CN113727541A

CN113727541A - Method for producing circuit board with selective electroplating holes and laser-made conductive patterns

Info

Publication number: CN113727541A
Application number: CN202111003252.6A
Authority: CN
Inventors: 胡宏宇; 刘天宇
Original assignee: Dct Tianjin Technology Development Co ltd
Current assignee: Dct Tianjin Technology Development Co ltd
Priority date: 2021-08-30
Filing date: 2021-08-30
Publication date: 2021-11-30

Abstract

The invention relates to a method for producing a circuit board with selectively plated holes and laser-made conductive patterns, which comprises the steps of coating a film material which has sparse chemical plating active seeds and is resistant to plating on a copper-clad plate, drilling, only activating hole walls, directly plating the hole walls only or firstly chemically plating and then plating the hole walls to a required thickness, removing the copper foil-made conductive patterns in a non-circuit area by using laser, removing a solder mask layer by using laser at an assembly site to prepare the solder mask patterns, and cleaning and performing weldability treatment on a welding area. The invention uses the anti-electroplating film material to mask the board surface, only deposits metal on the hole wall, the thickness of the plating layer is easy to control, the quality of the metallized hole is better, and the circuit board can better meet the electrical requirement; the laser spot diameter can be changed according to the pattern size, the material is directly removed to manufacture the pattern, the steps are few, and finer conductive patterns and solder resist patterns can be manufactured. The invention can optimize and shorten the manufacturing process of the circuit board on the whole, improve the quality and the efficiency, reduce the cost and is environment-friendly.

Description

Method for producing circuit board with selective electroplating holes and laser-made conductive patterns

Technical Field

The invention belongs to the technical field of circuit manufacturing, relates to a laser technology, and particularly relates to a method, a material and equipment for producing a circuit board with a selective electroplating hole and a laser conductive pattern.

Background

In the world today, electronic products are ubiquitous. One of the most important parts of electronic products is a circuit board which is an electrical connection channel among all components and determines respective electrical parameters and electrical logic relations; meanwhile, the mounting and fixing carrier is a mounting and fixing carrier of each component and is a framework of a product. The electric connection channel is realized by a conductive pattern and a metallized hole, the quality of element installation and fixation is closely related to the quality of a solder resist pattern and the weldability of a welding area, and the main production process of the circuit board also expands around the solderability of the conductive pattern, the metallized hole, the solder resist pattern and the welding area. However, in the conventional method for manufacturing the circuit board, the conductive pattern and the solder resist pattern are manufactured by pattern transfer, and the metallized holes are manufactured by using a copper foil substrate, which is an indirect technology essentially and cannot meet the requirements of an electronic technology on pattern precision and hole quality.

Spatially, the electrical connections on the circuit board can be divided into two groups: connections in the horizontal direction, i.e. parts commonly referred to as conductive patterns, are above the plane of the layers for making connections in the direction X, Y; connections in the vertical direction, made by metallized holes, pass through the insulating layer and the conductive layer in the Z-direction for making electrical interconnections between layers of the conductive pattern. In the conventional circuit board manufacturing technology, a conductive pattern in the horizontal direction is manufactured mainly by a subtractive method, that is: removing the redundant copper foil on the copper clad laminate, and using the remained copper foil as a conductive pattern as a part with an electrical connection function, such as a lead, a bonding pad and the like; the electrical interconnections between layers in the vertical direction are made predominantly by additive methods, namely: and adding conductive materials to the hole walls in the holes, and enabling the conductive hole walls to penetrate through the metal layers in the horizontal direction to realize electrical interconnection.

As an important link in the electrical connection link, in the process of manufacturing the circuit board, the thicknesses of the conductive pattern in the X, Y direction and the conductive layer on the hole wall in the Z direction should be separately controlled, so that the whole electrical channel meets the electrical requirements of the product, and particularly, the thickness of the conductive layer on the hole wall should be independently controlled, so that the conductive layer does not become a weak link in the connection link. However, in the general circuit board technology, the control of the hole wall copper thickness and the control of the line copper thickness interfere with each other, and the trade-off between the two has to be carried out, which is one of the problems affecting the electrical performance and reliability of the circuit board.

The holes are metallized, typically chemically. A thin layer of conductive material is deposited on the insulating walls of the hole by electroless plating or other means, and a conductive metal is plated on the initial conductive layer to a desired thickness by electroplating, so that the hole through the metal layer has a reliable electrical interconnection index between layers. Different process routes are derived based on different hole metallization technologies, including a hole masking method, a pattern electroplating etching method, and the like. The two process routes have advantages and disadvantages respectively, and the technical scheme and the key technology are briefly described as follows:

the pattern electroplating etching method, known as the reverse plating method, is a classic process route for manufacturing printed boards. The process after cutting starts from drilling and hole metallization, an initial conductive layer is formed on the hole wall by a chemical plating or direct electroplating method, metal copper is deposited on the hole wall and the plate surface to a certain thickness by an electroplating method, then pattern transfer is carried out, a layer of organic material thin layer, namely plating resist, is firstly used for masking the copper foil of the non-circuit part by photosensitive film pasting, exposure and development, and the surfaces of the circuit part, including a lead, a bonding pad, the hole wall and the like, are exposed. Therefore, the surface of the metal copper to be removed is masked, and is not contacted with the liquid medicine in the electroplating process, so that the metal is not continuously deposited; the part needing to be reserved, including the surface of the conducting wire, the bonding pad and the hole wall, is exposed outside and is contacted with the liquid medicine during electroplating, or copper is continuously electroplated firstly, or corrosion-resistant metal such as tin, tin-lead alloy, nickel, gold and the like are directly electroplated. And then removing the organic material masking layer to expose the copper foil of the non-circuit part, enabling the copper foil to react with an etchant in the etching process, dissolving the copper foil into a liquid medicine after oxidation, and enabling the copper foil to disappear from the plate surface, wherein the surfaces of the circuit parts such as the wires, the bonding pads, the hole walls and the like are shielded by a metal resist and are not contacted with the etchant, and the metal resist is remained on the plate to form a required conductive pattern. Finally, to make a solder resist pattern on the non-soldering area of the circuit board, a solderable material is applied over the area of the soldering area.

The circuit board is manufactured by the reverse plating method, the process is mature and stable, and particularly for electroplating, the circuit part and the non-circuit part can be processed differently; however, the process steps are numerous and the operation is complicated. After the initial conductive layer is formed by the hole metallization, depositing copper on the hole wall by an electroplating method for one time until the required final thickness is reached, and meanwhile, increasing the thickness of the copper conductive layer on the rest part of the board surface is called as a full-board electroplating etching method; after the hole is metallized, a thin layer of copper is electroplated on the hole wall and the board surface, the copper thickness is controlled to be just resistant to the subsequent process, and after the pattern is transferred, the copper electroplating is carried out to the required final thickness, namely, the conductive pattern part is only plated with thicker copper, and the non-conductive pattern part is plated with thinner copper.

The hole masking method is another common circuit board manufacturing process route. The process after cutting starts from drilling and hole metallization, an initial conductive layer is formed on the hole wall by a chemical plating or direct electroplating method, and metal copper is continuously deposited on the hole wall and the plate surface to the final required thickness by the electroplating method. Then, pattern transfer is performed, and the circuit portion including the conductive lines, pads, and holes is masked with a thin layer of an organic material called resist by attaching a photosensitive film, exposing, developing, and exposing the copper foil of the non-circuit portion. In the following etching process, the exposed non-circuit part of the surface of the copper foil contacts with the etchant to generate oxidation reaction, the dissolved medicine liquid disappears from the plate surface, and the surfaces of the circuit parts such as the conducting wire, the bonding pad, the hole wall and the like are not contacted with the etchant because of being shielded by the resist, and are remained on the plate to form the required conductive pattern. Like the reverse plating method, the via masking method also finally produces a solder resist pattern on the non-soldering area of the circuit board, and applies a solderable material on the soldering area. The hole masking process is characterized in that the whole board is electroplated with thickened copper, so that the process is relatively simple, but when the conductive pattern is manufactured, the process is more unfavorable for the production of a fine circuit structure because the thicker copper foil needs to be etched.

