CN113710011A

CN113710011A - Method for manufacturing circuit board by laser etching pattern after electroplating thickening and weldability processing hole

Info

Publication number: CN113710011A
Application number: CN202111002461.9A
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: 2021-11-26

Abstract

The invention relates to a method for manufacturing a circuit board by only electroplating thickened holes and processing etching patterns by laser after solderability, which comprises the steps of coating a sparse chemical plating active seed and electroplating-resistant organic masking material on a multilayer copper-clad plate which is manufactured by an inner layer circuit, drilling holes, electroplating and depositing copper on the hole wall to the required thickness, then electroplating and depositing a solderability etching-resistant metal layer, removing the masking layer of a non-circuit area by laser to expose the surface of the copper foil, and etching to manufacture a conductive pattern. According to the invention, the active seeds are thinned by chemical plating and the organic masking material which is resistant to electroplating is used for masking the board surface, so that metal can be deposited on the hole wall only, and the quality of the metallized hole of the circuit board is better so as to better meet the electrical requirement; the diameter of the laser spot is changed according to the size of the pattern, and the masking material removing speed is high and the consistency is good; the plating resistance, corrosion resistance and solder resistance patterns are directly manufactured by removing materials by laser, the steps are few, finer products can be manufactured, and the environment is friendly.

Description

Method for manufacturing circuit board by laser etching pattern after electroplating thickening and weldability processing hole

Technical Field

The invention belongs to the technical field of circuit manufacturing, relates to a laser processing technology, and particularly relates to a method for manufacturing a circuit board by laser etching patterns after electroplating thickening and performing hole weldability processing.

Background

The invention utilizes laser processing technology, uses non-photosensitive organic material with sparse chemical plating active seeds on the surface as a masking layer, only electroplates thickened hole wall copper, electroplates a weldable anti-corrosion metal layer on the hole wall, removes the masking material on a non-circuit area by laser, manufactures an anti-etching pattern, and manufactures a conductive pattern by etching. The invention can control the copper thickness of the hole wall, better meets the electrical requirements of electronic products on the circuit board, is particularly suitable for manufacturing fine conductive patterns, and is also suitable for producing various circuit boards in large batch, small batch, various varieties and samples.

The manufacturing process comprises the following steps: coating organic masking material on the surface of a double-sided copper-clad plate or a multilayer circuit board which completes the manufacture of an inner layer and an overlapped outer layer → drilling hole conducting → electroplating copper thickening hole cylinder → electroplating to deposit weldable metal resist on the hole wall → laser to remove the masking material of the non-circuit part to expose non-circuit copper → etching → coating and curing non-photosensitive solder resist on the non-circuit area at one time → using laser to manufacture a solder resist pattern → missing printing solder paste, and carrying out component mounting and welding.

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 on the wall of the hole, and penetrating the metal layer in the horizontal direction by using a conductive hole cylinder 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. Firstly, depositing a thin conductive material layer on the insulated hole wall by chemical plating or other means; on the initial conductive layer, a conductive metal is plated by electroplating to a desired thickness so that holes through the metal layer have 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, is mature and stable, has multiple working procedures and complex operation, and can carry out electroplating treatment on the circuit part and the non-circuit part in a distinguishing way. 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 process of electroless copper plating, also called electroless copper plating, is relatively complex, but more mature and stable, is one of the mainstream technologies of the prior hole metallization, and has wide application range. The electroless copper plating technique uses an autocatalytic redox reaction to deposit copper (Cu) from an electroless copper plating solution onto the walls of the hole²⁺) 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, and three methods, namely a carbon membrane method, a palladium membrane method and a high polymer membrane, are popular and are respectively suitable for different application scenes. Among them, the carbon membrane method is more popular, and has been in the mainstream position in the field of flexible circuit board manufacturing besides being applied to the manufacturing of part of rigid circuit boards, the polymer membrane method is emphasized in the production of part of low-layer rigid circuit boards, and the palladium membrane method is not widely applied due to the cost. The method directly coats or manufactures conductive carbon, palladium or high molecular material on the hole wallAfter the formation of the continuous thin layer, a base conductive film 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, the original copper foil on the substrate has to be used as the power line for plating copper on the hole wall, from this viewpoint, the conductive pattern on the X, Y plane only plays a role of plating.

