Control method for improving quality of cross-sectional hole

Abstract

A control method for improving the quality of a cross-sectional hole, the control method comprising: first preparing, on the basis of the size of a cross-sectional hole to be filled, a high-Tg prepreg matching the cross-sectional hole in terms of size, and filling the cross-sectional hole with the high-Tg prepreg, such that a surface of the high-Tg prepreg is flush with a surface of a circuit board. Multiple laminations can be performed by using the heat resistance of the high-Tg prepreg; after actual operation verification, the condition of a laminated surface is not defective, and no bubbles or local delamination occur on an electroplated product board; and after electroplating, the problem of liquid medicine seepage does not occur, so that the manufacturing process is not affected, and the production quality of the circuit board is effectively improved. By means of matching the size of the high-Tg prepreg with that of the cross-sectional hole to be filled, only the high-Tg prepreg needs to be plugged into the cross-sectional hole during filling, so that operation is simple, and the convenience of filling the cross-sectional hole with the high-Tg prepreg is improved.

Description

A method for improving the quality of sliced ​​holes Technical Field

[0001] This invention belongs to the field of circuit board slicing technology, and specifically relates to a control method for improving the quality of sliced ​​holes. Background Technology

[0002] In PCB manufacturing, to monitor the quality of laminated dielectric thickness, plated vias, and blind vias, slicing monitoring is performed at relevant stages to ensure the quality of the produced PCBs. Currently, the method for PCB slicing involves first cutting a small piece (typically 15mm x 10mm) containing plated vias and blind vias from a large sheet of PCB. This sample is then fixed and sliced. Finally, the sliced ​​sample is observed under a mirror microscope to examine a range of quality parameters, including laminated dielectric thickness, copper thickness of vias and blind vias, hole diameter, and hole shape. This allows for timely follow-up, handling, and improvement of any process or quality issues.

[0003] To improve the quality of circuit board production, the product stacking process requires multiple laminations. After each lamination, key processes require slicing for quality monitoring. To reduce the impact on subsequent product quality, the production boards with sliced ​​inner layers must be filled during lamination; otherwise, the semi-cured sheets of the current layer cannot fill such large slicing holes.

[0004] Currently, most methods for laminating and filling slices use ordinary FR4 material for manual filling. However, ordinary FR4 material has poor heat resistance, and after multiple laminations, delamination and bubbles may occur. It may also break during the electroplating process, causing board quality problems. Therefore, we need to propose a method to improve the control of slice hole quality to solve the above-mentioned problems and effectively improve the board quality. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the quality of sliced ​​holes. By using high Tg prepreg to fill the sliced ​​holes, multiple laminations can be performed. After actual operation verification, the surface condition of the laminated product is unblemished. No bubbles or local delamination are found in the electroplated product boards, and no chemical seepage problem is found after electroplating. This effectively improves the production quality of circuit boards and solves the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for improving the quality of sliced ​​wells includes the following steps:

[0008] S1. Prepare a high-Tg prepreg that matches the size of the slicing holes according to the size of the holes to be filled;

[0009] S2. When laminating and laying out the substrate, manually fill the cutting holes with the high Tg prepreg to make the surface of the high Tg prepreg flush with the surface of the circuit board.

[0010] S3. Laminate the circuit board filled with high Tg prepreg and confirm the surface quality of the product after lamination.

[0011] S4. Electroplating is performed on qualified products after lamination. Samples of the electroplated products are selected for cross-sectioning to confirm the quality of the electroplating.

[0012] Preferably, the preparation process of the high Tg prepreg is as follows:

[0013] A1. A matrix resin solution was prepared using bismaleimide diphenylmethane and cyanate ester resin as the main raw materials.

[0014] A2. A mixture is prepared using fillers, flame retardants, solvents, and coupling agents as the main raw materials;

[0015] A3. After melting the matrix resin liquid, add it to the sand mill along with the mixture, and then add the catalyst to the sand mill for sand milling to prepare the preimpregnation solution;

[0016] A4. Apply or impregnate the prepreg with fiber-reinforced material, and then bake it to obtain a semi-cured sheet.

