CN112911808B

CN112911808B - Multilayer PCB blind slot processing method and device

Info

Publication number: CN112911808B
Application number: CN202110070635.9A
Authority: CN
Inventors: 戴广乾; 蒋瑶珮; 徐诺心; 毛小红; 边方胜; 谢国平; 龚小林; 卢军; 易明生; 曾策
Original assignee: CETC 29 Research Institute
Current assignee: CETC 29 Research Institute
Priority date: 2021-01-19
Filing date: 2021-01-19
Publication date: 2022-09-06
Anticipated expiration: 2041-01-19
Also published as: CN112911808A

Abstract

The invention discloses a PCB blind slot processing method and a processing device, and belongs to the technical field of printed board production. The method comprises the steps of manufacturing coating lugs for filling blind grooves on the lower surfaces of an upper plate in batch in a mode of windowing a lower surface coating film and carrying out pattern electroplating, and realizing one-time batch filling of the coating lugs when alignment lamination is carried out; and after the grooving is controlled in depth, taking out the upper sub-plate and the coating bump material in the blind groove together to obtain a processed blind groove structure. The scheme of the invention avoids the defects of difficult alignment, complex mode, low efficiency and the like of manual filling and gasket removal in the prior art, improves the efficiency of manufacturing the blind slot of the multilayer PCB, and is particularly suitable for manufacturing the multilayer PCB with a plurality of blind slot structures.

Description

Multilayer PCB blind slot processing method and device

Technical Field

The invention belongs to the technical field of printed board production, and particularly discloses a method and a device for processing a multi-layer PCB blind slot.

Background

The PCB blind slot refers to a cavity region which does not penetrate through the circuit board, and the space in the printed board can be effectively utilized. On one hand, the blind slot can realize the input and output ports of electric signals of all layers in the printed board; on the other hand, the adhesive tape is also used as a cavity and a carrier for adhering and mounting components such as chips, capacitors, resistors and the like. With the progress of components and assembly technologies, the blind slot type printed circuit board is also developed towards diversification and complicated structure.

The method is characterized in that auxiliary gaskets are adopted for filling, and then the gaskets are removed by grooving in a mechanical or laser mode, so that the method is a manufacturing mode widely adopted in the industry for manufacturing blind groove structures.

For example, patent CN102523684B discloses a method for manufacturing a PCB with a stepped groove, which fills a blind groove with a silica gel sheet having a boss shape, thereby preventing surface glue flow while achieving good overflow in the groove.

Patent CN102523685B discloses a manufacturing method of a PCB with a stepped groove, blind grooves are filled by adopting a special core plate + PP + PTFE three-layer composite gasket, and the problems that blind groove cavities and gaskets are different in height and glue flowing is not easy to control are solved by utilizing high buffering of middle-layer PP.

Patent CN103517582A discloses a multilayer circuit board and a manufacturing method thereof, wherein a blind groove is filled with a copper sheet and a peelable film composite gasket, and the gasket is taken out after laser grooving, so that the problems that port patterns are easily damaged by laser grooving and PP (polypropylene) flow adhesive are solved.

Patent CN 102523688B discloses a method for manufacturing a PCB with a stepped groove, which solves the problems of high filling cost and easy displacement of a silica gel gasket by filling a blind groove with a gasket made of PTFE.

Patent CN103179792B discloses a method for improving the flatness of the side wall of a stepped groove, which solves the problem of uncontrollable glue flowing on the side wall of a blind groove by reducing the size of a PTFE gasket and expanding the filling mode of a prepreg groove.

Patent CN105338727B discloses a method for preparing a stepped slot of a stepped circuit board, which solves the problem that the sidewall of a blind slot is damaged by excessive expansion due to excessive glue overflow at the bottom of the gasket by a gasket filling mode of a composite structure of a bottom tight metal block and an upper gap insulating sheet.

Patent CN105682364B discloses a method for processing stepped grooves based on copper foil flow resistance, which fills blind grooves with copper foil gaskets having equal height to the height of the blind grooves, thereby solving the problem of layer formation risk caused by glue overflow and laser high temperature in conventional gasket filling blind grooves.

