DE102010048036A1 - Printed circuit board for use in electronic device, such as medical device or electronic component, has one or multiple wiring layers and protection device - Google Patents

Abstract

The printed circuit board (1) has one or multiple wiring layers (4) and a protection device. A layered protective element (5) is arranged on a wiring layer between two electrical wiring cables on the basis of an intrinsically conductive electric polymer. The electric protective element is electrically measured in form of a resistor between the both wiring cables. The protective element is made of polymers. An independent claim is also included for a method for manufacturing a printed circuit board with integrated protection device.

Description

The invention relates to a printed circuit board with at least one integrated protection device against unwanted replica, a manufacturing method and the application for the construction of an electronic device, such as a medical device or an electronic assembly with high security requirements with protection against replication.

Circuit board technologies and methods for manufacturing a printed circuit board and printed circuit board materials are subject to standardization worldwide by the IPC organization ( www.ipc.org ) is perceived. Through and with this organization or the standards adopted by this organization, design rules and printed circuit boards as such and their assembly, including all quality and tolerance matters, should be brought to a standard that is as uniform as possible worldwide. The disadvantage of any standardization lies in the simple undesired or unauthorized copying or the replica of the circuit board.

In the DE 10 2008 018 221 A1 Hankofer et al (Infineon Technologies AG, "Protection for Circuit Boards", filing date: 10.04.2008) is an integrated circuit device with an anti-engagement device, which is attached by means of an external contact to a circuit board, the anti-engagement device is connectable to the external contact, to switch the integrated circuit device to a safe mode upon application of a predetermined electrical condition at the external contact. There is stated in claim 4, that the electrical state of a resistor, a capacitance and / or inductance depends on the external contact.

However, the attachment of an anti-engagement device is easy to identify in an unwanted replica of the circuit board and therefore also easy to copy.

The US 7 180 008 B2 and US Pat. No. 7,457,547 B2 describe a completely covering a layer of a multilayer printed circuit protective layer. However, this is expensive and incidentally, the protective layer can be easily identified when splitting the layers.

It is also known to increase the anti-counterfeiting security of a circuit board to label this with a laser engraving. Such engraving, however, is easily identifiable by scanning the circuit board with high energy beams (X-rays, alpha, beta or gamma rays, as well as magnetic field analysis (MRI)).

The invention is therefore the object of developing a copy protection for a printed circuit board so that it can not be discovered in an attempted replica - or only with the use of exceptional - tools, so as to complicate an undesirable replica of the circuit board.

To solve the problem, the invention is characterized by the technical teaching of the independent claims.

An essential feature of the invention is that at least one additional layer-like protective element based on an intrinsically conductive polymer is arranged on at least one wiring level of the printed circuit board between at least two electrical wiring lines and this protective element is electrically formed in the form of a resistor.

However, the training as a resistance does not exclude that this protective element additionally has measurable and evaluable inductive, capacitive or magnetic properties that can be pulled to check the originality of a circuit board zoom.

So far intrinsically conductive polymers have become known for the corrosion protection of iron materials. They form a class of materials within the polymers, which are characterized by a switchability between a neutral and the oxidized state.

In the neutral state, the monomers form a linear chain of conjugated double bonds at regular 2,5-linkage; the material shows properties analogous to inorganic semiconductors in this form.

In oxidized form, in which up to about one third of the monomers are oxidized, anions are incorporated into the framework for charge compensation. This form shows conductivity close to the values of metals. Because of this property, intrinsic polymers are also called "synthetic metals".

It is therefore crucial to the conversion between neutral and oxidized form. Such a transformation can be detected, for example, by the example of the polymer called polythiophene.

In principle, the polymerization is carried out oxidatively. This can be done electrochemically or chemically using a suitable oxidizing agent. First, soluble oligomers are formed, which after reaching a relatively low Chain length (20-30 monomers) precipitate by forming suspensions or crystallizing on defects of the surface of the circuit board. Thus, the polymers undergo an unrepeatable construction on the printed circuit board, because they react with characteristic defects on the specific application location of the individual printed circuit board and depending on the characteristic defects of the individual printed circuit board at the application their special and thus for the PCB individual conductivity - only for this special application area - unfold.

The layers thus formed are voluminous, porous and of disordered structure by this formation process. In order to achieve the formation of dense and well-adherent layers, adhesion promoters have been developed which are integrated into the printing ink. Such adhesion promoters consist of a bond group attached to the surface of the printed circuit board, a - (CH 2) N chain as a spacer group and the thiophene as a head group. One such example is 11- (3-thienyl) and acrylicthrichlorosilane (TUTS). With these molecules, it was possible to form monomolecular layers of the primer molecule on various nonconductive circuit board surfaces, which initially only partially cover the surface, but gradually form a spot-like closed (dot-like or bar-shaped) layer which has a characteristic conductivity thanks to the individually fissured Deployed surface of the circuit board at the application and form a conductive oxide layer. The size of the layer should be chosen so that it is suitable for the conductive bridging (resistance bridging) of two adjacent interconnects.