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 is a clear requirement for the copper thickness of the metallized hole, which is 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, in general, the conventional circuit board manufacturing technology, whether manufacturing conductive patterns on X, Y planes or solder resist patterns, has the problems of high precision and manufacturing difficulty, belongs to transfer manufacturing technology/transfer process, and aims to achieve design by means of mask master-mold and intermediate material indirect processing/indirect processing. In the existing technology, photo-drawing is needed to manufacture a corrosion-resistant pattern, an anti-electroplating pattern and a solder-resistant pattern to be used as a mold and connected in series, and errors and defects of a single mold and a single procedure can be amplified in subsequent processing procedures, so that the existing circuit board technology is difficult to manufacture fine products. In the existing technical system, dry films, metal resists, scaling powders for hot air leveling and the like used for the pattern transfer process are not materials required by the mechanical and electrical properties of the circuit board, and are not finally present on the product, but technical materials adopted for realizing the processing target need to be removed after having the function of intermediate transition, and the materials need to be used and removed, and equipment such as photo-drawing, film pasting, exposure, development, etching, film removal and the like, so that the traditional circuit board technology has a complex manufacturing process, not only occupies capital and field, but also wastes materials, equipment and other resources, and increases the manufacturing difficulty. In addition, in the conventional techniques, the conductive pattern and the solder resist pattern are generated in the transfer process of the resist pattern and the plating resist pattern formed by the intermediate material and the mold, and most of them are required to be performed in water or chemical solution, and waste residue, waste liquid, and waste gas are generated, which causes a large environmental stress. Therefore, it is necessary to develop a technology mainly based on direct processing, which replaces the existing indirect processing technology with common materials instead of special materials, with no or little intermediate equipment, which is another object of the present invention.

Disclosure of Invention

Aiming at the defects that the prior art can not independently deposit conductive metal on the hole wall and adopt an indirect technology to manufacture a corrosion-resistant pattern, the invention provides a circuit board manufacturing method for manufacturing an etching pattern by laser after electroplating thickening and performing hole weldability processing, which can only electroplate and thicken a hole wall conductive layer and directly manufacture a corrosion-resistant pattern. The method comprises the following specific steps:

(1) coating an organic masking material on the surface of a workpiece which is internally provided with no or more than one layer of conductive patterns and is coated with copper foil on two sides;

(2) drilling according to the design requirement;

(3) conducting electricity through the holes;

(4) electroplating, namely depositing copper on the hole wall to thicken the conductive layer to the thickness required by final inspection;

(5) electroplating, namely depositing a weldable etching-resistant metal layer on the hole wall;

(6) laser removing the masking material layer on the surface of the non-circuit area;

(7) removing the copper foil layer on the non-circuit area by chemical etching to manufacture a conductive pattern;

(8) coating and curing a non-photosensitive solder resist on the non-circuit area at one time;

(9) removing the organic material on the electric conductor of the welding area by laser at an assembly site, manufacturing a solder resist pattern, and cleaning and performing weldability treatment on the surface of the welding area;

