CN113939103A - Circuit board manufacturing method for conducting on-off test and manufacturing solder resist pattern in assembly stage - Google Patents
Circuit board manufacturing method for conducting on-off test and manufacturing solder resist pattern in assembly stage Download PDFInfo
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- CN113939103A CN113939103A CN202111047047.XA CN202111047047A CN113939103A CN 113939103 A CN113939103 A CN 113939103A CN 202111047047 A CN202111047047 A CN 202111047047A CN 113939103 A CN113939103 A CN 113939103A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/22—Secondary treatment of printed circuits
- H05K3/28—Applying non-metallic protective coatings
- H05K3/282—Applying non-metallic protective coatings for inhibiting the corrosion of the circuit, e.g. for preserving the solderability
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- H05K3/00—Apparatus or processes for manufacturing printed circuits
- H05K3/30—Assembling printed circuits with electric components, e.g. with resistor
- H05K3/32—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits
- H05K3/34—Assembling printed circuits with electric components, e.g. with resistor electrically connecting electric components or wires to printed circuits by soldering
- H05K3/341—Surface mounted components
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- Microelectronics & Electronic Packaging (AREA)
- Electric Connection Of Electric Components To Printed Circuits (AREA)
Abstract
The invention relates to a circuit board manufacturing method for performing on-off test and manufacturing a solder resist pattern in an assembly stage, which comprises the following steps: step 1, coating solder resist on a whole board of a manufactured circuit board which is subjected to conductive pattern manufacturing and curing at one time; step 2, in an assembly site, directly puncturing a solder mask on a test point by using a test needle before assembly to carry out electrical on-off inspection on the circuit board; step 3, on the assembly site, processing the qualified circuit board by laser to manufacture a solder resist pattern and perform solderability surface treatment on a solder area; and 4, applying solder to the surface of the welding area to finish the assembly process of the component. The invention solves the defects that the solder resist is coated and cured once in the whole board manufacturing stage, the solder resist pattern is manufactured again and the solderability processing technology can not carry out on-off test in the component assembling stage, optimizes the manufacturing process of electronic products on the whole and ensures that only qualified circuit boards can enter the assembling stage.
Description
Technical Field
The invention is applied to the field of bare board manufacturing and component assembly of circuit boards, and relates to a circuit board production method which is used for carrying out on-off inspection after a whole board is coated with a solder resist material and is solidified, carrying out laser forming on a solder resist pattern on an assembly site and carrying out solderability treatment on a solder area, thereby integrally optimizing the manufacturing flow of electronic products.
Background
Electronic products generally go through three stages of design, preparation and assembly from concept to finished product.
After the physical design is finished, material preparation is carried out, including selection and customization of various components, connectors, input and output components, display modules and other functional modules and the like. One of the most important materials is a bare circuit board, which is used to support components and play a role in electrical interconnection between pins of the components, and is a key factor affecting the quality and reliability of electronic products and the difficulty, cost, and speed of the whole manufacturing process, and must be customized according to design requirements and product attributes. A bare circuit board, referred to as a bare board for short, refers to a circuit board on which components have not been mounted, and is also referred to as a printed circuit board, a printed wiring board, a printed board, a circuit board, and a printed board. The bare board is typically custom-made as needed by a manufacturer who specializes in manufacturing printed circuit boards. Taking a double-sided circuit board as an example, the process flow of the bare board manufacturing is roughly as follows: drilling a hole on a double-sided copper clad foil insulation substrate, metallizing the hole, manufacturing a conductive pattern, removing a metal corrosion resistant film or an organic corrosion resistant film, coating a solder resist, manufacturing a solder resist pattern and generating a welding area, performing solderability coating treatment on the surface of the welding area, inspecting electrical on-off, manufacturing a mark symbol, and delivering the product to an assembly stage.
The electronic product is assembled, namely, various materials are assembled, matched and combined together, and corresponding electrical connection and functional matching between the materials are realized through means of welding, fixing and the like. In a narrow sense, the assembly process of mounting and soldering components to a circuit board is often referred to as assembly. The product after the components are assembled is generally called an assembly board. Where distinction is not required, the bare board and the assembled board are generally referred to as circuit boards. The former assembly technique mainly uses through-hole insertion method, i.e. the pins of various components, connectors, functional modules, etc. are inserted into the mounting holes of bare board, then these pins, hole wall and soldering pad are soldered together by using soldering material so as to fix the components on the circuit board, and the electric interconnection between the pins of the components can be implemented by means of soldering pad, interconnection line and relay hole on the circuit board. At present, electronic products are more often assembled and connected by adopting a surface mounting technology, namely, soldering paste is coated on a connecting disc, namely a bonding pad, of a circuit board, pins of various components, connectors, functional modules and the like are correspondingly placed on a soldering paste layer of the connecting disc, finally, the circuit board is heated to melt the soldering paste, terminal electrodes of the components and the connecting disc are soldered together, so that the components are mounted and fixed on the surface of the circuit board, and the electrical interconnection among the components is realized through a conductive channel formed by the bonding pad, a lead and a hole on the circuit board. The assembly of the circuit board is carried out by professional assembly factories or is completed by an electronic product development mechanism. Taking the SMT technology as an example, the assembly process flow of the circuit board is roughly: a circuit board from a bare board manufacturing factory is printed with solder paste in a missing mode on a soldering tray, components are picked up and are attached to the surface of the circuit board, and the solder paste is heated to reflow so that soldering between pins and soldering pads is achieved.
