Circuit board and vertical copper deposition hole metallization method thereof

Abstract

The invention provides a circuit board and a vertical copper deposition hole metallization method thereof. The method comprises the following steps of obtaining a circuit board A which is sequentially subjected to swelling and degumming operation; the circuit board A is put into a neutralization cylinder for neutralization operation; putting the neutralized circuit board A into an oil-removing water-washing cylinder, and sequentially carrying out oil removal, continuous water-washing and hole-finishing operation, wherein the oil-removing water-washing cylinder adopts an ultrasonic process; putting the circuit board A after hole conditioning into a micro-etching cylinder for micro-etching operation, wherein the micro-etching cylinder adopts an ultrasonic process; the micro-etched circuit board A is put into an activation cylinder for activation operation, and the activation cylinder adopts an ultrasonic process; and putting the activated circuit board A into a copper deposition cylinder for copper deposition. According to the scheme, the ultrasonic process is added on the basis of the vertical copper deposition process, the oil removal agent in the blind hole can be removed by the aid of the water washing agent in the water washing operation after oil removal, when residual substances in the blind hole are completely removed, the copper deposition operation of the subsequent circuit board A is facilitated so that the circuit board can be manufactured, and the bottom of the blind hole and the copper deposition layer have good combining capacity.

Description

Technical Field

[0001] The present disclosure relates to the technical field of circuit board production, and in particular to a circuit board and a method for metallizing vertical copper vias thereof. Background Art

[0002] Copper deposition is also called hole metallization, which is divided into vertical copper deposition and horizontal copper deposition. Among them, horizontal copper deposition is to transfer a continuous sheet of the board horizontally to each medicine tank and water washing tank through a conveyor wheel until the board is out, so it is called horizontal copper deposition. Vertical copper deposition is to immerse dozens of boards in medicine or water washing tanks for treatment at one time. Except for the glue tank, micro-etching tank, and copper deposition tank, other medicine tanks only have filters for circulation and swinging, and the water washing tank is only cleaned by aeration and stirring. Therefore, the horizontal copper deposition process treatment and cleaning are more thorough and consistent than vertical copper deposition, and the effect is better than vertical copper deposition, which is more conducive to the bonding strength between the copper deposition layer and the bottom of the blind hole. However, the production efficiency of horizontal copper deposition is much lower than that of vertical copper deposition, and cannot meet the market demand.

[0003] In order to improve the production efficiency of circuit boards and meet market demand, a vertical copper deposition process is generally adopted, such as the prior art CN111575752B. However, the vertical copper deposition adopts immersion washing, which cannot ensure that the residual substances in the blind holes in the circuit board are completely removed, resulting in some blind holes having defects. The manifestations of the defects of the blind holes include but are not limited to uneven copper thickness in the blind holes, poor consistency of copper thickness, poor continuity of copper walls, etc., and then in the subsequent thermal current test, due to the defective blind holes, the bottom resistance is large, which easily causes the temperature to be too high, resulting in the bottom of the blind holes cracking, so that the test cannot be passed, which is not conducive to the subsequent use of electronic products.

[0004] Therefore, on the basis of adopting the vertical copper deposition process, how to ensure that the bottom of the blind hole can be combined with the copper deposition layer and can pass the thermal current test is still a problem that technicians need to solve. Summary of the invention

[0005] The purpose of the present disclosure is to overcome the deficiencies in the prior art and to provide a method and a circuit board for vertical copper via metallization that can improve efficiency and ensure that the circuit board can completely pass the thermal current test.

[0006] The purpose of this disclosure is achieved through the following technical solutions:

[0007] A method for metallizing a vertical copper-plated hole of a circuit board, wherein the circuit board has a blind hole, and the aperture ratio of the blind hole is 8.0 to 10.0. The method for metallizing a vertical copper-plated hole comprises the following steps:

[0008] Obtaining a circuit board A after undergoing swelling and degumming operations in a bulking cylinder and a degumming cylinder respectively;

[0009] The circuit board A is placed in a neutralization tank for neutralization operation, and the neutralization tank adopts an ultrasonic process to assist the neutralizer to flow into the blind hole, thereby removing the swelling agent and the debonding agent in the blind hole;

[0010] The neutralized circuit board A is placed in a degreasing water washing tank for degreasing, continuous water washing and hole-smoothing operations in sequence. The degreasing water washing tank adopts the ultrasonic process to assist the degreasing agent to flow into the blind hole during the degreasing operation and assist the clean water to remove the degreasing agent during the continuous water washing operation;

[0011] The circuit board A after hole trimming is placed in a micro-etching tank for micro-etching operation, and the micro-etching tank adopts the ultrasonic process to assist the micro-etching solution to roughen the copper hole wall of the blind hole;

[0012] The micro-etched circuit board A is placed in an activation tank for activation operation, and the activation tank adopts the ultrasonic process to assist the activator in activating the copper hole wall of the blind hole;

[0013] The activated circuit board A is placed in a copper deposition tank to perform a copper deposition step to form a circuit board.