[0017] A5. Cut the prepreg into high Tg prepregs that match the size of the cut hole.

[0018] Preferably, in step A1, the matrix resin solution is prepared by adding bismaleimide diphenylmethane and bisphenol A cyanate raw materials into a reaction vessel and heating and stirring at a temperature of 50-170°C for 10-200 minutes.

[0019] Preferably, in step A2, the filler is selected from silicon dioxide, magnesium hydroxide, graphite oxide, kaolin, and hollow glass microspheres.

[0020] Preferably, the solvent is one of acetone, butanone, and N,N-dimethylformamide, and the coupling agent is one of silane coupling agent, titanate coupling agent, and aluminate coupling agent.

[0021] Preferably, during the preparation of the mixture, the filler, flame retardant, solvent and coupling agent are sequentially added to a reaction vessel containing a matrix resin solution for mixing and stirring. The stirring speed is controlled at 100-600 r / min and the stirring time is 0.5-24 hours.

[0022] Preferably, in step A3, the catalyst is selected from benzoyl peroxide, N,N-dimethylbenzylamine, N,N-dimethylaniline, N,N-dimethyltoluidine, pyridine, quinoline, N-methylmorpholine, triethanolamine, triethylenediamine, and N-methylpiperidine.

[0023] Preferably, in the preparation of the prepreg, the matrix resin liquid is melted and then added to a sand mill along with the mixture and catalyst for sand milling. The prepreg is then obtained by rotary shearing through a high-speed shearing machine. The melting temperature is 50-200℃, the sand milling speed is 1000-6000 r / min, and the rotary shearing speed is 100-500 r / min.

[0024] Preferably, in step A4, the fibrous reinforcing material is one of glass fiber, carbon fiber, and aramid fiber, and the baking temperature of the coated or impregnated fibrous reinforcing material is 90-200℃, and the baking time is 5-30 minutes.

[0025] Preferably, in step S3, when laminating the circuit board filled with high-Tg prepreg, the circuit board containing the high-Tg prepreg is first stacked together with other circuit boards in sequence, and then laminated using a vacuum laminator. The lamination temperature is set at 180-200℃, and the pressure is 15-35 kg / cm². 3 After lamination, the product is cooled. Products with no bubbles, damage, or delamination on the surface are considered qualified. Products with one or more of the following defects are considered unqualified.

[0026] The present invention proposes a method for controlling the quality of sliced ​​holes, which has the following advantages compared with the prior art:

[0027] 1. This invention uses high-Tg prepreg to fill the slicing holes, making the high-Tg prepreg flush with the surface of the circuit board. Utilizing the heat resistance of the high-Tg prepreg, multiple laminations can be performed. After actual operation verification, the laminated surface condition is unblemished. The electroplated product board also shows no bubbles or local delamination, and no chemical seepage is found after electroplating. It does not affect subsequent manufacturing processes and effectively improves the production quality of the circuit board.

[0028] 2. This invention sets the size of the high Tg prepreg to match the size of the slicing hole to be filled. During filling, the high Tg prepreg is simply inserted into the slicing hole, which is simple to operate and improves the convenience of filling the high Tg prepreg and the slicing hole. Attached Figure Description

[0029] Figure 1 is a flowchart of the present invention;

[0030] Figure 2 is a flowchart of the preparation process of the high Tg semi-cured sheet of the present invention;

[0031] Figure 3 is a comparison diagram of the filling materials used in the embodiments of the present invention;

[0032] Figure 4 is a comparison of the quality confirmation of the high Tg prepreg and ordinary FR4 material filling the slicing holes of the layer plate according to the present invention.