Considering the whole process of manufacturing a bare board and assembling components of a circuit board, it is known that the processes of manufacturing holes, conductive patterns and solder resist patterns in the production stage of the bare board, and the processes of printing solder paste, reflow soldering and the like in the assembly production stage are essential to realize the mounting and fixing of the components and the electrical interconnection between the components. The solder resist pattern is produced and the solderability coating is completed in a bare board stage, but is the basis of production in an assembly stage.
On the surface of the bare circuit board, a solder resist pattern is formed in a region covered with a solder resist. The solder resist pattern is a protective covering layer for the circuit board, is selectively coated on the surface of a finished printed board, and is coated with a solder resist at all positions except for the inner walls of the bonding pads and the metallized holes. The solder resist masks and protects the surface of the printed wire and also masks and protects the blank area of the board surface, and when the component and the circuit board are welded together, the solder resist plays a role in isolation and can prevent the short circuit phenomenon between the wires or the pads caused by the free flow of the molten solder to a certain extent. In addition, the solder resist is insulating, heat-resistant and chemical-resistant, is a permanent protective layer on the surface of the printed board, plays a role in mechanical isolation, can prevent the printed board from being scratched and scratched when being stored and used, and also plays a role in protecting the printed board from moisture, salt mist, mold and other weather-resistant and environment-resistant three-proofing functions. Common methods for applying solder resists are screen printing and photo-chemical imaging, both of which require long process routes. Taking a photochemical imaging method as an example, the process route is as follows: preparing a substrate and ink, coating a first full plate, pre-drying, coating a second full plate, pre-drying, exposing, developing and post-curing.
Either method requires a photo-drawing master and then a pattern transfer. The method comprises the following steps of preparing a stencil printing plate by using a bottom plate, then printing a solder resist on the surface of a circuit board by using a screen printing technology, and curing at one time to form a solder resist pattern; or the whole board is coated with the liquid photosensitive solder mask paint, the circuit board is exposed by taking the bottom plate as a light-blocking masking film after pre-drying, unexposed solder mask on a masking area is removed by developing and washing to form an initial solder mask pattern, and then the formed solder mask pattern is completely cured to finish the solder mask pattern manufacturing flow. The screen printing method has low cost and limited pattern fineness, and is suitable for producing common circuit boards; the photochemical imaging method uses a photosensitive solder resist, and in order to prevent the bottom plate from being adhered to the solder resist, the solder resist is pre-cured before exposure, and after development, the solder resist can be completely cured.
In the development process of electronic product refinement, the solder resist pattern manufacturing technology is also improved to a certain extent, for example, a more advanced bottom plate manufacturing technology and a more advanced silk screen manufacturing technology are adopted; for example, a double-sided simultaneous stencil coating technique is employed; for example, a more precise exposure, development, and curing system is used. On one hand, however, when screen printing is missed, deformation of a screen printing plate and dislocation of patterns are difficult to avoid, and the manufacturing precision of a solder resist pattern is difficult to be substantially improved; on the other hand, the masking and protecting functions of the solder resist pattern have minimum requirements on the thickness of the solder resist pattern coating, and the photochemical imaging method is difficult to greatly improve the pattern precision. Therefore, to a large extent, due to the limitations of pattern resolution and position accuracy, it is difficult to clearly and cleanly form finer pattern structures, and the requirement of reliable soldering of fine-pitch package components for solder resist pattern precision cannot be met. For example, none of these methods can satisfactorily coat the solder resist on the middle surface of fine pitch smt (surface Mount technology) lands, often resulting in fine pitch component soldering problems.
On the circuit board, the area not covered with the solder resist and surrounded by the solder resist pattern is a land. The lands include lands for mounting SMD (surface Mounted devices) component terminal electrodes, i.e., SMD pads, and also include lands for receiving the inner walls of component holes and solder rings around the holes, i.e., pads. When the element lead is soldered with the printed board, the quality of the formed solder joint is related to the wetting property of the surface of the soldering area by molten solder, namely solderability. In order to obtain good solderability, in the manufacturing stage of the bare board, after a solder resist is coated to form a solder resist pattern, a part of the printed board without the solder resist pattern, namely a welding area, needs to be subjected to surface treatment, and a layer of material with solderability and protection is usually coated on a conductive material layer in an element insertion hole and a conductive material layer of a connecting pad, so that the surface of the welding area can be protected from deterioration caused by the environmental effect during the storage of the printed board, and the solderability coating layer can play a role in soldering.
