Method for processing PCB through two-fluid surface treatment

Abstract

The invention discloses a method for processing a PCB through two-fluid surface treatment. The method comprises the following steps: step 1, pre-treating a printed copper wire substrate; 2, conveying the printed copper wire substrate to a surface treatment chamber; a two-fluid nozzle in the surface treatment chamber sprays a surface treatment two-fluid to the substrate printed with the copper wire, and the surface treatment two-fluid comprises a plating solution and nitrogen which scatters the plating solution into atomized liquid drops. The plating solution reacts on the copper circuit, so that the surface of the copper circuit is plated with a metal layer; in the reaction process, air is pumped in the surface treatment chamber, and residual coating liquid and reacted liquid are pumped away; step 3, cleaning the substrate; and step 4, drying the cleaned substrate. In the reaction process, the residual surface treatment secondary fluid and reaction production liquid are pumped away by exhausting air in the surface treatment chamber, so that the problem of substrate pollution caused by long-time contact between the reaction production liquid and the substrate is avoided, and the thickness of a metal layer plated on the substrate can be accurately controlled.

Description

Technical Field

[0001] The invention relates to the technical field of PCB production, and in particular to a processing method for a two-fluid surface-treated PCB. Background Art

[0002] PCB surface treatment refers to plating a metal layer on the exposed copper circuit to increase its corrosion resistance and weldability. Common PCB surface treatment methods include electroplating, chemical gold plating, etc., among which chemical gold plating refers to immersing the printed copper circuit substrate in a liquid tank containing a plating solution. The plating solution includes soluble metal salts. The soluble metal salts react with the printed copper circuit to plate a metal layer on the copper circuit. However, during the reaction process, the following problems will exist: 1. The product of the reaction between the plating solution and the printed copper circuit will contaminate the plating solution in the entire liquid tank, resulting in a waste of plating solution. 2. The product of the reaction between the plating solution and the printed copper circuit will be in contact with the printed copper circuit board for a long time, which will contaminate the printed copper circuit substrate. 3. As the reaction proceeds, the concentration of soluble metal salts in the plating solution gradually decreases and needs to be replenished in time, otherwise it will affect the plating quality and thickness.

[0003] For example, a Chinese patent with the announcement number CN118785629A discloses a gold plating process for pads of step-density circuit boards, which includes the following steps: pretreatment: degreasing, micro-etching, activating and post-immersing the circuit board, and plating palladium on the copper surface of the circuit board; one-time water washing: washing the circuit board with a water washing solution; nickel plating: chemical nickel plating the circuit board after one-time water washing; in order to ensure the quality of nickel plating, before nickel plating, the potion in the nickel cylinder is tested to keep the nickel content in the potion at 5g-5.6g / L, and the reducing agent sodium hypophosphite is kept at 25g-30g / L. When adding nickel salt and reducing agent, they should be added evenly in small amounts multiple times to prevent violent reactions in local plating solutions, and a stirrer is used to stir continuously at a uniform speed. After stirring, the potion in the nickel cylinder is tested, resulting in a cumbersome nickel plating process.

[0004] In view of this, the present invention proposes a two-fluid surface treatment PCB processing method to solve the above problems. Summary of the invention

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

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A two-fluid surface treatment PCB processing method, characterized by comprising the following steps:

[0008] Step 1: Pre-treat the substrate for printing copper circuits;

[0009] 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, the two-fluid nozzles spray the surface treatment two-fluid on the side of the substrate printed with the copper circuit, the surface treatment two-fluid includes nitrogen and plating liquid, the plating liquid includes 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 sucked away by exhausting air in the surface treatment chamber;

[0010] Step 3: After the reaction is completed, the substrate is cleaned with deionized water;

[0011] Step 4: Dry the cleaned substrate.

[0012] Preferably, step 2 and step 3 are repeated to form at least two metal layers on the side of the substrate on which the copper circuit is printed.

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

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

[0015] Preferably, 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.

[0016] Preferably, 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.