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

And (1) coating an organic masking material on the surface of a workpiece which is internally provided with one or more layers of conductive patterns and is covered with copper foil 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 does not need to have photosensitive performance, but the surface of the masking film needs to have the property of thinning active substances for realizing hole metallization, and the masking film can resist the treatment of acid, alkali, organic matters and the like before hole metallization, resists electroplating and comprises photosensitive materials and non-photosensitive materials; comprises organic silicon and modified paint thereof, other resin and modified paint thereof; including Parylene/Parylene coatings, other polymer coatings; the film comprises a thermosetting, photo-curing and hot-pressing adhesive film made of polymer materials such as PET, PI, PTFE, PP, PA, PPE, PE, PVC, EVA and the like and modified substances thereof, a bonding agent compounded with the film, and a thermosetting, photo-curing and hot-pressing adhesive film compounded with other materials; comprises the above materials, and is overlapped layer by layer; the coating method of the material comprises the processing of rolling, hot pressing, printing, plating, spraying, curtain coating and other methods or the combination of the methods; in the range of 0.3 μm to 3000 μm, preferably 1um to 100um thick.

In the invention, because the removal of the material is not involved, the material does not need to have photosensitive performance, the rigidity and the strength of the material can be obviously higher than those of the traditional paste, the performances of acid resistance, alkali resistance, organic solvent resistance and the like are greatly improved, the shielding effect is good, the active particles are separated, the anti-deposition performance is good, and the effects of physically shielding the board surface, electrically insulating the copper-clad foil and preventing the deposition of the active particles and metal ions can be well achieved.

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.

If a mechanical drill bit is used for drilling holes, epoxy drilling dirt may appear on the hole wall, and before hole conductivity is carried out, the epoxy drilling dirt is removed by using a liquid medicine or a process which does not damage the high polymer film so as to ensure the hole metallization quality.

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

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 surface has the property of thinning the chemical plating active seeds, the plate surface is masked, and after the step of directly electroplating the black holes of the method 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 cylinder.

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 cylinder 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 cylinder and the electroplating balance block is covered by a mask which is made of insulating material and is not coated with copper in surface deposition although contacting with the electroplating liquid, so that only the hole cylinder and the balance block can deposit copper in the electroplating process, and the electroplating time is enough, so that a copper deposition layer with enough thickness can be obtained on the hole cylinder, and the purpose of selectively controlling the copper thickness of the hole wall is achieved.

And (5) electroplating a corrosion-resistant and weldable metal protective layer on the hole wall.

The plated metal is required to have corrosion resistance required in step (7), and at the same time, should protect the corresponding area during transportation and storage of the circuit board, and should function to increase solderability of the land during assembly of the circuit board.

The invention uses non-photosensitive plating-resistant material, has good masking capability, can endure longer electroplating time, and can also endure harsher plating solution and operation conditions. In addition, the other areas of the plate surface are masked by the high polymer film, so that metal can be deposited only on the hole wall, the welding disc and the surface of the electroplating balance block, the plating area is relatively small, and materials are saved. Therefore, more varieties of metals with corrosion resistance, protection and solderability can be selected, such as nickel, gold and tin.

And (6) removing the high polymer film layer in the non-circuit area by laser. The purpose is to expose the copper surface of the non-circuit area outside, so as to be convenient for chemical etching removal.

The width of the area needing to be removed is different for different circuit boards and different circuits. If the width of the removal area does not correspond to the beam diameter or a multiple thereof, the removal speed is reduced, overlapping can also occur, and overlapping can also occur, wherein the overlapping area is processed twice by laser during overlapping, so that the processing effect of the overlapping area is inconsistent. The invention changes the diameter of the focused laser beam according to the shape and the size of the removed area through data processing and equipment driving software, so that the diameter of the focused laser beam or the multiple thereof is exactly equal to the width of the area to be removed, thereby reducing or removing the overlapping of the laser processing area and improving the processing efficiency.

The high polymer film layer on the non-circuit area is removed, and the organic material on the surface of the copper foil at the corresponding position is only required to be removed in the same process of manufacturing the electroplating balance block and removing the high polymer 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.

And (7) chemically etching the copper foil layer on the non-circuit area to manufacture the conductive pattern.

