GB1584783A

GB1584783A - Semiconductor assemblies

Info

Publication number: GB1584783A
Application number: GB3694077A
Authority: GB
Original assignee: Semikron GmbH and Co KG
Current assignee: Semikron GmbH and Co KG
Priority date: 1976-09-04
Filing date: 1977-09-05
Publication date: 1981-02-18
Also published as: AT377386B; CH621435A5; DE2639979B2; DE2639979A1; JPS5332673A; FR2363893A1; ATA617777A; DE2639979C3

Abstract

The semiconductor module exhibits a series circuit of two semiconductor components (3, 4, 5; 13, 4, 6) mounted electrically insulated and thermally conductively on a metallic baseplate (1). It also exhibits three series-connected current-conducting terminals (7, 9), one of which (9) is allocated to the connecting conductor between the semiconductor components and is at one end of the series and the two other ones of which (7) are in each case mounted together with a semiconductor component on a common contact part and via an intermediate disk (2) of insulating material on the baseplate (1). The housing consists of the baseplate (1) and a plastic part (12). The baseplate (1) is constructed to be cup-shaped and is provided at its inner bottom surface with raised or depressed parts for holding the disk (2) of insulating material and the contact components. Furthermore, the edge zone (12a) of the plastic part (12) is constructed to be suitable for producing an edged connection with the baseplate (1) and is permanently connected to the side wall (1a) of the baseplate by edging, and for the baseplate, a material is selected which provides for a solid connection with components of copper or of light metal. This ensures correct mutual connection of the parts and good dissipation of the heat loss to a cooling component. <IMAGE>

Description

(54) IMPROVEMENTS IN OR RELATING TO SEMICONDUCTOR ASSEMBLIES (71) We, SEMIKRON, Gesellschaft fur Gleichrichterbau und Elekronik m.b.H., a Company organised and existing under the laws of the Federal German Republic of Wiesentalstrasse 40, 8500 Nurnberg, Bundesrepublik Deutschland, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed to be particularly described in and by the following statement:- This invention concerns a semiconductor assembly.

Semiconductor assemblies of the kind to which this invention relates are disclosed in accepted British Patent Application Specification No. 1 552 133. They are of compact design and permit multiple combinations of such assemblies in a desired electric circuit.

However, such assemblies also have certain disadvantages. For example, the locating of the insulating plate and of the contact parts associated with the semiconductor components during soldering of these parts, involves an undesirably large amount of work. Furthermore, the metal base which is provided to assist in firm engagement with a cooling component, does not really present a sufficiently fiat surface for good contact because the mechanical stresses inevitably resulting in the manufacture of the assembly due to relatively different thermal expansion of adjacent materials.

Thus the ability to transfer heat from the base to the cooling component is impaired.

Due to the curvature of the base which serves as one part of the housing, variations are liable to occur in the thickness of the adhesive film used to join the base to an associated upper housing part, and this, in turn, may give rise to undesirable stresses in the region of the adhesive joint during the subsequent filling of the housing with a hard-setting insulating material and also during the setting of this material. Such stresses may lead to further curvature of the base.

It is an object of the present invention to provide a new or improved semi-conductor assembly of the kind specified.

According to the present invention we provide a semi-conductor assembly wherein two semi conductor components in series connection are mounted in electrically insulated and thermo-conductive manner on a common metallic base in such a way that in each case current terminals are associated through respective connector parts respectively with input and output ends of the series circuit, and a third terminal is associated with an interconnecting part between the semi conductor components, said third terminal and one of the two first said terminals together with their associated semi conductor are mounted fixedly on respective contact parts and are secured with the latter on said base, with the interposition of a plate of electrically insulating but thermally conductive material, and in which the semiconductor components with their contact and connector parts are accommodated within a housing comprising said base and a housing part which latter is made of an electrically insulating material, characterised in that the base is of open-box, or trough, configuration with a plane exterior surface at the bottom thereof whilst the upper surface of the base is provided with means for locating the plate in the correct position for assembly of the unit, and in that the marginal zone of the housing part which is nearest to the base is adapted for rigid connection to the base through complementary interfitting portions respectively on the base and housing part.

The invention will now be described in more detail by way of example only with reference to the accompanying drawings, wherein: FIGURE 1 is a sectional view of a semiconductor assembly, FIGURE 2 is a plan view of the base for the assembly, FIGURE 3 illustrates part of the assembly showing in detail the means for location of the electrically insulating but thermally conductive plate and contact parts on the base, FIGURE 4 is a plan view of a plurality of semiconductor assembly units mounted on a common cooling member.

