阅读说明：本技术 一种稳定覆铜板电镀铜涨缩的方法 (Method for stabilizing copper-clad plate electroplated copper expansion and shrinkage ) 是由 罗学涛 刘文鑫 黄柳青 陈志城 吕凤洋 赵士忠 于 2021-06-16 设计创作，主要内容包括：本发明公开了一种稳定FPC基材—覆铜板在电镀铜时涨缩不定的方法,该方法在电镀铜的前处理中采用配有恒温箱的振动台对经过钻孔、等离子和黑孔的铜箔进行干燥振动处理,在干燥铜箔的同时释放残余内应力,之后用适当温度的热水进行水洗和预浸,以保证在正式镀铜之前的涨缩值为正。正式镀铜时合理设置电镀缸内溶液的温度、阴极的电流密度上限值,并通过安装激振器与连接杆于飞靶槽上,通过传递作用使铜箔在电镀杠内持续不断的发生振动,加速溶液的对流,有效的使阴极上的铜细晶化,从而稳定涨缩值,便于技术人员计算并给出相应涨缩补偿值。(The invention discloses a method for stabilizing the indeterminate expansion and contraction of an FPC (flexible printed circuit) substrate-copper clad laminate during copper electroplating, which comprises the steps of carrying out drying vibration treatment on a copper foil subjected to drilling, plasma and black holes by adopting a vibrating table provided with a constant temperature box in the pretreatment of copper electroplating, releasing residual internal stress while drying the copper foil, and then carrying out water washing and presoaking by using hot water at a proper temperature to ensure that the expansion and contraction value is positive before formal copper plating. The upper limit values of the temperature of the solution in the electroplating cylinder and the current density of the cathode are reasonably set during formal copper plating, and the copper foil continuously vibrates in the electroplating bar through the transmission action by installing a vibration exciter and a connecting rod on the flying target groove, so that the convection of the solution is accelerated, the copper on the cathode is effectively refined, the expansion and contraction value is stabilized, and technicians can calculate and give corresponding expansion and contraction compensation values conveniently.)

1. A method for stabilizing copper-clad plate electroplating copper expansion and shrinkage is characterized by comprising the following steps:

1) before electroplating copper, drying and vibrating the copper-clad plate at 40-50 ℃;

2) setting temperature gradient in the processes of water washing, micro etching and acid leaching;

3) copper plating is carried out on the copper-clad plate in a vibration state, and the density of cathode current is increased to 3.6-4.0 ASD; the temperature of the plating solution was 35. + -. 2 ℃.

2. The method for stabilizing copper expansion and shrinkage in copper-clad plate electroplating according to claim 1, wherein the vibration frequency of the copper-clad plate in the step 1) is 20-30 Hz.

3. The method for stabilizing copper-clad plate copper electroplating harmomegathus according to claim 2, wherein the vibration time of the copper-clad plate in the step 1) is 5-10min, and the amplitude is 3-5 mm.

4. The method for stabilizing copper-clad plate copper electroplating harmomegathus according to claim 1, wherein the temperature gradient of the step 2) is 2-5 ℃ after repeated water washing and gradually reduced etching, and the temperature gradually rises to 35 +/-2 ℃ during water washing and acid leaching.

5. The method for stabilizing copper-clad plate electro-coppering harmomegathus according to claim 4, characterized in that the specific steps of step 2) are as follows:

firstly, the copper-clad plate which is subjected to drying vibration treatment is washed by hot water at 40 +/-2 ℃, the temperature is continuously reduced, the copper-clad plate is repeatedly washed to 30 ℃, then hydrogen peroxide at 28 ℃ and a sulfuric acid microetching agent are added for microetching, and after the microetching is finished, the copper-clad plate is repeatedly washed by water at 30 ℃ and then placed in sulfuric acid at 35 +/-2 ℃ for acid leaching.

6. The method for stabilizing copper expansion and shrinkage in copper-clad plate electroplating according to claim 1, wherein the vibration frequency of the copper-clad plate in the step 3) is 30-40 Hz.

