CN106559961B - Conductive liquid, preparation method thereof and conductive treatment method - Google Patents
Conductive liquid, preparation method thereof and conductive treatment method Download PDFInfo
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- CN106559961B CN106559961B CN201610796813.5A CN201610796813A CN106559961B CN 106559961 B CN106559961 B CN 106559961B CN 201610796813 A CN201610796813 A CN 201610796813A CN 106559961 B CN106559961 B CN 106559961B
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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
- H05K3/40—Forming printed elements for providing electric connections to or between printed circuits
- H05K3/42—Plated through-holes or plated via connections
- H05K3/429—Plated through-holes specially for multilayer circuits, e.g. having connections to inner circuit layers
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
- B22F1/05—Metallic powder characterised by the size or surface area of the particles
- B22F1/054—Nanosized particles
- B22F1/0545—Dispersions or suspensions of nanosized particles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F9/00—Making metallic powder or suspensions thereof
- B22F9/16—Making metallic powder or suspensions thereof using chemical processes
- B22F9/18—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds
- B22F9/24—Making metallic powder or suspensions thereof using chemical processes with reduction of metal compounds starting from liquid metal compounds, e.g. solutions
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y40/00—Manufacture or treatment of nanostructures
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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
- H05K2203/00—Indexing scheme relating to apparatus or processes for manufacturing printed circuits covered by H05K3/00
- H05K2203/07—Treatments involving liquids, e.g. plating, rinsing
- H05K2203/0779—Treatments involving liquids, e.g. plating, rinsing characterised by the specific liquids involved
Abstract
The invention discloses a conductive liquid, a preparation method thereof and a conductive treatment method. The conductive liquid comprises the following raw materials in percentage by mass: 0.5-5% of nano carbon powder, 5-10% of silver nanoparticles, 0.5-5% of anionic surfactant and the balance of deionized water; by adjusting the proportion of the raw materials, the nano carbon powder and the silver nanoparticles are uniformly dispersed in water under the action of the anionic surfactant, and the prepared conductive liquid is used for conducting treatment on a PCB substrate hole wall insulating layer, so that the conductive liquid has good conductivity. The preparation method of the conductive liquid comprises the steps of firstly, uniformly dispersing nano carbon powder, silver nanoparticles and a surfactant in deionized water through ultrasonic waves, then carrying out ball milling on the well-dispersed mixed liquid, and finally obtaining the uniformly-dispersed small-particle-size nano carbon powder and silver nanoparticle conductive liquid. The conductive liquid has the advantages that the conductive performance of the conductive liquid is improved by adopting the ultrasonic wave and ball milling preparation method, and the manufacturing efficiency of the PCB is improved compared with that of the traditional chemical copper plating method.
Description
Technical Field
The invention relates to the technical field of PCB copper deposition, in particular to a conductive liquid, a preparation method and a conductive treatment method thereof.
Background
Printed Circuit Boards (PCBs) are substrates for connecting various electronic components, and are connected in-plane primarily by copper traces formed after exposure and etching, and interconnections between layers need to be made through metallized vias. The key point in the manufacture of printed circuit board is the copper deposition process, which mainly has the function of depositing a uniform conductive layer on the wall of non-metal hole of single-layer or multi-layer printed circuit board, and then electroplating, thickening and plating copper to achieve the purpose of circuit. To achieve the purpose, the insulating layer of the hole wall of the PCB substrate needs to be subjected to conductive treatment, so that subsequent electroplating thickening can be facilitated. The conductive liquid for conducting treatment on the insulating layer on the hole wall of the PCB substrate in the existing non-copper deposition technology is generally a conductive liquid made of graphite or carbon black, but the graphite or carbon black has poor hole conductivity and poor hole copper bonding force after conducting treatment on the insulating layer due to the defects of large particle size, poor dispersibility and the like.
Disclosure of Invention
In view of the defects of the prior art, the invention aims to provide a conductive liquid with excellent conductivity.
In order to achieve the purpose, the invention adopts the following technical scheme:
the conductive liquid comprises the following raw materials in percentage by mass: 0.5-5% of nano carbon powder, 5-10% of silver nanoparticles, 0.5-5% of anionic surfactant and the balance of deionized water, wherein the silver nanoparticles are prepared from a silver ion reducing agent and a silver ion complex in a weight ratio of (1-4): and (1) to (4) are prepared by reduction reaction under ultrasonic stirring. For example, the mass percentage of the nano carbon powder is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%; the silver nanoparticles account for 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5% and 10% by mass; the mass percentage of the anionic surfactant is 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%; the balance being deionized water.