[0014] In one of the embodiments, the swelling operation in the bulking cylinder uses an ultrasonic process to assist the swelling agent in flowing into the blind hole during the swelling operation, thereby expanding the drilling residue in the blind hole.

[0015] In one embodiment, the step of placing the circuit board A into a neutralization cylinder for neutralization may further include:

[0016] The neutralized circuit board A is placed in a water washing tank for impurity removal and water washing operation; the impurity removal and water washing operation includes:

[0017] Performing a first impurity removal water washing operation on the circuit board A to preliminarily remove the neutralizer remaining on the surface of the circuit board A and in the through-holes;

[0018] The circuit board A is subjected to a second impurity removal and water washing operation, wherein the second impurity removal and water washing operation adopts the ultrasonic process to assist the water washing agent to flow into the blind hole, thereby removing the neutralizing agent in the blind hole.

[0019] In one embodiment, the neutralized circuit board A is placed in a degreasing water washing tank and sequentially subjected to degreasing, continuous water washing and hole-smoothing operations, wherein the continuous water washing operation includes:

[0020] The degreased circuit board A is washed with hot water to remove the degreaser;

[0021] After the hot water washing operation, the circuit board A is subjected to overflow water washing operation to further continuously remove the residual degreasing agent.

[0022] In one embodiment, the water temperature of the hot water washing operation is X degrees, where 40≤X≤45.

[0023] In one embodiment, the circuit board A after the hot water washing operation is subjected to overflow water washing operation, comprising:

[0024] Performing a first overflow water washing operation on the circuit board A, wherein the first overflow water washing adopts the ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining on the surface of the circuit board A and in the through-holes;

[0025] The circuit board A is subjected to a second overflow water washing operation, wherein the second overflow water washing adopts the ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining in the blind hole.

[0026] In one embodiment, the washing time of the first overflow water washing operation and / or the second overflow water washing operation is Y hours; wherein Y≥6.

[0027] In one embodiment, the circuit board A after hole trimming is placed in a micro-etching tank for micro-etching, and then further comprises:

[0028] The micro-etched circuit board A is placed in a pre-preg tank for pre-preg operation.

[0029] In one of the embodiments, in the ultrasonic process adopted in the activation cylinder, the output power of the ultrasonic wave is 2.5kW-3kW.

[0030] A circuit board is manufactured by using the vertical copper via metallization method described in any one of the above embodiments.

[0031] Compared with the prior art, the present invention has at least the following advantages:

[0032] The vertical copper-plated hole metallization method of the present scheme adopts vertical copper plating to ensure the production efficiency of the circuit board, and adds an ultrasonic process to the vertical copper plating process. In addition to removing the residual permanganate, manganate, etc. in the blind hole in the neutralization step, the degreasing agent in the blind hole can be removed by auxiliary water washing agent in the water washing operation after degreasing. When the residual substances in the blind hole are completely removed, it is convenient for the subsequent copper plating operation of the circuit board A to make the circuit board, and the bottom of the blind hole has a good bonding ability with the copper plating layer, so that in the subsequent thermal current test, all circuit boards can pass the thermal current test, ensuring the user's subsequent usage experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present disclosure, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present disclosure and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0034] Figure 1 The present invention is a flow chart of a method for metallizing a circuit board and vertical copper vias thereof in one embodiment. DETAILED DESCRIPTION

[0035] In order to facilitate the understanding of the present disclosure, the present disclosure will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present disclosure are given in the drawings. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present disclosure more thoroughly and comprehensively understood.

[0036] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present disclosure. The terms used herein in the specification of the present disclosure are only for the purpose of describing specific embodiments and are not intended to limit the present disclosure. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0038] In order to better understand the technical solutions and beneficial effects of the present invention, the present invention is further described in detail below in conjunction with specific embodiments:

[0039] See also Figure 1 , which is a method for metallizing a vertical copper-plated hole of a circuit board according to an embodiment of the present invention, the circuit board has a blind hole, the aperture ratio of the blind hole is 8.0 to 10.0, and the method for metallizing a vertical copper-plated hole includes some or all of the following steps:

[0040] S101, obtaining a circuit board A after undergoing swelling and degumming operations in a swelling cylinder and a degumming cylinder respectively.

[0041] It can be understood that most of the existing circuit boards A use epoxy resin materials as substrates, and there will be residues in the hole wall during the processing. At this time, a swelling agent needs to be added to remove the residues in the hole wall. After the residue is removed, the remaining glue substances on the circuit board A need to be removed. At this time, a degumming agent needs to be added to effectively remove the glue substances (swelling substances) attached to the circuit board A, so as to facilitate the subsequent neutralization operation. Furthermore, the main components of the degumming agent are permanganate, hydroxide ions, etc. In this embodiment, the expansion cylinder is used to swell the hole wall residues of the circuit board A, and the degumming cylinder is used to remove the swollen glue from the circuit board A.

[0042] S102, placing the circuit board A into a neutralization tank for neutralization operation. The neutralization tank adopts an ultrasonic process to assist the neutralizer to flow into the blind hole, thereby removing the swelling agent and the debonding agent in the blind hole.

