CH719440A2 - Method for producing a multilayer printed circuit board with a blind hole contact and multilayer printed circuit board. - Google Patents

Abstract

The invention relates to a method for producing a multi-layer printed circuit board (1) with a blind hole contact (15), comprising: providing a multi-layer printed circuit board (1); Producing a blind hole recess in the multilayer printed circuit board (1) in the area of an external conductor section (2) up to an internal conductor section (6) through at least one insulating layer and depositing an electrically conductive contact material to form a blind hole contact (15) in the blind hole recess, such that the electrically conductive contact material covers wall sections of the blind hole recess and thus an electrical contact is formed between the outer conductor section (2) and the inner conductor section (6). The blind hole recess is produced by means of an at least two-stage method according to the invention, in which in a first process step a blind hole is formed by means of mechanical drilling and in a second process step the blind hole is expanded to produce the blind hole recess using laser machining. Furthermore, a multi-layer printed circuit board (1) according to the invention is created.

Description

The invention relates to a method for producing a multi-layer printed circuit board with a blind hole contact and a multi-layer printed circuit board.

background

Multilayer printed circuit boards have multiple conductor layers or layers that are electrically separated from one another in a stacked arrangement by insulating layers or layers. In addition to external conductor layers, which are formed on opposite outer sides of the multilayer printed circuit board, the conductor layers also regularly include internal conductor layers, which are embedded in the insulating material in the circuit board body in the area between the external conductor layers.

Different types of (through) contacts can be provided in the multilayer printed circuit board. These include, for example, through-hole contacts, in which a through-hole is formed through the circuit board body, the wall of which is provided with a coating of electrically conductive material to form the electrical contact. Alternatively or additionally, blind hole contacts can be provided, which are also referred to as “blind vias”. Here, a blind hole recess is formed and provided on the wall side with electrically conductive material in order to usually form a contact between one of the external conductor layers and an internal conductor section. Alternative techniques are known for producing the through hole or the blind hole recess. It can be provided that the through opening for the through contact or the recess for the blind hole contact is produced by means of (mechanical) drilling. Alternatively, laser machining can be used to produce the through hole or blind hole recess. The electrically conductive contact material is then deposited on the wall of the depression/through opening produced, in particular galvanically, in order to form the electrical contact.

Summary

The object of the invention is to provide a method for producing a multi-layer printed circuit board with a blind hole contact and a multi-layer printed circuit board with which the blind hole contact can be produced in a flexible design.

To solve this, a method for producing a multi-layer printed circuit board with a blind hole contact and a multi-layer printed circuit board according to independent claims 1 and 14 are created. Refinements are the subject of dependent subclaims.

According to one aspect, a method for producing a multilayer printed circuit board with a blind hole contact is provided, which comprises: providing a multilayer printed circuit board; Producing a blind hole recess in the multi-layer printed circuit board in the area of an external conductor section up to an internal conductor section through at least one insulating layer and depositing an electrically conductive contact material to form a blind hole contact in the blind hole recess, such that the electrically conductive Contact material covers wall sections of the blind hole recess and so an electrical contact is formed between the outer conductor section and the inner conductor section. The blind hole recess is produced using an at least two-stage process, in which in a first process step a blind hole is formed by means of mechanical drilling and in a second process step the blind hole is expanded to produce the blind hole recess using laser machining.

According to a further aspect, a multi-layer printed circuit board is created which has a blind hole contact, which is formed in a blind hole recess as an electrical contact between an external conductor section and an internal conductor section through at least one insulating layer, wherein the blind hole -Recess is formed with a blind hole recess section which is proximal in relation to the outer conductor section and is designed with a blind hole, and a blind hole recess section which is distal in relation to the outer conductor section and which is designed with a laser via.

[0008] The recess for the blind hole contact (“blind via”) is produced in a multi-stage process in which a blind hole is first made using mechanical drilling and then the blind hole recess is created in the desired shape using laser processing to produce, whereupon the electrically conductive contact material can then be deposited on the wall sections of the blind hole recess, for example by means of a galvanic deposition process. In one embodiment, copper is used as the electrically conductive contact material.