The weldable coating layer comprises metal and organic materials. The organic solder assist protective film is abbreviated as OSP (organic solder assist) and the coating technology of the material is simpler than the technology of coating metal, but the effective protective period for the covered surface of the protective film formed by the OSP is shorter, and the protective film is easy to scratch and scratch in the storage and transportation process of the circuit board. The process of coating the OSP comprises the following steps: oil removal, water washing, microetching, water washing, acid washing, water washing, film forming, water washing and drying.
The metal materials which are helpful for improving the solderability comprise tin, tin-lead alloy, silver, gold and the like, and the coating method is also various, and hot dipping, chemical plating, electroplating and other technologies are commonly used, but most methods are complex and have higher cost. The method is widely applied to coating tin-lead alloy by hot air Leveling (HotAir Solder Leveling), and is a hot dipping method, and the flow of coating the Solder resist and the solderability protection layer comprises the following steps: removing a metal corrosion resistant film or an organic corrosion resistant film, cleaning, coating liquid photosensitive solder resist ink on the whole plate, pre-drying, exposing, developing, post-curing, cleaning and micro-etching, pre-coating soldering flux, leveling and coating tin-lead alloy by hot air. The hot air leveling operation requires cleaning and microetching the printed board, then dipping the printed board in flux, then dipping the printed board in molten solder, leaving the solder in the molten solder for several seconds, and blowing off the excess solder with hot compressed air by passing through an air knife. With the development of SMT technology, the requirements for circuit boards are higher and higher, and the problem that the hot air leveling technology is difficult to overcome is solved. Firstly, the hot air leveling technology is very sensitive to the precision of a solder resist pattern, the quality of soldering flux and solder and the equipment level, and the defects of hole blocking and bridging can occur due to slight deviation of operating conditions; secondly, hot air leveling is carried out, a workpiece is immersed into high-temperature solder, so that the circuit board is subjected to severe thermal shock to cause deformation such as bending and distortion, and the solder on the surface of the pad is thin at the top and thick at the bottom and is not flat due to the gravity and surface tension of the solder in the process that the circuit board is lifted upwards from a solder groove during hot air leveling; in addition, the traditional hot air leveling method uses lead-containing solder, the solder needs to work at high temperature, the operation environment is severe, equipment needs stainless steel, titanium or other alloys, the equipment investment is large, the process is complex, the solder is not suitable for a lead-free process, and the environmental burden is large. It is generally recognized that hot air leveling techniques are not suitable for SMT with pitches less than 0.5mm and for fine pitch circuit boards.
The chemical nickel immersion gold plating layer has good dispersibility, good weldability, can be welded for multiple times, is compatible with various scaling powders, can protect the surface of a copper conducting layer, is used as a lead-free weldable plating layer, and is widely applied to a fine circuit board in recent years. An Electroless Nickel Immersion Gold plating process, which is called electroprocess Nickel/Immersion Gold in English, abbreviated as ENIG, and called Electroless Nickel Gold, Electroless Nickel Gold or Immersion Nickel Gold in Chinese, and the process flow for PCB surface treatment is as follows: plate feeding → oil removal → triple water washing → acid washing → double water washing → micro etching → double water washing → presoaking → activation → double water washing → chemical nickel → double water washing → chemical gold → gold recovery → double water washing → plate discharging. Compared with a hot air leveling technology, the nickel gold plate SMD welding disc is flat, does not have the problems of hole blocking, bridging and thermal shock, and is suitable for the SMD technology. However, the ENIG process flow is longer, the operation is still complex, the operation is improper, and plating problems, such as blackened nickel layer, uneven color, local blackened part, poor corrosion resistance, long black film between gold and nickel layers, white gold layer and other abnormal plating layers, or problems of diffusion plating and plating leakage, are easy to occur, so that the weldability and the protectiveness are affected; moreover, in the process, a large amount of chemical liquid and water are used, the environmental burden is large, furthermore, noble metal gold is consumed and used as a solderability and solderability-assisting material in the process of soldering between the terminal electrode of the component and the copper conducting layer of the circuit board connecting disc, and the reliability of connection is not proved to be favorable and may be influenced by the existence of gold in a soldering point after soldering.
In summary, the existing solder resist pattern and solderability processing technology has the disadvantages of complex flow, high difficulty, low precision, poor quality, high cost and large environmental pressure, and can not meet the requirements of the existing electronic technology and society on the quality, cost and environment of the circuit board, and needs to be improved.
