CN116095985A

CN116095985A - Back drilling method of printed circuit board and printed circuit board

Info

Publication number: CN116095985A
Application number: CN202211648548.8A
Authority: CN
Inventors: 蓝春华; 唐心权; 刘小伟
Original assignee: Kinwong Electronic Technology Longchuan Co Ltd
Current assignee: Kinwong Electronic Technology Longchuan Co Ltd
Priority date: 2022-12-19
Filing date: 2022-12-19
Publication date: 2023-05-09

Abstract

The application relates to the technical field of circuit boards and discloses a back drilling method of a printed circuit board and the printed circuit board. The back drilling method comprises the following steps: providing a multilayer board; manufacturing a metallized through hole on the multilayer board, wherein a copper layer is attached to the wall of the metallized through hole; manufacturing a tin layer on the hole wall, and enabling the tin layer to cover the copper layer; carrying out depth control back drilling on the metallized through holes to remove part of the copper layer and the tin layer, wherein the depth of the depth control back drilling is controlled between the inner layer circuits from the Nth layer to the N+1th layer, and back drilling stubs are reserved between the inner layer circuits from the Nth layer to the N+1th layer; removing the back drilling residual pile by etching; drilling the metallized through holes to remove copper scraps in the metallized through holes; the tin layer is removed by etching. According to the back drilling method and the printed circuit board, the technical problem that copper scraps are easy to remain in holes during back drilling of printed circuit board products can be solved by improving the back drilling flow.

Description

Back drilling method of printed circuit board and printed circuit board

Technical Field

The application relates to the technical field of circuit boards, in particular to a back drilling method of a printed circuit board and the printed circuit board.

Background

Hole metallization is one of the important steps in the production process flow of the circuit board, and particularly, a conductive copper layer is plated on the wall of an insulating hole so that the top layer and the bottom layer of the circuit board are connected with each other, and then transmission of electric signals between all circuit layers is realized. In practical application, the multilayer board comprises a connecting layer and a non-connecting layer, the circuit layers corresponding to the non-connecting layer are not required to be conducted, and the redundant copper layers on the hole wall can negatively influence signal transmission, so that the redundant copper layers are required to be removed through back drilling.

However, when the drill bit is used for removing the copper layer on the hole wall of the non-connecting layer, copper scraps with larger size are easy to form, and the drill bit cannot well bring out the copper scraps to cause the copper scraps to remain in the hole, and signal radiation generated by the copper scraps can cause interference to other surrounding signals, so that the signal transmission effect of the circuit board can be affected.

Disclosure of Invention

The utility model provides a back drilling method of a printed circuit board and the printed circuit board, which are used for solving the technical problem that copper scraps are easy to remain in holes in back drilling processing of the existing printed circuit board product.

To solve the above problems, in a first aspect, the present application provides a back drilling method of a printed circuit board, including:

providing a multilayer board, wherein the multilayer board comprises two outer layer circuits and an M inner layer circuit; m is an integer greater than 1;

manufacturing a metallized through hole on the multilayer board, wherein a copper layer is attached to the wall of the metallized through hole;

manufacturing a tin layer on the hole wall, and enabling the tin layer to cover the copper layer;

carrying out depth control back drilling on the metallized through hole to remove part of the copper layer and the tin layer, wherein the depth of the depth control back drilling is controlled between the inner layer circuits from the Nth layer to the N+1th layer, and back drilling stubs are reserved between the inner layer circuits from the Nth layer to the N+1th layer; n is an integer greater than 1 and N+1 is less than M;

removing the back drilling stub by etching;

drilling the metallized through holes to remove copper scraps in the metallized through holes;

the tin layer is removed by etching.

In an embodiment, the drilling the metallized via includes: and selecting a drill bit with a bit diameter smaller than or equal to the inner diameter of the metalized through hole, and drilling by taking the center of the metalized through hole as the center of the drill bit.

In one embodiment, the fabricating a tin layer on the hole wall includes: and depositing a tin layer on the hole wall by a chemical deposition mode.

In one embodiment, the tin layer has a thickness greater than 2 μm.

In an embodiment, the tin layer also covers the outer layer of wires.

In one embodiment, the making of the metallized through holes on the multi-layer board comprises:

drilling a through hole in the multilayer board;

and carrying out copper deposition on the inner wall of the through hole in a chemical deposition mode, and electroplating by adopting a pulse electroplating or small current electroplating mode after the copper deposition so as to form the copper layer on the inner wall of the through hole.

