DE10335805A1 - Circuit board with metal base forming potential reference plane and heat sink for power-dissipating components, includes both electrical and thermal vias for heat dissipation - Google Patents

Abstract

Through-contacts, also known as vias, are made from the pattern of tracks (7) and/or from fixing locations of power-dissipating components, (9) to make electrical connection with the metal base (1), in conventional manner. Additional to these, there are further through-contacts (10) (vias) from the tracks and/or component-fastening areas (8), which serve to dissipate heat from the power components into the metal base. An independent claim is included for the corresponding method of manufacture.

Description

The The invention relates to a printed circuit board with a heat sink and as a potential reference level metal base on which at least one insulating layer is located, which on its upper side Conductor pattern and mounting areas for power dissipation generating Wearing components. The invention also relates to a method for producing a printed circuit board, which with a arranged on an insulating layer conductor pattern and with attachment areas for Power loss generating components is provided and on a Bottom one as a potential reference level and as a heat sink having serving metal base.

It is known to be on an insulating layer of a printed circuit board located conductor pattern and active and passive electrical components of a circuit arrangement to release power loss in the form of heat energy during operation must be removed from the circuit. this happens by heat dissipation and heat radiation away from the top of the circuit board, but also by heat dissipation over the thin insulation layer or, in the case of multilayer printed circuit boards, over several thin insulation layers to one as a heat sink and serving as potential reference level metal base out. This heat dissipation path However, because of the poor thermal conductivity of the insulation layer or the insulating layers, even if they are comparatively kept thin are, a big one Heat conduction resistance.

Especially then, if certain components of the top of the circuit board located circuitry relatively large amounts of heat energy in operation release, which so to speak punctually within the circuit arrangement emerge, one is anxious over thin insulation liners the heat quickly to a comparatively thick, serving as a heat sink metal base derive from a copper plate or even an aluminum plate can be formed.

From a limited surface area the circuit arrangement on the circuit board is preferred there released heat loss first through the insulating layer or through insulating layers through to a limited surface area as a heat sink headed copper plate or aluminum plate and there due good heat conduction properties the metal base in the direction of the plane determined by them to the side derived and over distributed a larger area.

There the insulating layer or, in the case of multilayer printed circuit boards, the Insulation layers for reasons the effective electrical insulation between conductor planes not arbitrarily thin can be made or can be made remains with known PCBs the effectiveness of the metal base as a heat sink despite good heat conduction properties limited to the metal base itself.

By the invention to the problem to be solved, the heat dissipation from waste heat producing parts of conductor patterns and heat-generating ones Components on the top of a circuit board substantially to improve. Also, the goal is to be achieved, the PCB weight to reduce and the cost of the provision of the metal base of printed circuit boards of the above Kind of belittle.

These The object is achieved by a Printed circuit board solved with the features of the appended claim 1. A another solution This object is achieved by a method having the features of claim 5 scored. Advantageous embodiments and developments are The subject of claim 1 subordinate claims 2 to 4 or the claim 5 subordinate claims 6 to 10.

following Be exemplary embodiments Reference to the drawing closer explained. In this represent:

1 a schematic, drawn in section an illustration of a circuit board of the type specified here;

2 a schematic, in section drawn illustration of a part of a printed circuit board of the type specified here in a modified form; and

3 a schematic, drawn in section Figure of a part of a circuit board to explain certain procedures.

In the 1 in the section and in the neckline schematically illustrated circuit board includes a metal base 1 , In the embodiments of the circuit board shown in the drawings, the metal base has a core 2 in the form of an aluminum plate obtained by a zincate surface treatment with thin zincate surface treatment layers 3 provided with a good electroplating and with an upper and lower copper layer 4 respectively. 5 ver see is.

These Training has the advantage that the base plate with excellent electrical and thermal conductivity has less weight and costs less than one massive copper plate.

Instead of the galvanic copper layers 4 and 5 For example, to further increase the conductivity and increase the thermal conductivity, silver layers or, in certain cases, gold layers may also be applied since the zincate surface treatment layers 3 allow such galvanization.