The invention patent CN103052271A of German technology corporation, which is a method for making solder resist pattern and simultaneously performing solderability treatment on the surface of welding area, proposes a method for coating solder resist on the whole board in the manufacturing stage of bare circuit board, curing the solder resist in one step, selectively removing the solder resist material by using focused laser beam in the field in the assembling stage of circuit board, and performing solderability treatment on the welding area. However, in the conventional circuit board manufacturing technology, after the solder resist pattern and the solderability treatment are completed, the circuit board needs to be subjected to electrical on-off inspection, according to the steps of the patent, the solder resist pattern and the solderability treatment processing are not performed in the bare board manufacturing stage, the on-off test point is masked by the solder resist, and the condition for performing the on-off inspection in the bare board manufacturing stage does not exist. In addition, most of solder resists used in the traditional technology are negative photosensitive materials, namely photo-curing materials, when a solder resist pattern is manufactured, a negative film is adopted, namely, a part which does not need to be reserved with the solder resist after processing is opaque, and the part which needs to be reserved with the solder resist is transparent, so that even if the solder resist is coated on a board surface, the solder resist permeates into a hole, the shading point of the negative film blocks light energy projected to the hole, a connecting disc and the like during exposure, the solder resist of the parts can be removed in a developing stage, the possibility of the solder resist blocking the hole is low, according to the scheme of the German corporation patent CN103052271A, the solder resist needs to be cured once in a bare board manufacturing stage, and if the solder resist permeates into the hole during coating, how to remove the solder resist on an assembly site does not damage the hole wall, and the good weldability is ensured, which becomes a problem. Aiming at the defects of the prior art, the invention provides the circuit board manufacturing method for piercing the solder mask layer to perform on-off test and manufacturing the solder mask pattern in the assembling stage, which can further optimize the production flow of electronic products, reduce the cost and improve the quality.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provides a circuit board manufacturing method for performing on-off test and manufacturing a solder resist pattern in an assembly stage.
The above object of the present invention is achieved by the following technical solutions:
a circuit board manufacturing method for conducting on-off test and manufacturing solder resist patterns in an assembly stage is characterized by comprising the following steps:
step 1, coating solder resist on a whole board of a manufactured circuit board which is subjected to conductive pattern manufacturing and curing at one time;
step 2, in an assembly site, directly puncturing a solder mask on a test point by using a test needle before assembly to carry out electrical on-off inspection on the circuit board;
step 3, on the assembly site, processing the qualified circuit board by laser to manufacture a solder resist pattern and perform solderability surface treatment on a solder area;
and 4, applying solder to the surface of the welding area to finish the assembly process of the component.
Firstly, firstly: after the step 1 and before the step 2, before the circuit board enters the assembly stage, marks and symbols are made on the surface of the circuit board, and the circuit board is subjected to appearance inspection, packaging, shipment and transportation.
Further: and after the step 2 is completed and before the step 3 is carried out, carrying out short circuit, open circuit and solder resist missing repair on the circuit board.
Further: the solder resist adopts a high polymer material, and the solder resist adopts a single-component, multi-component, composite thermosetting material, photosetting material or polymerized material; the solder resist is attached to the circuit board by one or a combination of rolling, hot pressing, printing, plating, spraying, missing printing, spray printing, roller coating and curtain coating; the solder resist is in the form of paste, liquid coating or dry film; the thickness of the formed solder mask layer ranges from 0.5 μm to 1500 μm.
And further step (2): the thickness of the solder mask layer ranges from 10 μm to 500 μm.
Further: in step 2, selecting an on-off test instrument with a sharp needle-shaped contact point with the workpiece to be tested; when in testing, a certain pressure is applied to the testing needle, and the pressure is controlled to ensure that the testing needle can pierce through a solder mask on the testing point to form reliable electrical contact with the testing point and cannot pierce through a metal layer of the testing point.
Further: the laser used for the solderability surface treatment of the solder resist area in step 3 is the same as or shorter than the laser used for the manufacture of the solder resist pattern in wavelength, pulse duration.
Further: the laser wavelength range adopted for manufacturing the solder resist pattern is 355-10700 nm, and the pulse duration is 5 ps-1000 mu; the laser wavelength range adopted for carrying out the weldability surface treatment on the welding area is 246-1070 nm, and the pulse duration is 100 fs-100 ns.
Further, the method comprises the following steps: the laser wavelength range adopted for manufacturing the solder resist pattern is preferably 1000 nm-10700 nm, and the pulse duration is preferably 10 ps-1000 ns; the laser wavelength range for performing the solderability surface treatment on the welding area is preferably 355-1070 nm, and the pulse duration is preferably 200 fs-50 ns.
Further: CO is used for manufacturing solder resist patterns2Laser or pulsed fiber laser with wavelength of about 1 μm; the weldable surface treatment of the welding zone uses nanosecond ultraviolet laser, picosecond laser and femtosecond laser.
The invention has the advantages and effects that:
1. the invention can solve the defects that the solder resist is coated and cured once in the whole board manufacturing stage, and the solder resist pattern is remanufactured and the solderability processing technology cannot carry out the electrical on-off test on the circuit board in the component assembling stage, thereby integrally optimizing the manufacturing process of electronic products and ensuring that only qualified circuit boards can enter the assembling stage.