It can be seen that the technological improvements of the existing technology for filling and manufacturing the blind groove by using the gasket are mostly focused on the aspects of gasket shape, gasket size, gasket material and design and improvement of a composite gasket structure, but the specific operation modes of filling and removing the gasket are not involved. On the other hand, the filling and removing of the gasket in the prior art still adopts the mode of filling and removing one by hand. The inefficiency of blind slot gasket filling and removal is particularly acute in connection with filling and removal involving a large number, small size, high depth of blind slots.

Disclosure of Invention

The invention provides a method and a device for processing a multi-layer PCB blind slot, aiming at solving the problem of low efficiency of filling and removing a gasket in the existing gasket filling blind slot manufacturing technology and improving the efficiency of manufacturing the multi-layer PCB blind slot.

The technical scheme adopted by the invention is as follows:

a multilayer PCB blind slot processing method, through utilizing the conductivity of the metal copper foil of the lower surface of the upper and lower daughter boards, through the combination mode of the windowing of the cover film, selective growth of pattern electroplating, etching, make the lug of clad layer used for blind slot filling in batches on the lower surface of the upper and lower daughter boards, realize the disposable batch filling of the lug of clad layer while carrying on the alignment lamination; and after the depth control grooving, taking out the upper sub-plate and the coating bump material in the blind groove together to obtain a processed blind groove structure.

Further, the processing method specifically comprises the following steps:

(1) providing a first sub-board 1, and respectively sticking cover films 2 on the upper surface and the lower surface of the first sub-board 1;

(2) windowing the covering film 2 on the lower surface of the first sub-board 1 to obtain a covering film windowing 21;

(3) carrying out pattern electroplating treatment on the covering film windowing 21;

(4) removing the covering film 22 in the un-windowed area on the lower surface of the first sub-board 1;

(5) thinning the plating layer on the lower surface of the first daughter board 1 to obtain a plating layer bump 122 with the thinned plating layer;

(6) removing the covering film on the upper surface of the first sub-board 1;

(7) providing a lamination bonding sheet 3 and a second daughter board 4, carrying out alignment lamination according to the sequence of the first daughter board 1, the lamination bonding sheet 3 and the second daughter board 4 from top to bottom, and laminating and bonding the lamination bonding sheet and the second daughter board into a whole under high-temperature high-pressure vacuum;

(8) cutting a depth control blind slot;

(9) and taking out the blind groove inner block 51 to form the blind groove structure 5.

The first sub-board 1 is a double-layer wiring board or a multilayer wiring substrate, and an upper surface copper metal layer 11 and a lower surface copper metal layer 12 are respectively arranged on the upper surface and the lower surface of the first sub-board 1.

The cover film 2 is a photosensitive dry insulating film, and the thickness of the cover film is the same as that of the laminated adhesive sheet 3.

The size of the cover film windows 21 is equivalent to the size of the preset blind groove structures 5.

Further, the step (3) specifically includes performing pattern electroplating in the cover film windowing 21 region, wherein the growth thickness of the plating layer is the same as the thickness of the laminated adhesive sheet 3, and obtaining the plated bump 121 after the pattern electroplating.

In a preferred embodiment, the plating layer is a copper plating layer.

Correspondingly, the copper layer is thinned in the step (5), so that the reduced thickness of the copper layer is the same as the thickness of the copper layer 12 originally arranged on the lower surface of the first sub-board 1.

Further, the cutting of the depth control blind groove in the step (8) is carried out along a preset blind groove path, and the material at the top of the blind groove is cut and processed to obtain a blind groove inner block;

the depth control blind groove cut by the corresponding control depth K needs to penetrate through the laminated daughter board 1 to reach the copper bump 122 without penetrating through the copper bump 122.

In another aspect, the invention further provides a processing device, and the processing device is used for completing any processing method of the multilayer PCB blind slot structure.

In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:

(1) by utilizing the conductivity of the metal copper foil on the surface of the double-sided copper-clad substrate and the combined mode of cover film windowing, pattern electroplating selective growth and etching, the plating layer lug for filling the blind slot is manufactured on the lower surface of the upper plate in batch, the position precision is high, and the one-time batch high-precision batch filling of the plating layer lug can be realized during the contraposition lamination.

