CN112966468B - Flexible PCB etching process on-line regulation and control method based on wet chemical etching simulation - Google Patents

Abstract

The invention discloses a flexible PCB etching process on-line regulation and control method based on wet chemical etching simulation. The process parameter data which can appear on various production lines is taken as simulation boundary conditions, the process parameter data which can be arranged and combined are taken as simulation parameter data to be input into a simulation system for simulation calculation, and a database in which the simulation parameter data and simulation results are in one-to-one correspondence is obtained. And then matching the production line data acquired in real time with simulation parameter data in a database, calling a corresponding simulation result, stopping production and regulating and controlling process data if the simulation result exceeds the product index, thereby monitoring the process problems of the earlier production line and completing the online adjustment of the process parameters.

Description

An online control method of flexible PCB board etching process based on wet chemical etching simulation

technical field

The invention belongs to the field of optoelectronics and relates to a PCB board production process technology, in particular to an online control method for a flexible PCB board etching process based on wet chemical etching simulation.

Background technique

A flexible PCB board is a printed circuit board made of a flexible substrate, which has the characteristics of high reliability and excellent flexibility. At present, flexible PCB boards have been widely used in terminal consumption fields such as smartphones, automobiles, and wearable devices. With the rapid development of high integration and high precision of internal components such as personal computers and smartphones in recent years, as an electrical component Flexible PCB boards for device connectors will also accelerate the pace of high density. The production process of flexible PCB boards is generally: punching → coating → exposure → development → etching → film stripping → tinning → automatic optical inspection → ink printing → slitting → circuit inspection → final cleaning and packaging. In the production process, the etching process is one of the important processes in the production process of flexible PCB boards. If there is a deviation in the process parameters during the etching process, the quality of the finished product in the whole batch will be far from the expected. Parameter monitoring is very important.

At present, in the production process of flexible PCB boards, the quality inspection method of line etching is AOI (Automated Optical Inspection) quality inspection method, that is, after the processes of etching, film stripping, and tinization, the line quality is inspected. However, if a certain etching process parameter is wrong, and then the AOI system detects the circuit quality problem, the circuit boards produced in this batch will be unusable, which will lead to the scrapping of semi-finished products and the increase of processing costs, which will undoubtedly cause damage to the enterprise. The additional losses greatly reduce the profit margin of the business. The current AOI inspection method is to perform quality inspection after the etching process is completed, which has a certain hysteresis. This method is effective for improving product quality, but it is difficult to monitor the process problems of earlier production lines. The invention establishes a multi-physical field simulation model of the wet chemical etching process of the flexible PCB board, and uses the process parameter data that may appear in various production lines as the simulation boundary conditions, and uses the process parameter data that may be arranged and combined as the simulation parameter data. Input into the simulation system and carry out simulation calculation to obtain a database with one-to-one correspondence between data conditions and simulation results. Then collect and transmit the process parameter data online in real time, match the production line data collected in real time with the simulation parameter data in the database, retrieve the corresponding simulation results, and compare them with the product indicators, so as to detect the early changes in the etching process parameter data. monitor.

SUMMARY OF THE INVENTION

The purpose of the present invention is to solve the problem of the hysteresis of the current AOI system detection system, and propose a method for online control of the etching process of the flexible PCB board based on the wet chemical etching simulation. The method is based on the wet chemical etching simulation, combined with the flexible PCB The geometric modeling of the plate etching process has successfully achieved the simulation of the wet chemical etching process, and has carried out targeted example parameter research and verification.

In order to solve the above-mentioned technical problems, the technical scheme adopted in the present invention is as follows:

An on-line control method for a flexible PCB board etching process based on wet chemical etching simulation, characterized in that it comprises the following steps:

Step S1, build a physical model, set the geometric parameters of the flexible PCB board according to the actual situation through the simulation software, build a two-dimensional geometric model of the etching process simulation of the flexible PCB board, select the corresponding physical field module according to the actual production process, and set the simulation process parameters;

Step S2, setting simulation conditions, setting boundary conditions according to the actual production process, and completing the establishment of the simulation model;

Step S3, simulation calculation and establishment of a result database, combining and arranging the boundary conditions and process parameters that may appear on the actual production process line, obtaining simulation process parameter data, inputting the simulation process parameter data into the simulation model for simulation calculation, and establishing a simulation process A database of one-to-one correspondence between parameter data and simulation results;

Step S4, acquiring and inputting process data of the production line, collecting process parameter data of the production line in real time, the process parameter data including spray pressure, etching solution concentration and line running speed;

Step S5, real-time monitoring of the production line process data, match the production line process data of the production line collected in step S4 with the simulation process parameter data in the database, obtain corresponding simulation results, and then match the simulation results with the product indicators on the production line. Compare and process accordingly.