2. The invention uses the test needle to pierce the solder mask layer to carry out the electrical on-off test, has less steps and is convenient and easy to operate;
3. before the solder resist pattern is manufactured and assembled, on-off inspection is carried out, only qualified circuit boards are processed continuously, and the cost can be reduced;
4. the invention removes the solder resist material by laser according to CAM data photoetching, can use non-photosensitive material as solder resist, saves the pattern transfer process, material and equipment for manufacturing solder resist pattern, and improves the pattern precision.
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 invention discloses a circuit board manufacturing method for performing on-off test and manufacturing a solder resist pattern in an assembly stage, which is characterized by comprising the following steps of: after hole metallization and outer layer conductive pattern manufacturing are completed on the manufactured double-sided and multi-layer circuit board, coating solder resist on the whole board and curing the solder resist at one time; then, before assembly, a test needle is used for puncturing a solder mask on the test point to carry out electrical on-off inspection on the circuit board; finally, at the assembly site, the qualified circuit board is subjected to laser forming solder resist patterns and solderability treatment on the solder area.
And (1) coating solder resist on the whole circuit board to be manufactured, which is subjected to the conductive pattern manufacturing, and curing at one time. Unlike the traditional pattern transfer method of exposure and development, the invention uses laser photoetching to directly and selectively remove material to manufacture the solder resist pattern, does not need the solder resist to have photosensitivity or even printability, only needs the material to have enough shielding and protection for the surface of a circuit board in storage and use, especially a non-welding area conductive pattern, and needs the material to be removed by laser with lower energy or power density compared with the conductive pattern material of the circuit board, especially copper metal, so that the material can be removed by laser more easily without damaging the underlying metal copper to manufacture the solder resist pattern.
In fact, most polymeric materials meet these requirements, including paste, liquid coatings or dry films made from single component, multiple component, composite thermosettable, photocurable, or polymerized materials that are photosensitive and non-photosensitive. The coating method can be one of rolling, hot pressing, printing, plating, spraying, skip printing, spray printing, roll coating, curtain coating and the like or a combination of the methods under vacuum or normal pressure. The film or coating should cover both the surface of the conductive pattern and the sidewalls of the conductive pattern as well as the non-conductive pattern area and be of a full material without leaving air gaps between the solder resist material and the conductive pattern and insulating pattern of the non-conductive area that it covers or encapsulates. The thickness of the film or coating is in the range of 0.5 μm to 1500. mu.m, preferably the film thickness is 10 μm to 500. mu.m. Preferably, a dry film is used to avoid via-in defects of the solder resist material.
The invention is different from the traditional method that the solder resist needs to be gradually cured twice, and after the solder resist is coated on the surface of the circuit board, the manufacturing requirement of the circuit board can be met through a one-step complete curing process. In the conventional method, a liquid photosensitive solder resist is mainly used, and a pattern transfer step of exposure and development is used to manufacture a solder resist pattern. When exposing, a negative photo-resist negative film is used to shield the light source of the exposure machine from projecting light to a partial area, and in order to avoid distortion of the pattern, the negative film needs to be directly contacted with the surface of the workpiece, for example, the negative film and the workpiece are jointed together by the negative pressure generated by the vacuum system of the exposure machine and are closely contacted, so that the solder resist coating on the workpiece does not have the viscosity of the adhesive substance, otherwise, the negative film is adhered to the workpiece or damaged by the viscosity of the solder resist material layer on the workpiece. In this way, in the conventional method, after the solder resist is coated on the surface of the circuit board, the circuit board is pre-dried and baked, i.e. pre-cured, to remove the stickiness of the surface of the solder resist; then, after obtaining a solder resist pattern by exposure and development, the solder resist is subjected to a heat or light treatment again to completely cure the solder resist. This is, of course, a paradoxical process that is difficult to operate: the baking or the pre-curing is insufficient, the viscosity is not completely removed, and the solder resist light-blocking master plate can be damaged; baking or precuring is slightly excessive, which affects the removal effect, and when the photoresist is developed after exposure, part of the solder resist is already cured, so that solder resist material remains on a welding area, which causes a welding problem.
The invention uses laser to directly remove the solder resist material by photoetching, makes patterns, does not need a light-resistant negative film or a developing process, uses the liquid solder resist, simplifies the process into a one-time curing process no matter whether the liquid solder resist is a photosensitive material or a non-photosensitive material, and is easy to operate.
According to the invention, a thermoplastic film or a film with a pressure-sensitive, heat-sensitive and photosensitive adhesive layer is preferably used, so that a solder resist can be prevented from flowing into holes in a circuit board, and a laminating device with a hot-pressing device or a photo-curing device is preferably used for completing curing in the laminating process without a special curing process.
Different from the traditional technology, the solder resist pattern and the solderability coating process are immediately carried out after the solder resist is coated, and the circuit board manufactured by the method can enter the component assembly stage after the step (1) is finished. Before shipment, necessary shipment processes, such as marking, visual inspection, packaging, and transportation, are required.
