The invention relates to a substrate and in particular to a substrate that is suitable for use as a printed circuit board for electric circuits.
Substrates are known in the art that consist of a metallic base plate or base layer, which is provided on at least one surface with an insulating layer, on which a metallization is applied, for example in the form of a copper foil. The latter can be structured to form contact surfaces, conductor strip conductors, etc. using standard technologies, for example masking and etching. The metallic base layer or base plate gives such a substrate sufficient mechanical stability, and also provides for optimum cooling of the components provided on the printed circuit board. A further essential advantage of these substrates consists in the possibility of manufacturing them very inexpensively.
It is an object of the invention is to present a substrate of this type with improved properties.
A special feature of the substrate according to the invention is that the insulating layer, in addition to the at least one polymer component, also features a distance-maintaining component, which defines the distance between the at least one metallization and a surface bearing the insulating layer and therefore the thickness of the insulating layer. This distance-maintaining component is made of a dimensionally stable, electrically non-conductive material, preferably of an inorganic material.
The design according to the invention ensures a consistent thickness of the insulating layer, and simultaneously the economical manufacture of the substrate. In particular, the metallization is prevented from bearing directly against the metallic base layer as a result of production errors. The design according to the invention therefore achieves constant or essentially constant thermal conductivity and also a constant or nearly constant dielectric strength of the substrate over the entire surface of said substrate.
The invention is explained below in more detail based on exemplary embodiments with reference to the drawings, wherein:
The substrate 1 shown in a simplified partial view in cross section in
A special feature of the substrate 1 consists in the fact that the insulating layer 3 is made of at least two components, namely
The second component is a suitable polymer or synthetic material 5. The first component in the depicted embodiment is a fabric 6 made of a dimensionally stable inorganic material, for example a web made of glass fibers and/or ceramic fibers.
Suitable materials for the base layer 2 are, for example, aluminum, aluminum alloys, copper, copper alloys or other metals with good thermal conducting properties. Suitable materials for the metallization 4 are especially such metals that are normally used for printed circuit boards, in particular also copper or copper alloys.
The advantage of the substrate 1 consists in the fact that it can be manufactured inexpensively and that due to the first component or the corresponding fabric 6, a defined, constant distance between the base layer 2 and the metallization 4 exists, so that a constant, uniquely clearly defined thermal transfer between the metallization 4 and the base layer 2, which is provided for example with a cooler, exists especially for all areas of the substrate. For components arranged on a printed circuit board manufactured from the substrate 1, this results in defined and reproducible conditions for the thermal transfer and cooling. Also, the special design of the insulating layer 3 reliably prevents the formation of areas or defective spots during the manufacture of the substrate 1 where the metallization 4 is in direct contact with the base layer 2. The defined thickness of the insulating layer 3 also produces a constant, clearly defined dielectric strength between the base layer 2 and the metallization 4 over the entire surface of the substrate 1.
The two components 5 and 6 of the insulating layer 3 are formed, for example, from a prepreg material, i.e. from a fiber fabric, which is already impregnated with a polymer material, e.g. with a thermoplastic material. The manufacture of the substrate 1 is then effected for example in the manner that the insulating layer 3 or the material forming said insulating layer is applied to the base layer 2 and the foil forming the metallization 4 is then placed on top and that this series of layers is bonded to the substrate 1 by means of heating and pressing.
The substrate 1b or its insulating layer 3 is manufactured for example by applying the particles 8 forming the first component in combination with the polymer material forming the second component with a layer thickness that is approximately the same as the particles 8. Of course, there are also other possibilities for achieving the insulating layer 3 in this embodiment, for example by first applying a layer made of the polymer material to the base layer 2 and then for example by sprinkling and pressing the particles 8 into the polymer layer.
It goes without saying that also the substrates 1a and 1b of
In the depicted embodiment, the insulating layer 3 on the two surfaces of the base layer 2 consists of the two components, namely of the first spacer component and of the polymer material or the polymer component 5; although the spacer component in
The metallization 4, including the section 4.1, is manufactured in this embodiment for example by chemical and galvanic separation of metal, for example copper. The thickness of the metallization 4 in this embodiment is for example between 20 and 500 μm.
The strip conductors 12 and contact surfaces 13 are again provided on the insulating layer 3, which is designed in the same manner as described above for the substrates 1-1d, namely consisting at least of the first, spacer component and the second, polymer component. The insulating layer 3 is connected with its side facing away from the strip conductors 12 and contact surfaces 13 to the inner bottom surface of the housing sections 16.1, which in this embodiment forms the base layer corresponding to the base layer 2 and is designed in the same manner as described above for the base layer 2. The interior 17 of the housing 16 is hermetically sealed toward the outside using a seal 18, for example, and is closed tightly by the cover 16.2. The outer connections 19 emerging from the housing 16 are sealed and electrically insulated.
Other possibilities for fixing the substrate 1 on the inside of the housing element 16.1 are also possible or applicable. For example, it is also possible to design the substrate bearing the components 14 in deviation from the
All embodiments described above have in common that the respective insulating layer 3 is formed by at least two components, namely by the first, spacer component and by the second, polymer component. The spacer component is made of a dimensionally stable, preferable inorganic material, e.g. fiber material, fabric, fibrous web or particles. The polymer component is for example a cross-linked material, such as epoxy resin or thermoplast or aramide.
To increase the thermal conductivity, it is also possible for the polymer component to contain an additive of at least one electrically non-conductive and highly thermally conductive material, for example ceramic particles; however, the particles are then considerably smaller than the thickness of the insulating layer or smaller than the hollow spaces in the spacer component.
The material for the filling component, in particular the material of the particles forming said components has a thermal conductivity greater than 20 W/K. Suitable particles for the filling component are such particles made of glass, ceramic, e.g. Al2O3, Si3N4, AlN, BeO, SiC, BN or diamond. The materials of these particles can also be used in a much smaller form or as an additive or filling of the polymer component.
The thickness of the respective insulating layer 3 is for example between 20 and 150 μm. The thickness of the metallic base layer 2 is for example between 0.2 and 10 mm.
The metallization 4 is applied for example as a foil or is produced through chemical and galvanic separation of a metal, for example of copper. The thickness of the metallization is for example between approx. 20 and 500 μm.
The polymer component is selected so that the thermal stability of the insulating layer 3 is greater than 110° C., i.e. the thermal deformation point of the insulating layer is above 110° C.
The invention was described above based on exemplary embodiments. It goes without saying that numerous modifications and variations are possible without abandoning the underlying inventive idea upon which the invention is based.
It was assumed above that the spacer component is made of an inorganic material. Generally it is also possible to use an organic material for the spacer component, for example a duroplastic material or a thermoplastic material, for example polyamide, but in any case a material with a temperature stability or a deformation point which is significantly above the processing temperature for the manufacture and/or processing of the substrate and also significantly above the temperature stability or the thermal deformation point of the further, polymer component. Also in this embodiment the spacer component is then for example a fabric, a fibrous web and/or is formed by particles made of the aforementioned materials.
Number | Date | Country | Kind |
---|---|---|---|
10 2004 057 683.1 | Nov 2004 | DE | national |
10 2004 058 335.8 | Dec 2004 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/DE05/01682 | 9/23/2005 | WO | 00 | 5/25/2007 |