[0017] Preferably, in the step three, the substrate is cleaned in a spray chamber, and the substrate is transported to the surface treatment chamber and the spray chamber via a roller conveyor line, and the roller conveyor line runs through the surface treatment chamber and the spray chamber.

[0018] Preferably, in the surface treatment chamber, the substrate with printed copper circuits is placed on the roller conveyor line, the two-fluid nozzle is located above the roller conveyor line, and 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.

[0019] Preferably, the processing method sequentially plates a nickel layer, a palladium layer and a gold layer on a substrate of a printed copper circuit through three surface treatment chambers, and a spray chamber is arranged between the surface treatment chambers.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

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

[0022] 2. In the prior art, chemical gold deposition refers to immersing the printed copper circuit substrate in a chemical tank, which is filled with a plating liquid. The plating liquid reacts on the printed copper circuit substrate to form a metal layer. The product of the reaction between the plating liquid and the printed copper circuit will contaminate the plating liquid in the entire chemical tank. Compared with the prior art, the present invention allows the surface treatment two fluids to react with the copper circuit printed on the substrate, and removes the remaining surface treatment two fluids and reaction production liquid. The reaction production liquid will not contact and mix with the surface treatment two fluids sprayed from the two fluid nozzles, and there is no problem of plating liquid contamination in the surface treatment two fluids, thereby solving the problem of waste caused by chemical gold deposition plating liquid contamination in the prior art.

[0023] 3. The present invention can accurately control the solubility of metal salts and other components in the plating solution, and 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, and is particularly suitable for plating extremely thin metal layers on substrates.

[0024] 4. The present invention sprays the plating liquid evenly onto the substrate surface through a two-fluid nozzle, and the particle size of the atomized droplets is 0.5-1500um, which is relatively small, so that the substrate reacts fully with the plating liquid everywhere, thereby forming a metal layer of uniform thickness on the substrate. Moreover, the nitrogen in the two-fluid surface treatment can not only break up the plating liquid into atomized droplets, but also prevent the metal layer generated by the reaction from being oxidized.

[0025] 5. Compared with the prior art in which the substrate is immersed in the plating solution, more plating solution is required; the present invention sprays the substrate with two fluids for surface treatment, so that the plating solution can be concentrated in contact with the side of the substrate printed with copper circuits, reducing the amount of plating solution used, thereby reducing the cost of chemical gold plating. DETAILED DESCRIPTION

[0026] The features of the present invention and other related features are further described in detail below through embodiments to facilitate understanding by those skilled in the art:

[0027] A two-fluid surface treatment PCB processing method, characterized in that it includes the following steps in sequence:

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

[0029] Step 2: transport the pre-treated substrate to a surface treatment chamber; a plurality of two-fluid nozzles are arranged in the surface treatment chamber, and the two-fluid nozzles spray the surface treatment two-fluid to the side of the substrate printed with the copper circuit, and the surface treatment two-fluid includes nitrogen and plating liquid, and the plating liquid includes soluble metal salt, and the nitrogen breaks up the plating liquid into atomized droplets; the plating liquid reacts with the copper circuit to plate a metal layer on the surface of the copper circuit; during the reaction, the remaining surface treatment two-fluid and reaction production liquid are evacuated by exhausting air in the surface treatment chamber; and the substrate after the reaction is cleaned with ionized water.

[0030] Step 3: After the reaction is completed, clean the substrate with deionized water.

[0031] Step 4: Dry the cleaned substrate.

[0032] In some embodiments, the processing method repeats step 2 and step 3 to form at least two metal layers on the side of the substrate where the copper circuit is printed. After each reaction between the second surface treatment fluid and the printed copper circuit substrate, the printed copper circuit substrate needs to be cleaned with deionized water to prevent the residual plating liquid and the reaction mixture on the printed copper circuit substrate from affecting the next metal deposition.

