DE102014007429A1 - Printed circuit board with component and method for its production - Google Patents

Abstract

A method of contacting a device (30) in a circuit board layer sequence (10), comprising the steps of: providing a device (30) having contact surfaces (34, 36, 38) of a non-copper metal material; Producing a laminar laminate (10) with an embedded component; Creating one or more holes (V1, V2, VL) in a surface of the laminate laminate (10) to at least partially expose the contact surfaces (34, 36, 38) of the device (30); Treating oxide layers (35, 37) on the exposed contact surfaces (34, 36), depositing a base metal layer (40), and performing a plating process for reinforcing the base metal layer (40) with a copper layer (42). Printed circuit board having a printed circuit board layer structure (10) and a component (30) incorporated therein, wherein the component (30) has at least one contact surface (34, 36, 38) which is contacted via at least one blind hole (V1, V2, VL), wherein the Contact surface (34, 36, 38) in the region of the at least one vias (V1, V2, VL) has a layer of metallic material, which is not copper, to which directly and without the presence of a metal oxide layer (35, 37) a base metal layer ( 40) reinforced by plated copper (42).

Description

Technical area

The present invention relates to a method of contacting a device with a circuit board layer sequence and a printed circuit board having an embedded device.

In printed circuit boards introduced or embedded components such as semiconductors, power semiconductors, chips, field effect transistors u. Like. Must be contacted for connection to the integrated circuit. For this purpose, the components usually have suitable contact surfaces. For a galvanic Ankontaktierung of components, the contact surfaces are ideally made of copper or coated with copper. However, in the manufacture of printed circuit boards with integrated / embedded devices to be plated, the challenge is that many devices do not have copper terminations but contact surfaces with aluminum or an aluminum alloy surface.

According to the invention, a method for contacting a component in a circuit board layer sequence with the features of claim 1 and corresponding circuit boards having the features of claims 12 and 17 are proposed.

According to the invention, a method is provided which allows embedding and contacting of standard components with non-copper-coated contact surfaces. Such contact surfaces usually have surfaces of aluminum or an aluminum alloy such as AlSiCu or AlSi.

The invention is based on the recognition that contact surfaces made of a metal material which is not copper (non-copper metal) are treated in such a way that plating with copper on it is made possible. The treatment according to the invention may, for example, be removal of the oxide layer at least in a region of the contact surfaces (for example in an exposed region and / or a region intended for plating). Alternatively, the treatment of the invention may be a conditioning of the surface of the non-copper metal contact surface.

A base metal layer is then applied to the contact surface treated according to the invention. In the context of the present invention, a base metal layer is to be understood as meaning a single layer of a plateable metal (such as, for example, copper) or else a layer sequence to which a reinforced copper layer is applied in a subsequent electroplating step.

Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings.

It is understood that the features mentioned above and those yet to be explained below can be used not only in the particular combination indicated, but also in other combinations or in isolation, without departing from the scope of the present invention.

The invention is illustrated schematically by means of embodiments in the drawing and will be described in detail below with reference to the drawing.

Brief description of the drawing

1 shows in side sectional view of a Schichtabfolgelaminat with embedded device.

2 shows the laminar laminate of the 1 with introduced blind holes (vias) to the surface of the device.

3 FIG. 12 shows an alternate embodiment of the laminate laminate of FIG 2 with a trained as a surface or slot blind hole.

4 shows a detail enlargement A from the representation of 3 ,

5 shows the device surface of the 4 with oxide layers removed from the exposed contact surfaces.

6 shows the section of the Schichtabfolgelaminat the 5 after applying a base metal layer.

7 shows the section of the Schichtabfolgelaminat the 6 with reinforced copper coating.

8th shows the section of the Schichtabfolgelaminat the 7 with filled blind holes.

9 shows the laminar laminate of the 8th with selectively etched outer layer for potential separation.

10 shows a plan view of the Schichtabfolgelaminat the 9 ,

11 shows a further embodiment of a circuit board according to the invention in a lateral sectional view.

12 shows a variant of the Schichtabfolgelaminats with filled blind holes of 8th ,

Detailed description

1 shows in side sectional view of a Schichtabfolgelaminat 10 a circuit board.

The laminar laminate 10 has a built-in or embedded therein component 30 on. The layer sequence comprises a substrate layer in the illustrated embodiment 12 , which may be a conductive or non-conductive circuit board material, such as a FR-4 inner layer, and a copper inner layer deposited thereon 14 on which the component 30 by means of a contact layer or connecting layer 16 (Sintered layer or solder layer) is applied. The component 30 is in a prepreg or dielectric layer 18 embedded, with a copper foil applied to it 20 concludes. The latter could also be omitted in a variant, so that only one dielectric layer is used. In this case, the surface and the hole walls would have to be adhesively bonded and conductively coated before copper can be deposited. That could be z. B. by sputtering of copper.