The same parts have the same reference numerals in all the figures.

The assembly I shown in Figure 1, is built up on a base 1 of open box, or troughlike configuration and which is made from a metal having good heat conductivity, e.g.

copper, or aluminium, or a combination, or compound, or alloy of these metals.

Current conducting contact parts 3 and 13, are connected each to a semi-conductor component, and are also connected, for example, by soldering, to the upper surface of said base plate in relatively spaced apart positions, through the intermediary of a plate 2 of electrically insulating but thermally conductive material, e.g. an oxideceramics material. Alternatively, a separate plate of this type of material may be provided for each contact part. To enable location of the oxide-ceramic plate 2 in a pre-selected position, the side of the base 1 is formed with raised formations 111 between which the plate 2 is adapted to be located. Base 1, plate 2, and contact parts 3, 13 are then assembled vertically in the aforegoing order and are firmly connected to each other by soldering. To enable soldering to each other they are each provided with a coating of a metal which enhances a soldered joint.

The upper edge of the side walls la of the base is secured to an insulating housing part 12, e.g. by inter-engaging surfaces provided on both base 1 and housing part 12.

For this purpose the housing part 12, which is provided with a continuous wall but no bottom or cover, is shaped to correspond to the inner base area of the base 1, so that it fits within the side walls la and is thereby securely located during assembly of the unit.

The lower region 12a of the housing part 12 may be reinforced, or extended outwardly to increase the strength of the structure and the joint between the housing part 12 and the base 1. The extension may take the form of a flange.

The raised formations 111 which are formed on the upper surface of the base may also be of a form such that they extend sufficiently far to cooperate with the side walls la of the base to provide a receiving formation for reception of part of the housing 12 to provide firmer and more secure location of the housing part 12 than when it is connected solely to the base.

As shown in Figure 1, the contact parts 3, 13 may comprise a flat portion which is adapted to contact the oxide-ceramic plate 2, with a connecting portion, respectively numbered 3b and 13b in the drawing, extending away from said base portion, and an upper connecting portion 3c, 13c, entering at an angle from the said further portion 3b, 1 3b, respectively which enters in a direction towards the middle of the assembly, said last mentioned portion presenting a suitable flat surfaced support for a contact stud 7. The above described successive connecting portions of each contact part 3, 13 serve as current conductors for the respective contact electrodes of the associated semi-conductors 4 nearest to the base to the contact stud 7 each of which provides a current conductor terminal for the assembly.

The two semiconductor components are connected in series, electrically, by a connecting portion 1 3a of the contact part 13 which is associated with the second semiconductor component, which portion 1 3a is bent to form a step entering in the direction towards the first semiconductor component and is connected to the upper current conductor 5 of the said first semiconductor component.

Each contact stud 7 is provided with a threaded hole 27 for threaded engagement with external current conductors. The upper connecting portions 3c, 1 3c of the contact parts 3, 13, lie in a plane parallel to the plane of the base and each of these portions presents a supporting face for an interconnecting member 8 of insulating material.

In order to connect the semi-conductor components with associated switch and control elements this member 8 is provided with suitable solder and/or plug and socket connector elements 31, 33. The position of such connectors will be determined by the position of the semiconductors but they will protrude from the finished unit.

Finally, the contact stud 9 is fastened to the plate 8 and is connected through the bridge-piece 10 to the upper conductor 6 of the second semiconductor 4.

The contact parts and connector elements may be of any desired form and disposition and their design and disposition do not form part of this invention.

The illustrated assembly is contained within the open housing 12 which is closed at the bottom by base 1, and is embedded in a hard-setting, insulating material 22 so as to leave only the connector terminals of the unit protruding therefrom.

Figure 2 is a plan view of the base viewed from above. As shown in the left hand part of this figure, this top surface of the base may be formed with raised formations 111 which extend parallel to the longitudinal axis of the base 1. The raised formations as illustrated at llla may be provided along the longitudinal sides, and also lllb along the narrower sides of the base. These raised formations prevent lateral movement of the oxide-ceramic plate 2 when the latter is soldered to the base 1. The width of the raised formations along the longitudinal sides of the base 1, should be minimal whilst the width of the raised formations lllb is not critical. The height of the raised formations 111 is equal to, or less than the thickness of the ceramic disc. In order to assure adequate breakthrough resistance between the base 1 and the contact parts 3, 13, the oxide-ceramic plate 2 extends laterally beyond the contact parts 3, 13. The longitudinal dimensions of the raised formations 111 are not critical. It is also possible to combine one raised formation llla with a raised formation lllb in the form of a single combined raised formation 111 c, as shown in Figure 2.

