A method of processing a two-fluid surface treatment PCB

Abstract

The application discloses a processing method of a two-fluid surface treatment PCB, which comprises the following steps: step one, pretreating a printed copper circuit substrate; step two, conveying the printed copper circuit substrate to a surface treatment chamber; a two-fluid nozzle in the surface treatment chamber sprays a surface treatment two-fluid on the printed copper circuit substrate, the surface treatment two-fluid comprises a plating layer liquid and nitrogen for dispersing the plating layer liquid into atomized liquid drops; the plating layer liquid reacts on the copper circuit to make a metal layer plated on the surface of the copper circuit; air is drawn in the surface treatment chamber during the reaction to draw away the remaining plating layer liquid and the liquid after reaction; step three, cleaning the substrate; and step four, drying the cleaned substrate. During the reaction, the application draws air in the surface treatment chamber to draw away the remaining surface treatment two-fluid and the reaction production liquid, thereby avoiding the problem that the reaction production liquid is in contact with the substrate for a long time to cause the substrate to be polluted, and the thickness of the plated metal layer on the substrate can be accurately controlled.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of PCB production, in particular to a processing method of two-fluid surface treatment PCB. BACKGROUND

[0002] PCB surface treatment refers to plating a metal layer on the exposed copper circuit to increase its corrosion resistance and solderability. Common PCB surface treatment methods include electroplating, chemical gold plating, etc. Chemical gold plating refers to immersing a printed copper circuit board in a drug tank containing a plating solution, which includes a soluble metal salt. The soluble metal salt reacts with the printed copper circuit to form a metal layer on the copper circuit. However, during the reaction, the following problems may occur: 1. The reaction product of the plating solution and the printed copper circuit may contaminate the entire plating solution in the drug tank, resulting in waste of the plating solution. 2. The reaction product of the plating solution and the printed copper circuit may contaminate the printed copper circuit board if it is in contact with the printed copper circuit board for a long time. 3. As the reaction proceeds, the concentration of the soluble metal salt in the plating solution gradually decreases, which needs to be replenished in time, otherwise it may affect the plating quality and thickness.

[0003] For example, the Chinese patent with publication number CN118785629A discloses a pad gold plating process for high-density circuit boards, which includes the following steps: pretreatment, including oil removal, micro-etching, activation, and post-immersion of the circuit board, and palladium plating on the copper surface of the circuit board; first water washing, using a water washing solution to wash the circuit board; nickel plating, chemically plating nickel on the circuit board after the first water washing; to ensure the quality of the nickel plating, the drug solution in the nickel tank is detected before nickel plating, so that the composition of nickel in the drug solution is maintained at 5g-5.6g / L, and the reducing agent sodium hypophosphite is maintained at 25g-30g / L. When adding nickel salt and reducing agent, they should be added in small amounts and multiple times to prevent local plating solution from reacting violently, and a stirrer is used for continuous and uniform stirring. After stirring is completed, the drug solution in the nickel tank is detected, which makes the nickel plating process complicated.

[0004] In view of the above problems, the present application provides a processing method of two-fluid surface treatment PCB. SUMMARY

[0005] The present application overcomes the shortcomings of the above-mentioned technology and provides a processing method of two-fluid surface treatment PCB, which can accurately control the plating thickness and avoid the problem of plating failure caused by contamination of the plating solution.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] A processing method of two-fluid surface treatment PCB, characterized in that it comprises the following steps:

[0008] Step 1: pretreating the substrate of the printed copper circuit;

[0009] Step two: transport the pre-processed substrate to a surface treatment chamber; the surface treatment chamber is provided with a plurality of two-fluid nozzles, the two-fluid nozzles spray the surface treatment two-fluid on the side of the substrate printed with copper circuit, the surface treatment two-fluid includes nitrogen and plating solution, the plating solution includes soluble metal salt, and the nitrogen disperses the plating solution into atomized droplets; the plating solution reacts on the copper circuit to form a metal layer on the surface of the copper circuit; during the reaction, the remaining surface treatment two-fluid and reaction production liquid are removed by air suction in the surface treatment chamber;

[0010] Step three: after the reaction is completed, the substrate is cleaned with deionized water;

[0011] Step four: dry the cleaned substrate.