The external and internal conductor sections, which are connected to one another in an electrically conductive manner using the blind hole contact, can be part of an external and an internal conductor layer or layer, which are electrically insulated from one another by means of the at least one insulating layer.

The initially planned production of the blind hole using a drilling process and the subsequent production of the blind hole recess by expanding the blind hole using laser machining enables flexible and efficient formation of the desired blind hole depending on the desired application. A blind hole recess is created which, in relation to the external conductor section, has a proximal blind hole recess section, produced as a blind hole, and a blind hole recess section which is distal in relation to the external conductor section. The blind hole recess section extends to the inner conductor section, which is also referred to as the “landing pad”. In this way, it can be achieved in particular to design the shape and size of the blind hole recess in such a way that the desired material distribution of the electrically conductive contact material is supported during the subsequent deposition in the area of the wall sections of the blind hole recess.

In the second process step, the blind hole can be further deepened using laser processing. Here, the blind hole is produced with a first hole depth, which is then enlarged in the further process step by means of laser processing to a larger second hole depth in order to form the desired blind hole recess.

The blind hole formed in the first process step can end in the at least one insulating layer at a distance from the inner conductor section and can be expanded in the second process step by means of laser processing up to the inner conductor section. In order to avoid possible damage to the internal conductor section due to the drilling process, the blind hole ends here within the insulating layer, which is arranged over the internal conductor section. With the help of laser processing, the blind hole is then expanded, in particular deepened, up to the inner conductor section to the desired blind hole recess.

For the blind hole recess, in the first method step a blind hole recess section that is proximal with respect to the external conductor sections can be formed with a first cross section and in the second method step a blind hole recess section that is distal with respect to the external conductor section and has a second cross section can be formed , which is less than or equal to the first cross section. With the help of the different cross-sectional design for the proximal and distal blind hole recess sections, for example, a desired aspect ratio can be set depending on the application. The aspect ratio for the blind hole recess refers to the ratio of diameter (of the recess) to depth (or height of the recess).

Before the second method step, the blind hole can be measured or determined in a measuring step using a measuring device, in particular the position of the blind hole in the area of the external conductor section (xy plane) and / or a hole cross section, and the laser processing can within the blind hole with regard to the local formation of the expansion of the blind hole depending on the result of the measuring step. With the help of the measuring device, the blind hole is measured or calibrated, whereupon the laser processing device can then be positioned exactly in relation to the blind hole in order to carry out the laser processing within the blind hole in the desired manner, for example the expansion (recess) of the blind hole in relation to the cross section of the blind hole previously produced by drilling in a selected cross-sectional area in the bottom of the blind hole. The measuring device can be integrated with the laser processing device or designed separately from it.

Optionally, in various embodiments, after producing the blind hole, a step for checking or testing the blind hole produced can be carried out using a testing device, for example an optical test, in order to ensure that the blind hole is correctly formed in terms of shape and/or or depth to check. It can be provided to carry out the subsequent laser processing depending on the result of the test, for example to adjust the expansion/deepening to be produced by laser processing depending on the result of the test of the blind hole.

[0016] The expansion of the blind hole for producing the blind hole recess can be produced essentially centrally in relation to the cross section of the blind hole by means of laser machining.

In the method, a multi-layer printed circuit board can be provided in which the external conductor section has a layer thickness of at least approximately 15 μm, preferably at least approximately 18 μm.

In the method, a multi-layer printed circuit board can be provided in which, after the blind hole contact has been made, an insulation thickness below the internal conductor section in the area of the blind hole recess is less than approximately 200 μm, preferably less than approximately 150 μm.

In the method, a multi-layer printed circuit board can be provided in which a printed circuit board layer section, which borders on the one hand on the outer layer and on the opposite side on the inner conductor section and through which the blind hole recess is formed, has a layer thickness of at least approximately 100 μm , preferably of at least about 125 μm and more preferably of at least about 150 μm. The circuit board layer section can be designed as an insulating layer. In one embodiment, one or more internal conductor sections are embedded in the insulating material of the circuit board layer section.