[0043] In this embodiment, since the swelling agent and the degumming agent are partially present in the blind hole, especially at the bottom of the blind hole, the neutralization cylinder adopts an ultrasonic process. When the ultrasonic process is adopted, the ultrasonic wave will use its high-frequency characteristics to push the neutralizer into the through hole and the blind hole, especially the blind hole, so that the neutralizer can fully react with the swelling agent and the degumming agent remaining in the blind hole, which is convenient for removing the swelling agent and the degumming agent, and preventing the circuit board A from being disturbed by the swelling agent and / or the degumming agent during the degreasing process.

[0044] S103, placing the neutralized circuit board A into a degreasing water washing tank for degreasing, continuous water washing and hole filling operations in sequence. The degreasing water washing tank adopts an ultrasonic process to assist the degreasing agent to flow into the blind hole during the degreasing operation, and to assist clean water to remove the degreasing agent during the continuous water washing operation.

[0045] It can be understood that the degreasing agent is used to remove oil stains, fingerprints, oxides, and dust in the holes of the circuit board A. If there are oil stains, fingerprints, and the like on the surface and hole walls of the circuit board A, it will affect the bonding ability of the chemical copper plating layer and the base tube, especially the oil stains and fingerprints in the blind holes are difficult to handle. Therefore, in this embodiment, the degreasing water washing cylinder adopts an ultrasonic process. In this way, the ultrasonic wave will use its high-frequency characteristics to push the degreasing agent into the blind hole to fully remove the residual oil stains, oxides, and the like in the blind hole, so as to avoid the oil stains affecting the bonding between the inner wall of the blind hole and the copper layer during the subsequent copper deposition, thereby preventing the subsequent communication performance of the circuit board from being reduced during use. Further, the degreasing agent is an alkaline degreasing agent. It can be understood that the alkaline degreasing agent can not only effectively remove the oil stains, fingerprints, oxides, and dust in the holes of the circuit board, but also change the negative charge of the hole wall of the through hole, blind hole, and buried hole into a positive charge, which is convenient for the adsorption of colloidal palladium in the subsequent process, thereby ensuring the normal progress of the subsequent activation step. In addition, ultrasonic waves are used in the continuous water washing operation. It can be understood that after the degreasing is completed, continuous clean water is used to continuously remove the degreasing agent, and then an ultrasonic process is used to assist the clean water in removing the degreasing agent on the surface of the circuit board and in the through hole, and also to assist the clean water in flowing into the blind hole, thereby removing the residual degreasing agent in the blind hole. After thorough removal, the circuit board can be re-hole operated. Specifically, the blind hole is re-hole treated. After removing the residual degreasing agent in the blind hole and washing with water, the inner wall of the blind hole still has negative charges attached due to drilling. At this time, a hole re-hole agent should be added to adjust the charge state so that the wall of the blind hole has the characteristics of a positive charge to ensure the normal adsorption of colloidal palladium. In this embodiment, the degreasing water washing cylinder includes an oil removal cylinder and an oil removal agent water washing cylinder. The degreasing operation is performed in the oil removal cylinder, and the continuous water washing and hole re-hole operations are both performed in the oil removal agent water washing cylinder.

[0046] S104, placing the circuit board A after hole finishing into a micro-etching tank for micro-etching operation, wherein the micro-etching tank adopts ultrasonic process to assist micro-etching solution to roughen the copper hole wall of the blind hole.

[0047] In this embodiment, the micro-etching solution roughens the copper hole wall of the through hole and blind hole of the circuit board A, making the hole wall relatively rough, so that the base copper layer can absorb more activated palladium colloid, and also makes the base copper layer and the copper deposition layer better combined. Under the action of ultrasonic waves, the micro-etching solution is pushed into the blind hole, enhancing the exchange capacity of the solution in the blind hole, making it easier for the micro-etching solution to fully roughen the inner wall of the blind hole, making it rough, so that the base copper layer on the inner wall of the blind hole can absorb more activated palladium colloid.

[0048] S105, placing the micro-etched circuit board A into an activation tank for activation operation, wherein the activation tank adopts an ultrasonic process to assist the activator in activating the copper hole wall of the blind hole.

[0049] In this embodiment, after the through holes and blind holes of the circuit board A are micro-etched, an activation operation is performed, which requires an activator to activate the hole walls of the through holes and blind holes, and adsorb a layer of metal with catalytic ability on the substrate, that is, the activator converts the colloidal palladium into an activated palladium layer, so that the formed palladium layer has the ability to catalyze and reduce metals. Since the bottom of the blind hole is difficult to handle, ultrasonic waves are required to push the activator to the bottom of the blind hole to ensure that any inner wall of the bottom of the hole has a catalytic metal, which is convenient for the subsequent copper deposition step, specifically, to make the blind hole and the through hole wall have a certain amount of activated metal palladium.

[0050] S106, placing the activated circuit board A into a copper deposition tank to perform a copper deposition step to form a circuit board.

