DE102014210889B4 - Method for producing a multilayer printed circuit board - Google Patents

Abstract

The invention relates to a method for producing a multilayer printed circuit board in which a plurality of first layers (101, 102, 103) and one or more second layers (201, 202, 203) are used as the starting material, wherein a respective first layer (101, 102 , 103) comprises a cured dielectric material provided on at least one side with a conductive layer (L1, L2, L3, L4) in the form of a metallic conductor pattern (401, 402, ..., 409), and wherein a respective one second layer (201, 202, 203) comprises a non-cured dielectric material without a metallic conductor structure, wherein the following steps are carried out: a) connecting one wire (8) or several wires (8) with first wire ends (801) and second wire ends ( 802) at their first wire ends (801) each having a line position (L1, L2, L3, L4); b) stacking the first and second layers (101, 102, ..., 203), wherein in stacking, the wire or wires (8) are cut into openings (5) of those first and second layers (101, 102, ..., 203) following each other from the first wire end (801) of the respective wire (8) in the longitudinal direction of the wire (8), and wherein the second wire end (s) (802) of the wire (8) or the wires (8 ) end at an outer layer (L1, L4); c) pressing the stack formed in step b); d) connecting the wire or wires (8) at their second wire ends (802) each with an outer layer (L1, L4).

Description

The invention relates to a method for producing a multilayer printed circuit board and a corresponding multilayer printed circuit board.

Multilayer printed circuit boards comprise layers arranged on top of one another with conductor layers of metallic conductor structures applied thereon. For connecting conductor structures of different line layers vias are formed. Usually, these plated-through holes are produced by a galvanic process. However, the wet-chemical process of galvanic metal deposition is complex and represents a significant environmental impact due to the chemicals used (including strong acids and alkalis).

In principle, it is possible to mechanically insert metallic dowel pins or dowel sleeves into a through bore of a printed circuit board in order to connect the outer conductive layers of the printed circuit board to one another. However, this type of connection is associated with high time and cost and allows only the contacting of the outer cable layers.

The publication DE 11 2005 000 438 B4 discloses a stripline circuit having a plurality of layers wherein a contact pad in the stripline circuit is connected via a wire to another electrical device.

The DE 695 07 459 T2 discloses a multilayer substrate, which may be a printed circuit board, with tracks on inner layers, wherein by means of troughs in the outer layers on these tracks wires or pins can be soldered, which are used for contacting electrical connection components.

The US 2009/0201654 A1 also discloses a multilayer printed circuit board which is produced by laminating various layers and in which holes are provided, into which press-fitting pins for connecting a conductor track arranged on an inner layer and a conductor track arranged on an outer layer are pressed.

The object of the invention is to provide a simple and inexpensive method for producing a printed circuit board with plated-through holes.

This object is solved by the independent claim. Further developments of the invention are defined in the dependent claims.

The method according to the invention uses as starting material a plurality of first layers and one or more second layers, wherein a respective first layer comprises a hardened dielectric material which is provided on at least one side with a conductive layer in the form of a metallic conductor structure, and wherein a respective second layer comprises a non-cured dielectric material without a metallic conductor structure. In a particularly preferred embodiment, the dielectric material of the respective first and / or second layers comprises a resin and in particular an epoxy resin. When used in the first layers, this resin is cured, whereas it is not cured when used in the second layers. In particular, the first and / or second layers are formed as resin-impregnated fiber structures.