The blind hole recess can be formed through one or more internal conductor sections and several insulating layers. The blind hole contact extends here through one or more internal conductor sections to the internal conductor section to be contacted and through several insulating layers. Contact is then also made between the broken internal conductor sections.

[0021] It can be provided that the blind hole is formed in the first method step by at least a first of the plurality of internal conductor sections and in the second method step for producing the blind hole recess by means of laser processing is expanded through at least a second of the plurality of internal conductor sections. During the step-by-step formation of the blind hole, in this exemplary embodiment both the drilling when producing the blind hole and the laser processing when expanding, in particular deepening, the blind hole to the blind hole break through at least one of the inner conductor sections.

The wall sections of the blind hole recess can be essentially completely covered by the electrically conductive contact material when it is deposited.

The blind hole recess can be produced with an aspect ratio (diameter: height) of ≥ 1:1.

The configurations explained above in connection with the method for producing the multilayer printed circuit board with blind hole contacting can be provided accordingly in connection with the multilayer printed circuit board.

Description of exemplary embodiments

Further exemplary embodiments are explained below with reference to figures in a drawing. Here show: FIG. 1 a schematic representation of a section of a multi-layer printed circuit board in section; Fig. 2 is a schematic representation of the section of the multi-layer printed circuit board from Fig. 1, wherein a blind hole is formed; 3 shows a schematic representation of the section of the multi-layer printed circuit board from FIG. 1, wherein the blind hole is expanded into a blind hole recess by means of laser processing; 4 shows a schematic representation of the section of the multi-layer printed circuit board from FIG. 1, with a blind hole contact being formed in the blind hole recess between an external and an internal conductor section; and FIG. 5 shows a schematic representation in section of a section of a further multi-layer printed circuit board, in which a blind hole via is formed through an internal conductor layer.

A method for producing a multi-layer printed circuit board with a blind hole contact is described below with reference to FIGS. 1 to 4. A section of a multi-layer printed circuit board 1 is shown in section. In the case of the multi-layer printed circuit board 1, external conductor sections 2, 3 are provided on the top and bottom, which can be part of external conductor layers or layers. Furthermore, a circuit board body 4 has insulating layers or layers 5, in which an internal conductor section 6 and a further internal conductor section 7 are embedded. The further internal conductor section 7 extends into an area below the internal conductor section 6 and is electrically insulated from it by means of an insulating material section 8.

To produce a blind hole contact between the external conductor section 2 and the internal conductor section 6, a blind hole 10 is produced above the internal conductor section 6 using a drilling device 9, as shown in FIG.

3, it is then provided in a further method step to deepen the blind hole 10, which is carried out by laser machining using a laser machining device 11, so that a blind hole recess 12 is formed. The blind hole recess 12 has, in relation to the outer conductor section 2, a proximal blind hole recess section 13 and a distal blind hole recess section 14, the latter being designed as a laser via and extending up to the inner conductor section 6. A diameter of the proximal blind hole recess section 13 is greater than or equal to the diameter of the distal blind hole recess section 14.

It can optionally be provided that the blind hole 10 produced is measured or checked before laser processing using a measuring device (not shown), for example by means of an optical measurement. The result of the measurement can optionally be used to position the laser processing device 11 relative to the blind hole 10, for example for centrally producing the distal blind hole recess section 14 in the blind hole 10.

To form a blind hole contact 15, electrically conductive contact material is then deposited on wall sections 17 of the blind hole recess 12 using a deposition device 16 as shown in FIG.

5 shows a schematic representation of a section of another multi-layer printed circuit board 20 with the blind hole contact 15, which, in contrast to the embodiments in FIGS. 1 to 4, is formed through an additional internal conductor section 21. In Fig. 5, the same reference numbers as in Figs. 1 to 4 are used for the same features.

The features disclosed in the above description, the claims and the drawing can be important both individually and in any combination for the realization of the various designs.