7. The method for stabilizing copper-clad plate electro-coppering harmomegathus according to claim 1 or 6, characterized in that the vibration exciter is rigidly connected with the flying target groove through the connecting rod to drive the copper-clad plate clamped on the flying target to vibrate.

Technical Field

The invention relates to the field of electroplating, in particular to a method for stabilizing copper plating expansion and shrinkage of a copper-clad plate.

Background

The FPC is a flexible circuit board, also called a flexible printed circuit board, is an important support for the rapid development of modern electronic products, has the advantages of small volume, light weight, good toughness, rapid heat dissipation and the like, forms a core component of the electronic products, and determines the functions and the performances of the electronic products. At present, the manufacturing process of the FPC is rapidly developed, and the industry puts higher requirements on the FPC, that is, the FPC is required to have better dimensional stability and more accurate dimensional design, and the requirements are finally put on a substrate of the FPC, namely a copper-clad plate.

In the production process, how to control the copper-clad plate to expand and contract becomes a breakthrough for manufacturing excellent FPC. In the prior art, the harmomegathus generated in the copper plating link is not stable, and after copper plating, the harmomegathus value is positive or negative, and the floating is obvious, so that technicians cannot provide stable harmomegathus compensation values, and the alignment of a drill hole and a memory, the alignment of characters, the dimensional tolerance of a finished product and the like are influenced. There are many factors causing the substrate to expand and contract, and the expansion and contraction caused by the release of residual internal stress left by the substrate during drilling or cutting and the dimensional change caused by the moisture absorption of the substrate are most significant.

Disclosure of Invention

In order to solve the above mentioned problems, the present invention provides a method for stabilizing the copper plating swell-shrink value of FPC, so as to solve the problem that the swell-shrink value of FPC copper foil base material after copper plating is positive or negative and extremely unstable.

In order to achieve the purpose, the invention is realized by the following technical scheme:

a method for stabilizing copper-clad plate electroplating copper expansion and shrinkage comprises the following steps:

1) before electroplating copper, drying and vibrating the copper-clad plate at 40-50 ℃ to release residual internal stress caused by the previous working procedure.

2) The temperature gradient is set in the processes of water washing, micro etching and acid leaching, so that the shrinkage caused by overlarge temperature difference is avoided.

3) Copper plating is carried out on the copper-clad plate in a vibration state, and the density of cathode current is increased to 3.6-4.0 ASD; the temperature of the plating solution is 35 + -2 deg.C to make the plating layer fine-grained, thereby stabilizing the expansion and contraction. Wherein, if the temperature of the electroplating solution in the electroplating cylinder exceeds 40 ℃, the plating layer is rough and coarse in crystallization, and the temperature is lower than 30 ℃, the temperature gradient is large, the copper foil is easy to shrink, so the temperature of the solution is 35 +/-2 ℃; the copper-clad plate is driven to vibrate, so that bubbles, impurities and the like in holes can be discharged in time, the convection of the solution can be accelerated, metal ions consumed nearby the cathode solution can be supplemented in time, the cathode current density is improved, and a fine and compact coating can be obtained.

Further, the vibration frequency of the copper clad plate in the step 1) is 20-30 Hz.

Further, the vibration time of the copper-clad plate in the step 1) is 5-10min, and the amplitude is 3-5 mm.

Further, in the step 2), the temperature is gradually reduced by repeatedly washing with water and gradually increasing the etching temperature to 35 +/-2 ℃ during washing with water and acid leaching, wherein the temperature gradient is 2-5 ℃.

Further, the vibration frequency of the copper-clad plate in the step 3) is 30-40 Hz.

Further, the vibration exciter is rigidly connected with the flying target groove through the connecting rod to drive the copper-clad plate clamped on the flying target to vibrate.

The whole step for controlling the expansion and shrinkage of the copper plating process is as follows:

s1: placing the copper-clad plate subjected to the necessary procedures of drilling, plasma, black hole and the like into a vibration platform provided with a constant temperature box, setting the temperature of the constant temperature box to be 45 +/-5 ℃, setting the vibration platform to horizontally vibrate at the vibration frequency of 20-30Hz and the vibration amplitude of 3-5mm, and performing drying vibration treatment for 5-10 min.