(2) The plated bump is directly grown and manufactured on the daughter board, the adhesive force is good, after the depth control grooving, the upper daughter board and the plated bump material in the blind groove can be conveniently taken out together, and the processed blind groove structure is obtained.

(3) The method avoids the complex and low-efficiency manual filling and gasket removing mode in the prior art, improves the efficiency of manufacturing the blind grooves of the multilayer PCB, and is particularly suitable for manufacturing the multilayer PCB containing a plurality of blind groove structures.

Drawings

Fig. 1 is a flowchart of a method for processing a blind slot of a multilayer PCB according to an embodiment of the present invention.

Fig. 2 is a schematic view of attaching cover films to the upper and lower surfaces of the first daughter board according to an embodiment of the present invention.

Fig. 3 is a schematic view of the cover film windowing provided by the embodiment of the invention.

FIG. 4 is a schematic structural diagram of the pattern electroplated with copper according to the embodiment of the present invention.

Fig. 5 is a schematic structural diagram of the lower surface cover film removed according to the embodiment of the present invention.

Fig. 6 is a schematic structural diagram of the copper layer thinning and the upper surface coating film removal according to the embodiment of the present invention.

Fig. 7 is a schematic view of a stacked structure provided by an embodiment of the present invention.

Fig. 8 is a schematic diagram of a laminated structure provided by an embodiment of the invention.

Fig. 9 is a schematic illustration of the slotting provided by an embodiment of the present invention.

Fig. 10 is a schematic diagram of the blind groove inner block removal provided by the embodiment of the invention.

Fig. 11 is a schematic diagram of a blind trench structure formed according to an embodiment of the present invention.

The figures are numbered:

1-a first daughter board; 11-a metal copper layer on the upper surface of the first sub-board; 12-a metal copper layer on the lower surface of the first sub-board; 121-copper bump after pattern plating; 122-copper bump with thinned copper layer; 2-a cover film; 21-opening a covering film; 22-cover film of un-windowed area; 3-laminating an adhesive sheet; 31-windowing the laminated adhesive sheet; 4-a second daughter board; 41-a circuit layer on the upper surface of the second daughter board; 5-a blind groove structure; 51-blind groove inner block; and K, controlling the processing depth by depth.

Detailed Description

In order to make the technical solutions of the present invention better understood, the following description of the technical solutions of the present invention with reference to the accompanying drawings of the present invention is made clearly and completely, and other similar embodiments obtained by a person of ordinary skill in the art without any creative effort based on the embodiments in the present application shall fall within the protection scope of the present application.

In the prior art, the blind groove is generally processed by firstly providing a blind groove lower sub-plate, and then completing the blind groove processing through the processes of upper sub-plate windowing, adhesive film/PP windowing, gasket manufacturing, laminating and gasket taking out. In the process, the problems that the gasket is difficult to align and paste, the gasket is easy to remove residual glue and the like exist in the filling of the gasket.

The embodiment of the invention provides a method for etching after selectively growing pattern electroplating by utilizing the conductivity of metal copper foil on the lower surface of an upper daughter board and a lower daughter board through windowing a covering film, plating lugs for filling blind grooves are manufactured on the lower surface of the upper daughter board in batch, and one-time batch filling of the plating lugs is realized when alignment lamination is carried out; and after the depth control grooving, taking out the upper sub-plate and the coating bump material in the blind groove together to obtain a processed blind groove structure.

Example 1

Embodiment 1 is a multilayer PCB blind via processing method implemented by utilizing cover film windowing and pattern electroplating, as shown in fig. 1, the processing method specifically includes the following steps:

(1) a first sub-board 1 is provided, and cover films 2 are respectively attached to the upper and lower surfaces of the first sub-board 1, as shown in fig. 2.