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

[0034] In some embodiments, the particle size of the atomized droplets is 0.5 to 1500 um, and the atomized droplets are evenly sprayed onto the surface of the substrate through a two-fluid nozzle. The particle size of the atomized droplets is small, which is conducive to the atomized droplets being evenly spread on the surface of the substrate, so that the substrate reacts fully with the plating liquid everywhere, thereby forming a metal layer of uniform thickness on the substrate. Moreover, the surface treatment two fluids are sprayed onto the surface of the substrate through a two-fluid nozzle, and the thickness of the plating liquid on the surface of the substrate can be controlled to be very thin, and the plating liquid reacts on the surface of the substrate to generate an extremely thin metal layer. For example, the thickness of the nickel layer deposited on the printed copper circuit substrate is relatively large, which will affect the transmission and reception of electrical signals. Therefore, the processing method of the present invention is particularly suitable for plating an extremely thin metal layer on the substrate, and utilizing the transmission and reception of electrical signals of the printed copper circuit substrate.

[0035] In the prior art, the substrate is immersed in a liquid cylinder containing the plating liquid. In order to ensure uniform concentration of the plating liquid in the liquid cylinder, the plating liquid in the liquid cylinder needs to be stirred during the reaction process. The processing method of the present invention does not require stirring and the processing method is simpler.

[0036] In some embodiments, the nitrogen flow rate in the surface treatment two fluids is 400-500 L / min, and the coating liquid flow rate is 2-3 L / min, ensuring that the nitrogen can break up the coating liquid into atomized droplets. In addition, during the reaction, the nitrogen can also prevent the metal layer generated by the reaction from being oxidized.

[0037] In some embodiments, 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.

[0038] Degreasing is to immerse the printed copper circuit substrate in an acidic solution, which reacts to decompose the oil on the surface of the printed copper circuit substrate, and then clean the printed copper circuit substrate with deionized water.

[0039] Micro-etching is to immerse the printed copper circuit substrate in micro-etching liquid to further remove foreign contaminants and slightly corrode the surface of the copper circuit, increase the microscopic roughness of the copper circuit surface, improve the bonding force between the copper circuit and the subsequent metal plating, and ensure good adhesion between the metal plating and the substrate. After micro-etching, the printed copper circuit substrate is cleaned with deionized water. After micro-etching, the printed copper circuit substrate is cleaned with deionized water.

[0040] Pickling is the process of immersing the printed copper circuit substrate in an acid solution.

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

[0042] In some embodiments, in step three, the substrate is cleaned in the spray chamber, and the substrate is transported to the surface treatment chamber and the spray chamber via a roller conveyor line, and the roller conveyor line runs 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 conveyor line, which is beneficial to remove the residual plating liquid and the reaction mixture, and avoid the next metal deposition. The substrate is transported to the surface treatment chamber and the spray chamber via the roller conveyor line to ensure the continuity of the substrate gold deposition process and reduce the manual handling of the substrate.

[0043] In some embodiments, in the surface treatment chamber, the substrate of the printed copper circuit is placed on the roller conveyor line, the two-fluid nozzle is located above the roller conveyor line, and an exhaust device is provided below the roller conveyor line. The exhaust device is activated so that the pressure below the roller conveyor line is lower than the pressure above the roller conveyor line, and the remaining surface treatment two-fluid and reaction production liquid fall from the gap of the roller conveyor line to below the roller conveyor line and are then sucked away by the exhaust device. The two-fluid nozzle is arranged above the roller conveyor line, and the exhaust device is arranged below the roller conveyor line, so that the plating liquid sprayed by the two-fluid nozzle can contact and react with the printed copper circuit substrate as much as possible, thereby improving the utilization rate of the plating liquid.

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

[0045] An embodiment of the present invention provides a two-fluid surface treatment PCB processing method, which comprises the following steps in sequence:

[0046] Step 1: pre-treating the printed copper circuit substrate; the pre-treatment of the printed copper circuit substrate includes degreasing, water washing, micro-etching, water washing, acid washing, water washing, activation, and water washing in sequence.