In the two process routes now commonly used, the process of making Z-connections by hole metallization can be divided into two stages: the method comprises the steps of manufacturing an initial conducting layer on an insulated hole wall and electroplating and thickening the conducting layer on the hole wall.

The technology for manufacturing the initial conducting layer can be divided into two methods of chemical copper plating and direct electroplating. The chemical copper plating, also called chemical copper deposition, has relatively complex process, is more mature, stable and wide in application range, and utilizes a self-catalytic oxidation-reduction reaction to deposit copper (Cu) in chemical copper plating solution on the hole wall²⁺) The ions are reduced into Cu, and the reduced metal copper crystal nucleus itself becomes a catalyst of other copper ions in the solution, so that the reduction reaction of copper is continued on the surface of the new copper crystal nucleus, and finally a thin layer of metal copper layer is formed on the insulated hole wall. Compared with the chemical copper plating technology, the direct electroplating technology has the advantages of simple process and environment friendliness, three methods of a carbon membrane method, a palladium membrane method and a high polymer membrane are popular, conductive carbon, palladium or high polymer materials are directly coated or manufactured on the hole wall, and after a continuous thin layer is formed, a basic conductive membrane is provided for subsequent electroplating deposition.

From the technical realization, the economy and the electrical performance, the speed of forming the conductive layer by the direct electroplating and chemical copper deposition technology is slow, the physical property is poor, and the requirements of the electronic product on the conductive performance and the mechanical performance of the Z-direction link section cannot be met, so that after the thin-layer conductive object is in a continuous state and the thickness and the strength can endure the subsequent processing in the processing process, the electroplating technology is switched to the circuit board production, and the metal copper with better performance is continuously added on the hole wall by the power of an external power supply. As mentioned above, there are two alternative routes of full-plate electroplating and pattern electroplating, and although the difference between the two technologies is that the thickening range of electroplating copper is different, in essence, the important purpose of both technologies is to electroplate copper on the hole wall, and to electroplate copper on the hole wall, both have to rely on the original copper foil on the substrate as the power line for copper plating on the hole wall, from this point of view, the conductive pattern on the X, Y plane only plays a role of plating accompanying in electroplating the hole wall.

Analyzing the results of the current plating of the Z-direction link with the X, Y conductive pattern, it can be seen that the current technology will limit the improvement of the Z-direction link machine and the electrical performance, and also cause the difficulty of the subsequent conductive pattern manufacturing process, which affects the precision and the manufacturing cost of the whole circuit board.

First, comparing X, Y plane and Z-direction conductive layer, it can be seen that neither full-board plating nor pattern plating really solves the problem that the thickness of Z-direction conductive layer is consistent with that of X, Y direction conductive layer in the circuit board connection link, and the thickness difference between the hole wall conductive layer forming Z-direction link and the plate surface conductive layer forming X, Y link is also enlarged in the process of electroplating and thickening the initial conductive layer. Because, on the X, Y plane, the conducting layer is based on the inherent conductive copper foil on the base plate, the above-mentioned electroplating copper thickens the conducting layer of the hole wall, and also on the basis of the inherent copper foil on the plate surface, the thickness of the conducting layer is synchronously increased with the hole wall, and moreover, because of the factor of the power line step by step, and also because of the limitation of the depth capability and the uniform plating capability of the electroplating process, the thickness of the plate surface deposition layer is larger than that of the hole wall deposition layer. This runs counter to the increasing performance requirements of current and future electronic products for circuit board electrical connections, and in particular for Z-links. Therefore, it is necessary to develop a technique for selectively plating a thickened hole.

Secondly, the copper foil on the surface of the manufactured board and the copper foil on the surface of the original insulating substrate after the pattern electroplating and the full-board electroplating are analyzed, so that the thickness of the copper foil is increased, and the quality is deteriorated. In IPC standard IPC-6012, there are specific requirements on the wall thickness of the metallized holes, at least 20 μm. The current circuit board manufacturing process has limited deep plating capability, when the hole wall copper thickness reaches 20 microns, the copper thickness increased by the board surface exceeds the hole wall copper thickness, and after the added copper thickness is added with the original copper foil thickness of 18 microns, the total copper thickness exceeds 40 microns. Therefore, the conductive layer generated in the circuit board copper electroplating process becomes the top layer of the conductive layer of the future conductive pattern, and is the main medium for transmitting electrical signals with higher frequency under the action of the skin effect. However, it must be seen that the quality of the copper layer deposited by electroplating in the production of circuit boards is slightly lower than the purity of the original copper foil produced by electroforming or calendering, the crystal is slightly rough, and the quality of electrical and mechanical properties is slightly poor, in this sense, the increase of the thickness of the conductive layer is unfavorable for signal transmission. Therefore, it is necessary to develop a technique for independently plating an additional hole wall conductive layer without using the conductive pattern on the X, Y surface as a power supply line.

Furthermore, current circuit board production techniques, either pattern plating or full-plate plating, add a copper plating layer up to 25 μm thick based on the original copper foil material. The result of such hole metallization techniques, of course, greatly increases the difficulty of the process of manufacturing the conductive patterns. In the conventional technology, a conductive pattern is manufactured by using a chemical etching technology, an etching solution is contacted with a copper foil to perform etching in the processing process, the etching is performed in the depth direction of the copper foil, and the etching is performed in two lateral directions of a lead due to the contact of the etching solution and two side surfaces of the lead. The thicker and longer the copper layer is etched, the more severe the lateral etching phenomenon, which not only reduces the width of the conductive line but also causes disconnection when severe, and thus the thickness of the copper foil and the resulting lateral etching are a factor in the production of the fineness of the conductive pattern. In this regard, in order to manufacture a more precise conductive pattern, it is necessary to develop a technique for reducing the difficulty of manufacturing the conductive pattern by etching without increasing the thickness of the copper foil on the X, Y side.

In addition, the conductive pattern is manufactured by directly removing the conductive material in the non-circuit area by laser, so that the method has the advantages of high precision, few steps, high production flexibility, environmental friendliness and more extensive application in recent years. In patent application DE 102010019406 a1, a method of removing a metal foil layer in designated areas is disclosed. The area of the foil layer to be removed is first separated into small pieces insulated from each other by a laser along lines parallel to each other at an acute angle of 22.5 ° to the major axis (X, Y) formed by the known run of the wire, and then the separated small pieces are heated to reduce their adhesion to the substrate material while the small pieces are removed entirely with a fluid that is neither parallel to nor perpendicular to the channels, leaving the foil portion as the desired conductive pattern. The technical proposal of the patent is improved by the patent application CN103747626A of German technology company, firstly, an insulating envelope channel of a line part is made by laser, then a non-line part is separated by laser with a geometry body with complementary and reversed shape, and finally, a small block is stripped by laser heating. Patent application CN103769749A is along 45 ° or 135 ° direction with the horizontal line, dividing the non-circuit part into top narrowing, bottom widening and top widening with laser in turn, bottom narrowing strip shape, and finally heating back and forth with laser to peel off the small block. In the patents, the conductive material needs to be removed by laser photoetching, but the thickness of the hole-metalized conductive layer is uneven, a certain laser power is applied, so that the phenomenon that the laser power is too small in a region with larger copper foil thickness, the copper is not completely removed, and the insulation performance is influenced by residual copper is caused, or the phenomenon that the laser power is too large in a region with smaller copper foil thickness, the insulation material below the copper foil is ablated, and the quality of a circuit board is influenced is caused. In view of the foregoing, there is also a need for developing a technique for making conductive patterns on a large scale using direct laser processing instead of indirect chemical etching techniques, without using the original copper foil on the insulating substrate for plating.