[0051] In this embodiment, under the action of activated metal palladium and deposited copper, the copper ions in the copper plating solution are reduced, and a copper layer is precipitated on the inner walls of the through holes and blind holes, so that the inner walls of the circuit board have conductivity. Specifically, after the circuit board A has been subjected to the above operation, the inner walls of the blind holes can be cleaned, fully roughened and fully activated, so that in the subsequent copper plating step, the base copper layer on the inner walls of the blind holes can be combined with the copper plating layer, so that the blind holes have good conductivity. After the copper plating step is completed, the circuit board is manufactured and can pass the blind hole thermal current test.

[0052] The above-mentioned vertical copper-plated hole metallization method adopts vertical copper plating to ensure the production efficiency of the circuit board, and adds an ultrasonic process to the vertical copper plating process. In addition to removing the residual permanganate, manganate, etc. in the blind hole in the neutralization step, the degreasing agent in the blind hole can also be removed by auxiliary water washing agent in the water washing operation after degreasing. When the residual material in the blind hole is completely removed, it is convenient for the subsequent copper plating operation of the circuit board A to make the circuit board, and the bottom of the blind hole has a good bonding ability with the copper plating layer, so that in the subsequent thermal current test, all circuit boards can pass the thermal current test, ensuring the user's subsequent usage experience.

[0053] In one embodiment, during the swelling operation, the expansion cylinder uses an ultrasonic process to assist the swelling agent in flowing into the blind hole during the swelling operation, thereby expanding the drilling residue in the blind hole. It can be understood that after the circuit board A is drilled, since there is residue in the hole wall of the circuit board A, the existence of the residue will affect the subsequent production process of the circuit board. Therefore, it is necessary to treat the hole wall residue of the circuit board A. Specifically, the high molecular polymer of the residue is expanded by a swelling agent to soften it. In order to enhance the removal effect, the expansion cylinder uses an ultrasonic process, so that the ultrasonic wave assists the swelling agent to enter the blind hole, fully softens the hole wall residue in the blind hole, and forms a colloid, which is convenient for the subsequent degumming operation.

[0054] In one embodiment, the circuit board A is placed in a neutralization tank for neutralization, and then the neutralized circuit board A is placed in a water washing tank for impurity removal and water washing. It can be understood that under the action of the neutralizer, the residual swelling agent and degumming agent on the circuit board A are removed. At this time, before entering the degreasing step, the impurity removal and water washing operation is performed to remove impurities and residual agents on the surface, through holes, blind holes, etc. of the circuit board A, so as to prevent the circuit board A from being interfered by the residual impurities and agents in the subsequent degreasing step.

[0055] Furthermore, the impurity removal and water washing operation includes: performing a first impurity removal and water washing operation on the circuit board A to preliminarily remove the residual neutralizer on the surface of the circuit board A and in the through hole; performing a second impurity removal and water washing operation on the circuit board A, and the second impurity removal and water washing operation adopts an ultrasonic process to assist the water washing agent to flow into the blind hole, thereby removing the neutralizer in the blind hole. It can be understood that the impurity removal and washing operation is divided into the first impurity removal and washing operation and the second impurity removal and washing operation. The first impurity removal and washing operation is used to remove impurities on the surface of the circuit board A and in the through-holes, and plays a role of preliminary cleaning. Generally, the impurities and neutralizers remaining on the surface and in the through-holes are easily removed by the washing agent, which does not affect the subsequent degreasing process, so there is no need to add ultrasonic technology to reduce the overall production cost of the circuit board. Since the impurities and agents remaining in the blind holes are difficult to remove, when the residual impurities and neutralizers are attached to the inner wall of the blind holes, if the circuit board A is brought into the degreasing cylinder, the residual neutralizer and the degreasing agent will interact with each other, causing contamination of the degreasing cylinder. Therefore, in the second impurity removal and washing operation, an ultrasonic process is added to better push the washing agent into the blind hole, so that the washing agent can remove the residual neutralizer and acidic agent, thereby playing a deep cleaning role. Furthermore, the water washing tank is a double water washing tank, which is divided into a first water washing tank and a second water washing tank. The first impurity removal water washing operation is performed in the first water washing tank to preliminarily remove most impurities and residual liquid medicine, and the second impurity removal water washing operation is performed in the second water washing tank to ensure that the residual neutralizer and acidic agent in the circuit board A are completely removed, especially to ensure that the residual neutralizer and acidic agent in the blind hole are completely removed.