The nano carbon powder is the main part forming the conductive liquid, plays a role in conducting electricity, and when the content in the solution is lower than 0.5%, the conducting capacity is deteriorated; when the content of the solution is higher than 5%, the nano carbon powder is not uniformly dispersed, and the conductive capability is also deteriorated. The silver nanoparticles are applied to the conductive liquid due to the advantages of small particle size, high activity, good conductivity, bright color and the like, and when the content of the silver nanoparticles is lower than 5%, the conductive capability of the solution is weakened, and the electroplating effect of the PCB surface is deteriorated. When the content of the silver nanoparticles is higher than 10%, the solid content of the solution is increased, and the solution is not uniformly dispersed. The silver nanoparticles are characterized in that the silver nanoparticles are prepared from (1-4) a silver ion reducing agent and a silver ion complex, wherein the silver ion reducing agent comprises: the mass ratio of (1-4) is obtained by reduction reaction under the condition of ultrasonic stirring, for example, the mass ratio of the silver ion reducing agent to the silver ion complex is 1:1, 1:2, 1:3, 1:4, 2:1, 2:3, 3:1, 3:2, 3:4, 4:1, 4: 3. The silver ion complex is prepared by reducing silver ions in a silver ion complex into silver nanoparticles by a reducing agent molecule, further forming controllable small-size silver nanoparticles by ball milling, and selecting the mass ratio of (1-4): and (1) the silver ion reducing agent and the silver ion complex are synthesized into silver nanoparticles with small particle size, the synthesized silver nanoparticles have the characteristics of good stability, good dispersibility, good conductivity, small size and the like, and the silver nanoparticles and the nano carbon powder are uniformly dispersed in a medium under the action of an anionic surfactant, so that the conductive liquid has excellent conductivity, stability and associativity. The anionic surfactant can improve the stability and the wettability of the carbon powder suspension, can be well combined with the nano carbon powder in a certain proportion, and leads to excessive nano carbon powder and uneven solution dispersion when the content of the anionic surfactant is lower than 0.5 percent; when the content of the anionic surfactant is more than 5%, the solution stability is deteriorated. The invention makes the nanometer carbon powder and the silver nanometer particles evenly dispersed in the medium, namely deionized water under the action of the anion surfactant by adjusting the proportion of the raw materials, makes the nanometer carbon powder and the silver nanometer particle suspension liquid which is even in the solution keep stable by utilizing the anion surfactant in the solution, and has good wetting property, makes the nanometer carbon powder and the silver nanometer particle mixed suspension liquid fully absorbed on the surface of the wall of the hole of the nonconductor to form an even and tightly combined conducting layer.
Wherein the specific surface area of the nano carbon powder is 300-1500 m2G, e.g. 300m2/g、400m2/g、500m2/g、600m2/g、700m2/g、800m2/g、900m2/g、1000m2/g、1100m2/g、1200m2/g、1300m2/g、1400m2/g、1500m2/g。
Wherein the average particle size of the nano carbon powder is 100-200 nm, such as 100nm, 105nm, 110nm, 115nm, 120nm, 125nm, 130nm, 135nm, 140nm, 145nm, 150nm, 155nm, 160nm, 165nm, 170nm, 175nm, 180nm, 185nm, 190nm, 195nm and 200 nm; preferably, the average particle size of the nano carbon powder is 105 nm.
The silver ion reducing agent is one of potassium permanganate, ascorbic acid, sodium borohydride, sodium tricitrate, chloroauric acid and silver thioglycolate nano particles;
preferably, the silver ion complex is one of silver nitrate, silver chloride, silver sulfide, silver iodide, silver oxide and silver bromide;
preferably, the average particle size of the silver nanoparticles is 10-40 nm, such as 10nm, 15nm, 20nm, 25nm, 30nm, 35nm and 40nm, and the silver nanoparticles with small particle size are easy to be uniformly dispersed, so that the conductive liquid has good conductivity and strong stability.