[0033] Figure 5 shows the defect rate statistics of circuit board quality control using ordinary FR4 material to fill the slice holes;

[0034] Figure 6 is a statistical chart showing the defect rate of circuit boards controlled by filling the slice holes with high Tg prepreg. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] Example 1

[0037] This invention provides a method for improving the quality of sliced ​​holes, as shown in Figures 1-2, comprising the following steps:

[0038] S1. Prepare a high-Tg prepreg that matches the size of the slicing holes according to the size of the holes to be filled;

[0039] The preparation process of the high Tg prepreg is as follows:

[0040] A1. A matrix resin solution was prepared using bismaleimide diphenylmethane and cyanate ester resin as the main raw materials.

[0041] In the preparation of the matrix resin solution, bismaleimide diphenylmethane and bisphenol A cyanate raw materials are added to a reaction vessel and heated and stirred at a temperature of 50-170°C for 10-200 minutes to ensure the homogeneity of the mixture and ensure that the resin and other additives can be fully integrated to form a uniform solution. Each time a new component is added, it is necessary to continue stirring for 10-200 minutes to ensure the uniformity of the mixture. The bismaleimide and cyanate resin are used to increase the thermal stability and mechanical properties of the high Tg prepreg.

[0042] A2. A mixture is prepared using fillers, flame retardants, solvents and coupling agents as the main raw materials. By mixing the mixture with the matrix resin liquid, not only are the physical properties of the resin improved, such as its flame retardancy and mechanical strength, but also the process properties, such as viscosity and film-forming properties, are optimized.

[0043] The filler is selected from one of the following: silicon dioxide, magnesium hydroxide, graphite oxide, kaolin, and hollow glass microspheres.

[0044] The flame retardant is set as one of the following: magnesium-based flame retardant, boron-zinc-based flame retardant, molybdenum-tin-based flame retardant, and bromine-based flame retardant. Among them, the magnesium-based flame retardant mainly includes magnesium hydroxide and magnesium salt whiskers, the boron-zinc-based flame retardant includes zinc borate and ultrafine zinc borate, the molybdenum-tin-based flame retardant includes melamine molybdate and octamolate quaternary ammonium salt, and the bromine-based flame retardant includes decabromodiphenyl ether and tetrabromobisphenol A. The flame retardant is used to increase the flame retardant effect of the prepreg.

[0045] The solvent is selected from acetone, butanone, and N,N-dimethylformamide, and the coupling agent is selected from silane coupling agent, titanate coupling agent, and aluminate coupling agent.

[0046] In the preparation of the mixture, fillers, flame retardants, solvents and coupling agents are sequentially added to a reaction vessel containing a matrix resin solution for mixing and stirring. The stirring speed is controlled at 100-600 r / min and the stirring time is 0.5-24 hours to ensure that all components are uniformly dispersed and completely wet the reinforcing fibers.

[0047] A3. After melting the matrix resin liquid, add it to the sand mill along with the mixture, and then add the catalyst to the sand mill for sand milling to prepare the preimpregnation solution;

[0048] The catalyst is selected from benzoyl peroxide, N,N-dimethylbenzylamine, N,N-dimethylaniline, N,N-dimethyltoluidine, pyridine, quinoline, N-methylmorpholine, triethanolamine, triethylenediamine, and N-methylpiperidine.

[0049] In the preparation of the prepreg, the matrix resin liquid is melted and then added to a sand mill along with the mixture and catalyst for sand milling. The prepreg is then obtained by rotary shearing through a high-speed shearing machine. The melting temperature is 50-200℃, the sand milling speed is 1000-6000 r / min, and the rotary shearing speed is 100-500 r / min.

[0050] A4. Apply or impregnate the prepreg with fiber-reinforced material, and then bake it to obtain a semi-cured sheet.

[0051] The fiber-reinforcing material is selected from glass fiber, carbon fiber and aramid fiber. The baking temperature of the coated or impregnated fiber-reinforcing material is 90-200℃ and the baking time is 5-30 minutes.

[0052] A5. Cut the prepreg into high Tg prepregs that match the size of the cut hole.

[0053] S2. When laminating and laying out the substrate, manually fill the cutting holes with the high Tg prepreg to make the surface of the high Tg prepreg flush with the surface of the circuit board.