The raised formation should be situated so that their inner edge lies substantially along the circumferential outline of the plate 2 when in position.

Instead of the raised strip-like formations 111, it is possible to provide stud or humplike projections 112, the sides of which would bear against the oxide-ceramics plate 2 and the housing part 12 to assist location of these parts during assembly.

In an alternative embodiment of the invention, the base 1 comprises a recessed locating region 113 for the oxide-ceramics plate 2. The resulting decrease in thickness of the base in this region affords an additional advantage in that it enhances heat transfer between the contact parts 3, 13 and the cooling component which engages with the outer surface of the base.

The base 1 may be produced, e.g. by cold-flow pressing copper and aluminium parts to produce a base having an upper copper surface enabling a good connection to be made to the oxide-ceramics plate 2, and a lower aluminium layer which enables a good connection to be made to an adjacent aluminium cooling component. The thickness of the copper layer must exceed the depth of the recess 113, when provided, and the minimum thickness of the aluminium layer depends solely on the required mechanical strength of the base.

Alternatively the base may be made from an aluminium-magnesium alloy, in which event the interior surface would be provided with a nickel coating to facilitate the making of a solder joint with the oxide-ceramic plate 2.

Figure 3 is a sectional view of part of another embodiment of this invention. The base 1, instead of being provided with raised portions, is provided with holes 114 which may be either through bores or blind bores.

Bolt or stud-like locating elements 115 of an elastic plastics material are inserted into these holes 114, the dimensions of the bolts or studs being such that an interference or press fit is achieved. The locating elements 115 is such that the part of the shank portion extending out of the base is of a length substantially the same as the thickness of the oxide-ceramic plate 2, and which shank part laterally locates the oxide-ceramic plate 2. The locating elements 115 also have a head part which has a larger diameter than the shank part and which is adapted to align the contact part 3, 13. The material of these locating elements 115 must be stable at the soldering temperatures which are applied to the assembly and must also have sufficient elasticity to render any form changes in the stacked assembly of the parts harmless. The locating parts 115 may remain permanently in the assembled unit once the soldered connections have been completed.

The design of the base 1 as aforedescribed enables the semiconductor assembly to be assembled in a particularly simple and easy manner, the semiconductor assembly operating well in use in a wide range of applications.

Figure 4 illustrates one example of an application of a semiconductor assembly of the invention. The drawing shows a cooling component 20, preferably an extruding of the desired section, having slot, or groovelike recesses 21 in the surface on which the assembly or assemblies are to be mounted.

The housing part 12 of the assembly may be formed with an indentation 12b in each of its ends which indentations extend normal to the base, the latter being provided with a through-bore in line with said indentation for the passage therethrough of fasteners 23. Alternatively, the ends of the base may project beyond the housing part 12 the projecting regions having at least one through-bore through which a fastener may pass. It is also possible to arrange for the base to project from the housing part on all sides thereof and thus permit all-round fastening by means of a clamping flange.

Thanks to the arrangement of the terminals 17 of the semiconductor assemblies, a rotary or polyphase current bridge circuit may be obtained from three such assemblies by means of the two busbars 22. Since each unit also includes connector means for control and switching lines, or, is adapted to be provided with such, it is also possible, subject to the selection of a suitable profile for the cooling component, to additionally attach, for example, at least one circuit board 25 of insulating material, which may be secured in a further groove in the cooling member, and which may have secured thereto additional switch and circuit components 27 for the semiconductor assemblies, as well as to connect them to separate control sets in a very simple manner, for example by soldering or plug-and-socket connectors 28.

The use of the semiconductor assembly of the present invention is not limited to the illustrated circuit system, and the semi conductor components in these assemblies may have two or more electrodes and be of any desired structure. Any desired number of assemblies may be arranged either separately or in a common circuit and mounted on a common cooling component.

It is possible for an assembly mounted with others on a cooling member to be exchanged in a very simple way without effecting the other assemblies. Furthermore, it is possible to make up any desired circuit system with one or more assemblies per branch, either in series or in parallel, and also in combination with switching and control members.