The illustrated and described laminate construction is of course purely exemplary, and the skilled person will readily understand any other deviating structure.

The component 30 may be - as in the illustrated embodiment - a field effect transistor, with a semiconductor body 32 and disposed thereon terminals in the form of contact surfaces, denoted by the reference numerals 34 for the gate contact area, 36 for the source contact area and 38 are designated for the drain contact surface.

The skilled person will readily understand that any other form of component with corresponding contact surfaces for Ankontaktierung invention can be used.

Typically, for contacting the contact surfaces 34 . 36 and possibly 38 Holes in the form of blind holes introduced into the copper and laminate layers located above the contact surfaces. In the presentation of the 2 is a blind hole V1 on the gate contact surface 34 intended. Furthermore, also by the copper foil 20 and the dielectric 18 a plurality of further, substantially circular blind holes V2 on the source contact surface 36 intended.

Alternatively, in the illustrated embodiment, large-area source contact surface 36 Also, a significantly larger blind hole VL be provided in the form of a slot (see also the top view of the 10 ). Size and shape of such blind holes for Ankontaktierung (ie for attachment of so-called vias) will be apparent to those skilled readily. Furthermore, the source surface can be exposed over the entire surface, but this complicates a subsequent filling of the depression with copper for large source areas.

The example of in 3 illustrated embodiment, the further inventive method is described in the manufacture of the circuit board.

4 shows an enlarged detail according to section A of the 3 ,

4 shows in enlarged detail a section of the semiconductor body 32 of the component 30 , the gate contact surface mounted thereon 34 as well as a part of the likewise attached source contact surface 36 ,

The contact surfaces 34 . 36 of the component 30 are not made of copper, but of aluminum or an aluminum alloy such as AlSi or AlSiCu. For this reason, the galvanic Ankontaktierung the contact surfaces designed 34 . 36 with conventional methods as difficult or not possible. For this reason, the method according to the invention described below is appropriate.

Aluminum or aluminum alloys very rapidly form an oxide layer on their surface in an oxygen environment 4 with the reference numerals 35 respectively. 37 are designated. These oxide layers are treated according to the invention.

The term "treating" the oxide layer in the context of the present application means any form of physical and / or chemical processing that results in a platable surface at that location. In this case, according to the invention, it may be, for example, a removal of the oxide layer, but also a conditioning.

In the following, the invention is first described in more detail using the example of the removal of the oxide layer on the basis of the illustrated embodiment.

Before the removal of the oxide layer, a hole cleaning process for cleaning the surfaces of the substrate and the semiconductor and in particular also the hole walls. Wet-chemical cleaning, as known as standard technology (for example in the form of the desmear process), however, it can not be used because the hot alkaline aqueous solution attacks the amphoteric aluminum. Dry cleaning processes such as plasma cleaning or UV cleaning (also known as desmear processes) are therefore suitable as cleaning processes.

After cleaning the hole surfaces (walls and floors), the already mentioned removal of the oxide layers takes place 35 . 37 in the area of the exposure of the contact surfaces 34 . 36 like this in 5 is schematically illustrated with the arrows P1 and P2. To remove the oxide layers, for example, a sputtering method can be selected in which a portion of the accelerated gas ions reaches such a high energy that is sufficient to remove particles from the target surface (so-called back sputtering). For example, argon ions can be used for this purpose.

The removal of the oxide layer according to the invention can, for example, also be carried out by chemical reduction, for example by means of a reducing plasma. As a process gas in this case, for example, offers hydrogen, which reacts with the oxygen from the oxide layer to water. Another alternative is a chemical dissolution of the oxide layer, in which the oxide, for example. In alkaline solution as aluminate dissolves and exposed underlying metallic aluminum.

To reoxidize on the surface of the contact surfaces 34 . 36 In the case of plasma-assisted processes, it is appropriate to prevent at least the process of removing the oxide layers and of immediately following application of a base metal layer (cf. 6 ) in an essentially oxygen-free or oxygen-poor and / or pressure-reduced environment. Ideally, at least these two steps are performed in a vacuum environment. In chemical processes, the dissolution of the oxide layer and the deposition of the first base metal layer takes place "in situ".