In one embodiment, the copper deposition on the inner wall of the through hole by chemical deposition includes: and carrying out copper deposition treatment twice.

In one embodiment, the height of the backdrilling stub is 0.02mm-0.03mm.

According to the back drilling method of the printed circuit board, the back drilling flow is improved, on one hand, after back drilling is completed, the metallized through holes are drilled, residual copper scraps in the holes can be pushed out by using the drilling tool, and therefore the problem of residual copper scraps in the holes can be solved, and the influence of the residual copper scraps in the holes on signal transmission is eliminated. On the other hand, the depth of the back drilling is controlled, back drilling residual piles are reserved between the inner layer circuits from the N layer to the (n+1) th layer, and the back drilling can be prevented from being too deep; and the back drilling residual pile is etched and removed, so that the back drilling is prevented from being too shallow, and the back drilling precision can be effectively improved through the design of the back drilling residual pile.

In a second aspect, the present application provides a printed circuit board provided with a metallized through hole, wherein the metallized through hole is manufactured by the back drilling method of the printed circuit board according to the first aspect.

In one embodiment, the aperture of the metallized through hole is not greater than 0.2mm and the aspect ratio of the printed circuit board is greater than 12.

According to the printed circuit board, through improving the back drilling flow, specifically, after back drilling is finished, the metallized through holes are drilled, residual copper scraps in the holes can be pushed out by using the drilling tool, the problem of residual copper scraps in the holes can be solved, the influence of the residual copper scraps in the holes on signal transmission is eliminated, and therefore the signal transmission effect between the connecting layers of the circuit board can be improved; and controlling the depth of the depth-controlled back drill, reserving back drill stubs between the inner layer lines of the N-N+1 layers, and etching and removing the back drill stubs in the subsequent process, so that the back drill precision can be improved, and the signal transmission effect between the connecting layers of the circuit boards can be further improved.

Drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings that are required in the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a flowchart of a method for back drilling a printed circuit board according to an embodiment of the present application;

FIG. 2 is a flowchart of step S2 in FIG. 1;

fig. 3 is a schematic structural diagram of a printed circuit board with through holes drilled according to an embodiment of the present disclosure;

FIG. 4 is a schematic view of the printed circuit board of FIG. 3 after copper plating in the holes;

FIG. 5 is a schematic view of the printed circuit board shown in FIG. 4 after tin deposition in the holes;

FIG. 6 is a schematic diagram of the printed circuit board of FIG. 5 after deep back drilling;

FIG. 7 is a schematic view of the printed circuit board of FIG. 6 after the back drill stub has been removed;

FIG. 8 is a schematic diagram of a drilling process performed on the printed circuit board shown in FIG. 7;

fig. 9 is a schematic diagram of the printed circuit board shown in fig. 8 after removing the tin layer.

Description of main reference numerals:

100. a multi-layer board; 200. a drill;

1. an outer layer line; 2. an inner layer circuit; 3. an insulating dielectric layer; 4. metallizing the through holes; 5. a copper layer; 6. a tin layer; 7. back drilling the residual pile; 8. copper scraps; 9. and a through hole.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

It will be understood that when an element is referred to as being "mounted" or "disposed" on another element, it can be directly or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly or indirectly connected to the other element. The terms "upper," "lower," "left," "right," and the like are used for convenience of description based on the orientation or positional relationship shown in the drawings, and do not denote or imply that the devices or elements in question must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be construed as limiting of the patent. The terms "first," "second," and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features. The meaning of "a plurality of" is two or more, unless specifically defined otherwise.

Reference in the specification to "one embodiment," "some embodiments," or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in one or more embodiments of the application. Thus, appearances of the phrases "in one embodiment," "in some embodiments," "in other embodiments," and the like in the specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments" unless expressly specified otherwise. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

1-9, the present application provides a back drilling method of a printed circuit board, comprising:

s1, providing a multilayer board 100, wherein the multilayer board 100 comprises two layers of outer layer circuits 1 and M layers of inner layer circuits 2; m is an integer greater than 1.

As shown in fig. 3, the outer layer circuit 1 and the inner layer circuit 2 are circuit layers for manufacturing signal lines, mounting electronic components, and the like, and an insulating medium layer 3 is further provided between adjacent circuit layers.