Patent application publication No. CN101232782A discloses a technical solution in which after the conductive pattern is formed and drilled, the holes are metallized, resulting in the formation of an initial conductive layer on the walls of the holes, but at the same time, a thin layer of conductive material copper is added to the non-circuit portion of the board surface, so that all the holes on the whole board can be electrically connected to a plating power supply. Then, an anti-plating pattern which covers the board surface but exposes the hole body is manufactured by using a photosensitive material, and a current is provided for the hole wall by using a conductive material copper thin layer and the manufactured conductive pattern which are generated in a non-circuit area during hole metallization, so that the aim of depositing copper on the surface of the hole and thickening the hole wall is achieved. Finally, the non-circuit part conductive layer is removed by using a differential etching method. Compared with the traditional circuit board manufacturing process, the technical scheme has the advantages that a differential etching manufacturing process is added besides a manufacturing process of a masking plate surface exposed hole body, and the process is complicated. Moreover, any alignment error and shape error in the process of exposing the hole body can cause excessive deposition or insufficient deposition of copper when the hole wall is electroplated and thickened, so that a hole ring or a hole defect is caused; furthermore, the differential etching method, when etching away the thin copper layer in the non-circuit area, will etch the copper foil on the circuit surface without fail, which not only may result in insufficient copper thickness, but also increases the roughness of the circuit surface, which is not good for the transmission of current, especially high frequency current.

The inventor with the application number of CN201410190917.2 discloses a method for selectively plating conductive holes on a circuit board, which is suitable for a direct hole plating metallization process by a polymer conductive film method. The technical scheme is that the anti-electroplating material, the anti-polymer conductive film deposition material and the stripping material, namely the polyester film coated with the silicon rubber adhesive, are used for stripping the adhesive and masking all areas of the board surface, and the surface of the hole wall is exposed after drilling. Because the materials have the properties of resisting the pretreatment required by the deposition of the high-molecular conductive film and resisting the deposition of the high-molecular conductive film, in the subsequent direct electroplating process of the high-molecular conductive film, the high-molecular conductive film is only added on the hole wall, and during electroplating, an electroplating power supply provides current for the hole wall by using the copper foil on the board surface as a conductive linking channel, so that the electroplating processing of depositing copper on the hole wall is realized. The problem is that the hole metallization process of the direct electroplating by the polymer conductive film method needs to be carried out for 70 seconds by using a solution with the permanganate concentration of 100g/L or more at the temperature of 90 ℃, both strippable glue and an adhesive for adhering a polyester film can generate destructive oxidation, so that the bonding force between a masking material which has small adhesive force with a substrate and a copper-clad foil is reduced, the phenomena of bone separation, layering, seam formation and opening are generated, the masking plate surface effect is poor, and the problem of uneven thickness of the copper-clad plate surface can be aggravated by the actions of solution infiltration, overflow, soaking and the like after the hole wall is thickened by electroplating copper. In addition, the application range of the direct electroplating hole metallization process by the polymer conductive film method is limited, the process is not suitable for multilayer circuit boards, the factors such as quality and cost are comprehensively considered, and the difficult problems of metallization and hole wall electroplating only faced by the traditional chemical copper deposition hole metallization technology, the black hole direct electroplating hole metallization technology and the palladium film method direct electroplating hole metallization technology need to be solved. Because these techniques require acid, base or organic solvent treatment before hole metallization, it is clear that the above-mentioned solutions using peelable gel-like materials are not sufficiently robust and cannot be applied to the mainstream hole metallization techniques, and a more suitable material and method must be additionally sought.

Disclosure of Invention

Aiming at the defect that the wall of a thickened hole can not be electroplated independently in the prior art, the invention develops a method, a material and equipment for manufacturing a circuit board by selectively electroplating a hole and manufacturing a conductive pattern by laser. Masking the plate surface with an anti-plating film, drilling holes and depositing metal on the hole walls only; then, a conductive pattern, a solder resist pattern and a solderability treatment are directly made with laser. The method comprises the following specific steps:

(1) coating a high polymer masking film layer which is thinned with active seeds for chemical plating and is resistant to electroplating on the surface of a workpiece plate which is not provided with or provided with one or more layers of conductive patterns and is coated with copper foils on two sides;

(2) drilling according to the design requirement;

(3) conducting electricity through the holes;

(4) electroplating copper, and depositing copper on the hole wall to thicken the hole wall;

(5) removing the high polymer masking film layer on all the plate surfaces by laser;

(6) removing the copper foil layer on the non-circuit area by laser;

(7) pasting a solder mask on the surface of the workpiece;

(8) in an assembly field, removing a solder mask on the surface of a welding area by using laser to manufacture a solder mask pattern, and cleaning and performing weldability treatment on the surface of the welding area;

(9) adding solder to the connecting disc, carrying out component mounting and insertion, and carrying out remelting welding or wave soldering.

The invention adopts a hydrophobic chemical plating active seed and the high polymer masking film with electroplating resistance to mask the board surface, so that metal can be deposited on the hole wall to the required thickness; then, directly removing the conductive material in the non-circuit area by laser to manufacture a conductive pattern; after the solder mask is pasted, the solder mask is directly removed by laser to manufacture a solder mask pattern and the solder area is subjected to solderability treatment at the circuit board assembly site. Therefore, the invention applies the direct laser processing technology, has simple flow, can control the copper thickness of the hole wall, does not need the pattern transfer process, better meets the electrical requirements of electronic products on the circuit board, is suitable for the mass production of various circuit boards, and is also suitable for the sample and small-batch and various manufacture of the circuit board.

And (1) coating a high polymer masking film layer which is thinned with chemically plated active seeds and is resistant to electroplating on the surface of a workpiece plate which is internally provided with one or more layers of conductive patterns and is coated with copper foils on two sides.

In the prior art, a photoinduced dry film is generally used as an electroplating-resistant mask, the photoinduced dry film is of a three-layer structure, a photosensitive adhesive coating is arranged between a carrier film and a protective film and consists of an adhesive, a photopolymerization monomer and the like, the pattern forming process is complex, and the steps of photoplotting, plate making, film pasting, exposure and development are required; moreover, the mask is expensive, has low strength and large thickness, generally more than 20 μm, limited resolution and poor masking effect.

The masking film of the invention does not need to have light-sensitive performance, but the surface of the masking film needs to have hydrophobic chemical plating active seeds and the high polymer masking film materials which are resistant to electroplating, acid, alkali and organic treatment comprise dry PET, PI, RPP, BOPET, BOPP, PA, PPE, PTFE, PP, PE, PVC and EVA high polymer films made of single-component, multi-component, composite thermosetting, light-curing, hot-pressing adhesion and non-photosensitive and photosensitive materials, coating of organic silicon and modified substances thereof, coating of other resins and modified substances thereof, coating of Parylene/Parylene, coating of other polymers, and compounding of the films with bonding agents, thermosetting, light-curing and hot-pressing adhesion and adhesion of other materials, laminating of the above materials, and monomeric, prepolymerized or polymerized liquid and pasty materials; the coating method of the material comprises one or more than two combined processing of rolling, hot pressing, printing, plating, spraying, missing printing, spray printing, roller coating, curtain coating and vacuum meteorological deposition; the thickness of the material is between 0.3 μm and 1500 μm, and the preferred film thickness is 1 μm to 100 μm.

In fact, the common pre-coated pressure-sensitive coating film and the heat-sensitive coating high polymer film can meet the requirements after being treated by the hydrophobic chemical plating active seeds. For example, a thermo-sensitive PET or BOPET film with a thickness of 20 μm is hot-pressed as an electroplating-resistant mask.

