specifically this invention relates to a power semiconductor, which is mounted in a housing with connection wires, to a cooling surface and a spring element, and can be fixed in the housing and has at least one spring arm that presses the component against the cooling surface in a contact-pressure position of the spring element. 
     BACKGROUND 
     In order to ensure power semiconductors are cooled, the semiconductors are placed in thermally conductive contact with a heat sink. In cost-effective embodiments, this is usually realized with springs which press the semiconductor component against the heat sink. 
     An arrangement of this type is described in German utility model G 92 13 671.0. By virtue of a retaining spring element being pre-mounted in a housing part, the components to be cooled are pressed against an inner wall of the heat sink by spring tongues of the retaining spring when the housing parts are subsequently assembled. 
     In a similar way, U.S. Pat. No. 5,274,193, German laid-open specification 36 12 862 A1, German patent specification 195 43 260 C2 and German utility model DE 200 14 739 U1 describe spring elements which are clamped between power semiconductors and a housing. The difference in each case is the way in which the spring elements are supported on or fixed to the housing. For example, the spring element may be retained itself by recesses and webs of the housing or by means of additional fixing elements such as screws or clamping rails. 
     Some retaining apparatuses have a substantially U- or L-shaped spring clip that is placed (“clipped”) over a heat sink wall and at the same time over the component and in this way ensures the contact-pressure force between the bearing faces of the heat sink and of the component. 
     In all apparatuses without additional fixing elements, such as German utility model G 92 13 671.0, the problem arises of the component and the solder point being subjected to shear stresses. This can lead to damage to the component or the solder connection. The shear stresses are produced by forces which act on the component when the apparatus is assembled in a plane parallel to the cooling system surface of the components or the heat sink. Therefore, for example in G 92 13 671.0, the upper housing part is placed on the lower housing part from above by way of a snap-in retaining spring and in the process, the spring is guided along the perpendicular component, as a result of which a force acts in the direction of or in the opposite direction to the connection wires. The spring element may also be likewise inserted parallel to the bearing face of the component as per DE 195 43 260 C2 by means of being pressed in the opposite direction to the connection wires. Although in U.S. Pat. No. 5,274,193, no shear force acts on the components, the retaining spring has to be fixed and the retaining force of the spring element has to be generated by an additional clamping rail. 
     SUMMARY 
     The present invention provides an arrangement of the type described in the introduction which, with simple mounting, does not exert any shear forces on the electrical components in the direction of or in the opposite direction to the connection wires. 
     This is achieved, according to one embodiment of the invention, in that the spring element can be inserted into the housing without touching the component. The housing is provided with retaining means for the spring element in such a way that no shear forces are produced in the longitudinal direction of the connection wires when the spring element is mounted. The spring element can therefore initially be easily inserted into the housing without a great expenditure of force and be positioned in a first mounting position in front of the component. 
     The insertion grooves are arranged on the housing in such a way that the spring element can be inserted into the housing parallel to the cooling surface without touching the components. The power semiconductor component advantageously remains unaffected by shear forces in the direction of or in the opposite direction to the connection wires during the insertion process. 
     The retaining means are in the form of latching grooves and permit the spring element to be expediently automatically latched-in in a predefined position. Complicated alignment of the spring element is dispensed with. 
     The insertion grooves and the latching grooves are arranged on the housing in such a way that the spring element can be moved from the first mounting position to the contact-pressure position by means of a force acting perpendicular to the cooling surface. Even in this second mounting step, no shear force acts in the longitudinal direction of the connection wires; instead the spring element is expediently fixed in the contact-pressure position, from the first mounting position, by forces which act substantially perpendicularly on the cooling surface. 
     In another embodiment of the present invention, the spring element comprises spring arms which run parallel to one another and are fixed perpendicularly on a support element that connects the two lateral projections of the spring element to one another. On account of the rigidity, this embodiment permits high contact-pressure forces to be applied, with only one spring element advantageously being required for all the semiconductor components that are arranged in a uniform manner. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  shows a front view of a spring element according to one aspect of the present invention, 
         FIG. 2  shows a rear view of the spring element according to one aspect of the present invention, 
         FIG. 3  shows the spring element before it is inserted into an electronics housing, 
         FIG. 4  shows the spring element in a first mounting position, 
         FIG. 5  shows the spring element in a latched-in contact-pressure position, 
         FIG. 6  shows a detailed view of the spring element in the first mounting position, 
         FIG. 7  shows a detailed view of the spring element in a latched-in contact-pressure position. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the present disclosure or its application or uses. It should be understood that throughout the description and drawings, corresponding reference numerals indicate like or corresponding parts and features. 
