Metal core circuit board and method of making

State of the art

p0001The invention relates to a printed circuit board according to the preamble of the main claim. It is known by the company Fuba, "Fuba News", 1/89, page 6, a circuit board having a metal core as a conductive layer. The metal core has a thickness of 300 .mu.m to 1200 .mu.m and is provided with electrically insulated vias. The metal core is covered on its top and bottom, each with an insulating layer. The production of the printed circuit board is relatively expensive because for each via a hole must be drilled in the metal core.

ADVANTAGES OF THE INVENTION

p0002The circuit board according to the invention with the features of the main claim has the advantage that the conductive layer and the inventive method for manufacturing the circuit board according to claim 6 have the advantage that introduced holes for vias in formed as a conductive layer third layer using an etching method will. This method is simple to implement and are inexpensive. In this manner, holes can be introduced in any form in the third layer. Thus, the shape of the holes and thus the shape of the vias of the required heat dissipation to be adjusted. Thus, it is possible in an inexpensive manner, a circuit board having a metal core which is used for heat dissipation to manufacture.

p0003The measures specified in the dependent claims, advantageous refinements and improvements of the main claim of the circuit board and indicated in claim 6 method of manufacturing the printed circuit board are possible. The third layer preferably has a maximum thickness of 200 microns. With a thickness up to 200 microns, the third layer can be produced simply and inexpensively yet using etching techniques, and is simultaneously formed sufficiently thick for heat dissipation.

p0004Heat dissipation is improved by a first and / or second conductor structure is applied to the first and second insulating layer, which also conducts heat. Characterized a transportation of heat is improved in the lateral direction.

p0005A preferred embodiment of the circuit board is to organize a fourth thermally conductive layer. This design provides an optimized PCB is in relation to the production cost and the thus achieved thermal conduction of the circuit board. In addition, the first and second conductor pattern using the third and fourth layers can be placed on different electrical potentials.

p0006An improvement in the heat conduction in the vertical direction is achieved by the first and the second conductor structure and the third and / or fourth layers are thermally and / or electrically connected to one another via at least one plated-through hole.

drawing

p0007An embodiment of the invention is illustrated in the drawing and explained in more detail in the following description. 1 shows a circuit board with a power component and Figure 2 is a special type of circuit board.

Description of Embodiments

p00081 shows a printed circuit board 1, on top of which a first conductor pattern 2 is arranged. The conductor pattern 2 has at least one electrical line, which is used for the electrical contact of the power device or other not shown electrical components. Under the first conductor pattern 2, a first insulating layer 5 is introduced. After the first insulating layer 5 is followed by a third layer 4, which is also electrically and thermally conductive. In the third layer 4 followed by a second insulating layer 15 on the insulating layer 15, a second conductor pattern 3 is applied.

p0009The first conductor pattern 2 is connected electrically and thermally conductive through two through first vias 6 with the second conductor pattern 3 and the third layer. 4 In a simple embodiment extends a first via 6 from. Via the connection points 6 of the first through-contacts with the first conductor pattern 2, a power device 9 is applied.

p0010Further, the first conductor pattern 2 is preferably electrically and thermally conductive, for example via two parallel second vias 8 with the third layer fourth The third layer 4 is preferably electrically and thermally conductive, for example via two parallel third via holes 7 to the second conductor pattern 3rd The third layer 4 is located in the middle of the circuit board 1 and has a larger cross-section compared to the first and the second conductor pattern 2, 3. The first, second conductor structure and the third layer 2, 3, 4 are formed for example from copper. The first and second insulating layers are made of 5.15 PCB material.