[0012] Preferably, steps two and three are repeated to form at least two metal layers on the side of the substrate printed with copper circuit.

[0013] Preferably, the soluble metal salt is one of nickel salt, palladium salt and gold salt.

[0014] Preferably, the particle size of the atomized droplets is 0.5-1500um.

[0015] Preferably, the flow rate of nitrogen in the surface treatment two-fluid is 400-500L / min, and the flow rate of the plating solution is 2-3L / min.

[0016] Preferably, the pre-treatment of the substrate printed with copper circuit includes oil removal, water washing, micro-etching, water washing, pickling, water washing, activation and water washing.

[0017] Preferably, in the step three, the substrate is cleaned in a spraying chamber, and the substrate is transported into the surface treatment chamber and the spraying chamber through a roller conveying line, and the roller conveying line penetrates the surface treatment chamber and the spraying chamber.

[0018] Preferably, in the surface treatment chamber, the substrate printed with copper circuit is placed on the roller conveying line, the two-fluid nozzles are located above the roller conveying line, and an air suction device is arranged below the roller conveying line, and the air suction device is used to remove the remaining surface treatment two-fluid and reaction production liquid.

[0019] Preferably, the processing method is used to form a nickel layer, a palladium layer and a gold layer on the substrate printed with copper circuit through three surface treatment chambers, and a spraying chamber is arranged between the surface treatment chambers.

[0020] Compared with the prior art, the present application has the following advantages:

[0021] 1. The present invention allows the second surface treatment fluid to react with the side of the substrate printed with copper circuits. During the reaction, the remaining second surface treatment fluid and reaction production liquid are removed by exhausting air in the surface treatment chamber, thereby avoiding the problem of substrate contamination caused by long-term contact of the reaction production liquid with the substrate.

[0022] 2. In the prior art, electroless gold (EIG) involves immersing a printed copper circuit substrate in a bath containing a plating solution. The bath then reacts with the printed copper circuit substrate to form a metal layer. The reaction products from the plating solution and the printed copper circuits contaminate the entire bath. Compared to the prior art, the present invention allows a surface treatment fluid to react with the printed copper circuits on the substrate, then removes the remaining surface treatment fluid and reaction product liquid. This prevents the reaction product liquid from coming into contact with and mixing with the surface treatment fluid ejected from the fluid nozzle, eliminating the problem of plating liquid contamination in the surface treatment fluid. This solves the problem of waste caused by contaminated electroless gold plating solution in the prior art.

[0023] 3. The present invention can accurately control the solubility of metal salts and other components in the plating solution. In addition, by controlling the flow rate and spraying time of the two surface treatment fluids, the thickness of the metal layer plated on the substrate can be accurately controlled. It is particularly suitable for plating extremely thin metal layers on substrates.

[0024] 4. The present invention uses a two-fluid nozzle to evenly spray the plating solution onto the substrate surface. The atomized droplets have a small particle size of 0.5 to 1500 μm, allowing for a thorough reaction between the plating solution and the substrate, resulting in a uniform metal layer. Furthermore, the nitrogen in the surface treatment two-fluid spray not only breaks up the plating solution into atomized droplets but also prevents oxidation of the resulting metal layer.

[0025] 5. Compared with the prior art method of immersing the substrate in the plating solution, which requires more plating solution, the present invention sprays the substrate with two fluids through surface treatment, allowing the plating solution to be concentrated in contact with the side of the substrate printed with copper circuits, reducing the amount of plating solution used and thus reducing the cost of chemical gold plating. DETAILED DESCRIPTION

[0026] The following examples further illustrate the features of the present invention and other related features to facilitate understanding by those skilled in the art:

[0027] A method for processing a PCB using a two-fluid surface treatment, characterized by comprising the following steps in sequence:

[0028] Step 1: Pre-treat the substrate for printing copper circuits.