[0056] In one embodiment, the neutralized circuit board A is placed in a degreasing water washing tank for degreasing, continuous water washing and hole-filling operations in sequence, wherein the continuous water washing operation includes: performing a hot water washing operation on the degreasing circuit board A to remove the degreasing agent; performing an overflow water washing operation on the circuit board A after the hot water washing operation to further continuously remove the residual degreasing agent. In this embodiment, the degreasing agent is an oily substance, and it is difficult to remove the degreasing agent by general water washing at room temperature. The residual degreasing agent attached to the inner wall of the through hole and blind hole of the circuit board will also affect the bonding force between the copper layer and the through hole and blind hole wall during the subsequent copper deposition. Specifically, in the presence of the degreasing agent, the circuit board A is interfered by the degreasing agent during copper deposition, so that the degreasing agent and the copper deposition liquid interact with each other, which is not conducive to the formation of copper in the through hole and blind hole of the circuit board A. Therefore, this scheme adopts a hot water washing operation to make the oily molecules of the degreasing agent active and no longer easily attached to the circuit board A, so that hot water can effectively remove most of the degreasing agent. Furthermore, the water temperature of the hot water washing operation is X degrees, where 40≤X≤45, which reduces the oiliness of the degreasing agent under the condition of warm water, so that the degreasing agent falls off the circuit board A and is then removed by warm water washing. In a preferred embodiment, the water temperature is 40 degrees. In this way, the effect of removing the degreasing agent can be achieved without heating the water to a higher temperature, which not only reduces the heating time, but also reduces the cost required for heating, thereby reducing the overall cost of the circuit board process, reducing the difficulty of circuit board production, and improving the efficiency of circuit board production.

[0057] The above-mentioned hot water washing operation can effectively remove most of the degreaser, making the degreaser float on the water, but a small part of the degreaser adheres to the circuit board A. Among them, the degreaser remaining in the blind hole is more difficult to remove. Therefore, an overflow water washing operation is required to continuously remove the residual degreaser.

[0058] In one embodiment, the circuit board A after the hot water washing operation is subjected to an overflow water washing operation, comprising:

[0059] Performing a first overflow water washing operation on the circuit board A, wherein the first overflow water washing adopts an ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining on the surface of the circuit board A and in the through-holes;

[0060] The circuit board A is subjected to a second overflow water washing operation. The second overflow water washing adopts an ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining in the blind hole.

[0061] It can be understood that after most of the degreaser is removed by hot water washing, a certain amount of degreaser still exists in the degreaser washing tank. In order to prevent more degreaser from adhering to circuit board A again, overflow water washing is performed after hot water washing so that the overflow water can float up and remove the degreaser. Furthermore, the first overflow water washing adopts an ultrasonic process to assist the overflow water in continuously removing the degreaser remaining on the surface of circuit board A and in the through-holes, so that the degreaser attached to the surface of circuit board A and in the through-holes is emulsified under the combined action of overflow water and ultrasonic waves, and its adhesion is reduced, so that it is easily removed, thereby achieving the effect of cleaning the surface of circuit board A and the through-holes, but the degreaser remaining in the blind holes is not completely removed; the second overflow water washing adopts an ultrasonic process to assist the overflow water in continuously removing the degreaser remaining in the blind holes, and further, to assist the overflow water in continuously and deeply removing the degreaser remaining in the blind holes, thereby preventing the degreaser from adhering to circuit board A again and causing interference from the degreaser during the copper deposition operation, which is beneficial to the subsequent bonding of the base copper layer and the copper deposition layer in the blind holes of circuit board A during copper deposition, thereby ensuring that circuit board A can pass the thermal current test after it is manufactured. Furthermore, the degreasing water washing tank includes a first degreasing water washing tank and a second degreasing water washing tank, and the first degreasing water washing tank and the second degreasing water washing tank both adopt ultrasonic technology, wherein the first degreasing water washing tank adopts ultrasonic waves to act on the surface of the circuit board A and the degreasing agent remaining in the through hole for water washing, and the second degreasing water washing tank adopts ultrasonic waves to act on the degreasing agent remaining in the blind hole of the circuit board A for water washing, so as to ensure that the degreasing agent remaining in each area of ​​the circuit board A can be completely removed.

[0062] In another embodiment, a second overflow water washing operation is performed after a certain period of time has passed since the first overflow water washing operation was performed.

[0063] In one embodiment, the washing time of the first overflow water washing operation and / or the second overflow water washing operation is Y hours; wherein Y≥6. It can be understood that, compared with conventional water washing, overflow water washing has better continuous water washing characteristics. In the manufacturing process of circuit boards, in order to meet the communication performance requirements for subsequent use and ensure a better user experience, after completing the hot water washing operation, the degreaser remaining in the degreasing water washing tank and still remaining on the circuit board A is removed. This solution adopts an overflow water washing operation to continuously remove the degreaser that has fallen off from the circuit board A. It takes a certain amount of time to completely remove the residual degreaser, which needs to be continued during this time. Therefore, the ultrasonic wave should be kept running to ensure that the oiliness of the degreaser is effectively reduced, and further the degreaser content in the degreasing water washing tank is continuously reduced until the degreaser is completely removed and the whole hole operation of the circuit board A is performed. Specifically, when the first overflow water washing operation lasts for more than 6 hours, a water tank is replaced to prevent the emulsified degreaser in the degreaser water washing tank from accumulating and affecting removal, and then a second overflow water washing operation is performed to continuously remove the residual degreaser. In a preferred embodiment, the washing time of the first overflow water washing operation and / or the second overflow water washing operation is 6 hours.

