Machining tool for machining multilayer printed circuit boards

Abstract

The invention relates to a machining tool (1), said machining tool (1) having a substantially cylindrical main part (2), wherein the main part (2) comprises a shaft (3) and a cutting part (4) which allows the tool (1) to be precisely positioned directly on the workpiece as a starting point for a machining process. According to the invention, this is achieved in that at least the cutting part (4) is at least partly coated with an electrically conductive diamond coating (5).

Description

[0001] Cutting tool for machining multilayer printed circuit boards

[0002] The invention relates to a cutting tool which is particularly suitable for machining multi-layer printed circuit boards and / or for carrying out a deep drilling or contact drilling in printed circuit boards, a method for producing such a cutting tool and a method for machining a workpiece such as a multi-layer printed circuit board according to the preambles of claims 1, 13 and 15.

[0003] State of the art

[0004] Tool parts such as drills with diamond coating are known, for example, from DE 10 2019 216 199 Al.

[0005] In the printed circuit board industry, what is known as a deep drilling or contact drilling is often made in multi-layer printed circuit boards. The aim of this is to drill specifically into a layer of the multi-layer board in order to later place the required "chip" in the component. Due to the relatively thin thickness of the individual layers in the printed circuit board, positioning the spindle or tool relative to the board or its layers, i.e. precisely defining the zero point as the starting point for the actual drilling, via the machine control is not always possible due to the mechanical and manufacturing tolerances of the machine tool and the tolerances in the holder of the workpiece. If the zero point is not e.g.can be placed directly on the board, it can happen that the board is damaged when the cutting tool starts moving and before the actual machining or that the penetration depth of the tool into the workpiece is too great or too low, the desired layers in the board are not reached or undesired layers in the board are reached, etc.

[0006] According to the state of the art, precise machining when machining multi-layer printed circuit boards can be problematic due to manufacturing tolerances. Therefore, a different procedure is used on conventional machines to machine a workpiece such as a printed circuit board or a deep hole or contact bore: The cutting tool is first moved in the direction of the workpiece to be machined, with two electrodes of an interrupted contact circuit being attached to the cutting tool and the corresponding workpiece or to a specific conductive layer on the workpiece, so that when the tool comes into contact with the component the circuit is closed. The zero point for the further travel path for the actual machining of the workpiece is determined at the point at which contact is made and the circuit is closed.Therefore, simple conductive tools made of solid metal are used as cutting tools according to the state of the art.

[0007] Object and advantages of the invention

[0008] The object of the invention is to propose a cutting tool for deep and contact drilling in printed circuit boards, which enables faster and more precise, better quality machining of a workpiece with a longer service life.

[0009] This object is achieved by the features of claim 1, starting from a cutting tool of the type mentioned in the introduction. Advantageous embodiments and further developments of the invention are possible through the measures mentioned in the subclaims.

[0010] The cutting tool according to the invention enables precise positioning of the cutting tool directly on the workpiece as the starting point for machining, in order to perform the machining more precisely. Accordingly, a cutting tool according to the invention is characterized in that at least the cutting part is at least partially coated with an electrically conductive diamond coating.

[0011] The cutting tool itself has a base body comprising a shank and a cutting part. The shank and the cutting part can be arranged in longitudinal alignment with one another. The base body can be substantially cylindrical. The cutting tool is made of metal, steel, a metal alloy, or another suitable material. The cutting tool can be designed, for example, as a turning tool, drill, milling tool, or countersink drill.

[0012] Through these measures, the invention counters the technical prejudice that the cutting tool must not contain any electrically non-conductive components in the cutting part. Due to the inherent lack of electrical conductivity of previous CVD diamond coatings, such coatings were not even considered, i.e., deep drilling and contact drilling were previously only carried out with uncoated tools. The use of diamond-coated tools and the associated advantages, such as up to 50% higher cutting parameters and a 20-fold increase in tool life, is therefore only possible thanks to the invention.

[0013] The inventive combination of a cutting tool made of metal, preferably a solid carbide, with an electrically conductive diamond coating for machining a workpiece, such as contact drilling or deep milling in the printed circuit board industry, has both the advantages of the method mentioned and the advantages of a diamond drill: On the one hand, extremely precise drilling is possible thanks to an optimally set zero point on the printed circuit board, and on the other hand, the high hardness of the cutting tool not only provides extreme abrasion resistance and high thermal conductivity, but also the option of machining new and / or difficult-to-machine materials.