As an alternative to vacuum processes, so-called "open air" plasma processes can be used in which the plasma is generated spatially limited. Again, the plasma can first z. B. can be adjusted reducing by the addition of Wassersoff to remove oxide layers from the aluminum surfaces. Thereafter, while maintaining the plasma, the plasma can be supplied to the plasma with a carrier gas copper in particle form and thus take place in a direct consequence of deoxidation and copper coating. This coating process is adjusted so that the surfaces of the exposed contact surface areas and the hole walls are provided simultaneously with a sufficiently thick copper coating, so that then a galvanic reinforcement with z. B. copper is possible.

Applying the in 6 with the reference number 40 For example, by means of a sputtering method, copper is sputtered directly onto the aluminum or aluminum alloy surface freed from the oxide layer. The sputter layer should have a substantially nonporous coating on the aluminum surface as well as the hole walls of the dielectric 18 represent what is the case from about 200 to 300 nm layer thickness.

Depending on the size of the contact surface and alloy composition, it may be necessary to apply adhesion-improving layers or layer sequences. Such layer sequences can z. Ti, Ti-W, Ti-Cu or other combinations of Ti, Cu, W layers. In addition, a pure copper layer is sputtered onto these layers.

Alternatively, depositing a base metal layer of zinc on the metal surfaces 34 . 36 , carried out using a known from the prior art known as zincate process or a chemical deposition of nickel on the aluminum. In the case of the chemical metal deposition on Al, the hole walls of the dielectric must be coated in an electrically conductive manner by a method known from the prior art, before a galvanic reinforcement of the base metallization can take place.

In the context of the oxide layer removal by means of the zincate process as a wet-chemical application, the oxide layer is at least partially removed and in a water alkaline solution with ZnO a thin zinc layer is deposited on the aluminum.

Conductivity of the hole walls may be, for example, by depositing a conductive polymer on the resin material of the prepreg layer 18 take place, or alternatively by a chemical copper process. When applying the Zinkatprozesses plating takes place from a z. B. alkaline / cyanide Cu electrolyte, is deposited with the copper on the zinc layer and the hole wall. This is z. B. deposited with 5 microns, then the other typical PCB electroplating processes, such as the galvanic filling of the blind holes are possible. After the mentioned alternative chemical Cu process with sufficient layer thickness (about 2 microns) can be changed directly into an acidic electrolyte.

However, the invention is not limited to treating the non-copper-metal pads to remove the oxide layer thereon. Alternatively, according to the invention, a conditioning of the contact surface can take place, as will be described in more detail below.

At the above-described hole production and perforated wall cleaning can be carried out a direct (chemical) deposition of nickel on aluminum. This is followed by the already described processes of the deposition of chemical Cu or a conductive polymer on the hole walls and possibly the surface. This is followed by galvanic reinforcement, if necessary, until complete filling.

For a further variant of the galvanic coating with z. As copper, the comparatively thin oxide layer is left on the surface, possibly even reinforced in the layer thickness. In a conditioning step, the oxide layer is coated with a so-called conditioner (substrate improver). The conditioner has the property of docking to the surface, here aluminum oxide, by means of a reactive, often complexing group. The rest of the molecule is organic. The conditioning step takes place, for example, in a wet-chemical process. As a conditioner, for example, silanes with organic residue, polyolefins o. The like. Serve. The conditioner can be any adhesion promoter that can be applied to an oxide layer, with the aid of which the conductive polymer can be deposited on the surface. The step of conditioning thus essentially serves to apply a well-adhering conductive polymer layer with the aid of which Cu can be deposited galvanically on the relevant surface.

Thereafter, a conductive polymer is deposited on which copper is subsequently electrodeposited. The deposition of the conductive polymer takes place simultaneously on the hole wall and on the oxide surface. The oxide layer is so thin that it is of minor importance for the electrical function and contacting.

The base metal layer or base metal layer sequence applied by a method as described above 40 in a next step, electroplating with a copper layer 42 reinforced (cf. 7 ). This process is also known as "plating". Here, the blind holes V1, VL can be completely filled for later formation of vias (see. 8th ). Subsequently, a selective etching is carried out in order to produce a potential separation between the gate and source contact surfaces (cf. 44 in the 9 and 10 ). 12 shows a variant of the hole filling: from a certain area of the hole this is no longer completely filled, as shown in the representation of 8th is illustrated for the right in sections in the illustration sections shown slot VL, but there is only a partial filling 42 ' , like from the 12 seen.

Optionally, according to the invention before embedding the device 30 the aluminum oxide layer are reinforced. The reason for this is that alumina is a good adhesion partner for the impregnating resins of the prepreg layer 18 and a pore-free layer is required for even coverage with conditioner. In particular, during the subsequent hole drilling good adhesion to the oxide is mediated for the remaining resin. The aluminum oxide layer on chips has, according to experience, only a small, a few nanometer thin oxide layer whose tightness and stability may be too low. This reinforcement can be carried out by aging the corresponding surfaces at elevated temperature in an oxygen-containing environment or by wet-chemical treatment in oxidizing solutions.