• a) Verbinden eines Drahtes oder mehrerer Drähte mit ersten Drahtenden und zweiten Drahtenden an ihren ersten Drahtenden jeweils mit einer Leitungslage;
• b) Stapeln der ersten und zweiten Schichten derart, dass zwischen benachbarten ersten Schichten des Stapels zumindest eine zweite Schicht angeordnet ist, und der Stapel mit einer ersten Schicht als Stapelanfangsschicht beginnt und mit einer ersten Schicht als Stapelendschicht endet, und auf der Stapelanfangsschicht und/oder der Stapelendschicht eine Leitungslage in der Form einer Außenlage vorgesehen ist, wobei beim Stapeln der oder die Drähte in Öffnungen von denjenigen ersten und zweiten Schichten angeordnet werden, die ausgehend von dem ersten Drahtende des jeweiligen Drahts in Längsrichtung des Drahts aufeinander folgen, und wobei das oder die zweiten Drahtenden des Drahtes oder der Drähte bei einer Außenlage enden;
• c) Verpressen des in Schritt b) gebildeten Stapels, wobei das dielektrische Material der zweiten Schicht oder der Schichten schmilzt und dann aushärtet;
• d) Verbinden des oder der Drähte an deren zweiten Drahtenden jeweils mit einer anderen Leitungslage, welche die Außenlage ist, bei der das jeweilige zweite Drahtende endet.

In the process according to the invention, the following steps a) to d) are carried out:

• a) connecting a wire or a plurality of wires having first wire ends and second wire ends at their first wire ends each having a line position;
• b) stacking the first and second layers such that at least one second layer is disposed between adjacent first layers of the stack, and the stack begins with a first layer as a stack start layer and ends with a first layer as a stack end layer, and on the stack start layer and / or the stack end layer is provided with a conductive layer in the form of an outer layer, wherein in stacking the wire or wires are arranged in openings of those first and second layers following one another from the first wire end of the respective wire in the longitudinal direction of the wire, and wherein the or the second wire ends of the wire or wires terminate in an outer layer;
• c) compressing the stack formed in step b), wherein the dielectric material of the second layer or layers melts and then cures;
• d) connecting the wire or wires at the second wire ends in each case with a different wire position, which is the outer layer, in which the respective second wire end ends.

The inventive method has the advantage that without wet-chemical process, a connection between different line layers is achieved via a wire. In this way, a through-connection between the conductor layers of the printed circuit board is easily and inexpensively ensured.

Depending on the configuration, the first and the second end of the wire can be connected by means of various Connection technologies are connected to the appropriate line situation. Bonding, welding, soldering, gluing or sintering are preferably used as connection technologies. These connection technologies are known per se from the prior art and will therefore not be explained in detail.

In a further variant of the method according to the invention, one or more components and in particular one or more semiconductor components (eg a semiconductor chip) are each connected to a line layer. This step of bonding is preferably carried out before the above step b), in particular before the above step a) and / or in step a) and / or between step a) and b). In order to connect the component (s) to the conductor layer, in turn, the above-mentioned connection technologies of bonding or welding or soldering or sintering can be used.

In a further variant of the method according to the invention, at least part of the openings of the first and second layers, in which the wires are arranged, are formed in the context of the method. In particular, the openings are formed before the above step b) and particularly preferably before the above step a). Depending on the configuration, the openings z. B. are punched into the layers and / or drilled. Optionally, there is also the possibility that the individual layers with the corresponding openings are already prefabricated. In other words, in this case at least a part of the openings of the first and second layers is already provided in the starting material of the method.

In a further variant of the method according to the invention, a plurality of wires are arranged in the line plate, with all the wires extending from the first wire end in the direction of the stack end layer or in the opposite direction to the stack starting layer. Alternatively, it is also possible for some of the wires to extend from the first wire end in the direction of the stack end layer and for another part of the wires to extend from the first wire end in the direction of the stack start layer.

In a further variant, in which in turn a plurality of wires are arranged in the printed circuit board, a plurality of conductive layers are connected to the first wires and / or outer layers on both the Stapelanfangsschicht and on the Stapelendschicht be connected to second wire ends of the wires.

By the described method, a multilayer printed circuit board having a plurality of first layers and one or more second layers is obtained, wherein a respective first layer comprises a cured dielectric material provided on at least one side with a conductive layer in the form of a metallic conductor pattern, and wherein a respective second layer comprises a cured dielectric material without a metallic conductor structure. The circuit board contains a compressed stack of the first and second layers. In this stack, the first and second layers are stacked such that at least one second layer is disposed between adjacent first layers of the stack. Furthermore, one or more metallic wires are arranged in openings of first and second layers, wherein a first wire end of a respective wire is connected to a wire layer and a second wire end opposite to the first wire end of the respective wire is connected to another wire layer.