p0011The first and second conductor structures 2,3 preferably have a thickness of 30 microns, the first and the second insulating layer 5, 15 a thickness of 85μm, the third layer 4, which constitutes the metal core, preferably has a thickness of up to 200 .mu.m ,

p0012Since the third layer 4 has only a thickness of up to 200 micrometers, the holes for the vias using photolithographic method and using etching are introduced in the third layer fourth Up to a thickness of the third layer of 200 microns is sufficient unilateral etching. In printed circuit boards, which should allow a particularly high heat transfer, the third layer 4 is formed in a thickness of 200 .mu.m to 400 .mu.m to. At a layer thickness of 200 .mu.m to 400 .mu.m holes for introducing the two-sided etching process can be used. The holes for plated-through holes preferably have a diameter of 0.3 to 0.6 mm. PCBs are produced by known methods from the etched layers. 4 The advantage of the small layer thicknesses of up to 100 microns to 200 microns or from 200 microns is up to 400 .mu.m in the fact that the layer thicknesses provide a sufficient heat transport to the cooling of components and the holes for the vias in the layers by means of a simple etching process are introduced.

p0013The arrangement of Figure 1 works as follows:

p0014Through the first, second and third vias 6, 8, 7, heat generated by the power device 9, guided by the upper surface of the printed circuit board 1 on the third layer 4 and on the second conductor structure 3rd In this way, a fast heat transfer from the top to the bottom of the circuit board is carried out first, since the third layer 4 has a large cross-section, takes a good heat transport in the vertical direction in the circuit board 1 instead. To prevent weld on the surface of the circuit board 1, heat is very uniformly distributed over the entire board area and selectively avoided high temperatures at the power component.

p0015Figure 2 shows a further circuit board 13, which has on the upper side of the first conductor pattern 2 and on the bottom of the second conductor structure 3rd Under the first conductor pattern 2, the first insulating layer 5 is arranged. On the first insulation layer 5, the third layer is followed by 4. The third layer 4 has a thickness of up to 200 .mu.m on. In the third layer 4 a broadly trained third insulating layer follows 14. The thicknesses of the layers corresponding to the thicknesses of the layers of FIG. 1

p0016an electrically and thermally conductive fourth layer 10 is adjoined by the third insulating layer 14th The fourth layer 10 is separated by a second insulating layer 15 of the second conductor pattern 3rd The fourth layer 10 has a thickness of up to 200 microns and is constructed in analogy to the third layer fourth The first via 6 connecting the first and the second conductor structure 2.3 and the third and fourth layer 4,10 electrically and thermally conductive manner.

p0017For special applications, the first and the second conductor pattern 2, 3 are electrically insulated from each other, wherein the first via hole 6 is electrically insulated from the first and the second conductor pattern 2, third

p0018A fourth via 11 connects the first conductor pattern 2 with the third layer 4. A fifth via hole 12 connects the fourth layer 10 with the second conductor pattern 3. The vias are made for example of copper or soldering tin. Since the first and second insulating layers 5,15 are particularly thin, takes place in addition a good heat transfer from the first conductor pattern 2 on the third layer 4 or of the fourth layer 10 to the second conductor pattern 3rd

p0019The arrangement of the third layer 4 and the fourth layer 10 and the thermal bonding of the third layer 4 and the fourth layer 10 to the power component, an efficient heat transfer in the horizontal direction within the circuit board 13 is made possible. The third and fourth layers 4,10 are formed for example of copper.

p0020The circuit board according to figure 2 comprises two thermally and electrically conductive layers in the form of third and fourth layers 4,10. By an electric separation of the third layer 4 of the fourth layer 10 and an electric connection of the third layer 4 to the first conductor pattern 2 and the fourth layer 10 to the second conductor pattern 3, it is possible to use the conductor structures 2,3 at different electrical potential to hold.

p0021In this way, may be held devices which are connected to the first or second conductor pattern 2.3, at different potentials. This is of advantage in the use of components, whose work areas are adapted to different electrical potentials. Since the third and fourth layers 4,10 are electrically conductive, they can save as thermal conductors also serve as shields.

p0022The printed circuit boards 1 and 13 shown in Figures 1 and 2 offer the possibility to arrange it power devices and other components only after circuitry viewpoints on the circuit board, as a heat transfer takes place not only in the vertical direction, but also in the vertical direction within the circuit board, and thus a good distribution of the heat is ensured.