Thus, a unique and unique fingerprint of the printed circuit board is created at the point of application for deployment of a unique intrinsic conductivity characteristic of that location because the submicron surface defects of each printed circuit board are different with respect to the same location.

Such a tamper-evident feature is therefore not reproducible. It is also unidentifiable thanks to the other properties of the intrinsic polymers with high-energy rays (X-ray, laser, alpha, beta, gamma rays, magnetic fields).

The inventive integration of the polymer into a coupling agent provides excellent protection against delamination. So it can only be removed by destruction, which also destroys its electrical properties. Thus, it loses its bond to the place of application on the circuit board and the there given, characteristic (submicron) defects on the surface of the circuit board, which change its conductivity characteristically. If it is applied to a different location of the circuit board, there are other surface defects and it gets a different conductivity. A counterfeiting trial is thus easy to prove.

Hereinafter, the above-described intrinsic polymer will be referred to as a "protective element".

In the present invention, a protective element with a resistance or a capacitance or both is described, however, this protective element for x-ray analysis is largely invisible and also formed largely untraceable for a chemical or mechanical attack.

The protective element can be positioned very accurately positioned, for example by means of inkjet or dispenser or other application method, between two conductor tracks, wherein the protective element is locally brought into electrically conductive contact at least with the conductor tracks or optionally also covers the conductor tracks. Depending on the material used so that the resistance or capacitance between two tracks can be changed and thus this change can be recorded by means of electrical test. This electrical change is used as a safety feature in an electronic circuit sense of resistance or capacitance.

When replicating an electronic circuit, among other things, the circuit board must be analyzed. In a multilayer printed circuit board this can be done non-destructively by X-ray analysis. In principle, the individual layers of a multilayer can also be separated and analyzed chemically or mechanically.

For the purpose of generating an electrically measurable value, the protective element must have a specific electrical conductivity or have a different dielectric constant than conventional printed circuit board insulation materials.

In both cases, the material is not visible in X-radiation, preferably using very thin layer-like protective elements of small lateral extent and extremely small thickness.

Conventional printed conductor structures on or in printed circuit boards have a thickness of 35 μm or 18 μm or a thickness of 8 to 9 μm and are predominantly made of copper and are used structured by means of etching technology. Here are 100 microns trace width and trace spacing already Fine structures and can be generated with a very thin copper layer in the range of some 6 to 9 microns and structures of a few 10 microns trace width / trace spacing.

Depending on the printed circuit board layout, such small protective elements can now be arranged between at least two printed conductors or printed conductor elements, and a measurable electrical value between these printed conductor elements is changed. This change is controlled in a suitable electronic circuit or measured or compared and used as copy protection.

The subject of the present invention results not only from the subject matter of the individual claims, but also from the combination of the individual claims with each other.

All information and features disclosed in the documents, including the abstract, in particular the spatial design shown in the drawings, are claimed to be essential to the invention insofar as they are novel individually or in combination with respect to the prior art.

In the following, the invention will be explained in more detail with reference to drawings illustrating several execution paths. Here are from the drawings and their description further features essential to the invention and advantages of the invention.

Show it:

1 : the schematic plan view of a multiple use ( 3 ) with protective elements ( 5 )

2 FIG. 2: the schematic section AB through a wiring plane (FIG. 4 )

3 FIG. 2: the schematic section AB through a wiring plane (FIG. 4 ) in an enlarged view,

4 : the schematic section AB through a multilayer ( 9 ).

In 1 is the schematic plan view of a multiple use ( 3 ) of printed circuit boards with protective elements ( 5 ). In the printed circuit board industry usually multiple benefits ( 3 ) with dimensions of typically 610 × 610 mm or with 510 mm or 350 mm edge lengths, with large formats of 635 mm or 710 mm edge length to small formats with 250 mm edge length or even larger or smaller formats are used.

These multiple benefits ( 3 ) are usually already used in printed circuit board production in equipping ( 2 ) separated and final tested. The final test usually includes a 100% electrical function check. The placement benefit ( 2 ) is equipped with a component mounter with the appropriate components and then in single-use ( 1 ) separated.

The present invention relates essentially to multilayers ( 9 ) Printed circuit boards, ie on printed circuit boards with several wiring levels consisting of inner layers ( 13 ) and outer layers ( 14 ).