[0029] Step two: the pre-processed substrate is transported to a surface treatment chamber; the surface treatment chamber is provided with a plurality of two-fluid nozzles, the two-fluid nozzles spray a surface treatment two-fluid on the side of the substrate printed with copper circuit, the surface treatment two-fluid includes nitrogen and plating solution, the plating solution includes soluble metal salt, and the nitrogen disperses the plating solution into atomized droplets; the plating solution reacts with the copper circuit to form a metal layer on the surface of the copper circuit; during the reaction, the remaining surface treatment two-fluid and reaction product liquid are removed by air suction in the surface treatment chamber; and the substrate after the reaction is cleaned with ionized water.

[0030] Step three: after the reaction, the substrate is cleaned with deionized water.

[0031] Step four: the cleaned substrate is dried.

[0032] In some embodiments, the processing method repeats step two and step three, so that at least two metal layers are formed on the side of the substrate printed with copper circuit. After the reaction of the surface treatment two-fluid with the substrate printed with copper circuit, the substrate printed with copper circuit needs to be cleaned with deionized water to avoid the influence of the residual plating solution and the mixture after the reaction on the deposition of the next metal.

[0033] In some embodiments, the soluble metal salt is one of nickel salt, palladium salt and gold salt.

[0034] In some embodiments, the particle size of the atomized droplets is 0.5-1500 um, the atomized droplets are uniformly sprayed on the surface of the substrate through the two-fluid nozzles, the small particle size of the atomized droplets is beneficial to the uniform paving of the atomized droplets on the surface of the substrate, so that the substrate fully reacts with the plating solution everywhere, thereby forming a metal layer with uniform thickness. Moreover, the surface treatment two-fluid is sprayed on the surface of the substrate through the two-fluid nozzles, the thickness of the plating solution on the surface of the substrate can be controlled to be very thin, and the plating solution reacts on the surface of the substrate to form a metal layer with very thin thickness. For example, the deposition of a nickel layer with large thickness on the substrate printed with copper circuit will affect the transmission and reception of electrical signals, so the processing method of the present application is particularly suitable for depositing a metal layer with very thin thickness on the substrate, and is useful for the transmission and reception of electrical signals of the substrate printed with copper circuit.

[0035] In the prior art, the substrate is soaked in a liquid tank containing plating solution, and in order to ensure the uniform concentration of the plating solution in the liquid tank, the plating solution in the liquid tank needs to be stirred during the reaction. The processing method of the present application does not need to be stirred, and the processing method is simpler.

[0036] In some embodiments, the flow rate of nitrogen in the surface treatment two-fluid is 400-500 L / min, and the flow rate of the plating solution is 2-3 L / min, so that the nitrogen can disperse the plating solution into atomized droplets. Moreover, the nitrogen can also prevent the metal layer produced by the reaction from being oxidized.

[0037] In some embodiments, the substrate pretreatment of the printed copper circuit includes oil removal, water washing, micro-etching, water washing, pickling, water washing, activation, and water washing.

[0038] The oil removal is to immerse the printed copper circuit substrate in an acidic solution to react and decompose the oil stains on the surface of the printed copper circuit substrate, and then wash the printed copper circuit substrate with deionized water.

[0039] The micro-etching is to immerse the printed copper circuit substrate in a micro-etching solution to further remove foreign contaminants and slightly etch the surface of the copper circuit to increase the micro-roughness of the copper circuit surface, improve the adhesion between the copper circuit and the subsequent metal plating layer, and ensure good adhesion between the metal plating layer and the substrate. After micro-etching, the printed copper circuit substrate is washed with deionized water. After micro-etching, the printed copper circuit substrate is washed with deionized water.

[0040] The pickling is to immerse the printed copper circuit substrate in an acidic solution.