And (2) directly puncturing the solder mask on the test point by using a test needle to carry out electrical on-off inspection on the circuit board before assembly. The most important function of the circuit board is to provide electrical connections. Whether each network meets the design requirements including whether short circuit and open circuit exist is judged through electrical on-off inspection, and the method is one of important links in modern circuit board production. After the step (1) is carried out, the test points on the circuit board are masked by the solder resist, and the test points are in an insulation state. In the invention, an on-off test instrument with a sharp needle-shaped contact point with a workpiece to be tested is required to be selected. When in testing, a certain pressure is applied to the testing needle, the pressure is controlled to ensure that the testing needle pierces through a solder mask on the testing point to form reliable electrical contact with the testing point, and the metal layer of the testing point is not pierced properly. The basis for the test is the connection relationship determined when the circuit board is designed, and is provided by the network table in the CAM data. After the circuit board is subjected to electrical on-off inspection, the defective circuit board can be subjected to corresponding repair treatment, return treatment and scrapping treatment.
And (3) processing the qualified circuit board by laser on an assembly site to manufacture a solder resist pattern and perform solderability surface treatment on a solder area. The step only processes qualified circuit boards, which comprises removing solder resist materials on circuit board pads to manufacture solder resist patterns and carrying out solderability surface treatment on the circuit board pads, and also comprises removing the solder resist materials entering the holes and carrying out solderability treatment on the hole walls. Unlike the conventional technique, this step is performed on the component mounting site. Because the circuit board is protected by the solder resist and the solder resist pattern is made on site and subjected to solderability treatment, the storage and transportation conditions of the circuit board can be more relaxed than those of the conventional method.
The solder resist pattern and the solderability surface treatment can be made by using a laser processing head 1 for forming, such as a CO device with a wavelength of about 10 μm2Or the solder resist on the test point is selectively removed by the 1 μm optical fiber laser beam, and then the carbide is cleaned and treated with solderability by the surface treatment processing head 2, for example, the ultraviolet with the wavelength of 355nm or the green laser beam with the wavelength of 532nm is equipped, or the welding area with accurate size, clear boundary and good surface solderability is manufactured by directly removing and treating with the surface treatment processing head 2, for example, the ultraviolet laser beam with the wavelength of 355 nm.
In this step, a solder resist coating layer on the land is preferably removed by laser selective photo-etching to produce a solder resist pattern and generate the land. Most of the solder resists are high molecular polymers, and CO can be selected2And (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, and the copper has low laser absorption system to the band, but has good coupling with most high polymers, so that the copper can be removedThe high polymer has wide laser parameter range without damaging copper. Selection of CO2The laser can use a large-diameter light spot, has high removal efficiency, low cost and high cost performance, does not damage copper, and is suitable for removing the solder resist entering the hole by utilizing the characteristic of larger thermal action.
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.
In this step, to remove CO2The laser or fiber laser processing of the potentially generated carbide residue produces a clean, solderable surface of the pad, preferably with a shorter wavelength, i.e., higher photon energy, or shorter pulse time, i.e., higher laser power density, laser that removes solder resist residue from the surface of the pad and slightly etches the metal surface layer of the pad, removing metal oxide, exposing fresh metal surface, producing solderability that is readily wetted by the melted solder. Nanosecond ultraviolet laser, picosecond laser and femtosecond laser can be well absorbed by copper metal, and the surface of the copper metal is cleaned. 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 order to realize the processing target of the step (3) of the invention, the processing can be completed step by step on the same equipment, and can also be performed on different equipment respectively. The preferred equipment is a complete set of two different laser light sources and processing heads, and different laser processing functions in the step (3) are completed, namely respectively manufacturing a solder resist pattern and performing weldable surface treatment on a solder area. Wherein, the solder resist pattern is manufactured by removing a solder resist coating layer on a welding area through selective photoetching, and a laser processing head 1 for forming is used; the solderability surface treatment of the welding area is realized by removing the residual solder resist on the surface of the welding area and the metal surface layer of the micro-etched welding area, and the laser processing head 2 is used for surface treatment.
The processing efficiency and the processing quality can be considered by adopting two different laser processing methods, wherein the processing head 1 has large spot diameter and high pulse energy, and can quickly remove materials; the processing head 2 has smaller spot diameter, high pulse repetition rate and higher power density, and can change the welding performance of the metal surface. In the invention, compared with the laser light source adopted by the processing head 1, the laser light source adopted by the processing head 2 has the same or shorter wavelength and pulse duration; the wavelength range of a laser light source adopted by the laser processing head 1 is 355-10700 nm, the pulse duration is 5 ps-1000 mus, the preferred wavelength range is 1000 nm-10700 nm, the preferred pulse duration is 10 ps-1000 ns, the wavelength range of the laser light source adopted by the laser processing head 2 for selectively removing a solder resist coating on a welding area by photoetching is 246-1070 nm, the pulse duration is 100 fs-100 ns, the preferred wavelength range is 355-1070 nm, and the preferred pulse duration is 200 fs-50 ns.