According to the invention is now on an inner layer ( 4 ) between two wiring elements ( 6 . 7 ) a protective element ( 5 ) with the defined protection element length ( 15 ) arranged. Basically, such internal wiring elements ( 6 . 7 ) by means of plated-through holes ( 10 ) to other wiring elements, in particular to external wiring elements ( 12 ) electrically connected. This via ( 10 ) is only to be understood as an example, since the electrical connection of the wiring elements ( 6 . 7 ) can also be done with blind holes to other wiring levels or with a via to another inner layer structure ( 11 ).

In 2 FIG. 12 is a schematic section AB through a wiring plane (FIG. 4 ). In this schematic sectional view, only the inner layer ( 4 ) with the two wiring structures ( 6 . 7 ) and the protective element ( 5 ). The distance ( 8th ) of the two wiring lines ( 6 . 7 ) to each other and the length ( 15 ) define the protection element ( 5 ), wherein for electrical contacting of the protective element ( 5 ) with the wiring lines ( 6 . 7 ) a certain overlap of the wiring lines ( 6 . 7 ) necessary is. Usual wiring lines ( 6 . 7 ) are made by etching technique from full-surface copper foils on the corresponding inner layers ( 4 etched). As copper foil thicknesses 36 microns or 18 microns or even 9 microns or 70 microns are used and in principle, other thicknesses can be used.

The protective element ( 5 ) is applied in a first embodiment by means of screen printing and in a second embodiment digitally controlled by means of dispenser or ink jet or aerosol jet. As protective element ( 5 ) Material, an intrinsically electrically conductive polymer is preferably used, for example the polythiophene mentioned in the introduction or a polyacetylene or polyaniline or polyparaphenylene or polypyrrole or polythiophene or polyphenylene or poly (phenylene-sulfide) or poly (phenylenevinylene) or polypyrene or polyazepine or polyfulvene or polydophenine.

For all the intrinsic polymers mentioned here, the properties mentioned in the general description apply.

By way of example, a polyaniline-based inkjet ink from Ormecon-Enthone-Cookson with the designation Ormecon 7904-002-034i with a conductivity of up to 150 S / cm or a PEDT-based inkjet ink from HCStarck named Clevios ^™ P Jet N or P Jet HC poly (3,4-ethylenedioxythiophene) poly (styrene sulfonates) having a conductivity in the range 30 to 90 S / cm called.

The application of the protective element ( 5 ) is performed such that a correspondingly measurable resistance of a few ohms to a few kOhms, typically in the range of a few tens to a few 100 ohms, can be measured as electrical resistance by the protective element.

After the application is formed at the place of application on the circuit board with the existing there in submicron defects on the circuit board a characteristic only for this application site resistance of the protective element. This characteristic resistance thus also changes the resistance, the current flow or other electrical properties of the conductor tracks of the printed circuit board which are locally covered by the protective element. This change in the electrical properties of the tracks used for the measurement then forms the characteristic (unique and no longer reproducible) "fingerprint" of the entire printed circuit board.

The measurement and logging can be done at the 10% final electrical check. Because every single benefit ( 1 ) is detected metrologically, can be used per individual benefit and a digitally controlled individual ohmic Widerstrand, measured and logged and of course also be used later in the assembly of electrical or electronic components for a copy protection function.

The application of the protective element ( 5 ) must further be such that the electrical contacts to the line structures ( 6 . 7 ) are consistent. In the application of the protective element ( 5 ) by screen printing usually much larger layer thicknesses of the intrinsically conductive polymer are applied compared with an inkjet or dispenser application.

By screen printing, layer thicknesses of a few 5 .mu.m to more than 20 .mu.m are used, and less than 2 .mu.m to less than 1 .mu.m in the case of inkjet printing. By means of a dispenser, an almost arbitrarily thick protective element ( 5 ) are applied to submicron layer thicknesses.

For the InkJet application and for the dispenser application of the protective element ( 5 ) can furthermore be located in the edge region of the conductor structures ( 6 . 7 ) made of copper, a multiple-material application and it can be achieved secured the edge coverage of the copper structure.

For the copy protection function is a thinner layer thickness of advantage, since this is generally less easy to find.

Experiments have shown that conventional inkjet and dispenser-capable intrinsically conductive polymers are not visible in an inner layer of a multilayer printed circuit board using X-ray analysis.

Even when applied by screen printing, the non-visibility of the protective element ( 5 ) in an X-ray analysis, however, screen printing does not allow any individual resistance values to be obtained as in the case of inkjet and dispenser application by varying the layer thickness or the protective element length (FIG. 15 ) getting produced.