The nano carbon and silver nano particles are easy to agglomerate together in the aqueous solution to cause uneven dispersion, and a certain amount of surfactant is required to be added in order to ensure that the nano carbon and silver nano particles can be fully dispersed in the aqueous solution. The surfactant adopted by the invention is an anionic surfactant, so that the nano carbon and silver nanoparticles can be more uniformly dispersed in the aqueous solution. Wherein the anionic surfactant is sodium xanthate or sodium dodecyl benzene sulfonate.
In order to ensure the stability of the nanocarbon and silver nanoparticles after being uniformly dispersed in the aqueous solution, the pH value of the nanocarbon and silver nanoparticles needs to be adjusted, and generally, a pH regulator, such as NaOH or a pH regulator commonly used in the art, is added into the conductive liquid to adjust the pH value to 10-12.
In order to ensure the quality of the conductive liquid, additives such as a stabilizer, a dispersing agent and the like are also added into the conductive liquid, and the stabilizer and the dispersing agent used in the invention are all common additives in the field.
The invention also aims to provide a preparation method of the conductive liquid, which is characterized in that nano carbon powder and silver nanoparticles are uniformly dispersed in the conductive liquid, the dispersion performance is good, the particle diameters of the nano carbon powder and the silver nanoparticles are small, and the conductive liquid has good conductivity.
Wherein the ultrasonic stirring power is 80-500W, such as 80W, 100W, 200W, 300W and 500W, the ultrasonic power is too low, and the nano carbon powder and silver nano particle suspension are not uniformly dispersed; and (3) the ultrasonic power is too high, the uniformly dispersed nano carbon powder and the silver nano particle suspension are agglomerated together again, and preferably, the ultrasonic stirring power is 300W.
Wherein the ultrasonic stirring time is 10-120 min, such as 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min and 120min, the ultrasonic time is too short, and the nano carbon powder and silver nano particle suspension can not be completely dispersed in the medium; the ultrasonic time is too long, and the particle size of the nano carbon powder and silver nano particle suspension is increased. Preferably, the time of the ultrasonic agitation is 30 min.
Wherein the rotation speed in the ball milling process is 100-500 rpm, for example 100rpm, 200rpm, 300rpm, 400rpm, 500rpm, the rotation speed is too high, and the electroplating effect is poor due to too violent solution reaction; the rotating speed is too low, the ball milling is not sufficient, and the solution is not uniformly dispersed. Preferably, the ball milling speed is 300 rpm.
The ball milling process comprises the following specific steps: placing the uniformly dispersed mixed solution into an all-directional ball mill for ball milling, firstly, carrying out ball milling for 3min in a clockwise rotation mode, standing for 1-5 min, then, carrying out ball milling for 5min in an anticlockwise rotation mode, standing for 1-5 min, and taking the ball milling cycle as a ball milling cycle to carry out circulation, wherein the whole ball milling time is controlled to be 1-6 h, such as 1h, 2h, 3h, 4h, 5h and 6 h; preferably, the time of the ball milling is 2 h.
The diameter of the grinding ball adopted in the ball milling process is 3-10 mm, such as 3mm, 4mm, 5mm, 6mm, 7mm, 8mm, 9mm and 10 mm.
The present invention is also directed to a method for conducting a conductive solution, in which a PCB substrate after conducting has good conductivity and excellent hole-wall bonding capability.
The conductive treatment method comprises the steps of pretreatment of the PCB substrate by using the conditioning liquid, washing, conductive treatment by using the conductive liquid, drying, micro-etching, washing and drying.