Further, the geometric parameters of the flexible PCB board include the thickness of the etching substrate, the thickness of the mask and the width of the circuit.

Further, the established 2D geometric model includes copper layer, mask and flow field.

Further, the physics module includes a transport of dilute species module, a fluid flow module and a deformation geometry module.

Further, in step S1, the simulation process parameters include etching liquid incident velocity, etching liquid concentration and etching time, the etching liquid incident velocity is converted from spray pressure, and the etching time is calculated from the running speed of the line body.

Further, the simulation results include etching depth and undercut amount.

Further, in step S5, when the simulation result differs greatly from the actual product index, the process parameters of the production line are adjusted until the simulation result on the production line meets the product index.

The technical scheme of the present invention has the following advantages:

In view of the hysteresis of the existing etching detection method, the present invention uses multi-physics simulation software to simulate the wet chemical etching process of the flexible PCB board, and quickly completes the simulation calculation by using the process parameter data collected in real time during the production process. The simulation results predict the etching process, avoid batch problems in product quality due to changes in etching process parameters, save production consumables such as flexible PCB substrates, etching solutions, and reduce production costs.

Description of drawings

FIG. 1 is a schematic diagram of an online control method for an etching process of a flexible PCB board based on wet chemical etching simulation according to the present invention.

FIG. 2 is a specific flow chart of the online control method of the etching process of the flexible PCB board based on the wet chemical etching simulation of the present invention.

FIG. 3 is a logical frame diagram of an on-line control method for an etching process of a flexible PCB board based on wet chemical etching simulation according to the present invention.

FIG. 4 is a diagram of a two-dimensional geometric model for establishing an etching process of a flexible PCB board in an embodiment of the present invention.

5 shows that the linear velocity is 3.5m/min (etching time is 137s), the incident velocity is 4m/s, the etching solution concentration is 0.45mol/L and the linear velocity is 4m/min (etching time is 120s) in the embodiment of the present invention ), the etching simulation comparison diagram when the incident velocity is 4m/s and the etching solution concentration is 0.45mol/L.

Reference numerals: 1-etching solution inlet; 2-etching solution outlet; 3-etched surface; 4-photoresist; 5-copper film, 6-first region, 7-second region.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention fall within the protection scope of the present invention. In the present invention, the copper film is used as the etching substrate, the photoresist is used as the mask, and the CuCl ₂ solution is used as the etching solution as an example to illustrate.

As shown in Figure 1 and Figure 2, it is an online control method of flexible PCB board etching process based on wet chemical etching simulation, which mainly includes the following steps:

S1. Build a physical model. According to the production process, construct the corresponding physical model, set the geometric parameters of the flexible PCB board according to the actual situation through the simulation software, build a two-dimensional geometric model of the etching process simulation of the flexible PCB board, and select the corresponding physical field module according to the actual production process. , set the process parameter type.

S2. Set simulation conditions. The parameter conditions are set according to the actual production process to complete the establishment of the simulation model, and the parameter conditions include boundary conditions and etching boundary flux.

S3, simulation calculation and establishment of the result database. The simulation is carried out with the possible permutation and combination process parameter data of various production lines as the boundary conditions of the simulation, and the corresponding simulations are obtained under the conditions of various spray pressures, etching liquid concentrations and line operating speeds that may be encountered in actual production. As a result, such as the product index results such as the etching depth H and the side etching amount W, a database of one-to-one correspondence between the simulation process parameter data and the simulation results is established.

S4. Production line process data acquisition. Real-time collection of production line process parameter data. _The process data of the production line is collected in real time, such as the spray pressure at a certain time, the concentration of the etching solution, and the production process parameters such as the running speed of the line body. The content of copper ions in the solution is analyzed to measure, and the running speed of the wire is measured in real time by a rotational speed measuring instrument. the line speed. Self-fetching through MES (Manufacturing Execution System), then entering these data into simulation database.