WHAT WE CLAIM IS: 1. A semiconductor assembly wherein two semiconductor components in series connection are mounted in electrically insulated and thermo-conductive manner on a common metallic base in such a way that in each case current terminals are associated through respective connector parts respectively with input and output ends of the series circuit, and a third terminal is associated with an interconnecting part between the semiconductor components, said third terminal and one of the two first said terminals together with their associated semiconductor are mounted fixedly on respective contact parts and are secured with the latter on said base, with the interposition of a plate of electrically insulating but thermally conductive material, and in which the semi conductor components with their contact and connector parts are accommodated within a housing comprising said base and a housing part which latter is made of an electrically insulating material, characterised in that the base is of open-box, or trough, configuration with a plane exterior surface at the bottom thereof whilst the upper surface of the base is provided with means for locating the plate in the correct position for assembly of the unit, and in that the marginal zone of the housing which is nearest to the base is adapted for rigid connection to the base through complementary interfitting portions respectively on the base and housing part.

2. A semiconductor assembly according to claim 1 characterised in that the upper surface of the base is provided with raised formations situated on a circumerential outline determined by the subsequent engagement with the plate for locating said plate during the securing of the plate to the base.

3. A semiconductor assembly according to claim 2 characterised in that said raised formations are in the form of strips or humps and have a height equal to or less than that of the plate.

4. A semiconductor assembly according to claim 1 characterised in that the upper surface of the base is provided with one or more recesses corresponding in number to the plates and which recesses each are adapted to receive and locate one plate.

5. A semiconductor assembly according to claim 1, characterised in that the upper surface of the base is provided with recesses for the retention of stud-like locating elements, which stud-like locating elements cooperate with the plate and/or contact parts to locate them in a correct position, and in that said locating elements are made of a resilient plastics material and their shank portions are adapted to extend out of said base and cooperate with and locate said plate, and a head portion to cooperate with and locate said contact parts.

6. A semiconductor assembly according to Claim 5, characterised in that the studlike locating parts are made of a material which is stable at the temperature required soldering the base to the plate and the latter to the contact parts.

7. A semiconductor assembly according to any one of claims 1 to 5, characterised in that the base is made of an aluminium magnesium alloy with a nickel coating on its upper surface.

8. A semiconductor assembly according to Claim 4 or either of Claims 5 or 6 when appended to Claim 4 characterised in that the side of the base adjacent the plate is made of copper and the other side is made of aluminium and that the thickness of the copper layer is greater than the depth of said recess or each of said recesses and in that the thickness of the aluminium layer depends solely on the desired strength of the base.

9. In combination one or more semiconductor assemblies as claimed in any one of the preceding claims each secured by their base to a cooling component.

10. The combination as claimed in Claim 9 characterised in that a plurality of said assemblies are mounted on a common cooling element and are electrically connected to each other.

11. The combination as claimed in Claim 9 or Claim 10 characterised in that at least one circuit board of insulating material is fitted to one side of the cooling component for the mounting thereon of further circuit components for controlling and actuating the semiconductor assembly secured to said cooling component and also either solder connecting and/or plug-andsocket connector elements to enable connections to be made between the semiconductor assembly and other circuitry.

12. A semiconductor assembly as claimed in any one of the preceding claims wherein the housing part is provided with an outwardly entering flange and base is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. conductor components in these assemblies may have two or more electrodes and be of any desired structure. Any desired number of assemblies may be arranged either separately or in a common circuit and mounted on a common cooling component. It is possible for an assembly mounted with others on a cooling member to be exchanged in a very simple way without effecting the other assemblies. Furthermore, it is possible to make up any desired circuit system with one or more assemblies per branch, either in series or in parallel, and also in combination with switching and control members. WHAT WE CLAIM IS:

1. A semiconductor assembly wherein two semiconductor components in series connection are mounted in electrically insulated and thermo-conductive manner on a common metallic base in such a way that in each case current terminals are associated through respective connector parts respectively with input and output ends of the series circuit, and a third terminal is associated with an interconnecting part between the semiconductor components, said third terminal and one of the two first said terminals together with their associated semiconductor are mounted fixedly on respective contact parts and are secured with the latter on said base, with the interposition of a plate of electrically insulating but thermally conductive material, and in which the semi conductor components with their contact and connector parts are accommodated within a housing comprising said base and a housing part which latter is made of an electrically insulating material, characterised in that the base is of open-box, or trough, configuration with a plane exterior surface at the bottom thereof whilst the upper surface of the base is provided with means for locating the plate in the correct position for assembly of the unit, and in that the marginal zone of the housing which is nearest to the base is adapted for rigid connection to the base through complementary interfitting portions respectively on the base and housing part.

provided with an extension in the form of a side wall engageable with said flange.

13. A semiconductor assembly substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

14. In combination one or more semiconductor assemblies as claimed in Claim 13 mounted on a cooling member substantially as hereinbefore described with reference to and as illustrated in Figure 4 of the accompanying drawings.