Above the metal base 1 there is an insulation layer 6 and on the top, in turn, a conductor pattern 7 as well as attachment areas 8th for applied to the circuit board and on its surface to be fastened, for example, be soldered electrical components 9 ,

For the preparation of the previously described layer dressing from the metal base 1 , the insulation layer 6 and the conductor pattern 7 as well as the attachment areas 8th the copper surface or the copper surfaces of the metal base is provided with an adhesion promoter. This can be done by conventional methods in printed circuit board technology, such as by black oxidation or brown etching.

Then, a not yet cured insulating layer web, such as a prepreg sheet is placed on the metal base and a continuous conductor layer to form the conductor pattern 7 and the attachment areas 8th applied and the layer dressing is pressed using pressure and temperature, such that the resin of the insulating layer web 6 is hardened.

Thereafter, in the usual way from the superficial copper layer, the conductor pattern together with the attachment areas 8th formed, which can be done by techniques known in this field.

Now to certain circuit points of the line pattern 7 and certain attachment areas 8th with the metal base serving as the reference potential plane 1 To connect, drill holes from the relevant points of the ladder pattern 7 and the mounting areas to be connected to reference potential 8th through the superficial copper layer and through the insulation layer 6 through to the metal base 1 guided and the bore walls are galvanically copper-coated, so that vias occur.

However, according to a very important feature of the printed circuit board specified here, in addition to these vias serving for the connection of specific conductor patterns to the reference potential plane, additional vias serving for the thermal coupling are provided 10 from the conductor pattern 7 and / or the Befestigungsbe ranges 8th to the metal base 1 guided. It looks like 1 in that, for example, from the attachment area 8th about in the middle of 1 not just a single via, but three vias from the attachment area 8th to the metal base 1 pass. Likewise are from the Leitermusterteil 7 on the right side of 1 two vias to the metal base 1 guided, namely one of the mounting area under the component 9 on the right side of 1 and another of the subsequent conductor pattern part 7 also down to the metal base 1 ,

When mounted on the circuit board components 9 release heat loss to an increased extent, this heat can rapidly through heat conduction through the vias through the poorly heat-conducting insulating layer 6 discharged to the metal base and distributed by this along the plane determined by them and finally in turn be removed from the metal base, with a selective heating of the circuit board by power concentrations due to close together, heat loss releasing components 9 is avoided.

In the embodiment according to 2 , which a printed circuit board of the type specified here in a similar representation as in 1 are again, too 1 Corresponding parts provided with the same reference numbers.

2 shows two possible modifications of the embodiment 1 ,

The insulation layer 6 facing copper layer or silver layer or gold layer of the base plate 1 can in certain areas where an increased concentration of a component 9 Released power dissipation is expected to be carried out in greater thickness to dissipate the heat loss from the lower ends of the thermal vias 10 towards the side and into the core in the form of the aluminum plate 2 to accelerate.

The thermal vias and also the electrical vias can be filled with a good thermal conductivity filling 11 be provided. This filling can assist the heat conduction through the conductor coating of the bore walls of the vias.

Moreover, it should be noted that appropriate the thickness of the upper copper coating or silver coating or gold coating of the metal base 1 Overall, depending on the thermal load in the created on the circuit board circuit arrangement can be selected.

Based on 3 be two methods for forming thermal vias on a circuit board of the here indicated An explained. In 3 are for appropriate parts as in the 1 and 2 Again, the same reference numerals used, with a description of the training and functionality of these parts as far as in the explanation of 2 can be waived.

Is the stratigraphy of the metal base 1 , the insulation layer 6 and a metal layer, in particular a copper layer for forming the conductor pattern 7 manufactured, are to form the thermal vias and, where appropriate, for the formation of the electrical vias by means of a laser blind holes or blind holes 12 through the superficial copper layer and through the insulation layer 6 up to the metallic surface of the layer 4 the base plate drilled and the Bohrungswandungen are then galvanically plated, as in 13 is indicated. Because the blind holes 12 only up to the surface of the layer 4 Reach is at the bottom of the hole galvanisable material free. The blind hole will not reach the aluminum plate 2 Otherwise, the bottom of the hole would not be galvanisable and would require a further zincate treatment.