And (2) drilling according to design requirements. The material to be drilled is a composite material formed by alternately laminating conductive copper foil and insulating material, and different from the traditional technology, the material drilled by the invention is additionally provided with a high polymer masking film attached to the surface of the board. The drilling tool may be either a mechanical drill or a focused laser beam.

When the laser is used to remove the plating resist mask, the focused laser optical power density is set to a value greater than, e.g., greater than 1.2 times the minimum optical power density required to remove the material, but less than or close to the minimum optical power density required to remove the underlying metal copper layer.

If a mechanical drill bit is used for drilling, epoxy drilling fouling may occur on the hole wall, and before hole electroconductivity is carried out, the epoxy drilling fouling is removed by using a liquid medicine and a process which do not damage the high polymer film so as to ensure the quality of hole electroconductivity.

Wherein, in step (3), the hole is electrically conductive. The purpose of this step is to deposit an initial conductive layer on the hole walls to prime the next step of electroplating the hole walls.

The traditional chemical copper deposition process is that active noble metal particles are firstly deposited on the hole wall, and then copper hole metal is deposited to realize the surface conduction of the hole wall, so the hole conduction is the hole metallization process in the existing circuit board manufacturing technology; in the direct electroplating process, particularly in the carbon film method and the polymer film method, the substance for realizing the pore wall conductivity is not metal, so that the description of the process for forming the initial conductive layer by using the pore metallization is not accurate. In the present invention, the hole metallization is still used for description when referring to the prior art, and the hole conductivity is used for description when referring to the process of the present invention, and the hole conductivity includes both the hole conductivity process realized by metal and the hole conductivity process realized by non-metal materials.

There are two methods for achieving the object of this step, one is a direct electroplating method, for example, a carbon film method is used to blacken the hole, and an initial conductive layer is formed after the "pretreatment → black hole" step; the other is the traditional chemical copper deposition process, and the initial conducting layer is formed after the plating pretreatment → the activation treatment → the chemical copper plating. The thickness of the electroless copper plating is up to a lower limit, for example 1 μm, which ensures the reliability of the process.

In the step, because the plate surface is covered with the high polymer film, and the outer surface of the film has the property of thinning the active seeds of the chemical plating, and the plate surface is masked, after the step of directly electroplating the black holes or after the activation treatment of the chemical copper deposition method, the plate surface does not have conductive substances such as carbon black, graphite and the like, and does not adhere to metal palladium active particles with catalytic action, chemically deposited copper and the like. Therefore, the plate surface and the copper-clad foil conducting layer can be maintained in an electric insulation state, and no metal copper is deposited on the plate surface in the subsequent electroplating process, so that the purpose of electroplating the copper conducting layer on the hole wall only is achieved.

And (4) electroplating copper, and depositing copper on the hole wall to thicken the hole wall.

In order to solve the problems that the total area is too small, the power lines are not uniform step by step, the current density is not easy to control and the like when the hole wall is electroplated, an electroplating balance block which is beneficial to improving the quality can be manufactured on a workpiece. The method comprises the following steps: after the step (1) is carried out, before or after the steps (2) and (3) are carried out, before the step (4) is carried out, laser is used for removing dead copper areas without electric functions, which are not wires and have an interval of more than 30 microns and preferably more than 50 microns with the intervals with the wires, or areas, the conducting layers of which need to be removed and do not have negative influence on the subsequent removing process, or areas, the functions of which are not influenced by the copper thickness, or areas, the functions of which are positively influenced by the copper thickness, of which are added with anti-electroplating film masking layers, so that copper foil surfaces below the masking layers are exposed, and dispersed patterns favorable for the balanced distribution of electroplating current when the hole walls are electroplated are formed.

The electroplated balance block is manufactured by only removing the organic material on the surface of the copper foil at the corresponding part. In this case, the optical power density of the focused laser spot used is greater than the minimum power density required to remove the organic material and is lower than or close to the minimum power density required to remove the underlying metal layer. Preferably greater than 1.2 times the minimum optical power density required to remove the organic material.

The control point of the step (4) is the plating time. At the moment, the whole area except the hole wall and the electroplating balance block on the plate surface is covered by a mask which is an insulating material and is not coated with copper in deposition on the surface although contacting with the electroplating liquid, so that only the hole wall and the balance block can deposit copper in the electroplating process, the electroplating time is enough, a copper deposition layer with enough thickness can be obtained on the hole wall, and the purpose of selectively controlling the copper thickness of the hole wall is achieved.

And (5) laser removing the high polymer masking film layer on the whole plate surface.

The high polymer masking film coated on the surface of the board only plays a role of masking the lower copper foil during hole conduction and electroplating. After the hole wall is plated, the high polymer masking film on the whole board surface can be removed at one time; it is also possible to leave the high polymer masking film on the conductive pattern area and remove only the high polymer masking film in the non-circuit area together with the conductive material thereunder when the conductive pattern is made.

And removing the high polymer masking film layer, wherein the organic material on the surface of the copper foil at the corresponding part is only required to be removed in the same process of manufacturing the electroplating balance block and removing the high polymer masking film layer on the bonding pad. In this case, the optical power density of the focused laser spot used is greater than the minimum power density required to remove the organic material and is lower than or close to the minimum power density required to remove the underlying metal layer. Preferably greater than 1.2 times the minimum optical power density required to remove the organic material.

Removing the polymer film in large area by selecting CO₂And (4) processing equipment with a laser as a light source. CO 2₂The laser emitted by the laser has a wavelength of about 10 μm and is in a far infrared band. Copper has low laser absorption coefficient of the wave band, but the laser of the wave band has good coupling with most high polymers, so the laser parameter range for removing the high polymers without damaging the copper is wide. Selection of CO₂The laser can use large-diameter light spots, has high removal efficiency, low cost and high cost performance, and does not damage copper.

In addition to CO₂Besides laser, the pulse fiber laser with the wavelength of about 1 mu m has stable performance, convenient use and low cost, and is also suitable for removing the solder resist material and manufacturing the solder resist pattern.

Wherein, step (6), the laser removes the copper foil layer on the non-circuit area.

After the copper foil layer on the non-circuit area is removed, an insulating pattern is formed on the insulating substrate in the area without the copper foil, and a conductive pattern is formed on the insulating substrate by the conductive layer on the hole, the pad and the circuit area.

Because the present invention is capable of selectively plating holes, the technique of removing the conductive material of the non-wiring region with a laser is easier to implement. In the current common circuit board manufacturing technology, after the hole metallization electroplating process, due to the limitation of the plating uniformity of the hole metallization system, the deposition speed of copper is different in different areas on the same substrate material, so that the thickness of the total conductive layer is greatly different. Thus, when the laser is used for removing the conductive layer of the non-circuit part, if the laser parameters do not change along with the copper thickness, the copper removal is not clean at the part with large total copper thickness, the residual copper affects the insulation performance, or the energy applied to the part with small total copper thickness is too large, and the insulation material is ablated.

By implementing the technical scheme of the selective electroplating hole, copper can not be deposited in a non-line area, particularly on a laser photoetching removal path, a conducting layer under the laser photoetching path is kept to be an original copper foil, the thickness is uniform, and the laser processing difficulty is reduced. The invention adopts Striping and Stripping method/Striping and Striping of German and Chinese technology, firstly uses laser light etching to vaporize conductive material point by point and layer by layer to form a closed separation line, subdivides a conductive layer area to be removed into small pieces with mutually heat-insulated areas in a certain range, which is called Striping/Striping; the die is then heated with a laser to reduce the bonding force between the die and the substrate and release the die from the substrate, known as lift-off/striping.