       FIGS. 1 and 2  shows a spring element  2  according to one aspect of the present invention that is intended to be installed in an electronics housing  4  of an electric motor. The spring element  2  comprises a support element  8  that has integrally formed on its upper edge, six spring arms  10  and which has two angled-away projections  12   a ,  12   b  on the sides. One skilled in the art will recognize that a support element having a different number of spring arms is feasible. The projections  12   a ,  12   b  are formed with lugs  13 , which are folded-over inward at a right angle, at the upper and lower edge of the projections, in order to prevent the projections  12   a ,  12   b  from buckling. At the upper and lower edge, the support element likewise has narrow sections  14   a ,  14   b  which are folded over approximately at a right angle, with the lower section  14   a  pointing toward the side on which the spring arms  10  are located and the upper section  14   b  pointing in the opposite direction. Referring to  FIG. 2  the upper section  14   b  continues at equidistant distances and forms the spring arms  10  which run parallel to one another over the upper edge of the support element  8  in a manner bent downward in the direction of the section  14   a . At their lower end, the spring arms  10  have a contact region  16  which is curved convexly outward and presses against the components  24  in the contact-pressure position of the spring element  2 . A semicircular reinforcing bead  18  that is curved at the front and prevents the spring element  2  from bending runs beneath the center of the support element  8 , opposite the contact regions  16 , parallel to the upper and lower edge of the support element  8 . 
       FIGS. 3 to 7  show a possible variant of the spring element  2  according to another aspect of the invention in an electronics housing  4  of an electric motor  6 . Referring to  FIG. 3 , the electronics housing  4 , which accommodates a printed circuit board  20  with electronic components  22  and further electrical connecting elements, is mounted on a rotor housing  7  of the electric motor  6 . The electronics housing  4  substantially comprises a circumferential wall that is formed by a flat side wall  26 , which acts as a cooling surface, adjoining side walls  32 ,  33 , and a wall  34  that is opposite the flat side wall  26 . Mounts  36  with holes  37  for fixing of the housing are integrally formed on the side walls  32 ,  33  and on the opposite wall  34 . The electronics housing  4  can be closed by a housing cover (not illustrated) which engages in a circumferential groove  38  on the end face of the side walls  26 ,  32 ,  33 ,  34 . The housing cover is fixed to retaining protrusions  40  which have holes  41 . A printed circuit board  20  that is fitted with the electronic components  22 ,  24  is seated on the base of the electronics housing  4 . In one embodiment, power semiconductors  24  are soldered-in on the printed circuit board  20  such that they can be arranged in the interior of the electronics housing  4  on a flat side wall  26  of the electronics housing  4 . A thermally conductive electrical insulation layer  28  is inserted between the power semiconductor  24  and the flat side wall  26  in order to permit and to improve the transportation of heat to the side wall  26  that is provided with cooling ribs  30 . 
     Groove pairs which run perpendicularly downward and fulfill the function of insertion grooves  44   a ,  44   b  and latching grooves  46   a ,  46   b  are made in the side walls  32  and  33  that adjoin the flat side wall  26 . The two insertion grooves  44   a ,  44   b  are located on both sides of the flat side wall  26  in each case at about the same distance from said flat side wall opposite one another in the side walls  32 ,  33 . The spring element  2  is axially inserted into these insertion grooves  44   a ,  44   b  in accordance with arrow direction R shown in  FIG. 3  and assumes a first mounting position (insertion position). The lugs  13  which are fitted on the upper face may serve as application areas for the insertion forces that are applied manually. In addition to this function as a mounting aid, the upper lug pair  13  also has an additional task: when the spring element  2  is inserted into the electronics housing  4  but is not yet latched, a housing cover cannot be mounted since pins which are injection-molded on the housing cover would then rest on the upper lugs  13  and closing of the cover would be prevented. When the spring element  2  is correctly latched, the pin of the cover can engage in the cleared space and the cover can be mounted. As a result, it is possible to monitor whether the spring element  2  has been correctly mounted. The insertion position is illustrated in  FIG. 4 .  FIG. 6  shows a detailed view of the position of the spring element in this insertion position. It can be seen that the projection  12   a  is fixed by its end region resting in the insertion groove  44   a . When the insertion process is performed, the spring arms  10  do not yet come into contact with the power semiconductors  24 , and therefore do not exert any shear forces on the component  24  and its solder point. An air gap  45  remains between the spring arms  10  and the power semiconductors  24 . 
     The latching groove pair  46   a ,  46   b  adjoins the insertion grooves  44   a ,  44   b  and is made in the same way, but at a shorter distance from the flat side wall  26 . The transition region  48   a ,  48   b  between the insertion groove  44   a  ( 44   b ) and the latching grove  46   a  ( 46   b ) is formed in such a way that its resistance can be overcome by a force effect F on the spring element  2  perpendicular to the cooling surface as shown in  FIG. 4 . Referring to  FIG. 5 , the elastic side projections  12   a ,  12   b  are briefly compressed by the transition regions  48   a ,  48   b  during the forward movement in the direction of the power semiconductor  24 , before they rest in the latching grooves  46   a ,  46   b  in the contact-pressure position. 
       FIG. 7  shows a detailed view of the position of the spring element  2  on the side wall  32  in the contact-pressure position. The perpendicular edge, which is now embedded in the latching groove  46   a , of the end region of the projection  12   a  fixes the spring element  2 . In this contact-pressure position, the spring arms  10  now press on the power semiconductors  24  which as a result are pressed against the thermally conductive insulating layer  28  and thus against the side wall  26 , which is in the form of a cooling surface  27 . This ensures reliable heat dissipation without the use of further connecting elements, such as screws or clamps. The component  24  and the solder point are not subject to shear forces. 
     The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.