Claims (14)

1. Method for producing a multi-layer printed circuit board (1; 20) with a blind hole contact (15), with - Providing a multi-layer printed circuit board (1; 20); - Producing a blind hole recess (12) in the multi-layer printed circuit board (1; 20) in the area of an external conductor section (2) up to an internal conductor section (6) through at least one insulating layer and - Depositing an electrically conductive contact material to form a blind hole contact (15) in the blind hole recess (12), such that the electrically conductive contact material covers wall sections of the blind hole recess (12) and thus creates electrical contact between the external conductor section ( 2) and the inner conductor section (6); wherein the blind hole recess (12) is produced by means of an at least two-stage process, in which in a first process step a blind hole (10) is formed by means of mechanical drilling and in a second process step the blind hole (10) is used to produce the blind hole. Deepening (12) is expanded using laser processing. 2. The method according to claim 1, characterized in that in the second process step the blind hole (10) is further deepened by means of laser processing. 3. The method according to claim 1 or 2, characterized in that the blind hole (10) formed in the first method step - ends in the at least one insulating layer spaced from the internal conductor section (6) and - In the second process step, using laser processing, it is expanded up to the inner conductor section (6). 4. Method according to at least one of the preceding claims, characterized in that for the blind hole recess (12) - In the first method step, a blind hole recess section (13) which is proximal in relation to the external conductor section (2) and has a first cross section and - In the second method step, a blind hole recess section (14) distal with respect to the external conductor section is formed with a second cross section, which is less than or equal to the first cross section. 5. The method according to at least one of the preceding claims, characterized in that before the second method step, the blind hole (10) is measured in a measuring step using a measuring device and the laser processing within the blind hole (10) with regard to the local formation of the expansion the blind hole (10) is carried out depending on the result of the measuring step. 6. The method according to at least one of the preceding claims, characterized in that the expansion of the blind hole (10) for producing the blind hole recess (12) is produced essentially centrally in relation to the blind hole (10) by means of laser processing . 7. The method according to at least one of the preceding claims, characterized in that a multi-layer printed circuit board (1; 20) is provided, in which the external conductor section (2) has a layer thickness of at least approximately 15 µm, preferably of at least approximately 18 µm. 8. The method according to at least one of the preceding claims, characterized in that a multi-layer printed circuit board (1; 20) is provided, in which, after the blind hole contact (15) has been made, below the internal conductor section (6) in the area of the blind hole Depression (12) has an insulation thickness smaller than about 0.20 mm, preferably smaller than about 0.15 mm. 9. The method according to at least one of the preceding claims, characterized in that a multi-layer printed circuit board is provided, in which a printed circuit board layer section which borders on the one hand on the outer layer (2) and on the opposite side on the inner conductor section (6) and through which the Blind hole recess (12) is formed, has a layer thickness of at least about 100 μm, preferably of at least about 125 μm and more preferably of at least about 150 μm. 10. The method according to at least one of the preceding claims, characterized in that the blind hole recess (12) is formed through one or more internal conductor sections (21) and several insulating layers. 11. The method according to claim 10, characterized in that the blind hole (10) - formed in the first method step by at least a first of the several internal conductor sections and - In the second method step for producing the blind hole recess (12) is expanded by means of laser processing through at least a second of the plurality of internal conductor sections. 12. The method according to at least one of the preceding claims, characterized in that the wall sections (17) of the blind hole recess (12) are essentially completely covered by the electrically conductive contact material when it is deposited. 13. The method according to at least one of the preceding claims, characterized in that the blind hole recess (12) is produced with an aspect ratio (diameter: height) of ≥ 1: 1. 14. Multi-layer printed circuit board (1; 20), in particular produced according to a method according to at least one of the preceding claims, having a blind hole contact (15) which is in a blind hole recess (12) as an electrical contact between an external conductor section ( 2) and an internal conductor section (6) is formed through at least one insulating layer, with the blind hole recess (12). - A blind hole recess section (13) which is proximal in relation to the external conductor section (2), and which is designed with a blind hole (10), and - A blind hole recess section (14) distal in relation to the external conductor section (2) is formed, which is designed with a laser via.