In the invention, the copper foil layer to be removed is masked by the high polymer film in the processes of chemical plating and hole wall electroplating, no copper metal is deposited, the copper foil layer is still coated by the raw material, and compared with the prior art, the copper foil layer is not increased in thickness and is easier to etch and remove. Although the traditional chemical etching technology is adopted in the step, the copper foil layer to be removed is thinner than the traditional technology, the required time is shorter, the side corrosion phenomenon is reduced, and the quality of the side wall of the manufactured conductive pattern is better.

And after the conductive pattern is manufactured, the manufactured circuit board can be checked for electrical on-off. The most important function of the circuit board is to provide electrical connections. Whether each network meets the design requirements or not is judged through electrical on-off inspection, and the method is one of important links in modern circuit board production. In conventional circuit board technology, the on-off inspection is generally performed after forming a solder resist pattern and completing solderability coating of the lands and the insertion holes, such as after electroless nickel plating, gold plating, hot air leveling or immersion tin plating. The on-off inspection is carried out after the solder resist pattern and the solderability coating, and the method has the advantages that the surface of the pad of the test point is protected by the solderability metal, the inspection time period is suitable to be long, and the organization and management are convenient; a disadvantage is that if the circuit board has on-off problems, the problems mostly occur in the middle of the manufacturing process, because the problems are found late and it is costly to repair or scrap the circuit board. In the present invention, the electrical on-off check is arranged either after step (8), (9) or after step (11). The electrical on-off inspection is carried out before the solder mask is manufactured, and the defects that the time period suitable for inspection is short and the window for organization management is small; the method has the advantages of timely finding out the problem of the manufacturing process and low cost for repairing or scrapping the problem board.

And (8) covering a high polymer solder mask film on the surface of the non-circuit area.

The high polymer film, namely the solder resist, coated in the step has the effect 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 (9) removing the high polymer material on the surface of the welding area by using laser to manufacture the solder resist pattern.

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 removed by laser processing, is easier to find a window meeting the technical requirements, and can be finished by one wavelength laser, such as nanosecond UV pulse laser, or picosecond and femtosecond laser to produce a solder resist pattern; it can also be done by combining two wavelength lasers. For example, selecting a large 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.

And (10) adding solder to the connecting disc, carrying out component mounting and inserting, and carrying out remelting welding and wave soldering.

In the present invention, laser processing is used for both drilling and removing the high polymer 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 film is removed by laser or the copper foil on the non-circuit area is removed by laser, the energy and power on a unit area are constant according to the shape and the size of a processed area, 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 only electroplates and thickens 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 uses non-photosensitive material as corrosion resistant material and solder resist material, and has low cost.

3. The invention uses the laser direct removal method to manufacture the corrosion-resistant pattern and the solder-resistant pattern, does not need pattern transfer, reduces steps and related materials and equipment, reduces cost and can manufacture fine conductive patterns and solder-resistant patterns.

4. According to the technical scheme, only the holes and the bonding pads are electroplated, the thickness of the non-line part conductive layer is not increased, etching is easier, and the manufacturing of finer conductive patterns is facilitated.

5. 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.

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 6-10);

in the figure: 1. an insulating substrate 2, a copper-clad plate 3, an organic masking material layer 4, an initial conducting layer 5, an electroplated copper layer 6, a weldable corrosion-resistant metal layer 7 and a non-photosensitive solder resist layer; 8. solderability treated surface 9, solder 10, 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

A method, material and apparatus for manufacturing circuit boards by selective plating of holes, pads, laser resist patterns, chemical etching of conductive patterns, the method comprising:

(1) coating a PET film of organic silicon resin on the double-sided hot-pressing surface of a Fr4 copper-clad plate without a pattern inside to form an organic masking 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.