[0064] In one of the embodiments, the circuit board A after the whole hole is placed in a micro-etching cylinder for micro-etching operation, and then the circuit board A after micro-etching is placed in a pre-preg cylinder for pre-preg operation. In this embodiment, the circuit board A after micro-etching / roughening will be placed in the pre-preg cylinder. On the one hand, during the production process of the circuit board A, it will pass through different reaction cylinders, such as oil removal cylinder, micro-etching cylinder, activation cylinder, etc. Different reagents are used in different steps. After different operations, there are residual reagents on the surface, through holes, blind holes, etc. of the circuit board A. Therefore, in order to facilitate the subsequent activation operation and copper deposition operation, it is necessary to put the circuit board A into the pre-preg cylinder to effectively remove the residual reagents and prevent cross contamination caused by the action of multiple reagents. At the same time, it also provides a suitable environment for the subsequent activation step, which is convenient for the activator to enter the blind hole so that the blind hole wall is activated.

[0065] In one embodiment, the micro-etched circuit board A is placed in an activation cylinder for activation operation, and then the process further includes: accelerating the circuit board A. In this embodiment, when the hole walls of the through holes and blind holes of the circuit board A are activated, the hole walls have activated colloidal palladium, and the colloidal palladium becomes the catalytic center of the subsequent copper deposition reaction. At this time, in addition to the attached colloidal palladium, there are also free palladium groups and palladium ions in the activation cylinder. At this time, an accelerator is added. On the one hand, the accelerator accelerates the exposure of the palladium layer on the hole wall to facilitate the subsequent copper deposition step, thereby increasing the copper deposition rate. On the other hand, the loose or free palladium groups and palladium ions are removed, and the palladium groups and palladium ions are sunk, thereby ensuring that the palladium layer on the hole wall can be used as a catalytic medium, which is beneficial to the copper deposition step of the circuit board A.

[0066] In one embodiment, in the ultrasonic process used in the activation tank, the output power of the ultrasonic wave is 2.5kW-3kW.

[0067] It can be understood that the cylinder used in the production of circuit boards is a large-capacity cylinder. To achieve the effects of ultrasonic technology, such as enhanced oil removal, micro-etching, activation, etc., a larger output power is required to ensure better above-mentioned effects. When the output power of the ultrasonic wave reaches 2.5kW-3kW, the corresponding reagents can be pushed into the blind holes in different steps of the circuit board, so that the reagents can effectively remove certain substances in the blind holes, reducing the difficulty of removing substances in the blind holes. Furthermore, the output power of the ultrasonic wave is 3kW and the output frequency is 28kHz.

[0068] For circuit boards with blind holes, in order to meet the quality requirements, ultrasonic waves are added in multiple steps to assist the reagents in different steps to enter the blind holes and perform corresponding full reactions. However, when the output power of the ultrasonic waves is too large, it may also cause different degrees of damage to the circuit board. Specifically, when the activation operation is performed, the activator is pushed into the blind hole by ultrasonic waves to activate the colloidal palladium and turn it into activated palladium, so that the positively charged blind hole wall adsorbs the negatively charged activated palladium layer, thereby making the activated palladium layer have catalytic ability. If the ultrasonic output power in the activation cylinder is too large, the colloidal palladium in the through hole and the blind hole will be over-activated, and the colloidal palladium will be separated from the hole wall under the action of super strong ultrasonic waves and become free palladium ions, thereby weakening the catalytic ability of the activated palladium layer, resulting in a lower efficiency of the circuit board A during copper deposition, and even a decrease in the quality of copper deposition, resulting in a lower overall qualified rate of the circuit board after the finished product, which is not conducive to passing the thermal current test after the board is formed. In order to prevent the activated palladium attached to the hole wall from being washed away, when executing step S105, some or all of the following steps are included:

[0069] Obtain the state of ultrasonic output signal in the activation cylinder;

[0070] According to the output signal status, the ultrasonic output power value is displayed on the detection panel;

[0071] Detect whether the ultrasonic output power value exceeds the maximum allowable output power value;

[0072] If the ultrasonic output power value exceeds the maximum allowable output power value, a power reduction signal and an activator increase signal are simultaneously sent to the activation cylinder.

[0073] In the present embodiment, the maximum allowable output power value is 3kW. It is understandable that in order to ensure the normal activation of colloidal palladium, the output power of the general ultrasonic wave is not higher than 3kW, and the preferred output power is 3kW, so as to better turn the colloidal palladium into the activated palladium of negative charge, so that the activated palladium is adsorbed on the hole wall of the positive charge, and then the activated palladium has the ability of catalysis, and under the condition that the ultrasonic wave output power does not exceed the maximum allowable output power value, the activation operation is carried out normally, which is also conducive to the subsequent copper deposition operation. If the ultrasonic wave output power value exceeds the maximum allowable output power value, a power reduction signal and an activator signal are simultaneously sent to the activation cylinder to inform the operator to lower the output power of the ultrasonic wave, so as to prevent the output power from being too high and causing the activated palladium layer to fall off from the hole wall and lose the catalytic ability, when the ultrasonic wave output power is reduced, the effect of the activator being pushed into the blind hole is not obvious, and therefore, to ensure the activation effect and the activated palladium layer does not fall off, it is necessary to increase the supply of the activator to ensure that any position in the blind hole wall can normally adsorb the colloidal palladium to form the activated palladium layer.