S2: firstly, washing the copper-clad plate which is subjected to drying vibration treatment by using hot water at 40 +/-2 ℃, repeatedly washing to 30 ℃ while continuously reducing the temperature, then adding hydrogen peroxide at 28 ℃ and a sulfuric acid microetching agent for microetching, and after the microetching is finished, repeatedly washing by using water at 30 ℃ and then placing in sulfuric acid at 35 +/-2 ℃ for acid leaching;

s3: during formal electroplating, clamping the copper-clad plate by using a flying target, vertically placing the copper-clad plate in a copper sulfate solution, setting the moving speed of the flying target to be 1.8-2.0m/min and the current density to be 3.6-4.0ASD, and simultaneously starting a vibration exciter with the frequency of 30-40Hz to drive the copper-clad plate to vibrate in a reciprocating manner in the solution;

s4: after the electroplating is finished, washing with water of 35 ℃ for multiple times, blanking, carrying out post-treatment and moving to the next procedure.

The vibrating table with the thermostat is of a composite structure, the vibrating table is placed in the thermostat, the area of the vibrating table is 400mm multiplied by 400mm, the vibrating direction is horizontal, the vibrating frequency is 20-30Hz, the vibrating time is 5-10min, and the amplitude is 3-5 mm. The size of the inner box of the constant temperature box is 500mm multiplied by 500mm, and the set temperature is 45 +/-5 ℃.

The vibration exciter is rigidly connected with the flying target groove through the inherent connecting rod, the flying target groove and the flying target are also rigidly connected, the copper plate covered on the flying target can be clamped to vibrate through the transmission action, the frequency of the vibration exciter is set to be 30-40Hz, and the exciting force is set to be 1000N.

The temperature of the solution in the plating cylinder is raised to 35 +/-2 ℃, and the current density is increased to 3.6-4.0 ASD.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a method for stabilizing copper-clad plate electroplated copper harmomegathus, which comprises the steps of carrying out drying vibration on a copper-clad plate in the electroplating pretreatment, setting a temperature gradient washing and etching process, enabling the copper-clad plate to vibrate by a vibration exciter during electroplating, and simultaneously raising the solution temperature and the cathode current density to successfully realize fine grain copper-clad and stable harmomegathus.

In the process, after the copper-clad plate is drilled, the temperature is controlled to be 45 +/-5 ℃, vibration treatment is carried out under the natural frequency, residual internal stress is released in advance, the expansion and contraction value of the substrate in the direction of X, Y is enabled to be positive, meanwhile, the temperature gradient is set, the temperature of an acid dipping tank and the temperature of water washing are properly increased, the temperature of solution in an electroplating cylinder is increased, and the substrate is prevented from being contracted due to overlarge temperature difference. In addition, the crystal grains of the coating are refined by adding vibration on the target flying groove and improving the current density of the cathode, and the residual internal stress is stored to the grain boundary, so that the expansion and contraction can be effectively stabilized. In the drilling and copper plating processes, the expansion and contraction value is kept positive by the novel process method, so that stability is provided for compensation values generated by processes such as subsequent calculation and pressing, and the yield is further improved.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, and it is obvious that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1

S1: the copper-clad plate after drilling, plasma and black holes is placed on a vibration platform in a constant temperature box, the vibration frequency is set to be 20Hz, the vibration direction is horizontal vibration, the vibration time is 10min, and the temperature of the constant temperature box is set to be 40 ℃.

S2: taking out the copper-clad plate after drying and vibration, washing the copper-clad plate by water at 40 ℃, 35 ℃ and 30 ℃ respectively, soaking the copper-clad plate in hydrogen peroxide solution at 28 ℃ and 4% sulfuric acid solution for microetching, after the microetching is finished, washing the copper-clad plate by water at 30 ℃ and 35 ℃ respectively once, and then soaking the copper-clad plate in 10% sulfuric acid solution at 35 +/-2 ℃.