The specific process of the pretreatment of the conditioning fluid comprises the following steps: placing the PCB substrate with the holes in the conditioning fluid, stirring and soaking for 1.5min at room temperature, and pretreating to increase the conductivity of the hole walls, wherein the stirring force is moderate;
the specific process of water washing is as follows: repeatedly washing the PCB substrate pretreated by the conditioning solution for 3-5 times by using deionized water to remove residual conditioning solution on the surface;
the specific process of conducting treatment of the conducting liquid comprises the following steps: placing the washed PCB substrate in the conductive liquid prepared in the embodiment 1-6, stirring and soaking for 1.5min at room temperature, wherein the stirring force is moderate, and the nano carbon powder and the silver nano particles are combined on the hole wall through conductive treatment, so that the resin and the glass fiber bundles on the non-conductor part of the hole wall are metalized, and the hole wall has good conductivity so as to facilitate subsequent electro-plating;
the specific drying process comprises the following steps: placing the PCB substrate subjected to conductive treatment in an oven for 15min, and drying at 100-150 ℃, wherein the residual conductive liquid is solidified on the hole wall due to overhigh temperature, incomplete solidification is caused due to overlow temperature, and the conductive performance is influenced due to overhigh or overlow temperature, so that the drying temperature needs to be strictly controlled;
the specific process of the microetching is as follows: placing the dried PCB substrate in 8% NPS microetching solution, and carrying out microetching for 1-2 min at room temperature to remove organic pollutants on the surface of the substrate;
the specific process of water washing is as follows: further repeatedly washing the micro-etched PCB substrate for 3-5 times by using deionized water to remove residual conductive liquid and residual oil substances on the surface;
the specific process of drying is as follows: the PCB substrate after being washed by water is dried by a blower immediately, the residual substances and moisture on the surface are blown away by cold air, and then the PCB substrate is dried by hot air, so that the PCB substrate is prevented from being oxidized and the residual impurities on the surface are prevented.
Compared with the prior art, the invention has the beneficial effects that: the conductive liquid comprises the following raw materials in percentage by mass: 0.5-5% of nano carbon powder, 5-10% of silver nanoparticles, 0.5-5% of anionic surfactant and the balance of deionized water. The nanometer carbon powder and the silver nanometer particles are uniformly dispersed in a medium, namely deionized water under the action of an anionic surfactant by adjusting the proportion of the raw materials, and the uniform nanometer carbon powder and silver nanometer particle suspension is kept stable and has good wetting property by utilizing the anionic surfactant in the solution, so that the mixed suspension of the nanometer carbon powder and the silver nanometer particles is fully adsorbed on the surface of the wall of a non-conductor hole to form a uniform and tightly combined conducting layer. The silver nanoparticles are prepared from a silver ion reducing agent and a silver ion complex in a weight ratio of (1-4): the mass ratio of (1-4) is obtained by reduction reaction under the condition of ultrasonic stirring, silver ions in the silver ion complex are reduced into silver nanoparticles by reducing agent molecules, controllable small-size silver nanoparticles are further formed by ball milling, and the mass ratio is selected to be (1-4): and (1) the silver ion reducing agent and the silver ion complex are synthesized into silver nanoparticles with small particle size, the synthesized silver nanoparticles have the characteristics of good stability, good dispersibility, good conductivity, small size and the like, and the silver nanoparticles and the nano carbon powder are uniformly dispersed in a medium under the action of an anionic surfactant, so that the conductive liquid has excellent conductivity, stability and associativity.
According to the preparation method of the conductive liquid, firstly, the nano carbon powder and the silver nanoparticles are uniformly dispersed in the conductive liquid through ultrasonic dispersion, then the uniformly dispersed conductive liquid is ball-milled by a ball mill to obtain the uniformly dispersed conductive liquid mixed by the small-particle-size nano carbon powder and the silver nanoparticles, the conductive performance and the hole wall bonding force of the conductive liquid are increased by adopting the ultrasonic and ball-milling mixing method, the insulating layer used for the hole wall of the PCB substrate enables the non-conductive insulating hole wall to have good conductive capacity, the hole copper bonding force of the hole wall is improved, the subsequent electroplating process is facilitated, and the manufacturing efficiency of the PCB electroplating plate is improved. The method for conducting treatment of the conductive liquid simplifies the process of the metallized hole, saves working hours, reduces material consumption, and the PCB substrate after conducting treatment has good conductive performance and excellent hole wall combining capacity, and can be widely applied to the manufacture of the PCB substrate.
Drawings
Fig. 1 is a diagram illustrating a backlight level determination criterion in the prior art.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Unless otherwise specified, various starting materials of the present invention are commercially available or prepared according to conventional methods in the art.