[0054] By matching the size of the high Tg prepreg with the size of the slicing hole to be filled, the high Tg prepreg can be simply inserted into the slicing hole during filling, which is simple and improves the convenience of filling the high Tg prepreg with the slicing hole.

[0055] S3. Laminate the circuit board filled with high Tg prepreg and confirm the surface quality of the product after lamination.

[0056] When laminating circuit boards filled with high-Tg prepreg, first stack the circuit board containing the high-Tg prepreg together with other circuit boards in sequence, and then perform lamination using a vacuum laminator. The lamination temperature is set at 180-200℃, and the pressure is 15-35 kg / cm². 3 After lamination, the product is cooled. Products with no bubbles, damage, or delamination on the surface are considered qualified. Products with one or more of the following defects are considered unqualified.

[0057] S4. Electroplating is performed on qualified products after lamination, and samples of electroplated products are selected for cross-sectioning to confirm the quality of electroplating.

[0058] High Tg prepreg is made by impregnating treated electronic-grade glass fiber cloth with epoxy resin. After heat treatment (pre-baking), the resin enters a semi-cured state (stage B). The high Tg prepreg softens under heating and pressure, and then cures upon cooling. It provides the inner and outer insulating medium for multilayer boards, controls the accuracy of characteristic impedance, and ensures the performance of multilayer board circuits. The Tg value is the temperature critical point for the transformation of amorphous polymers into a highly elastic state. High Tg means that the board can maintain stable physical properties under high temperature conditions and is not prone to deformation, breakage, or other problems.

[0059] By using high-Tg prepreg to fill the slicing holes, the high-Tg prepreg is flush with the surface of the circuit board. Utilizing the heat resistance of the high-Tg prepreg, multiple laminations can be performed. After actual operation verification, the laminated surface condition is unblemished. The electroplated product board also shows no bubbles or local delamination, and no chemical seepage issues were found after electroplating. This does not affect subsequent manufacturing processes and effectively improves the production quality of the circuit board.

[0060] Example 2

[0061] Actual production verification was performed according to the method provided in Example 1, and compared with the method of laminating after filling the slicing holes using ordinary FR4 material, to confirm the effectiveness of the improvement provided in Example 1. As shown in Figures 3-5, the verification results are as follows:

[0062] 1. Select high-Tg prepreg and ordinary FR4 material with the same size as the slicing hole, as shown in Figure 3. The group using high-Tg prepreg is named the experimental group, and the group using ordinary FR4 material is named the control group.

[0063] 2. Fill the cut holes in the laminate with high Tg prepreg and ordinary FR4 material respectively, and perform lamination and electroplating to confirm the results, as shown in Figure 4. The confirmation results are as follows:

[0064] Experimental group: By using Tg prepreg to fill the holes in the slices, there were no bubbles or delamination on the board surface after lamination, and there was no damage or serious contamination on the board surface after electroplating.

[0065] Control group: After lamination, the board surface showed varying degrees of delamination and bubbles, and the board surface was severely contaminated, by using ordinary FR4 material to fill the slicing holes.

[0066] 3. As shown in Figure 5, the quality control of PCBs using ordinary FR4 material to fill the slicing holes throughout 2022 resulted in an average inner layer open circuit defect rate of 2.87%, an average inner layer short circuit defect rate of 2.66%, and an average notch defect rate of 1.9%. Figure 6 shows the quality control of PCBs using high Tg prepreg to fill the slicing holes in 2023. The average inner layer open circuit defect rate was approximately 1.87%, the average inner layer short circuit defect rate was approximately 1.66%, and the average notch defect rate was approximately 0.9%. Through year-round batch verification, it was found that using high Tg prepreg to fill the slicing holes improved the quality and yield of PCB production.

[0067] Therefore, by using high Tg prepreg to fill the slicing holes, the lamination surface of the circuit board is unaffected during lamination, and the electroplated circuit board does not have bubbles or local delamination. No chemical seepage problem was found after electroplating, which does not affect the production process and effectively improves the production quality of the circuit board.