The first sub-board 1 is a double-layer wiring board or a multilayer wiring substrate, and an upper surface metal copper layer 11 and a lower surface metal copper layer 12 are respectively distributed on the upper surface and the lower surface of the first sub-board 1;

the upper surface copper layer 11 is used for subsequently manufacturing a multilayer board graphic circuit;

(2) The cover film 2 on the lower surface of the first sub-board 1 is windowed.

Adopting a common mask plate exposure and development process of a printed board to realize windowing of the covering film 2 along a preset blind slot path to obtain a covering film windowing 21, and leaving a covering film 22 in an un-windowed area as shown in fig. 3;

The preset blind groove path is a closed figure surrounding a circle, and the shape of the preset blind groove path includes but is not limited to rectangle, circle, abnormity and the like.

(3) And (6) pattern electroplating.

In the region of the cover film window 21, a plated bump is obtained by pattern plating using the conductivity of the metal copper foil on the lower surface of the upper board and the lower board, as shown in fig. 4. In one embodiment the patterned plating is a copper plating layer grown to the same thickness as the laminate adhesive sheet 3, resulting in a patterned plated copper bump 121.

In the process, because the covering film 2 of the upper surface metal copper layer 11 is not provided with the windows, the thickness of the original copper layer is kept unchanged in the pattern electroplating process, so that the manufacturing precision of the subsequent multilayer board pattern circuit is ensured.

(4) The cover film 22 is removed from the un-windowed area of the lower surface of the first daughter board 1 as shown in fig. 5.

(5) And thinning the copper layer on the lower surface of the first sub-board 1 to obtain the copper bump 122 with the thinned copper layer.

The copper layer is thinned by adopting the commonly used acidic etching and alkaline etching processes of the printed board;

the copper layer is thinned to make the reduced thickness of the copper layer the same as the thickness of the original copper layer 12 on the lower surface.

(6) The covering film on the upper surface of the first sub-board 1 is removed to form an isolated copper bump 122 structure on the lower surface of the first sub-board 1, as shown in fig. 6.

(7) The adhesive sheet 3 and the second sub-sheet 4 are laminated, and the first sub-sheet 1, the adhesive sheet 3 and the second sub-sheet 4 are aligned and laminated in this order from top to bottom, as shown in fig. 6, and laminated and bonded in a high-temperature high-pressure vacuum manner to form a whole, as shown in fig. 7.

In a preferred embodiment the high temperature and high pressure conditions are: the temperature is higher than 180 ℃ and the pressure is higher than 150PSI, and the specific value is determined according to the process requirements of the used laminated adhesive sheet.

An independent copper bump structure 122 is attached to the lower surface of the first sub-board 1;

the laminated adhesive sheet 3 is provided with a window 31 at the position of the preset blind slot, and the size of the window 31 is not less than that of the preset blind slot 5; the thickness of the laminated adhesive sheet 3 is the same as that of the copper bump 122; the value range of the thickness of the laminated bonding sheet 3 and the thickness of the copper bump 122 is 0.025-0.2 mm;

in a preferred embodiment, the size of the window 31 on the laminated adhesive sheet 3 is 0-0.1 mm larger than the size of the preset blind groove 5;

the second sub-board 4 is a double-layer wiring board or a multi-layer wiring substrate, and a wiring layer 41 is arranged on the upper surface of the second sub-board 4 at a preset blind slot.

8) And (5) depth control numerical control blind slot cutting.

The numerical control blind slot cutting is carried out along a preset blind slot path, and the material at the top of the blind slot is cut and processed, as shown in fig. 8; the control depth K corresponding to the numerical control blind slot cutting needs to penetrate through the laminated first sub-board 1 to reach the copper bump 122 without penetrating through the copper bump 122.

9) The blind groove inner block 51 is removed as shown in fig. 9 to form the blind groove structure 5 as shown in fig. 10.

The material of the blind groove inner block 51 is composed of the first sub-board 1 and the copper bump 122 on the lower surface of the first sub-board.

Example 2

After the processing of the blind slot structure 5 is preliminarily completed, the bottom patterned circuit 41 and other circuits of the blind slot structure 5 may be subjected to surface coating according to actual production and application requirements. Including but not limited to electroplated gold, electroless nickel gold, electroplated nickel gold, electroless nickel palladium gold, and the like.