[0014] The high hardness of the diamond coating also ensures good sliding properties of the cutting tool and significant cost savings due to longer tool life, as well as high dimensional accuracy and process capability due to minimal tool wear. Furthermore, tool life can be increased, meaning the tool does not need to be replaced as frequently, resulting in cost advantages and enabling increased production.

[0015] In an advantageous embodiment, the diamond layer is made electrically conductive by adding boron.

[0016] The cutting part of the cutting tool is preferably spiral or straight. This enables precise machining of the workpiece. High precision is particularly important for multi-layer workpieces.

[0017] It is conceivable that the cutting tool is designed as a drilling tool or a milling tool. For these tool types, the combination with an electrically conductive diamond coating is particularly advantageous.

[0018] Advantageously, the cutting tool has an axis of rotation, wherein the axis of rotation is present in the longitudinal direction of the cutting tool.

[0019] It is conceivable that the diamond coating is formed in one, two, or more layers, so that the tool can be adapted to the intended purpose. Depending on the tool's requirements, the number of layers and the respective thicknesses of the layers can lead to different properties of the cutting tool, so that it can be optimally adapted to the intended purpose.

[0020] It can be advantageous if there is a space between the cutting part and

[0021] An intermediate layer is present between the diamond coating. This intermediate layer can, for example, make it easier to apply the diamond coating to the base body. Furthermore, the adhesive properties can be improved, so that the tool suffers less wear. It is also conceivable that intermediate layers are present between individual diamond layers.

[0022] The diamond coating is preferably nanocrystalline and / or multicrystalline. The electrical and thermodynamic properties of crystals depend on their size; through precise processing of the material, the extent of these properties can be controlled and adapted to the specific cutting tool.

[0023] Advantageously, the diamond coating is formed as a combination of two or more different diamond layers. Due to the different layers' characteristics, they exhibit different properties. The coating can be better adapted to the machining purpose or the workpiece to be machined.

[0024] A method according to the invention for producing a cutting tool as described above is characterized in that the diamond coating is applied to the base body by means of a chemical vapor deposition process. Chemical vapor deposition has the great advantage that it can even form the coating on complex or angled structures. It is also conceivable that a physical vapor deposition process could be used for the process.

[0025] Preferably, thermal activation in vapor deposition is carried out by hot filaments, which is suitable, for example, for the production of polycrystalline diamond layers.

[0026] A method according to the invention for machining a workpiece, in particular a printed circuit board, using a cutting tool as described above, in which in a first method step the cutting tool is moved in the direction of the workpiece, and in a second step an electrical circuit is closed when the cutting tool comes into contact with the workpiece, wherein the closing of the circuit determines the zero point for a travel path of the cutting tool in a subsequent machining method step, and in a third step the cutting tool is moved along the travel path from the zero point. In this way it can be ensured that the workpiece is not damaged by the cutting tool before the piece is machined.

[0027] If the cutting tool is moved onto the workpiece to be machined before machining, the aim is to bring the cutting tool into contact with the workpiece so that machining can then take place. Due to mechanical tolerances or tolerances in the alignment or exact thickness of the workpiece, simple positioning of the cutting tool using a machine control system is not always possible. If the cutting tool is stopped before contact occurs, the travel path of the cutting tool starts too early and machining, for example a hole would not penetrate deeply enough into the workpiece. On the other hand, if the cutting tool stops too late after contact with the workpiece, there is a risk of damage to the workpiece.

[0028] By applying a contact current to the cutting tool and the corresponding workpiece and the resulting circuit closure upon contact of the tool with the component, the cutting tool can be automatically stopped at exactly this point and the zero point for the further travel path for the actual machining of the workpiece can be optimally set. Figure description

[0029] An embodiment of the invention is shown in the drawing and is explained in more detail below with reference to the figures.

[0030] In detail:

[0031] Figure 1 shows a schematic structure of a cutting tool according to the invention and

[0032] Figure 2 shows a schematic representation of a method for machining a workpiece according to the invention.

[0033] Figure 1 shows a cutting tool 1 according to the invention. The cutting tool 1 has a base body 2 composed of a shank 3 and a cutting part 4. In the embodiment shown here, the cutting tool 1 also has a rotation axis D.

[0034] A diamond coating 5 is applied to a section of the cutting tool 1 by means of vapor deposition. In the illustrated embodiment, this diamond coating 5 completely covers the cutting part 4 and a section of the shaft 3. It is also conceivable for the diamond coating 5 to completely or partially cover the entire base body 2 or only the cutting part 4.

[0035] The diamond coating 5 can consist of one or more individual layers, which can be separated from one another or from the base body 2 by intermediate layers.