The processing steps of the slitting and stripping method are as follows in sequence: firstly, projecting light etching laser point by point, vaporizing and removing the conductive material under the envelope curve of each conductive pattern, and manufacturing a closed insulating channel by taking a contour line as a boundary; then, projecting light etching laser point by point, vaporizing and removing the conductive material under the separation line, and subdividing the large conductive material to be removed into small heat-insulated pieces; and then, the heating laser is projected onto the small pieces in sequence, the bonding force between the small pieces and the base material is reduced, the small pieces deform, and the small pieces are separated from the workpiece under the combined action of auxiliary gas and are transferred and collected.

When the strip is divided and stripped, the insulation space S between the two conductors is wider, and the numerical value satisfies S>2d_maxWhen the processing scheme is nd + (n-1) D, i.e., n photoetched evaporatively removed beam diameters of D and (n-1) beam diametersIs the thermal stripping removal of D, wherein n is more than or equal to 2, and the preferred value of n is the minimum; when the width S of the conductive layer between two conductors satisfies 2d_max≥S≥d_maxWhen the conductor is etched, S-d 1+ d2 is selected, that is, two photoetching laser beams with photoetching diameters of d1 and d2 are selected to remove the conductive material between the two conductors, wherein d1 and d2 can be the same or different; when the insulation space S between two conductors is smaller than the maximum beam waist diameter of the task of photoetching, i.e. d_maxWhen the diameter of the light beam is larger than or equal to S, the processing scheme is S-d, namely the diameter of the light beam is selected, so that the conducting material between the two conductors is removed by just one photoetching laser beam with the diameter of the light beam being d. Wherein S is the insulation space between two conductors, namely the width of the conductive layer to be removed, D is the diameter of a photoetching laser beam, D is the diameter of a heating laser beam, and n is an integer of 1, 2, 3, 4 and the like.

The laser striping and stripping technology is implemented, the electroplating-resistant masking film-high polymer film in the non-circuit area is not necessarily removed, for example, when the ultraviolet band laser processing is used, or picosecond laser is used for striping, the masking film and the copper foil layer below the masking film can be vaporized together by laser photoetching until the insulating substrate layer stops to form a heat insulation channel; in the peeling, the masking film and the copper foil layer thereunder are heated together, and the masking film and the copper foil layer are peeled off in bulk by thermal deformation and reduction of the bonding force with the insulating base material. To be suitable for laser processing, the anti-plating masking film may be selected to be colored to produce better absorption.

And (7) covering a solder mask on the surface of the workpiece.

The solder mask, namely the solder resist, coated in the step has the function of preventing short circuit caused by the overflow of solder between welding points when components are welded in the assembly stage of the circuit board; firstly, the surface and the side wall of a conducting wire forming a conducting pattern on the circuit board are physically shielded, and damages such as oxidation, scratch and the like caused by the external environment are prevented.

In the prior art, liquid photosensitive ink is generally adopted as a solder resist, the solder resist contains an adhesive and a photopolymerization monomer, the pattern forming process is very complicated, and multiple processes such as coating, pre-baking, exposure, development, curing and the like are required; moreover, the cost is high, the resolution ratio is not high, and the coating quality between the fine pitch connecting discs is difficult to guarantee.

The invention uses laser light etching to remove the means to make solder resist pattern, the solder resist does not need to have light sensitivity, the common precoating pressure sensitive coating film and heat sensitive coating film can meet the requirement, the price is cheap, the resolution ratio is high, can make the meticulous pattern structure. In addition, the invention adopts hot-pressing coating, does not need an additional curing process, leaves the solder resist pattern to be manufactured by laser on site before the component is assembled, and has simple flow. For example, a thermo-sensitive PI, PVC, PC, PET, PP, RPP, BOPET, BOPP, PA, PPE, parylene film with a thickness of 20 μm to 200 μm is used as a solder resist.

And (8) removing the solder mask on the surface of the welding area by using laser in an assembly field to manufacture a solder mask pattern, and cleaning and performing weldability treatment on the surface of the welding area.

The key point of the step is that the solder mask pattern is manufactured on an assembly site, and once the solder mask pattern is manufactured, a fresh copper foil is exposed, and the processes of coating solder on the surface of the bonding pad, pasting the bonding pad, welding or inserting and welding are immediately carried out.

The laser processing in the step has the functions of selectively removing the solder resist material and manufacturing the solder resist pattern; but also has the function of cleaning the welding area and performing weldability treatment on the welding surface.

The technical key points of using laser to manufacture the solder resist pattern are as follows: the pattern size is accurate and smooth, and no burr is generated; the solder resist is removed cleanly, and the solder resist has no residue and no carbonization; the metal performance of the welding area is kept, the metal is not damaged, and remelting and color change are avoided; the adhesive force between the bonding pad and the base material is not affected, no overheating exists, the bonding pad is not raised, and the adhesive force is not reduced. The solder resist is generally a high molecular polymer, has large difference with metals physically and chemically, is easy to remove by laser processing, finds a window meeting the technical requirements, can be completed in one step by using laser with one wavelength in the same equipment, and can also be performed in two steps on different equipment.

Nanosecond ultraviolet laser, picosecond laser and femtosecond laser can be absorbed by high polymer to play a role in removing; can be well absorbed by copper metal, and plays a role in cleaning the surface of the copper metal. Particularly, picosecond and femtosecond laser has small single pulse energy, but the intensity of light, namely the laser power per unit area is large, only trace substances can be removed, but the surface performance of the material is changed, so that the method is a better choice for performing the weldability treatment on the surface of the bare copper. In the step, the laser processing system can be selected, and the solder mask pattern is manufactured by one step or multiple steps by using the same equipment, and the welding area is subjected to weldability processing.

CO₂The laser and the fiber laser have high absorption rate when being acted with high polymer and low absorption rate when being acted with copper. In general, such a laser cannot combine the functions of removing a high polymer solder resist pattern on a copper foil and cleaning and treating the solder area. Thus, another option for this step is to use two types of laser sources in two steps: selecting large light spot CO₂Removing the high polymer with high efficiency by laser to manufacture patterns; and removing the solder resist residues by nanosecond UV pulse laser or picosecond and femtosecond laser.

The first step is as follows: making a solder resist pattern, and generating a welding area: using longer wavelength CO₂And selectively photoetching a solder resist coating on the welding area by using a large-diameter laser spot emitted by a laser, removing the solder resist which possibly enters the hole, manufacturing a solder resist pattern, and generating the welding area.

And secondly, cleaning and performing solderability treatment on the surface of the welding area, removing residual solder resist on the surface of the welding area by using UV wave band with short wavelength or picosecond and femtosecond pulse laser with large light intensity, slightly photoetching the surface layer of the metal of the welding area, removing metal oxide, exposing the fresh surface of the metal, and generating solderability which is easily soaked by molten solder.

And (9) adding solder to the connecting disc, carrying out component mounting and inserting, and carrying out remelting welding and wave soldering.

In the method of the present invention, since the laser-treated fresh copper surface is used in place of the solderability coating layer of the pad, step (9) should be performed in as short a time as possible after step (8) is completed to avoid oxidation of the pad surface, and component attachment is completed under the condition that the solderability after laser treatment is excellent. The assembling process comprises the steps of carrying out component insertion, and directly applying welding flux to a laser-processed welding area to complete component welding; or directly printing solder paste on the laser-processed welding area in a missing mode, and then carrying out component mounting and reflow soldering; or component assembly according to other techniques.

In the present invention, laser processing is used for both drilling and removing the high polymer masking film on the copper foil layer and also for removing the copper foil. The laser processing equipment comprises one or more sets of data acquisition and processing systems, an equipment operating system, a laser light source, a light beam shaping and transmission system, a laser focusing system, a workpiece clamping and automatic and manual feeding and discharging system, a workpiece positioning and light beam movement and control system, a visual detection and laser power monitoring and compensation system, a cleaning and constant temperature system, a laser and equipment safe use system and the like; when the high polymer masking film is removed by laser or the copper foil on the non-circuit area is removed by laser, according to the shape and the size of the processed area, the energy and the power on the unit area are constant, the diameter of a light spot interacting with a material is taken as a variable, and one or a combination of high processing speed, no overlapping or certain overlapping when a processing path is overlapped, certain overlapping amount or spacing amount between pulses is taken as priority to generate laser parameters and processing data; during processing, the diameter of a light spot can be changed on line according to the preset laser parameters and the processing path requirements aiming at the structure of a processed pattern.