S2, manufacturing a metalized through hole 4 on the multilayer board 100, wherein a copper layer 5 is attached to the wall of the metalized through hole 4.

As shown in fig. 4, the metallized through hole 4 penetrates through the whole multi-layer board 100, and the copper layer 5 attached to the hole wall is used for connecting each layer of circuit to realize signal conduction between circuit layers.

S3, manufacturing a tin layer 6 on the hole wall, and enabling the tin layer 6 to cover the copper layer 5.

As shown in fig. 5, the tin layer 6 covers the copper layer 5 and can serve as a protective film for the copper layer 5.

S4, carrying out depth control back drilling on the metalized through hole 4 to remove part of the copper layer 5 and the tin layer 6, wherein the depth of the depth control back drilling is controlled between an N layer and an N+1th layer of inner layer circuits 2, and back drilling stubs 7 are reserved between the N layer and the N+1th layer of inner layer circuits 2; n is an integer greater than 1 and n+1 is less than M.

Two opposite outer layer lines 1 are defined as a first outer layer line and a second outer layer line respectively, wherein the first outer layer line is used as a starting layer of the depth-control back drill. The first outer layer circuit to the n+1th inner layer circuit 2 are non-connecting layers, and the copper layer 5 on the corresponding hole wall needs to be removed; the n+1th inner layer circuit 2 to the second outer layer circuit are connecting layers, which are required to be reserved corresponding to the copper layer 5 on the hole wall.

Optionally, in an embodiment, as shown in fig. 6, the layers L01-L04 are non-connection layers, the layers L04-L08 are connection layers, the back drilling stub 7 refers to a boundary between the non-connection layers and the connection layers, that is, the copper layer 5 and the tin layer 6 on the corresponding hole wall between the layers L03-L04, which are not completely removed, and the tin layer 6 at the back drilling hole of the back drilling stub 7 is removed, and the copper layer 5 is exposed.

When the depth control back drilling is carried out, the depth from the surface layer to the target layer, namely the thickness of the non-connecting layer, is required to be calculated, and the depth of the depth control back drilling is required to be smaller than the thickness of the non-connecting layer, so that the back drilling residual pile 7 can be reserved on the hole wall, and the problem of over-deep back drilling caused by the deviation of the back drilling equipment precision is solved.

It should be noted that, when the back drill is too deep, the connection layer is broken, so that the connection between the connection layers fails, and the signal integrity is affected; when the back drilling is too shallow, the non-connection layer residual copper layer 5 radiates signals and causes signal interference between connection layers, thereby affecting the signal transmission effect.

S5, removing the back drilling stub 7 by etching.

As shown in fig. 6 and 7, the back drilling stub 7 remains on the hole wall of the inner layer circuit 2 from the nth layer to the n+1th layer, and the back drilling stub 7 is in a copper exposure state, and the copper layer 5 of the back drilling stub 7 can be directly etched and removed by using alkaline etching solution; and the tin layer 6 is covered outside the copper layer 5 corresponding to the connecting layer, the tin layer 6 can provide protection for the copper layer 5, and the integrity of the copper layer 5 at the connecting layer can be maintained when the back drilling stub 7 is etched.

The etching rate should be controlled to ensure the cleaning effect of the back drilling stub 7 when etching the back drilling stub 7. Alternatively, the etching rate may be controlled to be 1/3 of the conventional rate to ensure etching accuracy.

It will be appreciated that when the back drill stub 7 is etched away by the etchant, the etchant flows into the hole and the copper scraps 8 remain in the hole.

S6, drilling the metallized through holes 4 to remove copper scraps 8 in the metallized through holes 4.

As shown in fig. 7 and 8, after the back drilling stub 7 is etched away, a part of copper scraps 8 remain in the metallized through hole 4, and the drill 200 can push the part of copper scraps 8 out of the hole during the drilling process.

During the drilling process, the drill 200 should avoid the copper layer 5 to ensure the integrity of the copper layer 5 of the connection layer.

And S7, removing the tin layer 6 by etching.

Specifically, the tin layer 6 is removed by etching with an alkaline etching liquid. As shown in fig. 9, a schematic view is shown after removal of the tin layer 6.