Example 1
Weighing 0.5% of nano carbon powder, 5% of silver nanoparticles, 0.5% of sodium dodecyl benzene sulfonate, 2% of sodium hydroxide, 1% of stabilizer and 2% of dispersant by mass percent, adding the silver nanoparticles, the sodium dodecyl benzene sulfonate, the 2% of sodium hydroxide, the 1% of stabilizer and the 2% of dispersant into 89% of deionized water, wherein the silver nanoparticles are prepared by reduction reaction of potassium permanganate and silver nitrate with the mass ratio of 1:1, fully mixing, placing the mixture into an ultrasonic mixing tank, ultrasonically stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 300rpm, firstly, carrying out ball milling for 3min in a clockwise direction, standing for 2min, then carrying out ball milling for 5min in a counterclockwise direction, standing for 2min, and taking the ball milling cycle as a ball milling cycle to circulate, controlling the whole ball milling time to be 1h, and controlling the diameter of the used ball to be 3mm to prepare the conductive liquid.
Example 2
Weighing 1% of nano carbon powder, 6% of silver nanoparticles, 1% of sodium xanthate, 1.5% of sodium hydroxide, 1.5% of stabilizer and 2% of dispersant by mass percent, adding the mixture into 87% of deionized water, wherein the silver nanoparticles are prepared by ascorbic acid and silver chloride in a mass ratio of 1:2 through reduction reaction, fully mixing, placing the mixture into an ultrasonic mixing tank, ultrasonically stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 400rpm, firstly, carrying out ball milling for 3min in a clockwise manner, standing for 3min, then carrying out ball milling for 5min in a counterclockwise manner, standing for 3min, and circulating the ball milling circulation by taking the ball milling circulation, controlling the whole ball milling time to be 2h, and controlling the diameter of the used ball to be 5mm to prepare the conductive liquid.
Example 3
Weighing 2% of nano carbon powder, 7% of silver nanoparticles, 2% of sodium xanthate, 1% of sodium hydroxide, 3% of stabilizer and 1% of dispersant by mass, adding the silver nanoparticles, the 1% of sodium hydroxide, the 3% of stabilizer and the 1% of dispersant into 84% of deionized water, wherein the silver nanoparticles are prepared by reduction reaction of sodium borohydride and silver sulfide in a mass ratio of 1:3, fully mixing, placing the mixture into an ultrasonic mixing tank, ultrasonically stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 200rpm, firstly, rotating the ball mill clockwise for 3min, standing for 5min, then rotating the ball mill counterclockwise for 5min, standing for 5min, and using the ball milling circulation to control the whole ball milling time to be 3h, and controlling the diameter of the used ball to be 6mm to prepare the conductive liquid.
Example 4
Weighing 3% of nano carbon powder, 8% of silver nanoparticles, 3% of sodium dodecyl benzene sulfonate, 1% of sodium hydroxide, 1% of stabilizer and 3% of dispersant by mass, adding the nano carbon powder, the silver nanoparticles, the sodium dodecyl benzene sulfonate, the 1% of sodium hydroxide, the 1% of stabilizer and the 3% of dispersant into 81% of water, wherein the silver nanoparticles are prepared by reduction reaction of sodium tricitrate and silver iodide in a mass ratio of 1:4, fully mixing, placing the mixture into an ultrasonic mixing tank, ultrasonically stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 500rpm, firstly, rotating the ball mill clockwise for 3min, standing for 5min, then rotating the ball mill counterclockwise for 5min, standing for 5min, and taking the ball milling cycle as a ball milling cycle for circulation, controlling the whole ball milling time to be 4h, and controlling the diameter of the used ball to be 7mm to prepare the conductive liquid.
Example 5
Weighing 4% of nano carbon powder, 9% of silver nanoparticles, 4% of sodium xanthate, 0.8% of sodium hydroxide, 2.5% of stabilizer and 1.7% of dispersant by mass percent, adding the silver nanoparticles into 78% of water, wherein the silver nanoparticles are prepared by carrying out reduction reaction on chloroauric acid and silver oxide in a mass ratio of 2:1, fully mixing, placing the mixture into an ultrasonic mixing tank, carrying out ultrasonic stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 300rpm, firstly carrying out ball milling for 3min in a clockwise manner, standing for 5min, then carrying out ball milling for 5min in a counterclockwise manner, standing for 5min, and taking the ball milling circulation as a ball milling circulation to control the whole ball milling time to be 5h, wherein the diameter of the used ball is 8mm, thus preparing the conductive liquid.