The invention has the advantages and effects that:

1. the invention adopts the masking film with the sparse chemical plating active seeds on the surface, can only electroplate and thicken the hole wall, is easy to control the thickness of the plating layer and can solve the problem that the thickness of the plating layer of the hole wall is thinner.

2. The invention realizes only electroplating holes, the thickness of the non-circuit part conductive layer is not increased, the invention is suitable for directly removing the copper foil at the non-circuit part by using laser to manufacture the conductive pattern, and the anti-electroplating mask is removed at the same time when the conductive pattern is manufactured by using the laser, so that a special film removing process is not needed, the steps are few, and the finer conductive pattern can be manufactured.

3. The conductive pattern is manufactured by laser, the solder resist pattern is manufactured by laser on an assembly site, and the non-photosensitive material is used, so that the processing steps are few, and the requirement on materials is low.

4. In the laser pattern manufacturing process, the diameter of the focused laser beam is changed according to the shape and the size of the removed area, so that the diameter of the focused laser beam or the multiple of the diameter of the focused laser beam is exactly equal to the width of the area to be removed, the overlapping of laser processing areas can be reduced or removed, and the processing efficiency is improved.

5. The invention uses the film pre-coated with the heat-sensitive and pressure-sensitive solder-resisting materials as the solder resist, and uses the lasers with different wavelengths, pulse widths and power densities to manufacture the solder-resisting pattern and carry out welding area cleaning and solderability treatment, thereby having higher efficiency and better treatment effect.

Drawings

FIG. 1a is a process flow diagram of the present invention (steps 1-5);

FIG. 1b is a process flow diagram of the present invention (steps 6-9);

in the figure: 1. an insulating substrate; 2. copper-clad plate copper layer; 3. a layer of plating resistant polymeric masking film material; 4. starting a conductive layer; 5. electroplating a copper layer; 6. solder mask; 7. a cleaned and solderability treated surface; 8. welding flux; 9. and (3) a component.

Detailed Description

The invention will be further described with reference to the following examples. The following examples are illustrative and not intended to be limiting, and are not intended to limit the scope of the invention.

The common copper clad laminate in the electronic industry is used as a base material for manufacturing a circuit board, and comprises an insulating substrate 1 and a copper clad laminate 2.

Example 1

(1) And hot-pressing a BOPP film coated with glue on the double surfaces of the Fr4 copper-clad plate without the pattern inside to form the electroplating-resistant high polymer masking film material layer 3.

A German and China DCT-BR300 type board brushing machine is used for performing double-sided board brushing (the board feeding speed is 1.2 mm/min; the swing frequency is 70 times/min) on the 1.5H/H copper-clad plate, compressed air is used for blowing off the moisture on the board surface, and the board is dried slightly or naturally.

And (3) laminating/laminating, respectively laminating the front surface and the back surface of the copper-clad plate with BOPP films with the same size (the glue-coated surfaces are tightly adhered to the copper foils), slightly rolling by using a rubber roller, and discharging air between the laminating surfaces to enable the laminating surfaces to be tightly adhered so as to ensure that relative sliding is not generated in subsequent operation.

And (3) laminating the BOPP-coated double-sided film board by using DE-Zhong DCT-LA400 hot-pressing equipment (15 kilograms force, 100 ℃, and the board moving speed is 100 mm/min).

(2) Drilling according to design requirements

Holes were drilled as per design requirements using midrange DCT-DM350 equipment. The designed data is imported into German Circuit CAM software, after the data is processed by the software, available punching data of equipment is generated, DM350 equipment is imported, the pressed board is placed on an equipment platform, CCD is positioned, full-automatic punching processing is carried out, specific drilling parameters are different according to different apertures, and the main parameter ranges are as follows: the rotating speed of the drill bit is 45000-100000 r/min, the feed speed is 15-30 mm/s, and the withdrawal speed is 25-40 mm/s.

(3) Activating and chemically depositing copper to form the initial conductive layer 4.

Removing oil with alkaline oil removing agent (50-60 deg.C, 5-8 min); pre-soaking with dilute hydrochloric acid solution (room temperature, 1-2 min); activating the palladium salt solution (25-30 ℃, 3-5 min); treating the dispergation solution (45-50 deg.C, 5-8 min); and (4) carrying out copper deposition on the alkaline copper deposition solution (40-45 ℃ and 60-80 min).

In this step, only the hole wall part can contact with the liquid medicine, and the rest of the plate surface is completely covered by the film. The BOPP film surface has hydrophobic chemical activation characteristic, so that a chemical copper deposition layer cannot be formed, and a thinner chemical copper deposition layer is formed on the surface of the hole wall.

(4) And electroplating to form an electroplated copper layer 5.

And (3) thickening electroplating of the hole wall copper layer by using Dezhong DCT-TP300 hole forming equipment. The uniformity of the hole wall plating is improved by adopting a small-current and long-time (0.2-0.25 ampere, 20min) mode. In order to further improve the uniform plating and deep plating capability, the DCT-TP300 hole equipment is also provided with a liquid medicine jet flow circulation structure, a pulse direct current electroplating function and a reverse pulse electroplating function.

In this step, since the BOPP film has no conductive ability on the surface, electroplating is only performed on the hole wall.

(5) BOPP film with all board surfaces removed by laser

Importing the data into German China Circuit CAM software, and generating a path for removing all BOPP films on the board surface by laser after software processing and calculation; and (3) importing the path data into dreamCreaTor equipment operation software, placing the board on an equipment platform, and automatically aligning the CCD and then automatically removing the BOPP film on the whole board surface by laser.

In the step, when the circuitous CAM software calculates the laser processing path, the diameter of the large light spot is matched and a corresponding processing path is generated according to the characteristics of the removal area and the size; the device under the drive of DreamRefeaTor software executes laser processing, and laser removal is completed with high efficiency and high quality. In the process, the related key laser processing parameters are as follows:

wavelength of light

Pulse width

Spot diameter

Focal shift

Average power

Frequency of pulses

Speed of processing

Number of working operations

10600nm

--

250um

0mm

25

20kHz

800mm/s

1 time of

(6) Laser removal of copper foil layer on non-circuit area

According to data patterns and materials involved in processing, a nanosecond ultraviolet laser device U5 is preferably used as a processing device; according to the circuit pattern, the German computer CAM software is used for calculating a circuit insulation enveloping circuit path, a strip slicing path of a non-circuit area (namely a copper foil area needing to be removed) and a heating stripping removal path.

First, the insulating envelope of the line region is laser-machined with a photoresist. According to the calculated path of the line insulation enveloping line, laser is projected to the conductive material, photoetching is carried out, the conductive material is vaporized point by point to be removed to the surface of the insulating material, and a closed insulation enveloping channel is manufactured around the conductive material to be reserved.

Then, the division and slicing processing is performed by the photoetching laser. Projecting laser to the conducting material, photoetching, evaporating point by point to remove the conducting material to the surface of the insulating material, and subdividing the large piece of conducting material to be removed into small strips or small pieces which are mutually insulated.

And finally, carrying out stripping processing by using heating laser, sequentially projecting laser on the small strips or the small pieces which are mutually insulated, heating the small strips or the small pieces to deform the small strips or the small pieces so as to reduce the bonding force between the small strips or the small pieces and the insulating material, separating the small strips or the small pieces from the insulating material under the combined action of auxiliary gas, separating the small strips or the small pieces from the surface of the insulating material, transferring the small strips or the small pieces to be collected, and stripping and removing the small strips or the small pieces from the insulating material one by one or one by one.