According to the back drilling method of the printed circuit board, the back drilling flow is improved, on one hand, after back drilling is completed, the metallized through hole 4 is drilled, and the drill bit 200 is utilized to push out residual copper scraps 8 in the hole, so that the problem of residual copper scraps in the hole can be solved, and the influence of the residual copper scraps 8 in the hole on signal transmission is eliminated. On the other hand, the depth of the back drilling is controlled, and back drilling residual piles 7 are reserved between the inner layer lines 2 from the Nth layer to the n+1 layer, so that the back drilling can be prevented from being too deep; and, etch and get rid of the back and bore the stub 7, can avoid back to bore shallowly too to through the design back and bore the stub 7 and can also effectively promote back and bore the precision.

The back drilling method of the printed circuit board can be used for processing the printed circuit board with high thickness-to-diameter ratio, and particularly can be used for a circuit board product with the aperture of the metalized through hole 4 not more than 0.2mm and the thickness-to-diameter ratio more than 12.

In the embodiment provided in the present application, the drilling process for the metallized through hole 4 includes: and selecting a drill bit 200 with a bit diameter smaller than or equal to the inner diameter of the metalized through hole 4, and drilling by taking the center of the metalized through hole 4 as the center of the drill bit 200.

The aperture of the metallized through hole 4 is the diameter after the copper layer 5 is manufactured, and the inner diameter of the metallized through hole 4 is the diameter after the tin layer 6 is manufactured.

When drilling holes with the drill bit 200, the drill bit 200 may scratch the tin layer 6 but not contact the copper layer 5. Alternatively, in one embodiment, the diameter of the drill bit 200 is smaller than the diameter of the plated copper of the metallized via 4 and equal to the diameter of the plated tin.

By adopting the design, the small-cutter diameter drilling tool 200 is utilized to drill holes in a concentric circular drilling mode, so that the positioning accuracy is high, the drilling difficulty is low, and the functional copper layer 5 is not easy to damage in the drilling process.

It will be appreciated that in some embodiments, the small-diameter drill may be used to drill holes in a circular movement manner, and the design may be specifically designed according to the actual situation, which is not limited herein.

In the embodiment provided by the application, the making of the tin layer 6 on the hole wall comprises: a tin layer 6 is deposited on the walls of the holes by means of chemical deposition.

The electroless tin plating is one of the circuit board tin plating processes, and mainly adopts a dip plating liquid deposition mode, and a tin layer 6 is formed on the board surface of the circuit board by utilizing a displacement reaction.

The tin coating in the hole is greatly influenced by the hole diameter, when the hole diameter is too small, the problems of difficult tin coating in the middle of the hole wall and uneven tin coating on the hole wall are easy to occur due to poor liquid medicine circulation, and by adopting the design, on one hand, the chemical tin coating can meet the tin coating requirement of a product with high thickness-to-diameter ratio, and the tin coating 6 can be manufactured by utilizing a chemical tin coating mode, so that the tin coating effect on the hole wall can be ensured; on the other hand, the chemical tin plating process is simple, the immersion plating liquid is stable in quality, and long-time continuous processing can be realized.

It will be appreciated that in some embodiments, when the thickness-to-diameter ratio of the product meets the requirement, the tin layer 6 may be made by electroplating tin, and the design may be specifically performed according to the actual situation, which is not limited herein.

In the examples provided herein, the tin layer 6 has a thickness of greater than 2 μm.

When the tin layer 6 is manufactured by using the chemical tin deposition method, parameters such as tin deposition time, immersion plating liquid medicine concentration and the like need to be controlled so as to control the thickness of the tin deposition.

By adopting the design, the thickness of the tin layer 6 meets the requirements, the surface structure of the tin layer 6 is dense, the hardness is high, the scraping is not easy, and the protection can be better provided for the copper layer 5.

It can be understood that the thickness of the tin layer 6 can be adjusted according to different aperture designs and different processing flows of the metallized through holes 4, and the design can be specifically performed according to practical situations, which is not limited herein.

In the embodiment provided in the present application, the tin layer 6 also covers the outer layer wire 1.

With the adoption of the design, the tin layer 6 can also provide protection for the outer-layer circuit 1, so that the damage risk of a circuit board product can be reduced.

It will be appreciated that the tin layer 6 should also be removed when the tin layer 6 is removed, which is the tin layer 6 that covers the outer layer of wires 1.

In the embodiment provided in the present application, as shown in fig. 1 and 2, making the metallized through hole 4 on the multilayer board 100 includes:

s21, drilling a through hole 9 in the multilayer board 100.

Specifically, the through hole 9 may be drilled by mechanical drilling or laser drilling. As shown in fig. 3, a schematic view is shown after drilling the through hole 9.