The multilayer printed circuit board just described can thus be produced by the method according to the invention or one or more preferred variants of the method according to the invention. Exemplary features of the printed circuit board, which are the result of steps of preferred variants of the method according to the invention, can thus be present in the printed circuit board, such. B. the components described above. Embodiments of the invention are described below in detail with reference to the accompanying drawings.

Show it:

1 to 7 schematic cross-sectional views illustrating the steps according to an embodiment of the method according to the invention;

8th a modification of the method step of 7 ; and

9 a sectional view of a modified printed circuit board, which can be produced by the method according to the invention.

The embodiments of the invention described below use as the starting material first layers and second layers of dielectric material in the form of impregnated with epoxy resin fiber mats, such. B. glass fiber mats. The thickness of the individual layers is in the range of 100 μm or even less or more. According to the sectional view of 1 become three first layers 101 . 102 and 103 used. The dielectric material is indicated hatched and is already cured for these layers. On the first layers is at least on one side a line layer with a conductor structure made of copper. The lowest first layer 101 includes both on the top and on the bottom a Leitungslage. The cable position on the underside is denoted by L1 and the line position on the top by L2. Corresponding conductor surfaces or contact surfaces of the conductor structure in the line position L2 are with 401 . 402 . 403 and 404 designated. Similarly, conductor surfaces of the conductor structure in the line position L1 with 403 ' and 404 ' designated. Over a metallic through-hole in an opening 1 that in the layer 101 is formed, the area stands 403 with the area 403 ' and the area 404 with the area 404 ' in connection.

Unlike the layer 101 cover the layers 102 and 103 only on its upper side corresponding line layers L3 and L4. In the line position L3 is the metallic conductor or contact surface 405 intended. In line position L4, the two conductor or contact surfaces 406 and 407 intended. In addition to the first layers 101 to 103 Further, in the manufacture of the circuit board, the second layers 201 . 202 and 203 used, which are arranged in the later stacking of the layers between the first layers. As already mentioned, the second layers consist of a fiber mat impregnated with epoxy resin, but they do not comprise any conductive layers. The horizontal extent of the layers 201 and 203 corresponds to the horizontal extent of the first layers 101 to 103 , In contrast, the layer has 202 in the horizontal direction a much smaller extent than the remaining layers. In contrast to the first layers, the epoxy resin of the second layers is not yet cured. As a term for the second layers, the term "prepreg" is also commonly used.

In the 1 illustrated line layers are to be plated through openings in the layers. In the starting material of 1 These openings are not yet formed. As a result, in a first method step, which is described in 2 is shown, first corresponding openings 5 introduced into the individual layers. These openings can z. B. be formed by drilling or punching. In this case, superimposed openings in the individual layers may possibly also be drilled or punched simultaneously.

In the embodiment described here, a semiconductor chip is embedded therein in the manufacture of the printed circuit board. For this purpose, according to the next method step of 3 the corresponding chip 7 with the conductor surfaces 401 and 402 connected to the L2 location. The connection is made by soldering, wherein the solder used for this purpose by the reference numeral 6 is designated. If necessary, the chip can also be used in different ways with the conductor surfaces 401 respectively. 402 be connected, such. B. on welding, bonding, gluing and the like.

In order to achieve a via without wet-chemical process, in the in 4 reproduced process step wires 8th with cable layers of the first layers 101 and 102 connected. For clarity, are in 4 the second layers are omitted. In particular, the three, in 4 reproduced wires a first wire end 801 and second wire end 802 , Via the first wire ends, a connection is made with conductor surfaces of the corresponding line layers. The left wire is doing with the conductor surface 401 connected L2, the middle wire with the conductor surface 403 Layer L2 and the right wire with the conductor surface 405 able L3. The individual wires extend vertically up to the first layers in a vertical direction.