Example 6
Weighing 5% of nano carbon powder, 10% of silver nanoparticles, 5% of sodium dodecyl benzene sulfonate, 1% of sodium hydroxide, 3% of stabilizer and 3% of dispersant by mass percent, adding the silver nanoparticles, the 1% of sodium hydroxide, the 3% of stabilizer and the 3% of dispersant into 73% of water, wherein the silver nanoparticles are prepared by reduction reaction of thioglycolic acid and silver bromide with the mass ratio of 3:1, fully mixing, placing the mixture into an ultrasonic mixing tank, ultrasonically stirring for 30min under the power of 300W, placing the uniformly dispersed mixed solution into an omnibearing ball mill for ball milling, controlling the ball milling rotation speed to be 300rpm, firstly, carrying out ball milling in a clockwise rotation mode for 3min, standing for 5min, then carrying out ball milling in a counterclockwise rotation mode for 5min, standing for 5min, using the ball milling circulation to control the whole ball milling time to be 6h, and controlling the diameter of the used milling balls to be 10mm, and preparing the conductive liquid.
Comparative example
Weighing 3% of carbon powder, 25% of sodium dodecyl sulfate and 2% of NaOH by mass percent, adding into 70% of deionized water, and fully stirring for 4 hours to prepare the conductive liquid of the comparative example.
The conductive liquid prepared in the embodiments 1 to 6 and the comparative example is used for conductive treatment of the insulating side layer of the hole wall of the PCB substrate, and the conductive treatment process comprises pretreatment of conditioning liquid, washing, conductive liquid conductive treatment, drying, micro-etching, washing and blow-drying, and the specific process is as follows:
1) pretreatment of the conditioning fluid: placing the PCB substrate with the holes in the conditioning fluid, stirring and soaking for 1.5min at room temperature, and pretreating to increase the conductivity of the hole walls, wherein the stirring force is moderate;
2) washing with water: repeatedly washing the PCB substrate pretreated by the conditioning solution for 3-5 times by using deionized water to remove residual conditioning solution on the surface;
3) conducting treatment by using a conducting liquid: placing the washed PCB substrate in the conductive liquid prepared in the embodiment 1-6, stirring and soaking for 1.5min at room temperature, wherein the stirring force is moderate, and the nano carbon powder and the silver nano particles are combined on the hole wall through conductive treatment, so that the resin and the glass fiber bundles on the non-conductor part of the hole wall are metalized, and the hole wall has good conductivity so as to facilitate subsequent electro-plating;
4) drying: placing the PCB substrate subjected to conductive treatment in an oven for 15min, and drying at 100-150 ℃, wherein the residual conductive liquid is solidified on the hole wall due to overhigh temperature, incomplete solidification is caused due to overlow temperature, and the conductive performance is influenced due to overhigh or overlow temperature, so that the drying temperature needs to be strictly controlled;
5) micro-etching: placing the dried PCB substrate in 8% NPS microetching solution, and carrying out microetching for 1-2 min at room temperature to remove organic pollutants on the surface of the substrate;
6) washing with water: further repeatedly washing the micro-etched PCB substrate for 3-5 times by using deionized water to remove residual conductive liquid and residual oil substances on the surface;
7) drying: the PCB substrate after being washed by water is dried by a blower immediately, the residual substances and moisture on the surface are blown away by cold air, and then the PCB substrate is dried by hot air, so that the PCB substrate is prevented from being oxidized and the residual impurities on the surface are prevented.
The basic parameters of the conductive liquids of examples 1 to 6 and comparative example were tested, and the conductive liquids were applied to conductive treatment and electroplating of PCB substrates, and the solderability (according to IPC TM-650) and backlight grade of the treated PCB substrates were tested, and the experimental data are shown in table 1.
TABLE 1
The backlight is a verification examination on the copper deposition effect, and whether the substrate is transparent or not can be observed after a light source is dimmed under a 50X microscope. The less light transmission indicates better effect, generally grade 10 is taken as a rating standard (as shown in figure 1), at least grade 8 is required, if the backlight grade is too low, copper in holes is easy to be eliminated, and the conductivity and reliability of the PCB are affected. The backlight grade is above D8 grade, which shows that the hole wall binding force is better. In the embodiments 1-6 of the invention, the backlight grades of the six embodiments are all larger than or equal to 8 grades by using a slicing experimental method through observation by an inverted metallographic microscope and judging a diagram according to the electroplating backlight grade, which shows that the backlight effect is better, and further shows that the conductive liquid has a good electroplating effect.