S22, carrying out copper deposition treatment on the inner wall of the through hole 9 by a chemical deposition mode, and electroplating by adopting a pulse electroplating or small current electroplating mode after the copper deposition treatment so as to form a copper layer 5 on the inner wall of the through hole 9. As shown in fig. 4, a schematic view is shown after depositing a copper layer 5 on the inner walls of the via hole 9.

The through holes 9 are primary processing holes, the through holes 9 should be pre-enlarged when the through holes 9 are manufactured, and the aperture after copper deposition electroplating is the same as the aperture of the finished product.

By adopting the design, copper plating is carried out by combining chemical copper deposition with pulse plating or low-current plating, the copper plating effect is good, the copper plating requirement of a product with high thickness-to-diameter ratio can be met, and a uniform copper layer 5 can be formed on the hole wall.

After copper plating, the aperture of the metallized through hole 4 is smaller, so that the corresponding thickness-to-diameter ratio is increased. Taking the plate thickness of 2.5mm as an example, the aperture of the drilled through hole 9 is 0.2mm, the corresponding thickness-to-diameter ratio is larger than 11:1, the aperture of the metallized through hole 4 is about 0.15mm after copper deposition electroplating, and the corresponding thickness-to-diameter ratio is larger than 12:1.

In the embodiment provided by the application, the copper deposition treatment on the inner wall of the through hole 9 by chemical deposition comprises the following steps: and carrying out copper deposition treatment twice.

By adopting the design, the uniformity of copper deposition on the hole wall can be further improved.

In the embodiment provided by the application, the height of the back drilling stub 7 is 0.02mm-0.03mm.

The back drilling residual pile 7 needs to be etched and removed by using etching liquid, and if the height of the back drilling residual pile 7 is too high, the problem of incomplete etching is easy to occur; if the height of the back drilling residual pile 7 is too low, the problem of over-etching is easy to occur. By adopting the design, the height of the back drilling stump 7 is set reasonably, and the subsequent etching treatment is convenient.

In the embodiment provided by the application, before etching the backdrilling removal backdrilling stub 7, the method further comprises: the backdrilling depth is checked and the height of the backdrilling stub 7 is determined.

By adopting the design, the real height of the back drilling residual pile 7 can be determined, and the etching parameters can be adjusted according to the real height of the back drilling residual pile 7, so that the etching precision can be improved, and the back drilling precision can be further improved.

The back drilling method provided in the present application will be described below with eight-layer boards as an example.

The circuit layers of the eight layers are respectively L01-L08, wherein L01 and L08 are outer layer circuits 1, and L02-L07 are inner layer circuits 2. The plate thickness of the eight-layer plate is 2.5mm, the aperture of the metalized through hole 4 is 0.15mm, the L01-L04 layer is a non-connecting layer, the L04-L08 layer is a connecting layer, and the thickness of the L01-L04 layer is 1.1mm. The eight-layer plate complete processing method comprises the following steps:

s01, preprocessing, including cutting, inner layer circuit 2 manufacturing, pressing plate processing and the like.

S02, drilling, namely drilling a through hole 9 at a preset position by using a 0.2mm drill 200 according to the design requirement of the circuit board.

S03, copper deposition is carried out, and a copper layer 5 is deposited on the wall of the through hole 9 in a chemical deposition mode. It will be appreciated that copper deposition is also required in the via hole 9 without back drilling.

S04, carrying out metallization treatment, namely carrying out electroplating treatment on the copper layer 5 on the hole wall to form a metallized through hole 4, wherein the aperture is 0.15mm after copper plating. It will be appreciated that the metallization process also requires machining of the via hole 9 without back drilling.

S05, manufacturing a circuit pattern, and forming the circuit pattern on the outer layer circuit 1 by pattern transfer, etching and the like according to design requirements.

S06, tin deposition is carried out, a tin layer 6 is deposited on the hole wall of the metallized through hole 4 in a chemical tin deposition mode, the copper layer 5 is covered by the tin layer 6, and the thickness of the tin layer 6 is larger than 2 mu m.

S07, controlling the depth of the back drilling, namely controlling the depth of the back drilling to the metallized through hole 4 needing the back drilling, and removing the copper layer 5 and the tin layer 6 on the corresponding hole wall of the non-connecting layer to obtain the back drilling with the non-connecting layer and the copper connection.