[0041] The activation is to immerse the printed copper circuit substrate in an activation solution to adsorb a layer of catalytic metal particles on the surface of the substrate, so that the entire substrate surface can smoothly perform subsequent chemical metal deposition reactions.

[0042] In some embodiments, in the third step, the substrate is cleaned in the spray chamber, and the substrate is transported through the surface treatment chamber and the spray chamber by the roller conveying line arranged through the surface treatment chamber and the spray chamber. In the spray chamber, the substrate is cleaned by spraying deionized water, and the sprayed deionized water also cleans the roller conveying line, which is beneficial to remove residual plating solution and reaction mixture to avoid deposition of the next metal. The substrate is transported through the surface treatment chamber and the spray chamber by the roller conveying line to ensure the continuity of the substrate gold deposition process and reduce manual handling of the substrate.

[0043] In some embodiments, in the surface treatment chamber, the printed copper circuit substrate is placed on the roller conveying line, the two-fluid nozzle is located above the roller conveying line, and the air extraction device is arranged below the roller conveying line. When the air extraction device is started, the pressure below the roller conveying line is less than the pressure above the roller conveying line, and the remaining surface treatment two-fluid and reaction production liquid fall from the gap of the roller conveying line to the lower part of the roller conveying line, and then are extracted by the air extraction device. The two-fluid nozzle is arranged above the roller conveying line, and the air extraction device is arranged below the roller conveying line, so that the plating solution sprayed by the two-fluid nozzle can be in contact with the printed copper circuit substrate as much as possible to improve the utilization rate of the plating solution.

[0044] In some embodiments, the processing method is to sequentially plate a nickel layer, a palladium layer, and a gold layer on the substrate of the printed copper circuit through three surface treatment chambers, and a spray chamber is arranged between the surface treatment chambers.

[0045] The embodiment of the present application provides a processing method of two-fluid surface treatment PCB, which sequentially comprises the following steps:

[0046] Step one: pre-treating the printed copper circuit board; the pre-treatment of the printed copper circuit board comprises the following steps of oil removal, water washing, micro-etching, water washing, pickling, water washing, activation, and water washing.

[0047] Step two: conveying the pre-treated substrate to the first surface treatment chamber; a plurality of two-fluid nozzles are arranged on the top of the surface treatment chamber. The plating layer liquid entering the two-fluid nozzle is a nickel plating liquid, the pressure of the nickel plating liquid is 2 Bar, the pressure of the nitrogen gas entering the two-fluid nozzle is 3 Bar, and the nickel plating liquid is scattered into atomized liquid drops with a particle size of 0.5-1500 um by the nitrogen gas. The two-fluid nozzle sprays the surface treatment two-fluid on the printed copper circuit board, the flow rate of the nitrogen gas in the surface treatment two-fluid is 400-500 L / min, the flow rate of the nickel plating liquid is 2-3 L / min, the spraying time is 1-2 minutes, and the nickel layer with a thickness of 0.3 um is formed on the copper circuit by the reaction of the nickel plating liquid. In the reaction process, the soluble nickel salt concentration of the nickel plating liquid is reduced, and the reaction product is increased in the nickel plating liquid. The surface treatment two-fluid and the reaction product liquid are removed by air draft in the surface treatment chamber, and the substrate after the reaction is cleaned by ionized water.

[0048] Step three: conveying the printed copper circuit board after the reaction to the spraying chamber, and cleaning the printed copper circuit board by spraying the deionized water in the spraying chamber.

[0049] Step four: conveying the printed copper circuit board to the second surface treatment chamber; the two-fluid nozzles in the surface treatment chamber spray the surface treatment two-fluid on one side of the substrate plated with the nickel layer. The surface treatment two-fluid comprises nitrogen gas and palladium plating liquid, and the palladium plating liquid is scattered into atomized liquid drops by the nitrogen gas. The palladium plating liquid is replaced with the nickel layer, so that the palladium layer is formed on the nickel layer. In the reaction process, the soluble palladium salt concentration of the palladium plating liquid is reduced, and the nickel ion is increased in the palladium plating liquid. The surface treatment two-fluid and the reaction product liquid are removed by air draft in the surface treatment chamber, and the substrate after the reaction is cleaned by ionized water.