S3: clamping the copper-clad plate by using a flying target, immersing the copper-clad plate into an electroplating cylinder, starting a vibration exciter, setting the output frequency to be 30Hz, the moving speed of the flying target to be 1.8m/min, the cathode current density to be 4.0ASD, and raising the temperature of the solution in the electroplating cylinder to 35 +/-2 ℃.

S4: taking the electroplated copper-clad plate out of the flying target, washing with water at 30 ℃ twice, removing the observation surface, and calculating the expansion and contraction value by using a corresponding instrument, wherein the specific conditions are as follows:

whether the surface is flat or not: flat, without bumps or pits

Copper plating condition: the through holes and the blind holes are plated with copper well

Expansion and contraction in the X direction: 1.0005 (5% increase in size compared with original one)⁰/₀₀₀)

Expansion and contraction in the Y direction: 1.0014

Grain size grade: 5

Example 2

This example controls the expansion and contraction according to the method of example 1, except that the vibration table equipped with the oven is not used, as follows:

because residual internal stress left by the steps of drying, vibrating, drilling and the like is avoided, the copper-clad plate can not ensure that the expansion and contraction value is positive during the copper-plating pretreatment. In some of the copper-plated plates tested, the expansion and contraction values were negative:

whether the surface is flat or not: flat, without bumps or pits

Copper plating condition: the through holes and the blind holes are plated with copper well

Expansion and contraction in the X direction: 0.9987 (13 times smaller than original size)⁰/₀₀₀)

Expansion and contraction in the Y direction: 0.9981

Grain size grade: 5

Example 3

The embodiment controls the harmomegathus according to the method of embodiment 1, except that the specific conditions for controlling the water washing without setting the temperature gradient are as follows:

the copper clad laminate is not buffered by temperature gradient, has larger temperature difference, and can not ensure that the expansion and contraction value is positive during the copper plating pretreatment. In the test copper-clad plate, the condition that the expansion and contraction value is negative exists:

whether the surface is flat or not: flat, without bumps or pits

Copper plating condition: the through holes and the blind holes are plated with copper well

Expansion and contraction in the X direction: 0.9997 (reduced in size by 3 compared with the original size)⁰/₀₀₀)

Expansion and contraction in the Y direction: 0.9991

Grain size grade: 5

Example 4

The embodiment controls the expansion and shrinkage according to the method of the embodiment 1, except that the copper-clad plate is not subjected to vibration treatment by using a vibration exciter, and the specific conditions are as follows:

no vibration exciter is used, but the increase of the cathode current density can cause the generation of dendrite, and in the tested copper-clad plate, the copper surface is not flat:

whether the surface is flat or not: some slight bulge, the coating is in the shape of sponge

Copper plating condition: through hole and blind hole are plated with copper generally and have plating leakage

Expansion and contraction in the X direction: 1.0004 (increased by 4 from original size)⁰/₀₀₀)

Expansion and contraction in the Y direction: 1.0007

Grain size grade: 5

Example 5

This example controls the expansion and contraction as in example 1, except that the temperature and current density settings in the conventional plating cylinder were maintained without changing the temperature and current density settings, wherein the temperature was 24 ± 3 ℃ and the current density was 3.0ASD, as follows:

because the solution convection is accelerated due to vibration, metal cations can be supplemented at the cathode, the upper limit value of the current density is reduced, the concentration polarization effect of the cathode is reduced, and the crystal grains can be enabled to be abnormally large:

whether the surface is flat or not: flat, without bumps or pits

Copper plating condition: the through holes and the blind holes are plated with copper well

Expansion and contraction in the X direction: 1.0002 (2 dimensional expansion compared with original size)⁰/₀₀₀)

Expansion and contraction in the Y direction: 1.0004

Grain size grade: 3

Comparing the examples 1 to 5, it can be seen that compared with the examples 2 to 5, the electroplated copper-clad plate prepared by applying the embodiment 1 of the technical scheme of the invention has better expansion and contraction rate and higher grain size grade.

The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.