The conducting layer in the laser removing area is the original copper foil, the thickness is uniform, and the laser processing difficulty is greatly reduced.

The processing parameters are as follows:

(7) double-sided lamination of PI film as solder resist 6 (full-sheet lamination)

And (3) laminating the double-sided board and the PI film which are laminated by using a Dezhong DCT-MP300 laminating machine, wherein a silicon rubber pad is used as a hot-pressing gasket for buffering pressure and balancing distribution of heat on the plane of the board surface during lamination. According to the material characteristics, the hot pressing is carried out in five steps: step1 normal temperature low pressure (5 min; 25 deg.C; 24N/cm)²) (ii) a step2 Medium temperature and Medium pressure (30 min; 140 ℃; 94N/cm)²) (ii) a step3 high temperature and high pressure (60 min; 220 ℃; 188N/cm)²) (ii) a step4 pressure maintaining cooling (45 min; 188N/cm)²)。

The dry film used in this example was a 50um DuPont Kapton HN film.

(8) The assembly field laser removes the PI film covering the surface of the pad (pad and part of the plug-in hole) to form a cleaned and solderably treated surface 7.

The method adopts DCT-3000P equipment integrated with double laser heads, and the two laser sources are respectively as follows: a nanosecond laser with the wavelength of 1064 nm; a 355nm picosecond wavelength laser.

The step is subdivided into three steps: a. processing contour lines along the edge of a hole and the edge of a bonding pad of which the surface PI covering film needs to be removed by 355nm picosecond laser in a focusing mode, ensuring that the PI film is cut completely without damaging the copper foil of the bottom layer as much as possible, automatically falling off because the lower layer of the PI film covering the hole is not in contact with any other layer, sucking away by an online vacuum dust collection device, and dividing the PI film covering the surface of the bonding pad into isolated areas; b. covering the surface of the bonding pad by 1064-nanometer nanosecond laser and removing the PI film which is divided into isolated areas; c. and removing residues on the surface of the bonding pad and further cleaning the copper surface by using 355nm picosecond laser in a defocusing mode to reach the direct weldable degree.

In the step, German computer CAM software is adopted to process and calculate the processing data to generate a corresponding laser processing path, then DreamRefeTor equipment operation software of DCT-3000P is introduced, the circuit board coated with the PI film is placed on a processing table, the CCD is automatically positioned, and automatic processing is started. Wherein, the switching of the light source, the change of the spot diameter and the like are automatically executed on line. The key laser processing parameters related in the step are as follows:

(9) solder 8 is added, and a component 9 is mounted.

Adding solid conductive paste to bonding areas such as bonding pads, assembling components, and performing final curing through reflow soldering.

Example 2

(1) Hot-pressing PET film for board with 2 layers of patterns inside and copper foil laminated on surface but not used for circuit production

And (3) performing double-sided board brushing (the board feeding speed is 1.2mm/min and the swing frequency is 70 times/min) by using a German and China DCT-BR300 type board brushing machine, blowing off the moisture on the board surface by using compressed air, and drying by using slight heat or naturally.

And (3) performing hot-pressing on the double-sided board and the PET film which are laminated by using DE-Zhong DCT-LA400 hot-pressing film sticking equipment. (12 kg-force, 100-105 ℃, board-moving speed 200 mm/min).

The initial board adopted in this example, i.e. the four-layer board with two conductive patterns inside and two copper foils laminated outside, for the purpose of clear subsequent description, the four conductive layers are referred to as top layer, secondary bottom layer and bottom layer in turn according to the cross-sectional structure, and the middle three dielectric layers are also referred to as medium layer, medium layer two and medium layer three in this way.

(2) Laser drilling

And D, punching according to design requirements by using a De-Zhong DCT-D6 (femtosecond ultraviolet) laser device. And (3) importing the designed data into German Circuit CAM software, generating punching data available for equipment after the data is processed by the software, importing D6 equipment operation software DreamRefetor, placing the pressed board on an equipment platform, positioning a CCD (charge coupled device) and performing full-automatic punching.

Laser drilling key parameters:

wavelength of light

Pulse width

Spot diameter

Average power

Frequency of pulses

Speed of processing

Number of working operations

355nm

600fs

20um

12.5W

1200kHz

800mm/s

12 times (twice)

(3) Filling conductive silver paste into the hole to make the hole conductive

Removing residual glue residue on the inner wall of the hole by using an alkaline degumming agent (at 50 ℃, for 40min, adding swing); rinsing the board surface and the hole wall with clear water (2min), and removing the residual degumming agent; after the compressed air dries the water on the board surface and in the holes, the hot air dries the board surface and the hole walls again, and particularly, the hole walls are dried without water vapor; placing the board on a Delzhong DCT-VT300 vacuum hole filling equipment platform, filling silver paste (Shengtian 801) into the hole along the hole opening until the hole opening is completely covered, starting a vacuum pump to vacuumize, enabling the silver paste at the top of the hole to flow to the bottom of the hole along the hole wall, enabling a layer of conductive silver paste to be attached to the inner wall of the hole, turning the board over in order to enable the attached conductive layer to be more uniform, and repeating the operation; cleaning the board surface by using dust-free cloth, and wiping off slurry attached around the orifice on the board surface; the plate was placed in an oven to cure the conductive silver paste attached to the walls of the wells (125 ℃, 30min) to form the starting conductive layer.

(4) Current balance area/plating accompanying area fabrication

According to the circuit design requirement, the PET film on the surface of the current balance area/plating accompanying area defining area on the board is removed, and the copper foil on the lower layer is exposed, so that the current is only used for balancing when the hole wall is electroplated.

The specific method comprises the steps of importing data into Germany China Circuit CAM software, and generating a path for removing the PET film on the surface of a current balance area/a plating accompanying area by laser through software processing and calculation; the path data is led into DreamRefeTor equipment operation software of German DCT-U5 equipment, a board is placed on an equipment platform, after CCD is automatically aligned, a laser automatically removes a current balance area/PET film on the surface of a plating accompanying area, and the main processing parameters are as follows:

(5) electrolytic copper plating

And (3) electroplating copper (1.25 amperes, 20min-30min, which is the optimized electroplating parameters considering the influence of a current balance area/plating accompanying area) by using German DCT-TP300 hole equipment, so that a thicker electroplated copper layer is formed on the surface of the uniform silver initial conducting layer formed on the surface of the hole wall.

(6) Laser-removed copper foil in non-circuit area and PET film covered on copper foil

The route of the circuit insulation enveloping circuit, the dividing and slicing route of the non-circuit area (namely the copper foil area to be removed, including the copper foil and the PET film covered on the copper foil) and the heating stripping removal route (the removal route of the copper foil and the PET film) are calculated by using the German computer Circuit CAM software.

The path data is imported into DreamRefeTor equipment operation software of German DCT-S5 equipment, a board is placed on an equipment platform, after CCD is automatically aligned, laser is automatically processed, and main processing parameters are as follows:

(7) double-sided hot-pressing PET film as solder mask

And (3) laminating the double-sided board and the PET film which are laminated by using a DE-Zhong DCT-MP300 laminating machine, wherein a silicon rubber pad is used as a hot-pressing pad during lamination, and the hot-pressing stage and parameters are as follows:

(8) laser-removed welding area (bonding pad and partial plug-in hole) surface PET film

The procedure used a De Zhong DCT-U6 apparatus equipped with a 355nm picosecond laser.