[0068] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for controlling the quality of sliced ​​holes, characterized in that: Includes the following steps: S1. Prepare a high-Tg prepreg that matches the size of the slicing holes according to the size of the holes to be filled; S2. When laminating and laying out the substrate, manually fill the cutting holes with the high Tg prepreg to make the surface of the high Tg prepreg flush with the surface of the circuit board. S3. Laminate the circuit board filled with high Tg prepreg and confirm the surface quality of the product after lamination. S4. Electroplating is performed on qualified products after lamination. Samples of the electroplated products are selected for cross-sectioning to confirm the quality of the electroplating.

2. The method for controlling the quality of sliced ​​holes according to claim 1, characterized in that: The preparation process of the high Tg semi-cured sheet is as follows: A1. A matrix resin solution was prepared using bismaleimide diphenylmethane and cyanate ester resin as the main raw materials. A2. A mixture is prepared using fillers, flame retardants, solvents, and coupling agents as the main raw materials; A3. After melting the matrix resin liquid, add it to the sand mill along with the mixture, and then add the catalyst to the sand mill for sand milling to prepare the preimpregnation solution; A4. Apply or impregnate the prepreg with fiber-reinforced material, and then bake it to obtain a semi-cured sheet. A5. Cut the prepreg into high Tg prepregs that match the size of the cut hole.

3. The method for controlling the quality of sliced ​​holes according to claim 2, characterized in that: In step A1, the matrix resin solution is prepared by adding bismaleimide diphenylmethane and bisphenol A cyanate raw materials into a reaction vessel and heating and stirring at a temperature of 50-170°C for 10-200 minutes.

4. The method for controlling the quality of sliced ​​holes according to claim 3, characterized in that: In step A2, the filler is selected from one of the following: silicon dioxide, magnesium hydroxide, graphite oxide, kaolin, and hollow glass microspheres.

5. The method for controlling the quality of sliced ​​holes according to claim 4, characterized in that: The solvent is selected from acetone, butanone, and N,N-dimethylformamide, and the coupling agent is selected from silane coupling agent, titanate coupling agent, and aluminate coupling agent.

6. The method for controlling the quality of sliced ​​holes according to claim 5, characterized in that: The mixture is prepared by sequentially adding filler, flame retardant, solvent and coupling agent into a reaction vessel containing matrix resin solution and mixing and stirring. The stirring speed is controlled at 100-600 r / min and the stirring time is 0.5-24 hours.

7. The method for improving the quality of sliced ​​holes according to claim 6, characterized in that: In step A3, the catalyst is selected from benzoyl peroxide, N,N-dimethylbenzylamine, N,N-dimethylaniline, N,N-dimethyltoluidine, pyridine, quinoline, N-methylmorpholine, triethanolamine, triethylenediamine, and N-methylpiperidine.

8. The method for controlling the quality of sliced ​​holes according to claim 7, characterized in that: In the preparation of the prepreg, the matrix resin liquid is melted and then added to a sand mill along with the mixture and catalyst for sand milling. The prepreg is then obtained by rotary shearing through a high-speed shearing machine. The melting temperature is 50-200℃, the sand milling speed is 1000-6000 r / min, and the rotary shearing speed is 100-500 r / min.

9. The method for controlling the quality of sliced ​​holes according to claim 8, characterized in that: In step A4, the fiber reinforcement material is selected from glass fiber, carbon fiber and aramid fiber, and the baking temperature of the coated or impregnated fiber reinforcement material is 90-200℃, and the baking time is 5-30 minutes.

10. The method for improving the quality of sliced ​​holes according to claim 9, characterized in that: In step S3, when laminating the circuit board filled with high-Tg prepreg, the circuit board containing the high-Tg prepreg is first stacked together with other circuit boards in sequence, and then laminated using a vacuum laminator. The lamination temperature is set at 180-200℃, and the pressure is 15-35 kg / cm². 3 After lamination, the product is cooled. Products with no bubbles, damage, or delamination on the surface are considered qualified. Products with one or more of the following defects are considered unqualified.

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