Specifically, the back drilling is performed by using the drilling tool 200 with the tool diameter not smaller than 0.2mm, the back drilling depth is controlled to be between 0.8mm and 0.9mm, the back drilling stub 7 is formed between the L03 layer and the L04 layer, and the height of the back drilling stub 7 is 0.2mm to 0.3mm.

S08, backdrilling depth inspection, namely detecting the backdrilling depth and determining the actual height of the backdrilling stump 7 so as to provide subsequent etching parameters.

And S09, removing the back drilling residual pile 7, and etching and removing the copper layer 5 of the back drilling residual pile 7 by using etching solution according to the actual height of the back drilling residual pile 7 obtained at the side in the step S08.

S10, drilling, namely, drilling the metallized through hole 4 again by using a drill bit 200 with the bit diameter smaller than 0.15mm so as to push all the copper scraps 8 remained in the hole out of the hole.

S11, removing the tin layer 6, and etching the hole wall and the tin layer 6 attached on the outer layer circuit 1 by using etching solution.

S12, checking the back drilling depth, detecting the back drilling depth again, and determining that the back drilling precision meets the requirement.

S13, post-process production, including AOI, welding prevention, molding, electric testing and appearance inspection.

In conclusion, the back drilling method of the printed circuit board can effectively improve the back drilling precision by improving the back drilling process, and can effectively remove copper scraps 8 in holes on the premise of ensuring the integrity of hole copper between connecting layers.

In a second aspect, the present application provides a printed circuit board provided with metallized through holes 4, the metallized through holes 4 being manufactured by a back drilling method of the printed circuit board as in the first aspect.

According to the printed circuit board, through improving the back drilling flow, specifically, after back drilling is finished, the metallized through holes 4 are drilled, residual copper scraps 8 in holes can be pushed out by using the drilling tool 200, the problem of residual copper scraps 8 in holes can be solved, the influence of the residual copper scraps 8 in holes on signal transmission is eliminated, and therefore the signal transmission effect between the connecting layers of the circuit board can be improved; and controlling the depth of the back drilling, reserving back drilling stubs 7 between the N-N+1 layer inner layer circuits 2, and etching and removing the back drilling stubs 7 in the subsequent process, so that the back drilling precision can be improved, and the signal transmission effect between the connecting layers of the circuit boards can be further improved.

In the embodiment provided by the application, the aperture of the metalized through hole 4 is not more than 0.2mm, and the thickness-to-diameter ratio of the printed circuit board is more than 12.

The back drilling method can effectively improve the copper and tin depositing effect in the metallized through hole 4 by improving the copper and tin depositing method, and solves the problem that the high-thickness-diameter-ratio product is difficult to copper and tin, thereby being beneficial to improving the quality of the metallized through hole 4 and the quality of the circuit board product.

The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.

Claims

1. A method of back drilling a printed circuit board, comprising:

removing the back drilling stub by etching;

the tin layer is removed by etching.

2. The method of back drilling a printed circuit board of claim 1, wherein the drilling the metallized through hole comprises: and selecting a drill bit with a bit diameter smaller than or equal to the inner diameter of the metalized through hole, and drilling by taking the center of the metalized through hole as the center of the drill bit.

3. The method of back drilling a printed circuit board of claim 1, wherein the fabricating a tin layer on the hole wall comprises: and depositing a tin layer on the hole wall by a chemical deposition mode.

4. A method of back drilling a printed circuit board according to claim 1 or 3, wherein the tin layer has a thickness of greater than 2 μm.

5. A method of back drilling a printed circuit board according to claim 1 or 3, wherein the tin layer also covers the outer layer of wires.

6. The method of back drilling a printed circuit board of claim 1, wherein the making of the metallized through holes on the multi-layer board comprises:

drilling a through hole in the multilayer board;

7. The back drilling method of the printed circuit board according to claim 6, wherein the copper deposition process on the inner wall of the through hole by chemical deposition comprises: and carrying out copper deposition treatment twice.

8. The back drilling method of the printed circuit board according to claim 1, wherein the height of the back drilling stub is 0.02mm-0.03mm.

9. A printed circuit board, characterized in that it is provided with metallized through holes, which are manufactured by means of the back drilling method of a printed circuit board according to any one of claims 1-8.

10. The printed circuit board of claim 9, wherein the aperture of the metallized via is no greater than 0.2mm and the aspect ratio of the printed circuit board is greater than 12.