[0036] Figure 2 shows a schematic structure of a method for machining a workpiece 6 by a cutting tool 1. The cutting tool 1 is moved in the direction of the multi-layer workpiece 6

[0037] By applying a contact current to the cutting tool 1 and the corresponding workpiece 6, an electrical circuit 7 is closed when the tool comes into contact with an electrical contact on the workpiece 6, thereby causing the movement of the cutting tool 1 to stop. In this way, the zero point for the further travel path V for the actual machining of the workpiece 6 can be set precisely. The electrical circuit 7 is only shown schematically; it comprises a voltage source U and a measuring device (shown here as a simple ammeter 9), which indicates whether a current is flowing and whether contact has thus been made. One electrode of the open electrical circuit 7 is attached to the tool 1, the other to the corresponding position on the workpiece.

[0038] The volume of the workpiece 6 which is machined by the cutting tool 1 through the travel path V is shown in dotted lines.

[0039] Reference symbol list

[0040] 1 Cutting tool 2 Base body

[0041] 3 shaft

[0042] 4 Cutting part

[0043] 5 Diamond coating

[0044] 6 Workpiece 7 Circuit

[0045] 8 electrical contact

[0046] 9 ammeters

[0047] D Rotation axis U Voltage source

[0048] V travel path

Claims

Claims 1. Cutting tool (1), in particular for machining multi-layer printed circuit boards and / or for carrying out a deep drilling or contact drilling in printed circuit boards, wherein the cutting tool (1) has a substantially cylindrical base body (2), wherein the base body (2) comprises a shaft (3) and a cutting part (4), characterized in that at least the cutting part (4) is at least partially coated with an electrically conductive diamond coating (5), which preferably contains boron.

2. Cutting tool (1) according to claim 1, characterized in that the cutting part (4) is spiral or straight.

3. Cutting tool (1) according to one of the preceding claims, characterized in that the cutting tool (1) is designed as a drilling tool or as a milling tool.

4. Cutting tool (1) according to one of the preceding claims, characterized in that the cutting tool (2) has an axis of rotation (D), wherein the axis of rotation (D) is present in the longitudinal direction of the cutting tool (1).

5. Cutting tool (1) according to one of the preceding claims, characterized in that the diamond coating (5) is present in a single layer.

6. Cutting tool (1) according to one of the preceding claims, characterized in that the diamond coating (5) is formed in two or more layers.

7. Cutting tool (1) according to one of the preceding claims, characterized in that an intermediate layer is present between the base body (2) and the diamond coating (5).

8. Cutting tool (1) according to one of the preceding claims, characterized in that the diamond coating (5) is nanocrystalline and / or multicrystalline.

9. Cutting tool (1) according to one of the preceding claims, characterized in that the diamond coating (5) is formed as a combination of two or more different layers.

10. Cutting tool (1) according to one of the preceding claims, characterized in that the cutting tool (1) is electrically conductive: • on the section between the shaft (3) and the cutting part (4) and / or • on the section between the surface of the shaft (3) and the surface of the cutting part (4) .

11. Cutting tool (1) according to one of the preceding claims, obtainable by a method for producing the cutting tool (1), wherein a hot-wire-activated vapor deposition is used for the diamond coating and the thermal activation is carried out by hot filaments.

12. Cutting tool (1) according to one of claims 1-10, obtainable by a method for producing the cutting tool (1), wherein the diamond coating (5) is applied to the base body (2) by means of a chemical vapor deposition process.

13. A method for producing a cutting tool (1) according to claim 11, characterized in that the diamond coating (5) is applied to the base body (2) by means of a chemical vapor deposition process.

14. A method for producing a cutting tool (1) according to claim 12, characterized in that a hot-wire activated vapor deposition is used for diamond coating and the thermal activation is carried out by hot filaments.

15. Method for machining a workpiece (6), in particular a printed circuit board, preferably for performing a deep drilling or contact drilling in multi-layer printed circuit boards, • wherein a cutting tool (1) according to one of claims 1-12 is used for machining the workpiece (6), • wherein in a first process step the cutting tool (1) is moved in the direction of the workpiece (6), • wherein in a second step, an electrical circuit (7) is closed upon contact of the cutting tool (1) with the workpiece (6) and / or with a conductive layer of the circuit board, • whereby the zero point for a travel path (V) of the cutting tool (1) is determined in a subsequent machining step by closing the circuit (7), • wherein in a third step the cutting tool (1) is moved along the travel path (V) from the zero point.

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