S5. Real-time monitoring of production line process data. The data is read by the MES, and the real-time process parameter data of the production line is matched with the simulation process parameter data in the database, and the simulation results corresponding to the simulation process parameter data are retrieved, such as the product index results such as the etching depth H and the side etching amount W. . Then compare the results with the product indicators. If the product indicators are exceeded, the system will issue a warning, immediately suspend production, and adjust the online process parameters in real time, such as changing the concentration of the etching solution. If the calculation result is within expectations, it means that the data is within the normal range and production can continue.

Specifically, in the step S1, the simulation software used is COMSOL Multiphysics 5.5. According to the actual production process, the geometric parameters of the flexible PCB board are obtained from the actual production line, and the thickness h of the copper layer, the thickness of the mask t, and the width of the line are set. 1. Complete the construction of a two-dimensional geometric model for wet chemical etching simulation, and the obtained two-dimensional geometric model is shown in FIG. 4. The two-dimensional geometric model includes a copper film 5 as an etching substrate and a photoresist 4 as a mask. and the flow field domain, the flow field domain is to select the area between the photoresist layers as the etching target and establish a T-shaped etching model, and the flow field domain consists of the first region 6 between the photoresist layers and the photoresist layer. The second area 7 of the surface etching liquid flow boundary is formed, wherein the width and height of the first area 6 are determined by the width of the line and the thickness of the photoresist 4, and the second area 7 is the flow boundary of the spray liquid on the surface of the photoresist , the top boundary of the second region 7 is the etching liquid inlet 1, and the two sides are the etching liquid outlet 2, and the size is not the research object of the present invention.

According to the actual production changes, the convection and diffusion of the etchant are studied using the Transport of Diluted Species Module in COMSOL, the etchant flow field is studied using the Fluid Flow Module, and the shape evolution of the etching cavity is studied using the Deformed Geometry Module. In order to simulate the etching process more accurately. In the actual etching process, the flexible PCB board will be transported to the spray etching equipment in a roll-to-roll manner, and the etching solution is sprayed from the spray nozzle to the surface of the copper film, and transported to the etching surface 3 by convection and diffusion. The concentration distribution of the etching solution in the etching cavity is related to the flux of the etching solution through the etching surface 3, and the shape change of the etching cavity is tracked by the moving boundary. Use the Transport of Diluted Species module to study the convection and diffusion of the etchant, the Fluid Flow module to study the flow field changes of the etchant, and the Deformed Geometry module to study the shape evolution of the etched cavity. The following assumptions are made during the simulation:

1 Since the size of the etching chamber is on the micrometer scale, it is assumed that the etching solution is an incompressible and stable laminar flow.

2 The effect of only one etchant in the etchant is considered in the etching reaction following linear kinetics.

3 An inhibitor is added to the etching solution, so the etching process is anisotropic.

The set simulation parameters specifically include etching time, incident speed of etching solution, CuCl ₂ concentration and ambient temperature. The set boundary conditions specifically include that the boundary condition of the inlet velocity is set to v ₀ m/s, the boundary condition of the outlet velocity is set to the pressure boundary, and the pressure is set to 0Pa, and the dilute species transport module studies the diffusion and convection provided by the etchant. The mass flux, given by the equation:

where D is the diffusion coefficient, c is the concentration value of CuCl ₂ , t is the time, u is the flow velocity of the etching solution, and ▽ is the gradient operator. By solving the equation and combining the boundary conditions, the concentration of the etching solution in the etching chamber can be obtained. distributed.

The model equation used by the fluid flow module is:

In formula (2), ρ is the fluid density of the etching solution, p is the external pressure, I is the unit vector, μ is the dynamic viscosity, and F is the boundary stress.

The deformation geometry module is described by the boundary movement equation, and the equation describing the boundary movement is

where α is the anisotropic diffusion coefficient and k is the rate constant of the etching reaction. n is the normal vector pointing outward to the boundary, n _x is the component of n in the direction of the x-axis, and _ny is the component of n in the direction of the y-axis. M and ρ _Cu are the molar mass and density of copper, respectively. Other boundaries are set as fixed walls.

_The boundary condition of the CuCl2 solution concentration at the inlet is set as c ₀ mol/L, the flux condition of the etched surface 3 is satisfied by the following equation, and the other boundaries are set as the no-flux condition.