And (4) applying solder to the surface of the welding area, and continuing the assembly process of the component. According to the method of the present invention, since the laser-treated fresh copper surface is used to replace the solderability coating layer of the pad, after the step (3) is finished, the step (4) should be performed in as short a time as possible to avoid oxidation of the pad surface, and under the condition that the solderability after the laser treatment is excellent, component assembly including component mounting is completed and solder is directly applied to the laser-treated pad to complete component soldering; or directly printing solder paste on the laser-processed welding area, and then carrying out component mounting and reflow or wave soldering; or component assembly according to other techniques.
The invention is further illustrated by the following two specific examples.
Example 1
In this embodiment, taking a 6-layer circuit board with a completed conductive pattern as an example, the method specifically includes the following steps:
and (1) hot-pressing a PI film on the 6-layer circuit board with the conductive pattern as a solder resist material.
Specifically, a laminating machine is used for laminating the laminated circuit board and a PI film, wherein the PI film is a Kapton HN film produced by DuPont and has the thickness of 25um, and a silicone rubber pad is used as a hot-pressing pad during lamination. The thermocompression bonding stage and parameters are as follows, depending on the material properties:
| serial number | Pressing pressure (N/cm2) | Pressing temperature (. degree.C.) | Pressing time (minutes) |
| Stage 1 | 24 | 80 | 15 |
| Stage 2 | 94 | 140 | 25 |
| Stage 3 | 188 | 180 | 25 |
| Stage 4 | 188 | 220 | 60 |
| Stage 5 | 188 | Cooling to room temperature | 45 |
Step (2) using the test needle to directly pierce the PI layer on the test point to check the electrical on-off of the circuit board
In the invention, an on-off test instrument with a sharp needle-shaped contact point with a workpiece to be tested is required to be selected. When in testing, a certain pressure is applied to the testing needle, the pressure is controlled to ensure that the testing needle pierces through a solder mask on the testing point to form reliable electrical contact with the testing point, and the metal layer of the testing point is not pierced properly. Specifically, the multilayer circuit board is placed on a switching test machine to carry out electrical performance switching test, and the question board is picked out. And for the defective circuit board, corresponding repairing treatment, returning treatment and scrapping treatment can be carried out.
And (3) on the assembly site, processing the qualified circuit board by laser, manufacturing a solder resist pattern and carrying out solderability surface treatment on a solder area.
Specifically, in this embodiment, a 20W ultraviolet nanosecond laser machine is used to fabricate the solder resist pattern, the circuit board is placed on a laser device adsorption table, engineering data of laser processing is imported, the circuit board and the processing data are accurately aligned, and the laser photoetching PI forms the solder resist pattern. And after the top surface is processed, the circuit board is turned over, and the bottom surface solder resist pattern is manufactured by the same method. The processing parameters are as follows:
| power/W | frequency/kHz | Pulse width/ns | Processing speed/mm/s | Number of working operations |
| 6 | 200 | 20 | 600 | 1 |
Further, the weldability treatment of the welding zone is completed by replacing another laser. Specifically, the step adopts a 20W ultraviolet picosecond laser machine to complete the cleaning and weldability treatment of the welding zone, the circuit board is placed on a laser equipment adsorption table, engineering data of laser processing is led in, the circuit board is accurately aligned with processing data, and the top surface of the welding zone is cleaned and treated with weldability by laser. After the processing is completed, the circuit board is turned over, and the solderability treatment of the bottom surface welding area is completed in the same way. The processing parameters are as follows:
| power/W | frequency/kHz | Pulse width/ps | Processing speed/mm/s | Number of working operations |
| 10 | 1000 | 12 | 2000 | 1 |
And (4) inserting elements onto the connecting disc, and performing wave soldering.
Example 2
In this embodiment, taking a double-sided circuit board with a hole metallization and a conductive pattern as an example, the method specifically includes the following steps:
step (1) coating solder resist on the whole circuit board to be manufactured and completing the manufacture of the conductive pattern and curing at one time
Specifically, KSM-386 thermosetting ink of Suzhou Guangxin new photosensitive material GmbH is printed on two sides of a double-sided circuit board in a spraying mode, and the double-sided circuit board is kept stand for 10-20 min after printing missing.
Step (2) using the test needle to directly pierce the solder mask on the test point to check the electrical on-off of the circuit board
In the invention, an on-off test instrument with a sharp needle-shaped contact point with a workpiece to be tested is required to be selected. When in testing, a certain pressure is applied to the testing needle, the pressure is controlled to ensure that the testing needle pierces through a solder mask on the testing point to form reliable electrical contact with the testing point, and the metal layer of the testing point is not pierced properly. Specifically, the circuit board is placed on a make-and-break test machine to perform electrical performance make-and-break test, and the question board is picked out. And for the defective circuit board, corresponding repairing treatment, returning treatment and scrapping treatment can be carried out.