And optionally, further milling the printing plate shape according to a preset size. The embodiment of the invention does not limit the specific way of the subsequent processing.

Example 3

The embodiment provides a processing device which is used for completing the processing method of the blind slot of the multilayer PCB in any one of the previous embodiments.

While the foregoing is directed to embodiments of the present invention, it should be understood that those skilled in the art may make various improvements and modifications without departing from the spirit of the present invention, such as, for example, when manufacturing individual copper bumps, the copper layer on the lower surface of the first sub-board is first thinned, and then patterned to improve the shape of the copper bumps. Such modifications and refinements are also considered to be within the scope of the present invention.

All of the features disclosed in this specification, or all of the steps in any method or process so disclosed, may be combined in any combination, except combinations of features and/or steps that are mutually exclusive. The invention is not limited to the foregoing embodiments. The invention extends to any novel feature or any novel combination of features disclosed in this specification, and to any novel method or process steps or any novel combination of steps disclosed.

Claims

1. A multilayer PCB blind slot processing method is characterized in that the conductivity of metal copper foil on the lower surface of an upper sub-board is utilized, plating layer lugs for blind slot filling are manufactured on the lower surface of the upper sub-board in batch in a combined mode of cover film windowing, pattern electroplating selective growth and etching, and one-time batch filling of the plating layer lugs is realized when alignment lamination is carried out; after the groove is opened by depth control, the upper sub-plate and the coating bump material in the blind groove are taken out together to obtain a processed blind groove structure;

the method specifically comprises the following steps:

(1) providing a first sub-board, and respectively sticking cover films on the upper surface and the lower surface of the first sub-board;

(2) windowing the covering film on the lower surface of the first sub-board to obtain a covering film windowing;

(3) performing pattern electroplating treatment on the opening window of the covering film;

(4) removing the covering film of the region without the window on the lower surface of the first sub-board;

(5) thinning the plating layer on the lower surface of the first sub-board to obtain a plating layer bump with the thinned plating layer;

(6) removing the covering film on the upper surface of the first sub-board;

(7) providing a lamination bonding sheet and a second sub-board, aligning and laminating the first sub-board, the lamination bonding sheet and the second sub-board from top to bottom in sequence, and laminating and bonding the first sub-board, the lamination bonding sheet and the second sub-board into a whole under high-temperature high-pressure vacuum;

(8) cutting a depth control blind slot;

(9) taking out the inner block of the blind groove to form a blind groove structure;

the step (3) specifically comprises the steps of carrying out pattern electroplating on a windowing area of the covering film, wherein the growth thickness of a plating layer is the same as that of the laminated adhesive sheet, and obtaining a plating layer bump after pattern electroplating;

cutting the depth control blind groove in the step (8) along a preset blind groove path, and cutting and processing the material at the top of the blind groove to obtain a blind groove inner block;

the depth control blind slot is used for cutting a corresponding control depth K which needs to penetrate through the first sub-board to reach the copper bump and does not penetrate through the copper bump.

2. The method for processing the blind via of the multi-layer PCB as claimed in claim 1, wherein the first sub-board is a dual-layer wiring board or a multi-layer wiring substrate, and the upper surface and the lower surface of the first sub-board are respectively provided with an upper surface copper metal layer and a lower surface copper metal layer.

3. The method for processing the blind via of the multi-layer PCB as claimed in claim 2, wherein the cover film is a photosensitive dry insulating film having a thickness equal to that of the lamination adhesive sheet.

4. The method for processing the blind via of the multi-layer PCB as claimed in claim 2, wherein the size of the window of the cover film is the same as the size of the predetermined blind via structure.

5. The method for processing the blind via of the multi-layer PCB as claimed in claim 2, wherein the plating layer in step (5) is thinned to reduce the thickness of the plating layer to be the same as the thickness of the copper layer originally formed on the lower surface of the first sub-board.

6. The method of claim 5, wherein the plating layer is a copper plating layer.

7. A machining device, characterized in that the machining device is used for completing the machining method of the blind slot of the multilayer PCB as claimed in any one of claims 1 to 6.