Laminating/laminating is carried out, the front side and the back side of the copper-clad plate are respectively jointed with the PET film with the same size and the surface coated with the organic silicon resin and slightly rolled by a rubber roller, because the surface of the copper-clad plate is clean and free from dust after being brushed, the surface of the PET film with the surface coated with the organic silicon resin is also very clean, the PET film can be tightly jointed, the relative sliding can be ensured not to be generated in the subsequent operation process, the rolling of the rubber roller is carried out to discharge the air between the jointing surfaces, and the thickness of the PET film with the surface coated with the organic silicon resin is 10 mu m.

And (3) laminating the double-sided PET film-coated double-sided board by using DE-Zhong DCT-LA400 hot-pressing equipment (12 kilograms, 105-115 ℃, and the board moving speed is 200 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 an 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 the step, only the hole wall part can be contacted with the liquid medicine, and the rest part is completely covered by the PET film coated with the organic silicon resin on the surface. The organic silicon resin on the surface of the PET film has the characteristic of hydrophobic chemical activation, so that a chemical copper deposition layer cannot be formed on the final surface, and a thin chemical copper deposition layer is formed on the surface of the hole wall.

(4) 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 layer is increased by adopting a small-current and long-time (0.1-0.15 ampere, 20-30 min) 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 surface of the PET film coated with the silicone resin has no conductivity, the plating is performed only for the hole walls.

(5) Electroplating tin and lead on the hole wall to form a solderable corrosion-resistant metal layer 6

Using a fluoborate plating solution with a tin-lead ratio of 6:4 and a current density of 1.6A/dm²Electroplating for 25min, cleaning the board surface, and air drying with compressed air.

Because the PET film coated with the organic silicon resin on the surface has plating resistance, a tin-lead alloy electroplated layer is only formed on the copper layer of the exposed welding disc and the hole wall.

(6) Laser-removed PET film in non-circuit area

Importing the data into German China Circuit CAM software, and generating a path for removing the PET film on the surface of the bonding pad by laser after software processing and calculation; and (3) leading the path data into DreamRefeaTor equipment operation software of a Dezhong DCT-U5 equipment, placing the board on an equipment platform, and automatically aligning the CCD and then automatically removing the PET film on the surface of the bonding pad by laser.

In the step, when the circuitous CAM software calculates the laser processing path, the circuitous CAM software matches a proper spot diameter according to the size of a specific graph and generates a corresponding processing path; during the laser processing executed by the DreamRefeaTor software, the diameter of a light spot can be automatically changed in real time according to data, and the power can be adjusted, so that the laser removal can be completed with high efficiency and high quality. In the process, the related key laser processing parameters are as follows:

(7) chemical etching to remove the copper layer in the non-circuit region

The German China DCT-EU400 automatic etching equipment integrates the functions of etching, cleaning and drying into a whole, and the board moving speed is 2.0 m/min.

(8) The non-circuit region double-sided hot-pressed PET film forms a non-photosensitive solder resist layer 7

(9) Removing the PET film covered on the surface of the welding area (bonding pad and part of the plug-in hole) by laser to produce a solder resist pattern, and cleaning and performing solderability treatment on the surface of the welding area to form a solderability treated surface 8

Different from the step (5), the step adopts DCT-3000P equipment integrating double laser heads, and the two laser light 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 PET covering film is required to be removed by 355nm picosecond laser in a focusing mode, ensuring that the PET film is cut completely without damaging the copper foil of the bottom layer as much as possible, 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, then sucking away the PET film by an online vacuum dust collection device, and dividing the PI film covered on 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 PET 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, processing data is processed and calculated by adopting German China Circuit CAM software to generate a corresponding laser processing path, then DreamRefetor equipment operating software of DCT-3000P is introduced, the circuit board coated with the PET film is placed on a processing table, and the CCD is automatically positioned to start automatic processing. 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:

(10) solder 9 is added to the lands, and component 10 is mounted and inserted, and reflow soldering and wave soldering are performed.

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

Example 2

(1) laminating PI film on board having 2 layers of patterns inside and copper foil laminated on surface but not having circuit

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.