The process is subdivided into two steps: a. the method comprises the following steps of (1) processing contour lines along the edge of a hole and the edge of a bonding pad of a PET film to be removed in a focusing mode, ensuring that the PET film is cut completely without damaging a copper foil on the bottom layer as much as possible, and automatically falling off the PET film covered above the hole because the lower layer of the PET film is not in contact with any other layer, and then sucking away the PET film by an online vacuum dust collection device; b. and (3) processing the PET film covered on the surface of the bonding pad one by one filling line by adopting a defocusing large light spot mode, removing by photoetching, removing residues on the surface of the bonding pad and further cleaning the copper surface by adopting a mode of increasing pass under copper parameters to achieve the degree of direct welding.

The key laser processing parameters related in the step are as follows:

(9) adding solder to mount the component

The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various changes and modifications can be made without departing from the inventive concept, and these changes and modifications are all within the scope of the present invention.

Claims

1. A method for producing a circuit board with a conductive pattern formed by selective hole electroplating and laser is characterized in that: firstly, coating a high polymer masking film material which has sparse chemical plating active seeds and is electroplating-resistant on a copper-clad plate, drilling holes, only activating hole walls, directly electroplating or firstly chemically plating and then electroplating metal copper to a required thickness, then changing the diameter of light spots on line according to the size and the shape of a processed pattern, directly removing a non-circuit area copper foil to prepare a conductive pattern by laser, removing a solder mask to prepare a solder mask pattern by laser and cleaning and performing weldability treatment on a welding area on an assembly site, wherein the processing steps are as follows:

(1) coating a high polymer masking film material layer which is thinned with active seeds for chemical plating and is resistant to electroplating on the surface of a workpiece plate which is not provided with or provided with one or more layers of conductive patterns inside and is coated with copper foils on two sides;

(2) drilling according to the design requirement;

(3) conducting electricity through the holes;

(4) directly electroplating or firstly chemically plating and then electroplating copper, and depositing copper on the hole wall to thicken the hole wall;

(6) removing the copper foil layer on the non-circuit area by laser;

(7) pasting a solder mask on the surface of the workpiece;

2. The method of claim 1, wherein: the polymer masking film material for thinning the electroless plating active seeds and resisting electroplating comprises a dry PET, PI, RPP, BOPET, BOPP, PA, PPE, PTFE, PP, PE, PVC and EVA polymer film made of a single-component, multi-component, composite thermosetting, photocuring, hot-pressing adhesion and non-photosensitive and photosensitive material, comprises organosilicon and modified coating thereof, comprises Parylene/Parylene coating layers and is compounded with a binder, and the material is a monomeric, prepolymerized or polymerized liquid or paste material; the coating method of the material comprises one or more than two combined processing of rolling, hot pressing, printing, plating, spraying, missing printing, spray printing, roller coating, curtain coating and vacuum meteorological deposition; the thickness of the material is between 0.3 μm and 1500 μm.

3. The method of claim 1, wherein: the laser removing equipment comprises one or more sets of data acquisition and processing systems, an equipment operating system, a laser light source, a light beam shaping and transmission system, a laser focusing system, a workpiece clamping and automatic and manual feeding and blanking system, a workpiece positioning and movement and control system between the workpiece positioning and light beams, a visual detection and laser power monitoring and compensation system, a cleaning and constant temperature system, wherein the types of the light beams comprise Gaussian, flat top, annular, Bessel and multipoint nanosecond ultraviolet laser, picosecond and femtosecond laser beams, when a high polymer masking film or a copper foil on a non-line area is removed by the laser, energy and power on a unit area can be constant according to the shape and the size of a processed area, the diameter of a light spot interacted with the material is variable, one or the combination of high processing speed, no overlapping or a certain amount of overlapping when a processing path is overlapped, and a certain amount of overlapping or spacing amount of pulses is preferred, generating laser parameters and processing data; during processing, the diameter of a light spot can be changed on line according to the preset laser parameters and the processing path requirements aiming at the structure of a processed pattern.

4. Method according to claim 1, characterized in that: and (3) drilling in the step (2) by mechanical means or laser drilling or combined drilling of machinery and laser.

5. The method of claim 1, wherein: the hole electroconducting in the step (3) comprises a chemical copper deposition process of forming an initial conducting layer through activation of deposited colloidal palladium and chemical copper plating; also comprises a direct electroplating process of depositing carbon black, graphite, colloid palladium and ion palladium in the holes and directly forming an initial conducting layer by conducting polymers; comprises physically brushing, wiping, grinding or chemically removing the residual active conductive active material on the surface of the plate after direct electroplating or before electroless copper plating after activation.

6. The method of claim 1, wherein: after the step (1) is carried out, before or after the steps (2) and (3) are carried out, and before the step (4) is carried out, a plate surface anti-electroplating masking layer formed by a material thinning the active substance for realizing hole metallization at the clamping point of the electroplating clamp on the plate surface is removed by laser, and a copper foil surface below the plate surface anti-electroplating masking layer is exposed, so that a current path from the electroplating clamp, the plate surface copper foil at the contact point and the plate surface copper foil to the hole wall conducting layer is realized during electroplating.

7. The method of claim 1, wherein: after the step (1) and before the step (4) are carried out, before or after the steps (2) and (3) are carried out, laser is used for removing dead copper areas without electric functions, which are not lines and have an interval of more than 30 mu m with the lines, or areas, the conductive layers of which need to be removed and do not have negative influence on the subsequent removal process, or areas, the functions of which are not influenced by the copper thickness, or areas, the functions of which are positively influenced by the copper thickness, of which are added with high polymer masking film layers to expose the copper foil surfaces below the high polymer masking film layers, so that scattered patterns favorable for the balanced distribution of electroplating current during electroplating of hole walls are formed.

8. The method of claim 1, wherein: and (5) omitting the step (5), directly entering the step (6), and directly removing the copper foil material on the surface of the non-circuit area point by point or in a block manner by using a laser together with the high polymer masking film layer.

9. The method of claim 1, wherein: the step (6) is that the photoetching laser is firstly projected point by point, the conductive material under the envelope curve of each conductive pattern is removed by vaporization, and a closed insulating channel is manufactured by taking the contour line as a boundary; then, projecting light etching laser point by point, vaporizing and removing the conductive material under the separation line, and subdividing the large conductive material to be removed into small heat-insulated pieces; and then, the heating laser is projected onto the small pieces in sequence, the bonding force between the small pieces and the base material is reduced, the small pieces deform, and the small pieces are separated from the workpiece under the combined action of auxiliary gas and are transferred and collected.

10. The method of claim 7, wherein: when the insulation space S between the two conductors is wider, the value satisfies S>2d_maxWhen the processing scheme is nd + (n-1) D, namely n light etching vaporization removal with the beam diameter of D and (n-1) heating stripping removal with the beam diameter of D, wherein n is more than or equal to 2, and the n value is preferably the minimum; when the width S of the conductive layer between two conductors satisfies 2d_max≥S≥d_maxWhen the conductor is etched, S-d 1+ d2 is selected, that is, two photoetching laser beams with photoetching diameters of d1 and d2 are selected to remove the conductive material between the two conductors, wherein d1 and d2 can be the same or different; when the insulation space S between two conductors is smaller than the maximum beam waist diameter of the task of photoetching, i.e. d_maxWhen the diameter of the light beam is larger than or equal to S, the processing scheme is S-d, namely the diameter of the light beam is selected, so that the conducting material between the two conductors is removed by just one photoetching laser beam with the diameter of the light beam being d.

11. The method of claim 1 or 3 or 5 or 6 or 7 or 8, wherein: when the metal is removed or the metal and the adjacent organic material are removed in the steps (2), (5), (6) and (8), the optical power density of the used focused laser spot is greater than the minimum optical power density required by removing the conductive metal copper layer and is less than 3 times of the minimum optical power density required by removing the conductive metal copper layer; when only organic material is removed, the focused laser spot optical power density used is greater than the minimum power density required to remove the organic material.