In 3 FIG. 12 is a schematic section AB through a wiring plane (FIG. 4 ) shown in an enlarged view. The distance ( 8th ) of the two interconnect structures ( 6 . 7 ) is in the range of 30 to 500 microns, in particular in the range of 80 microns to 200 microns and the coverage of the protective element ( 5 ) on the two interconnect structures ( 6 . 7 ) is some 10 to 200 microns and is typically about half the width of the tracks ( 6 . 7 ). Also in this schematic sectional view is only an inner layer ( 4 ).

In 4 is a schematic section AB through a multilayer ( 9 ). In this example, three inner layers ( 13 ) and two outer layers ( 14 ) with the inner layer copper structures ( 11 ) and the outer layer copper structures ( 12 ). The wiring structures ( 6 . 7 ), the corresponding inner layer copper structure ( 11 ) by at least two vias ( 10 ) with the outer layer structure ( 12 ) connected.

In principle, blind hole contacts or inner layer contacts can also be used. In all cases, the at least one protective element ( 5 ) in an inner layer ( 4 ) electrically conductive with the outer layer structure ( 12 ) and can thus be electrically contacted and the ohm value measured and recorded and used in a subsequent component assembly for the establishment of a copy protection function.

Instead of using an intrinsically conductive polymer, that is, the use of a resistor in the range of 10 ohms to about 1,000 or 2,000 ohms, a capacitive element can be used in a development of the invention, which is not found in X-Ray radiation.

LIST OF REFERENCE NUMBERS

1

PCB single use

2

PCB double use (assembly benefit)

3

Multiple benefits (PCB manufacturing benefits)

4

wiring level

5

Protective element: self-supporting or non-self-supporting layered

6

First wiring line

7

Second wiring line

8th

Distance between the two wiring lines

9

Multilayer: multilayer printed circuit board

10

via

11

Innerlayer copper structure

12

Backsheet copper structure

13

inner layer

14

backsheet

15

Protective element length

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008018221 A1 [0003]
• US 7180008 B2 [0005]
• US 7457547 B2 [0005]

Cited non-patent literature

• www.ipc.org [0002]

Claims (12)

Printed circuit board with one or more wiring levels and a protective device against replication, characterized in that at least one layer-like protective element based on an intrinsically conductive polymer is arranged in an electrically conductive manner between at least two electrical wiring lines on a wiring plane. Printed circuit board according to claim 1, characterized in that the protective element is electrically measurable electrically in the form of a resistor between the at least two wiring lines. Printed circuit board according to claim 1 or 2, characterized in that the protective element is not identifiable by a radiation analysis with rays such as X-rays, alpha, beta, gamma rays. Printed circuit board according to one of claims 1 to 3, characterized in that the at least one additional self-supporting or non-self-supporting layer-like protective element between at least two electrical wiring lines of an inner layer or an outer layer, in particular an inner layer is arranged and is arranged in multiple use. Printed circuit board according to one of claims 1 to 4, characterized in that the protective element by means of inkjet printing system or dispenser-Appliziersystem or by means of Transfer-Appliziersystem is arranged individually for the benefit of a multiple use. Printed circuit board according to one of claims 1 to 4, characterized in that the protective element is arranged by means of screen printing technology or stencil printing or inkjet printing system or dispenser-Appliziersystem or by means of Transfer-Appliziersystem at the same positions of a multiple use. Printed circuit board according to one of claims 1 to 5, characterized in that the material of the protective element consists of intrinsically conductive polymers. Printed circuit board according to one of claims 1 to 6, characterized in that the protective element generates an electrical resistance between at least two electrical wiring lines of a wiring level and locally has a few mm dimensions, in particular only the distance between two conductor tracks piecewise covered. Printed circuit board according to one of claims 1 to 7, characterized in that the protective element polymerized during application on the circuit board and thereby reacts with characteristic defects on the specific application of the circuit board and depending on the characteristic defects of the individual circuit board at the application his special and thus for the printed circuit board individual conductivity - only for this special application area - unfolds. Printed circuit board according to one of claims 1 to 8, characterized in that the protective element formed as a polymer is incorporated in a bonding agent which undergoes an electrical bond on the printed circuit board and the covered printed conductors during the polymerization. Method for producing a printed circuit board with integrated protective device against replication according to one of claims 1 to 9, characterized in that the protective element is applied in multiple use and the electrical parameter resistance in the final electrical test in Plückungsutzen determined and logged and as a copy protection feature in the electronic components equipped printed circuit board is used. Application of a printed circuit board with built-in protective device manufactured according to one or more of the preceding claims for the construction of an electronic device, such as a medical device or an electronic assembly with high security requirements and thus the protection against reproduction.

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