The finished laminated double-sided plate and PI film were processed using a DE-MEDIA DCT-MP300 laminatorAnd (3) laminating, wherein a silicone rubber pad is used as a hot-pressing pad for buffering pressure and balancing heat distribution on the plane of the plate surface during laminating. According to the material characteristics, the hot pressing is carried out in five steps: step1 normal temperature low pressure (15 min; 80 ℃; 24N/cm)²) (ii) a step2 Medium temperature and Medium pressure (25 min; 140 ℃; 94N/cm)²) (ii) a step3 medium temperature and high pressure (25 min; 180 ℃; 188N/cm)²) (ii) a step4 high temperature and high pressure (60 min; 220 ℃; 188N/cm)²) (ii) a step5 was pressure-maintained and cooled (45 min; 188N/cm)²)。

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.

The dry film used in this example was a 25um dupont kapton hn film.

(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) Black hole

Removing oil with alkaline oil removing agent (45-50 deg.C, 10-15min, and oscillating); carrying out black hole (10-15min, adding swing) on suspension (black hole liquid) containing micro-nano carbon particles; removing trace black hole liquid attached to the board surface by using compressed air; natural air drying or low heat drying (25-40 deg.C) to evaporate the black pore liquid solvent and form a continuous carbon dielectric film in the step pores (pore wall and surface of annular boss) as the conductive precursor for electroplating copper.

Two key subdivision steps in the step, namely oil removal and black hole, are carried out on DCT-TP300 hole equipment in Germany.

(4) Current balance area/plating accompanying area fabrication

And according to the design requirement of the circuit, removing the PI film on the surface of the current balance area/plating accompanying area defining area on the board, and exposing the lower copper foil to balance the current only when the hole wall is electroplated.

The method specifically comprises the steps of importing data into Germany China Circuit CAM software, and generating a path for removing a PI film on the surface of a current balance area/a plating accompanying area by laser after software processing and calculation; and guiding the path data into DreamReceaTor equipment operation software of Dezhong DCT-U5 equipment, placing the board on an equipment platform, and automatically aligning the CCD, and then automatically removing the PI film on the surface of the current balance area/the co-plating area by laser.

(5) Copper electroplating on hole wall

And (3) thickening electroplating of the hole wall copper layer by using Dezhong DCT-TP300 hole equipment (1.25 amperes, 20min-30min, which is the optimized electroplating parameter considering the influence of a current balance area/accompanying plating area).

(6) Electroplating tin-lead

Using a fluoborate plating solution with a tin-lead ratio of 6:4 and a current density of 1.6A/dm²And the time is 40min, cleaning the board surface, and drying by using compressed air to form a corrosion-resistant metal layer on the surface of the hole wall.

(7) Laser removing PI film on surface of non-circuit area

Importing the data into German China Circuit CAM software, and generating a path for removing the PI film on the non-line surface by laser after software processing and calculation; the path data is led into DreamReferTor equipment operation software of German DCT-U5(20W, nanosecond ultraviolet light source) equipment, a board is placed on an equipment platform, after CCD is automatically aligned, PI films on the surface of a bonding pad and the surface of a circuit are automatically removed by laser.

(8) Chemical etching to remove the copper layer in the non-circuit region to form a conductive pattern

The DE-ZHONG DCT-EU400 automatic etching equipment integrates the functions of etching, cleaning and drying, and the board moving speed is 2.5 m/min.

(9) Lamination of PI film to non-wiring area as solder resist

The lamination parameters were as in step (1) of this example.

(10) Laser removing PI film on surface of welding area (welding pad and partial plug-in hole)

Importing the solder resist data into Germany Circuit CAM software, and generating a path for removing a PI film on the surface of a welding area by laser after software processing and calculation; the path data is led into DreamRefeTor equipment operation software of German DCT-U5(20W, nanosecond ultraviolet light source) equipment, a board is placed on an equipment platform, and after CCD is automatically aligned, laser is automatically removed.