Step (3) in the assembly field, for the qualified circuit board, using laser processing to manufacture the solder resist pattern and carrying out solderability surface treatment on the solder resist area
The steps include removing the solder resist material on the circuit board pad to make the solder resist pattern and performing the solderability surface treatment on the circuit board pad, and also include removing the solder resist material in the hole and performing the solderability treatment on the hole wall.
Specifically, in this embodiment, a 40W optical fiber infrared laser machine is used to manufacture the solder resist pattern, the circuit board is placed on a laser equipment adsorption table, engineering data of laser processing is imported, the circuit board and the processing data are accurately aligned, and the solder resist pattern is formed by laser photoetching. And after the top surface is processed, the circuit board is turned over, and the bottom surface solder resist pattern is manufactured by the same method. The processing parameters are as follows:
| power/W | frequency/kHz | Pulse width/ns | Processing speed/mm/s | Number of working operations |
| 8 | 100 | 30 | 800 | 1 |
Further, the weldability treatment of the welding zone is completed by replacing another laser. Specifically, the step adopts a 20W ultraviolet picosecond laser machine to complete the cleaning and the weldability treatment of the surface of the welding area, the circuit board is placed on a laser equipment adsorption table, engineering data of laser processing is led in, the circuit board is accurately aligned with processing data, and the top surface of the welding area is cleaned and subjected to the weldability treatment by laser. After the processing is completed, the circuit board is turned over, and the solderability treatment of the bottom surface welding area is completed in the same way. The processing parameters are as follows:
| power/W | frequency/kHz | Pulse width/ps | Processing speed/mm/s | Number of working operations |
| 10 | 1000 | 12 | 2000 | 1 |
And (4) applying solder to the surface of the welding area to carry out SMT component mounting.
Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the embodiments disclosed.
Claims (10)
1. A circuit board manufacturing method for conducting on-off test and manufacturing solder resist patterns in an assembly stage is characterized by comprising the following steps:
step 1, coating solder resist on a whole board of a manufactured circuit board which is subjected to conductive pattern manufacturing and curing at one time;
step 2, in an assembly site, directly puncturing a solder mask on a test point by using a test needle before assembly to carry out electrical on-off inspection on the circuit board;
step 3, on the assembly site, processing the qualified circuit board by laser to manufacture a solder resist pattern and perform solderability surface treatment on a solder area;
and 4, applying solder to the surface of the welding area to finish the assembly process of the component.
2. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: after the step 1 and before the step 2, before the circuit board enters the assembly stage, marks and symbols are made on the surface of the circuit board, and the circuit board is subjected to appearance inspection, packaging, shipment and transportation.
3. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: and after the step 2 is completed and before the step 3 is carried out, carrying out short circuit, open circuit and solder resist missing repair on the circuit board.
4. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: the solder resist adopts a high polymer material, and the solder resist adopts a single-component, multi-component, composite thermosetting material, photosetting material or polymerized material; the solder resist is attached to the circuit board by one or a combination of rolling, hot pressing, printing, plating, spraying, missing printing, spray printing, roller coating and curtain coating; the solder resist is in the form of paste, liquid coating or dry film; the thickness of the formed solder mask layer ranges from 0.5 μm to 1500 μm.
5. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 4, characterized in that: the thickness of the solder mask layer ranges from 10 μm to 500 μm.
6. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: in step 2, selecting an on-off test instrument with a sharp needle-shaped contact point with the workpiece to be tested; when in testing, a certain pressure is applied to the testing needle, and the pressure is controlled to ensure that the testing needle can pierce through a solder mask on the testing point to form reliable electrical contact with the testing point and cannot pierce through a metal layer of the testing point.
7. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: the laser used for the solderability surface treatment of the solder resist area in step 3 is the same as or shorter than the laser used for the manufacture of the solder resist pattern in wavelength, pulse duration.
8. A method for manufacturing a circuit board for on-off testing by piercing a solder resist according to claim 7, characterized in that: the laser wavelength range adopted for manufacturing the solder resist pattern is 355-10700 nm, and the pulse duration is 5 ps-1000 mu; the laser wavelength range adopted for carrying out the weldability surface treatment on the welding area is 246-1070 nm, and the pulse duration is 100 fs-100 ns.
9. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 8, characterized in that: the laser wavelength range adopted for manufacturing the solder resist pattern is 1000 nm-10700 nm, and the pulse duration is 10 ps-1000 ns; the laser wavelength range for performing the solderability surface treatment on the welding area is 355-1070 nm, and the pulse duration is 200 fs-50 ns.
10. The circuit board manufacturing method of on-off testing and solder resist pattern manufacturing in the assembly stage according to claim 1, characterized in that: CO is used for manufacturing solder resist patterns2Laser or pulsed fiber laser with wavelength of about 1 μm; the weldable surface treatment of the welding zone uses nanosecond ultraviolet laser, picosecond laser and femtosecond laser.
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Application publication date: 20220114 |