According to the conductive liquid prepared by the invention, the dispersibility of the nano carbon powder and the silver nanoparticles in the conductive liquid is good, and the median of the particle size is kept between 100 and 200nm, so that the solution is uniform and the dispersibility is good; the conductivity of the solution is kept below 10k omega, which shows that the conductivity of the solution is good; the observation of the adsorption performance of the glass rod shows that the stronger the adsorption performance of the glass rod is, the more uniform the solution is dispersed, the better the bonding force of the hole wall is, and the better the conductivity of the PCB substrate is; the copper deposition backlight grade is above D8, which proves the effective feasibility of the method. The conductive liquid prepared by the invention is applied to the insulating layer of the hole wall of the PCB substrate, so that the PCB substrate has good conductive performance and excellent hole wall combining ability.
The applicant states that the present invention is illustrated by the above examples to show the detailed process equipment and process flow of the present invention, but the present invention is not limited to the above detailed process equipment and process flow, i.e. it does not mean that the present invention must rely on the above detailed process equipment and process flow to be implemented. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (11)
1. The conductive liquid is characterized by comprising the following raw materials in percentage by mass: 0.5-5% of nano carbon powder, 5-10% of silver nanoparticles, 0.5-5% of anionic surfactant and the balance of deionized water, wherein the silver nanoparticles are prepared by carrying out reduction reaction on a silver ion reducing agent and a silver ion complex in a mass ratio of (1-4) to (1-4) under the condition of ultrasonic stirring;
the silver ion reducing agent is one of ascorbic acid, sodium borohydride, sodium tricitrate, chloroauric acid and silver thioglycolate nano particles;
the silver ion complex is one of silver nitrate, silver chloride, silver iodide, silver oxide and silver bromide;
the average particle size of the silver nanoparticles is 10-40 nm.
2. The conductive liquid as claimed in claim 1, wherein the specific surface area of the nano carbon powder is 300-1500 m2/g。
3. The conductive liquid as claimed in claim 1, wherein the average particle size of the nano carbon powder is 100 to 200 nm.
4. The conductive liquid as claimed in claim 1, wherein the average particle size of the nano carbon powder is 105 nm.
5. The conductive fluid as recited in claim 1, wherein the anionic surfactant is sodium xanthate or sodium dodecylbenzenesulfonate.
6. The conductive liquid as recited in claim 1, wherein the raw materials further comprise a pH adjuster, a stabilizer, and a dispersant.
7. The preparation method of the conductive liquid as claimed in claim 1, comprising the steps of weighing 0.5-5% of nano carbon powder, 5-10% of silver nanoparticles and 0.5-5% of anionic surfactant by mass percent, adding into the balance of deionized water, fully mixing, placing into an ultrasonic mixing tank for ultrasonic stirring, placing the uniformly dispersed mixed liquid into a ball mill for ball milling, and preparing the conductive liquid.
8. The preparation method according to claim 7, wherein the power of the ultrasonic stirring is 80-500W, the time of the ultrasonic stirring is 10-120 min, and the rotation speed of the ball milling process is 100-500 rpm;
the specific process of ball milling is as follows: and (3) placing the uniformly dispersed mixed solution into an all-directional ball mill for ball milling, firstly, carrying out ball milling for 3min in a clockwise rotation mode, standing for 1-5 min, then, carrying out ball milling for 5min in an anticlockwise rotation mode, standing for 1-5 min, circulating by taking the ball milling cycle as a ball milling cycle, and controlling the whole ball milling time to be 1-6 h.
9. The method of claim 8, wherein the ball milling time is 2 hours.
10. The preparation method of claim 8, wherein the diameter of the grinding balls used in the ball milling process is 3-10 mm.
11. The method for conducting treatment of the conductive liquid according to claim 1, wherein the method for conducting treatment comprises the steps of pretreatment of the PCB substrate by the conditioning liquid, washing, black hole treatment of the conductive liquid, drying, micro-etching, washing and drying.
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| US4911796A (en) * | 1985-04-16 | 1990-03-27 | Protocad, Inc. | Plated through-holes in a printed circuit board |
| US4964948A (en) * | 1985-04-16 | 1990-10-23 | Protocad, Inc. | Printed circuit board through hole technique |
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