In the embodiment described here, the connection of the individual wires to the conductor surfaces takes place via bonding. The wires are therefore so-called. Bond wires. The wire is in the embodiment described here of copper, but can also be made of other metals or alloys, such as. As silver or gold exist. In the process step of 4 If necessary, the wires can be connected simultaneously to the individual cable layers.

In the next step of the 5 The first and second layers are stacked on top of each other. Here are the openings 5 disposed in the individual layers such that the wires extend through the layers toward the top conductive layer L4. When stacking, make sure that the holes that receive the same wire are exactly aligned so that the wires thread through the holes.

After stacking according to 5 a compression of the stacked layers, as in 6 is indicated. For reasons of clarity, distances between the individual layers and between the wires and the layers are shown even after the pressing. However, these distances are actually no longer present after pressing. The pressing takes place at a temperature of about 200 ° C and with appropriate pressure on the top and bottom of the stacked layer structure. As a result, the as yet uncured resin of the second layers or prepregs melts 201 to 203 so that the openings 5 fill with resin. The resin, which has cured after pressing, causes the layers to bond to one another, so that the layers are connected to one another via this. At the same time is the chip 7 embedded in the interior of the printed circuit board structure.

In the next step according to 7 become the second ends 802 the individual wires 8th connected to the top line layer L4 of the layer stack. For this purpose, the second ends of the wires are suitably bent and then connected by welding with conductor surfaces of the layer L4. Alternatively, other connection technologies than welding are possible. A modified connection of the wire ends 802 with the line L4 is in 8th exemplified. The wire is no longer bent, but it is a solder paste 9 on the upper ends 802 the wires applied. As part of a soldering process, the connection between the wires and the conductor surfaces of the line layer L4 is then effected. Alternatively, a conductive adhesive may be used instead of a solder paste to connect the top ends to the conductor surfaces.

In the foregoing, an embodiment of the invention has been described in which a through-connection of inner conductor layers is always effected towards the uppermost conductor layer L4 via wires. Nevertheless, the invention can also be used to effect through-plating from inner conductor layers to the lowermost conductor layer L1. This is exemplified by 9 clarified. This figure shows a sectional view of a section of a modified printed circuit board, which is also produced by the method according to the invention.

In contrast to the previous figures are in 9 Conductor surfaces on top of first layers uniformly with the reference numeral 408 whereas conductor surfaces on the underside of first layers are designated by the reference numeral 409 are designated. As can be seen, the illustrated structure now comprises the further inner conductor layer L4 ', which in addition on the underside of the uppermost layer 103 is provided. The left and the middle wire 8th of the 9 extend from conductor surfaces 408 upwards and stand out of the line L4. There they are according to the process step of 7 respectively. 8th with the conductor surface 408 connected to the location L4. In contrast to the previous embodiments, the right-hand wire now extends from a conductor surface 409 the line position L4 'down and out of the line position L1 out. He will then turn based on the process steps of 7 respectively. 8th with a conductor surface 409 connected to the line L1. With the embodiment of the 9 Vias can be achieved both to the top and to the bottom of the circuit board.

In a further variant of the method according to the invention, at least a part of the openings extends continuously from the lowermost cable layer to the uppermost cable layer and the wire inserted therein protrudes from both the lowermost and the uppermost cable layer. The wire is again positioned in the openings prior to compression.

The embodiments of the invention described above have a number of advantages. In particular, a multilayer printed circuit board with plated-through holes without galvanic or wet-chemical processes is produced. This is achieved by introducing bond wires for the contacting prior to pressing the layers of the printed circuit board, which are connected to inner conductor layers and outer conductor layers by means of connection technologies known per se. The wires can be applied quickly and possibly also parallel to several cable layers simultaneously. The diameter and the thus realizable current conductivity as well as the stability of the wires are freely selectable. In particular, bond wires with different bond wire thicknesses are available.