[0050] Step five: conveying the printed copper circuit board after the reaction to the spraying chamber, and cleaning the printed copper circuit board by spraying the deionized water in the spraying chamber.

[0051] Step six: conveying the printed copper circuit board to the third surface treatment chamber; the two-fluid nozzles in the surface treatment chamber spray the surface treatment two-fluid on one side of the substrate plated with the palladium layer. The surface treatment two-fluid comprises nitrogen gas and gold plating liquid, and the gold plating liquid is scattered into atomized liquid drops by the nitrogen gas. The gold plating liquid is replaced with the palladium layer, so that the gold layer is formed on the palladium layer. In the reaction process, the surface treatment chamber is air-drafted to remove the surface treatment two-fluid and the reaction product liquid, and the substrate after the reaction is cleaned by ionized water.

[0052] Step seven: the printed copper circuit board after reaction is transmitted to a spraying chamber, and the spraying chamber cleans the printed copper circuit board by spraying deionized water.

[0053] Step eight: the cleaned printed copper circuit board is dried by cold air, and then dried further by hot air.

[0054] The above only describes the preferred embodiments of the present application, and does not limit the patent scope of the present application, and any equivalent structural transformation made by using the present application specification, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A two-fluid surface treatment PCB processing method, characterized in that: The following steps are involved: Step 1: Pre-treat the substrate for printing copper circuits; Step 2: transporting the pre-treated substrate to a surface treatment chamber; the surface treatment chamber is provided with a plurality of two-fluid nozzles, which spray the surface treatment two-fluid onto the side of the substrate printed with the copper circuit, wherein the surface treatment two-fluid comprises nitrogen and a plating liquid, wherein the plating liquid comprises a soluble metal salt, and the nitrogen breaks up the plating liquid into atomized droplets; the plating liquid reacts on the copper circuit, so that a metal layer is plated on the surface of the copper circuit; during the reaction process, the remaining surface treatment two-fluid and reaction production liquid are removed by exhausting air in the surface treatment chamber; Step 3: After the reaction is completed, the substrate is cleaned with deionized water; Step 4: Drying the cleaned substrate; In the step three, the substrate is cleaned in the spray chamber, and the substrate is transported to the surface treatment chamber and the spray chamber through a roller conveyor line, and the roller conveyor line runs through the surface treatment chamber and the spray chamber; in the surface treatment chamber, the substrate with printed copper circuits is placed on the roller conveyor line, and the two-fluid nozzle is located above the roller conveyor line. An exhaust device is provided below the roller conveyor line, and the exhaust device is used to extract the remaining surface treatment two fluids and reaction production liquid.

2. The method for processing a two-fluid surface-treated PCB according to claim 1, characterized in that: Repeat steps 2 and 3 to form at least two metal layers on the side of the substrate where the copper circuit is printed.

3. The method for processing a PCB with a two-fluid surface treatment according to claim 1, characterized in that: The soluble metal salt is one of nickel salt, palladium salt and gold salt.

4. The method for processing a PCB with a two-fluid surface treatment according to claim 1, characterized in that: The particle size of the atomized droplets is 0.5~1500um.

5. The method for processing a two-fluid surface treated PCB according to claim 1, characterized in that: The nitrogen flow rate in the surface treatment two fluids is 400-500 L / min, and the plating liquid flow rate is 2-3 L / min.

6. The method for processing a two-fluid surface treated PCB according to claim 1, characterized in that: The substrate pretreatment of the printed copper circuit includes degreasing, water washing, micro-etching, water washing, acid washing, water washing, activation and water washing in sequence.

7. The method for processing a two-fluid surface treated PCB according to claim 1, characterized in that: The substrate of the printed copper circuit is plated with nickel layer, palladium layer and gold layer in sequence through three surface treatment chambers, and a spray chamber is set between the surface treatment chambers.