Be plated through holes for thermal and electrical coupling of Leitermusterteilen or mounting areas in such a way that according to the illustration on the right side of 3 mechanically through holes are made through the entire PCB, as in 3 at 14 indicated, then the through holes 14 after purification, another zincate treatment may be performed to obtain a 3 With 15 designated zincate treatment surface at the bore walls in the region of the aluminum plate 2 to produce, which then together with the remaining parts of the bore wall again with a copper coating 16 provided.

Claims (11)

Printed circuit board with a metal base serving as a heat sink and as a potential reference plane ( 1 ), on which at least one insulation layer ( 6 ), which on its upper side a conductor pattern ( 7 ) as well as attachment areas ( 8th ) for power dissipating devices ( 9 ), characterized in that of the conductor pattern ( 7 ) and / or the mounting areas for power-dissipating components ( 9 ) except for their electrical coupling to the metal base ( 1 ) through-vias (vias) ( 10 ) additional, for thermal coupling vias ( 10 ) of the conductor pattern ( 7 ) and / or the attachment areas ( 8th ) are performed for power dissipation generating components. Printed circuit board according to Claim 1, characterized in that the plated-through holes ( 10 ) are provided in density per unit area corresponding to the loss power density on the circuit board. Printed circuit board according to Claim 1 or 2, characterized in that the metal base ( 1 ) is a metal plate of uniform, good heat conducting and highly electrically conductive material, in particular of copper or silver or gold. Printed circuit board with a metal base serving as a heat sink and as a potential reference plane ( 1 ), on which at least one insulation layer ( 6 ), which on its upper side a conductor pattern ( 7 ) as well as attachment areas ( 8th ) for power dissipating devices ( 9 ), in particular according to claim 1 or 2, characterized in that the metal base ( 1 ) of an aluminum plate ( 2 ) is formed, which at least in the connection points of the vias ( 10 ) with a zincate surface treatment layer ( 3 ) and a copper coating or silver coating or gold coating ( 4 . 5 ) is provided. Printed circuit board according to Claim 4, characterized that the Copper or silver or gold coating has a thickness, the dependent from the amount of the payable Power loss is chosen differently. Method for producing a printed circuit board, which is provided with an insulating layer ( 6 ) arranged conductor pattern ( 7 ) and with attachment areas ( 8th ) for power dissipating devices ( 9 ), and on a lower side serving as a potential reference plane and as a heat sink metal base ( 1 ), characterized in that the metal base ( 1 ) having a surface made of copper or silver or gold, provided with a primer layer, and firmly bonded to an insulating layer and a surface conductor layer so that the surface conductor layer is formed into a conductor pattern by drilling through areas of the conductor pattern and the insulating layer at least to the metal base ( 1 ), the number of holes being selected beyond the number required for the electrical coupling of conductor pattern areas to the metal base and providing the bore walls with a metallization coating that thermally couples the respective conductor pattern regions and the underlying metal base regions. Process according to Claim 6, characterized in that the formation of the metal base ( 1 ) an aluminum plate ( 2 ) and subjected to a zincate treatment, through which a galvanisable surface layer ( 3 ) of the aluminum plate, and then that the zincate surface treatment layer ( 3 ) with a copper layer or silver layer or gold layer ( 4 . 5 ). Method according to claim 6 or 7, characterized in that the holes are drilled as blind bores ( 12 ), in particular by means of laser, to the copper or silver or gold surface of the metal base ( 1 ). Method according to Claim 6 or 7, characterized in that the bores are in the form of through-holes ( 14 ), which also through the aluminum plate ( 2 ), and that prior to the metallization of the bore walls, they are subjected to a new zincate treatment. Method according to one of claims 6 to 9, characterized in that the through-holes ( 10 ) with a good heat-conducting filler material ( 11 ) fill out. Method according to one of claims 6 to 10, characterized in that the metal base ( 1 ), which are used as uncured insulating layer web ( 6 ) provided insulation layer and the surface conductor layer ( 7 ) with hardening of the insulating layer ( 6 ) are pressed.