[0047] Step 2: transport the pre-treated substrate to the first surface treatment chamber; a plurality of two-fluid nozzles are provided on the top of the surface treatment chamber. The plating liquid entering the two-fluid nozzle is a nickel plating liquid, the pressure of the nickel plating liquid is 2Bar, and the pressure of the nitrogen entering the two-fluid nozzle is 3Bar. The nitrogen breaks up the nickel plating liquid into atomized droplets with a particle size of 0.5 to 1500um. The two-fluid nozzle sprays the surface treatment two-fluid on the printed copper circuit substrate. The flow rate of nitrogen in the surface treatment two-fluid is 400 to 500L / min, the flow rate of the nickel plating liquid is 2 to 3L / min, and the spraying time is 1 to 2 minutes. The nickel plating liquid reacts on the copper circuit to form a nickel layer with a thickness of 0.3um. During the reaction, the concentration of soluble nickel salts in the nickel plating liquid decreases, and the reaction products will increase in the nickel plating liquid. By exhausting the surface treatment chamber, the remaining surface treatment two-fluid and reaction production liquid are extracted; the substrate after the reaction is cleaned with ionized water.

[0048] Step 3: The printed copper circuit substrate after the reaction is transferred to a spray chamber, and the spray chamber cleans the printed copper circuit substrate by spraying deionized water.

[0049] Step 4: transport the printed copper circuit substrate to the second surface treatment chamber; the two-fluid nozzle in the surface treatment chamber sprays the surface treatment two-fluid to one side of the substrate plated with a nickel layer. The surface treatment two-fluid includes nitrogen and palladium plating liquid, and the palladium plating liquid is broken up into atomized droplets by nitrogen. The palladium plating liquid replaces the nickel layer, so that a palladium layer is formed on the nickel layer. During the reaction, the concentration of soluble palladium salts in the palladium plating liquid decreases, and the nickel ions generated by the reaction will increase in the palladium plating liquid. The remaining surface treatment two-fluid and reaction production liquid are evacuated by exhausting the surface treatment chamber; the substrate after the reaction is cleaned with ionized water.

[0050] Step 5: The printed copper circuit substrate after the reaction is transferred to a spray chamber, and the spray chamber cleans the printed copper circuit substrate by spraying deionized water.

[0051] Step 6: transport the printed copper circuit substrate to the third surface treatment chamber; the two-fluid nozzle in the surface treatment chamber sprays the surface treatment two-fluid on one side of the substrate plated with the palladium layer. The surface treatment two-fluid includes nitrogen and gold plating liquid, and the gold plating liquid is broken up into atomized droplets by nitrogen. The gold plating liquid replaces the palladium layer, so that a gold layer is formed on the palladium layer. During the reaction, the surface treatment chamber is ventilated to remove the remaining surface treatment two-fluid and the reaction production liquid; the substrate after the reaction is cleaned with ionized water.

[0052] Step 7: The printed copper circuit substrate after the reaction is transferred to a spray chamber, and the spray chamber cleans the printed copper circuit substrate by spraying deionized water.

[0053] Step 8: Dry the cleaned printed copper circuit substrate with cold air, and then further dry it with hot air.

[0054] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structural transformation made using the specification of the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

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, the two-fluid nozzles spray the surface treatment two-fluid on the side of the substrate printed with the copper circuit, the surface treatment two-fluid includes nitrogen and plating liquid, the plating liquid includes 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 sucked away by exhausting air in the surface treatment chamber; Step 3: After the reaction is completed, the substrate is cleaned with deionized water; Step 4: Dry the cleaned substrate.

2. The method for processing a two-fluid surface treated PCB according to claim 1, characterized in that: Repeat step 2 and step 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 two-fluid surface treated PCB 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 two-fluid surface treated PCB according to claim 1, characterized in that: The particle size of the atomized liquid droplets is 0.5 to 1500 um.

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: 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 via a roller conveyor line, and the roller conveyor line runs through the surface treatment chamber and the spray chamber.

8. The method for processing a two-fluid surface treated PCB according to claim 7, characterized in that: In the surface treatment chamber, the substrate with printed copper circuits is placed on the roller conveyor line, the two-fluid nozzle is located above the roller conveyor line, and 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.

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