[0074] The blind hole wall is made positively charged by the hole-filling operation. However, if the circuit board A is over-washed during the continuous water washing step, it will cause different degrees of damage to the circuit board A, such as corrosion of the copper layer of the hole wall matrix and damage to the copper layer. In addition, there is residual degreasing agent on the circuit board, which still needs to be continuously washed to ensure that the degreasing agent can be completely removed to prevent the subsequent steps from being interfered by the degreasing agent. When the water flow rate of the clean water is insufficient, the degreasing agent is not fully removed, which requires increasing the continuous water washing time. However, if the continuous water washing time is too long, it will also cause different degrees of damage to the circuit board A mentioned above. The above situations make it more difficult to fill the blind hole wall in the subsequent hole-filling operation. Therefore, when executing step S103, some or all of the following steps are included:

[0075] The continuous water washing section sequence time and the water flow information of the cleaning water of the circuit board A are obtained respectively;

[0076] Check whether the continuous water washing time is less than the preset degreasing water washing time;

[0077] If the continuous water washing section time is less than the preset degreasing water washing time, check whether the water flow of the clean water is less than the preset water flow, otherwise, send a signal to execute the whole hole to the degreasing water washing cylinder;

[0078] If the detected water flow rate of the cleaning water is less than the preset water flow rate, a water flow increase signal is sent to the degreasing water washing tank, and the preset degreasing water washing time is shortened.

[0079] In this embodiment, the preset degreasing water washing time is the maximum critical time of the continuous water washing segment time. When the circuit board A completes the degreasing operation, the continuous water washing operation is performed, and the continuous water washing segment time is recorded at the same time. At this time, the step of continuously removing the degreasing agent is being performed. When the water flow rate of the cleaning water is normal, the time is continuously recorded until the continuous water washing segment time is greater than or equal to the preset degreasing water washing time, and a hole-straightening signal is sent to the degreasing water washing cylinder to inform the operator to perform the hole-straightening operation on the circuit board A to prevent the circuit board A from being excessively and continuously washed and causing unnecessary damage. Further, during the continuous water washing operation, when the water flow rate of the cleaning water is less than the preset water flow rate, the degreasing agent will not be fully removed, which prolongs the continuous water washing time. Therefore, it is necessary to adjust the water flow state of the cleaning water to meet the intensity requirements for removing the degreasing agent, and at the same time shorten the preset degreasing water washing time to reduce unnecessary damage caused by excessive continuous cleaning, so that the continuous water washing segment time reaches the shortened preset degreasing water washing time, and then the hole-straightening operation can be performed.

[0080] In another embodiment, if the detected water flow rate of the cleaning water is greater than the preset water flow rate, the water flow rate state of the cleaning water is reduced while maintaining the preset degreasing water washing time unchanged to ensure the effect of completely removing the degreasing agent.

[0081] Furthermore, the continuous water washing sequence time includes the hot water washing sequence time, the first overflow water washing sequence time and the second overflow water washing sequence time, and the preset degreasing water washing time includes the upper limit of the hot water washing time, the upper limit of the first overflow water washing and the upper limit of the second overflow water washing. The water flow rate of the cleaning water includes but is not limited to the water flow rate of the cleaning hot water, the water flow rate of the first overflow water and the water flow rate of the second overflow water.

[0082] The present disclosure also provides a circuit board, which is made by the method of vertical copper-plating hole metallization of any of the above-mentioned embodiments. It can be understood that the circuit board adopts the vertical copper plating method, which is more efficient for the production of circuit boards compared to horizontal copper plating. In the case of adding an ultrasonic process, ultrasonic waves are added to the multiple steps of vertical copper plating to facilitate the removal of multiple agents that interfere with the reaction, such as residual swelling agents, degumming agents, degreasing agents, and residual oil stains, etc., to ensure that after the circuit board passes through copper plating, the base copper layer and the copper plating layer can be combined, which is conducive to passing the subsequent thermal current test. Among them, the residual degreasing agent can be effectively removed by continuous water washing operation to prevent the degreasing agent from interfering with the copper plating reaction of the circuit board during the copper plating step.

[0083] In one of the embodiments, a thermal current test is performed on the manufactured circuit board. It is understandable that in order to ensure that the electronic products using the circuit board can be powered on and communicate for a long time and to ensure the user experience, the present solution also requires a thermal current test on the circuit board, specifically a thermal current test on the blind holes of the circuit board, to simulate the effect of long-term communication of the equipment, and then determine whether there is a situation where the blind holes are poorly powered. When the circuit board is manufactured using the above-mentioned vertical copper plated hole metallization method, it can be ensured that the base copper layer and the copper plated layer of the blind hole are normally combined during the copper plated step of the circuit board, further ensuring that the blind holes of the circuit board have good conductivity after being manufactured, and there will be no poor power supply, which is suitable for use in equipment for long-term communication.