Claims (9)

Method for producing a multilayer printed circuit board in which several first layers ( 101 . 102 . 103 ) and one or more second layers ( 201 . 202 . 203 ), wherein a respective first layer ( 101 . 102 . 103 ) comprises a hardened dielectric material having on at least one side a conductive layer (L1, L2, L3, L4) in the form of a metallic conductor structure ( 401 . 402 , ..., 409 ), and wherein a respective second layer ( 201 . 202 . 203 ) comprises a non-cured dielectric material without a metallic conductor structure, the following steps being carried out in the following order: a) connecting a wire ( 8th ) or multiple wires ( 8th ) with first wire ends ( 801 ) and second wire ends ( 802 ) at their first wire ends ( 801 ) each with a line position (L1, L2, L3, L4); b) stacking the first and second layers ( 101 . 102 , ..., 203 ) such that between adjacent first layers ( 101 . 102 , ..., 103 ) of the stack at least one second layer ( 201 . 202 . 203 ), and the stack with a first layer ( 101 ) starts as a stack start layer and with a first layer ( 103 ) ends as a stack end layer, and on the Stapelanfangsschicht and / or the Stapelendschicht a conduction layer in the form of an outer layer (L1, L4) is provided, wherein in stacking the wire ( 8th ) or the wires ( 8th ) in openings ( 5 ) of those first and second layers ( 101 . 102 , ..., 203 ) are arranged, which starting from the first wire end ( 801 ) of the respective wire ( 8th ) in the longitudinal direction of the wire ( 8th ), and wherein the one or more wire ends ( 802 ) of Wire ( 8th ) or the wires ( 8th ) end at an outer layer (L1, L4); c) pressing the stack formed in step b), wherein the dielectric material of the second layer or layers ( 201 . 202 . 203 ) melts and then hardens; d) connecting the wire ( 8th ) or the wires ( 8th ) at the second wire ends ( 802 ) each with a different line position, which is the outer layer (L1, L4), in which the respective second wire end ( 802 ) ends. Method according to claim 1, characterized in that the dielectric material of the respective first and / or second layers ( 101 . 102 , ..., 203 ) comprises a resin, wherein the first and / or second layers ( 101 . 102 , ..., 203 ) are preferably resin-impregnated fiber structures. Method according to one of the preceding claims, characterized in that the first and / or second wire end ( 801 . 802 ) of a respective wire ( 8th ) is connected to the conductor layer (L1, L2, L3, L4) via bonding or welding or soldering or gluing or sintering. Method according to one of the preceding claims, characterized in that one or more components ( 7 ) are each connected to a line position (L1, L2, L3, L4). Method according to claim 4, characterized in that the component or components ( 7 ) are connected to the conductor layer (L1, L2, L3, L4) via bonding or welding or soldering or gluing or sintering. Method according to one of the preceding claims, characterized in that at least a part of the openings ( 5 ) of the first and second layers ( 101 . 102 , ..., 203 ), in which the wire ( 8th ) or the wires ( 8th ), is formed in the context of the method. Method according to one of the preceding claims, characterized in that at least a part of the openings ( 5 ) of the first and second layers ( 101 . 102 , ..., 203 ), in which the wire ( 8th ) or the wires ( 8th ), is already provided in the starting material of the process. Method according to one of the preceding claims, characterized in that a plurality of wires ( 8th ) are arranged in the circuit board, with all wires ( 8th ) starting from the first wire end ( 801 ) extend in the direction of the stack end layer or in the direction of the stack starting layer or in which part of the wires ( 8th ) starting from the first wire end ( 801 ) extends towards the stack end layer and another part of the wires ( 8th ) starting from the first wire end ( 801 ) extends in the direction of the Stapelanfangsschicht. Method according to one of the preceding claims, characterized in that a plurality of wires ( 8th ) are arranged in the circuit board, wherein a plurality of metallic conductor structures ( 408 . 409 ) with first wire ends ( 801 ) and / or outer layers (L1, L4) both on the stack start layer and on the stack end layer with second wire ends ( 802 ) get connected.

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