Specifically, in the step S3, the simulation is performed using the permutation and combination process parameter data that may appear in various production lines as the boundary conditions of the simulation, and the corresponding simulation calculation results under the process data conditions are obtained and recorded in the database. Through the simulation of various possible process parameters, a database of one-to-one correspondence between the simulation process parameter data and the results is obtained.

Specifically, in the step S4, the collected production line process data specifically includes: the running speed of the line body (the length of the line body is 8m, which needs to be converted into the corresponding etching time), the spray pressure (which affects the incident speed and needs to be converted into etching solution) incident velocity), _CuCl2 concentration, etc.

Specifically, in the step S5, the actual production line process data is matched with the simulation process parameters in the database, the corresponding simulation results are obtained quickly, and then compared with the product index, the actual product index requires that the copper layer can be completely etched, That is, the etching depth H is required to reach 8 μm, and the side etching amount W is less than 2 μm. If it exceeds the product index, the system will issue a warning, immediately suspend production, and adjust the data in real time, such as changing the etching time. If the calculation result is within expectations, it means that the data is within the normal range and production can continue.

In the embodiment, the linear running speed of the collected production line is 3.5m/min (corresponding etching time is 137s), the incident speed is 4m/s, and the etching solution concentration is 0.45mol/L, which is input into the database, The obtained etching depth is 9.34 μm, and the side etching amount is 2.03 μm, which exceeds the product index and fails to meet the product standard. Therefore, the real-time adjustment of the running speed of the line body is 4m/min (the etching time is 120s), the incident speed and the concentration of the etching solution remain unchanged, and the simulation system is re-entered. standard, and its simulation results meet the product specifications. The simulation results of etching depth corresponding to different etching times are shown in Figure 5.

The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited to this. Several improvements and modifications are made, which should also be considered within the scope of the present invention.

Claims (7)

1. a flexible PCB board etching process online regulation method based on wet chemical etching simulation, is characterized in that, comprises the following steps: Step S1, build a physical model, set the geometric parameters of the flexible PCB board according to the actual situation through the simulation software, build a two-dimensional geometric model of the etching process simulation of the flexible PCB board, select the corresponding physical field module according to the actual production process, and set the simulation process parameters; Step S2, setting simulation conditions, setting boundary conditions according to the actual production process, and completing the establishment of the simulation model; Step S3, simulation calculation and establishment of a result database, combining and arranging the boundary conditions and process parameters that may appear on the actual production process line, obtaining simulation process parameter data, inputting the simulation process parameter data into the simulation model for simulation calculation, and establishing a simulation process A database of one-to-one correspondence between parameter data and simulation results; Step S4, acquiring and inputting process data of the production line, collecting process parameter data of the production line in real time, the process parameter data including spray pressure, etching solution concentration and line running speed; Step S5, real-time monitoring of the production line process data, match the production line process data of the production line collected in step S4 with the simulation process parameter data in the database, obtain corresponding simulation results, and then match the simulation results with the product indicators on the production line. Compare and process accordingly. 2 . The online control method of the etching process of the flexible PCB board according to claim 1 , wherein the geometric parameters of the flexible PCB board include the thickness of the etching substrate, the thickness of the mask and the width of the line. 3 . 3. The method for online regulation and control of an etching process of a flexible PCB board according to claim 2, wherein the established two-dimensional geometric model includes a copper layer, a mask and a flow field. 4 . The online control method for an etching process of a flexible PCB board according to claim 1 , wherein the physical field module comprises a dilute species transfer module, a fluid flow module and a deformation geometry module. 5 . 5. The method for online regulation and control of flexible PCB board etching process as claimed in claim 1, characterized in that: in step S1, the simulation process parameters include etching liquid incident velocity, etching liquid concentration and etching time, and the etching liquid incident velocity Converted from the spray pressure, the etching time is calculated from the running speed of the wire. 6. The method for online regulation and control of an etching process of a flexible PCB board according to claim 1, wherein the simulation result includes an etching depth and an undercut amount. 7. The on-line control method for etching process of flexible PCB board as claimed in claim 1, it is characterized in that: in step S4, when the simulation result differs greatly from the product index on the actual production, the production line process parameter adjustment is carried out, until the production line is adjusted. The online simulation results are in line with the product specifications.

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