[0084] Compared with the prior art, the present invention has at least the following advantages:

[0085] The vertical copper-plated hole metallization method of the present scheme adopts vertical copper plating to ensure the production efficiency of the circuit board, and adds an ultrasonic process to the vertical copper plating process. In addition to removing the residual permanganate, manganate, etc. in the blind hole in the neutralization step, the degreasing agent in the blind hole can be removed by auxiliary water washing agent in the water washing operation after degreasing. When the residual substances in the blind hole are completely removed, it is convenient for the subsequent copper plating operation of the circuit board A to make the circuit board, and the bottom of the blind hole has a good bonding ability with the copper plating layer, so that in the subsequent thermal current test, all circuit boards can pass the thermal current test, ensuring the user's subsequent usage experience.

[0086] The above-mentioned embodiments only express several implementation methods of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the disclosed patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present disclosure, and these all belong to the protection scope of the present disclosure. Therefore, the protection scope of the disclosed patent shall be subject to the attached claims.

Claims

1. A method for metallizing vertical copper-plated holes of a circuit board, wherein the circuit board has a blind hole, and the aperture ratio of the blind hole is 8.0 to 10.0, characterized in that: The method for vertical copper-plated hole metallization comprises the following steps: Obtaining a circuit board A after undergoing swelling and degumming operations in a bulking cylinder and a degumming cylinder respectively; The circuit board A is placed in a neutralization tank for neutralization operation, and the neutralization tank adopts an ultrasonic process to assist the neutralizer to flow into the blind hole, thereby removing the swelling agent and the debonding agent in the blind hole; The neutralized circuit board A is placed in a degreasing water washing tank for degreasing, continuous water washing and hole-smoothing operations in sequence. The degreasing water washing tank adopts the ultrasonic process to assist the degreasing agent to flow into the blind hole during the degreasing operation and assist the clean water to remove the degreasing agent during the continuous water washing operation; The circuit board A after hole trimming is placed in a micro-etching tank for micro-etching operation, and the micro-etching tank adopts the ultrasonic process to assist the micro-etching solution to roughen the copper hole wall of the blind hole; The micro-etched circuit board A is placed in an activation tank for activation operation, and the activation tank adopts the ultrasonic process to assist the activator in activating the copper hole wall of the blind hole; The activated circuit board A is placed in a copper deposition tank to perform a copper deposition step to form a circuit board.

2. The method for vertical copper via metallization according to claim 1, characterized in that: The swelling operation in the bulking cylinder adopts an ultrasonic process to assist the swelling agent to flow into the blind hole during the swelling operation, thereby expanding the drilling residue in the blind hole.

3. The method for vertical copper via metallization according to claim 1, characterized in that: The circuit board A is placed in a neutralization cylinder for neutralization, and then the process further comprises: The neutralized circuit board A is placed in a water washing tank for impurity removal and water washing operation; the impurity removal and water washing operation includes: Performing a first impurity removal water washing operation on the circuit board A to preliminarily remove the neutralizer remaining on the surface of the circuit board A and in the through-holes; The circuit board A is subjected to a second impurity removal and water washing operation, wherein the second impurity removal and water washing operation adopts the ultrasonic process to assist the water washing agent to flow into the blind hole, thereby removing the neutralizing agent in the blind hole.

4. The method for vertical copper via metallization according to claim 1, characterized in that: The neutralized circuit board A is placed in a degreasing water washing tank for degreasing, continuous water washing and hole trimming operations, wherein the continuous water washing operation includes: The degreased circuit board A is washed with hot water to remove the degreaser; After the hot water washing operation, the circuit board A is subjected to overflow water washing operation to further continuously remove the residual degreasing agent.

5. The method for vertical copper via metallization according to claim 4, characterized in that: The water temperature of the hot water washing operation is X degrees, wherein 40≤X≤45.

6. The method for vertical copper via metallization according to claim 4, characterized in that: The method of performing overflow water washing on the circuit board A after the hot water washing operation comprises: Performing a first overflow water washing operation on the circuit board A, wherein the first overflow water washing adopts the ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining on the surface of the circuit board A and in the through-holes; The circuit board A is subjected to a second overflow water washing operation, wherein the second overflow water washing adopts the ultrasonic process to assist the overflow water in continuously removing the degreasing agent remaining in the blind hole.

7. The method for vertical copper via metallization according to claim 6, characterized in that: The washing time of the first overflow water washing operation and / or the second overflow water washing operation is Y hours; wherein Y≥6.

8. The method for vertical copper via metallization according to claim 1, characterized in that: The circuit board A after hole trimming is placed in a micro-etching tank for micro-etching operation, and then further comprising: The micro-etched circuit board A is placed in a pre-preg tank for pre-preg operation.

9. The method for vertical copper via metallization according to claim 1, characterized in that: In the ultrasonic process adopted in the activation cylinder, the output power of the ultrasonic wave is 2.5kW-3kW.

10. A circuit board, characterized in that: The vertical copper-plated hole is manufactured by the metallization method described in any one of claims 1 to 9.

Images