(11) Adding solder to mount the component

The circuit board can be continuously manufactured by the traditional method based on any step of the invention; in the steps of the invention, conventional circuit board processes, such as on-off inspection, such as printing of a label, may be inserted; double-sided, multi-layer, and various substrate materials may be suitable.

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 manufacturing a circuit board by only electroplating thickened holes and processing etched patterns by laser after solderability processing is characterized in that: coating an organic masking material which is sparse and chemically plated with active seeds and is resistant to electroplating on a multilayer copper-clad laminate on which inner-layer circuits are manufactured, drilling holes, electroplating and depositing copper on hole walls to a required thickness, electroplating and depositing a weldable anti-etching metal layer, removing the masking layer of a non-circuit area by laser to expose the surface of the copper foil, and etching to manufacture a conductive pattern, wherein the processing steps are as follows:

(2) drilling according to the design requirement;

(3) conducting electricity through the holes;

2. The method of claim 1, wherein: the organic masking material is thinned with chemically plated active seeds, resists the treatment of acid, alkali and organic matters before hole metallization and resists electroplating; the coating comprises dry PET, PI, RPP, BOPET, BOPP, PA, PPE, PTFE, PP, PE, PVC and EVA high molecular materials which are made of single-component, multi-component, composite thermosetting, photo-curing, hot-pressing adhesion and non-photosensitive and photosensitive materials, and comprises organosilicon and modified paint thereof, Parylene coating and other polymer coating; the film comprises thermosetting, light-curing and hot-pressing adhesive films made of the materials and modified substances thereof, and a composite adhesive for the films, wherein the film comprises the materials which are overlapped layer by layer and monomeric, prepolymerized or polymerized liquid and paste materials; the coating method of the material comprises one or more of rolling, hot pressing, printing, plating, spraying and curtain coating; the thickness of the material is greater than the total metal thickness thickened on the line, and is in the range of 0.3-3000 μm.

3. The method of claim 1, wherein: the method used in the step (2) comprises the steps of drilling holes by mechanical means; comprises drilling holes with laser; comprises mechanical and laser combined drilling; comprises the processing steps of deburring and removing glue residues after drilling.

4. The method of claim 1, wherein: the laser processing equipment used in the steps (2), (6) and (9) can convert the diameter of the light spot interacted with the material on line according to the circuit graph structure by taking energy and power on a unit area as constant quantities; 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 movement and control system with light beams, a visual detection and laser power monitoring and compensation system, a cleaning and constant temperature system, and light beam types comprise Gaussian, flat top, annular, Bessel and multipoint nanosecond ultraviolet laser beams, picoseconds and femtosecond laser beams.

5. The method of claim 1, wherein: the hole electroconducting in the step (3) comprises a chemical copper deposition process of forming an initial conductive layer through colloid palladium activation and chemical copper plating; also comprises a diameter electroplating process for directly forming an initial conductive layer by depositing carbon black, graphite, colloidal palladium and ionic palladium in the hole and using conductive 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, removing the anti-electroplating masking film layer on the surface of the clamping point of the electroplating clamp by using laser to expose the copper surface of the contact area with the electroplating clamp; and removing dead copper areas without electric function, or areas with conductive layers needing to be removed and having no negative influence on the subsequent removal process, or areas with copper thickness not influencing the function of the dead copper areas, or areas with copper thickness having positive influence on the function by increasing the electroplating-resistant film masking layer on the areas with copper thickness by using laser, wherein the dead copper areas are not on the non-circuit and have an interval more than 30 mu m with the circuit, or areas with conductive layers needing to be removed and having no negative influence on the subsequent removal process, or areas with copper thickness not influencing the function of the dead copper areas, or areas with copper thickness having positive influence on the function of the dead copper areas are increased, and the copper foil surfaces below the areas are exposed, so that a dispersed pattern which is beneficial to the balanced distribution of electroplating current when the hole wall is electroplated is formed.