11 shows an embodiment of a Schichtabfolgelaminats 10 ' with a component embedded therein and ankontaktkontaktten 30 , which is not deposited on a drain side of a substrate, but in a kind of symmetrical structure also on the side of the drain contact surface 38 having an Ankontaktierung invention.

Claims (18)

Method for contacting a component ( 30 ) in a circuit board layer sequence ( 10 ) comprising the following steps: - providing a component ( 30 ) with contact surfaces ( 34 . 36 . 38 ) of a non-copper metal material, - making a laminate laminate ( 10 embedded component, producing one or more holes (V1, V2, VL) in a surface of the laminate laminate ( 10 ) for at least partially exposing the contact surfaces ( 34 . 36 . 38 ) of the component ( 30 ), - treating oxide layers ( 35 . 37 ) on the exposed contact surfaces ( 34 . 36 ), - applying a base metal layer ( 40 ) and - performing a plating process for reinforcing the base metal layer ( 40 ) with a copper layer ( 42 ). The method of claim 1, including the step of performing a hole cleaning process prior to the step of treating. Method according to claim 1 or 2, wherein at least the steps of treating the oxide layers ( 35 . 37 ) and the application of the base metal layer ( 40 ) in a substantially oxygen-free or oxygen-poor and / or reduced pressure environment are performed. Method according to claim 1 or 2, wherein between the step of treating the oxide layers ( 35 . 37 ) and the application of the base metal layer ( 40 ) an adhesive layer is applied. Method according to one of claims 1 to 4, wherein the step of treating the oxide layers, the removal of the oxide layers ( 35 . 37 ). The method of claim 5, wherein the step of removing the oxide layers ( 35 . 37 ) is carried out by means of a back-sputtering process or by means of a reduction or by dissolving the oxide layer. Method according to one of claims 1 to 4, wherein the step of treating the oxide layers, the conditioning of the oxide layers ( 35 . 37 ). Method according to one of claims 1 to 7, wherein the application of the base metal layer ( 40 ) by means of plasma coating (plasma sputtering) or by means of a chemical or wet-chemical process. Method according to one of claims 1 to 8, wherein the base metal layer ( 40 ) has a thickness between about 200 nm and about 2 microns. Method according to one of claims 1 to 9, wherein prior to the step of applying the base metal layer ( 40 ) a conductive polymer is deposited. Method according to one of claims 1 to 10, wherein prior to the production of the laminate laminate ( 10 ) with embedded component ( 30 ) the oxide layers ( 35 . 37 ) on the non-copper pads ( 34 . 36 . 38 ) of the component ( 30 ). Printed circuit board with a printed circuit board layer construction ( 10 ) and incorporated therein component ( 30 ), wherein the component ( 30 ) at least one contact surface ( 34 . 36 . 38 ), which is contacted via at least one blind hole (V1, V2, VL), wherein the contact surface ( 34 . 36 . 38 ) in the region of the at least one vias (V1, V2, VL) has a layer of metallic material which is not copper, to which directly and without the presence of a metal oxide layer ( 35 . 37 ) a base metal layer ( 40 ), which is supported by electroplated copper ( 42 ) is reinforced. Printed circuit board according to claim 12, in which the base metal layer ( 40 ) is applied by means of plasma coating (plasma sputtering) or by means of a chemical or wet-chemical process. A printed circuit board according to claim 12 or 13, wherein the base metal layer ( 40 ) consists of copper, or in which the base metal layer ( 40 ) consists of a layer sequence comprising zinc and / or a conductive polymer. Printed circuit board according to one of Claims 12 to 14, in which the at least one contact surface ( 34 . 36 . 38 ) outside the region of the at least one vias (V1, V2, VL) on the layer of metallic material that is not copper, a metal oxide layer ( 35 . 37 ) having. Printed circuit board according to one of Claims 12 to 15, in which the base metal layer ( 40 ) has a thickness between about 200 nm and about 2 microns. Printed circuit board with a printed circuit board layer construction ( 10 ) and incorporated therein component ( 30 ), wherein the component ( 30 ) at least one contact surface ( 34 . 36 . 38 ), which is contacted via at least one blind hole (V1, V2, VL), wherein the contact surface ( 34 . 36 . 38 ) has in the region of the at least one vias (V1, V2, VL) a layer of metallic material which is not copper, which is followed by a conductive polymer formed by electrodeposited copper ( 42 ) is reinforced. A circuit board according to claim 17, wherein the base metal layer is nickel.

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