CN113365430A

CN113365430A - Processing method of circuit flush printed board

Info

Publication number: CN113365430A
Application number: CN202110662004.6A
Authority: CN
Inventors: 雷雨辰; 高静茹
Original assignee: Xian Microelectronics Technology Institute
Current assignee: Xian Microelectronics Technology Institute
Priority date: 2021-06-15
Filing date: 2021-06-15
Publication date: 2021-09-07

Abstract

The invention discloses a method for processing a circuit flush printed board, and belongs to the field of circuit printing boards. According to the invention, the copper foil needing to be provided with the circuit is bonded with the technical copper-clad layer through specific resin, the required printed pattern is firstly processed, then the embedding of the printed conductor is realized by reversely filling glue, then the technical copper-clad layer is removed by etching, and the resin is removed by using alkaline solution, so that the embedded conductor can be exposed, and the function of leveling the circuit is achieved. The copper thickness of the outer layer has no special requirement, the adaptable products have more varieties, and the coplanarity consistency of the products is higher. The polishing process in the traditional processing method is avoided, the manufacturing difficulty of the product is reduced, and the application field of the flush printed board is improved.

Description

Processing method of circuit flush printed board

Technical Field

The invention belongs to the field of circuit printing plates, and relates to a method for processing a circuit flush printed board.

Background

The printed board with the flush circuit is characterized in that printed wires are embedded in an insulating base material, so that the wires are flush with the surface of a substrate, the functions of switch conversion, control switching and the like are integrated, and the printed board with the flush circuit has the advantages of reliability, durability, miniaturization, light weight and the like, and is a printed board product with a special structure. A normal flush printed board is processed by adopting a forward addition method, firstly, a printed pattern is manufactured according to a process method of a conventional printed board product, then an epoxy resin prepreg is pressed to embed the printed pattern, then, resin covering the printed pattern is removed by polishing, the printed pattern is exposed, and the flush of a lead and a base material is realized, wherein the preparation method is shown in figure 1.

On one hand, the resin has higher hardness after being cured, the plane polishing speed is slower, and labor and time are wasted; on the other hand, the coplanarity of polishing is different, a phenomenon that a part of a printed pattern is polished and exposed, and the other part of the printed pattern is not polished completely by resin exists, and in order to prevent the printed pattern which is polished firstly from being excessively polished, a thicker copper-clad thickness is generally adopted, and the copper-clad thickness is generally not less than 50 microns. These factors increase the difficulty of processing flush printed boards and limit their field of application.

Disclosure of Invention

In order to overcome the defects of low polishing efficiency and large polishing coplanarity difference of the polishing method in the prior art, the invention aims to provide a processing method of a printed board with a flush circuit.

In order to achieve the purpose, the invention adopts the following technical scheme to realize the purpose:

a processing method of a circuit flush printed board comprises the following steps:

step 1) preparing two copper foils, covering resin on the surface of one copper foil to obtain a resin copper foil, quickly pressing the resin copper foil and the other copper foil together, and then baking and curing to obtain a substrate;

step 2) completely covering one surface of the substrate with a dry film, pasting the dry film on the other surface of the substrate according to a preset printed pattern, and etching the substrate covered with the dry film to obtain a sheet with the printed pattern;

step 3) laminating and laminating the sheets, the prepregs and the insulating base materials according to the requirements of products, and then etching to obtain a printing plate prefabricated body;

and 4) placing the printing plate preform in a strong alkaline solution for degreasing to obtain the printed plate with the flush circuit.

Preferably, in step 1), the copper foil has a thickness of at least 18 μm;

the thickness of the resin is 5 to 25 μm.

Preferably, in step 1), the two copper foils have the same thickness and size.

Preferably, in step 1), the resin is an acrylic resin.

Preferably, in step 1), the condition parameters of the fast pressing are as follows: the temperature is 100-180 ℃; the pressure is 10-20 Psi; the time is 1-10 min.

Preferably, in step 1), the baking and curing conditions are as follows: the temperature is 100-180 ℃; the time is 1-4 h.

Preferably, the etching of step 2) and step 3) is an acidic etching using a copper chloride solution.

Preferably, the mass percent of the strong base in the strong base solution in the step 4) is 20-30%; the temperature of the strong alkali solution is 40-70 ℃.

Preferably, the strong alkaline solution is a sodium hydroxide or potassium hydroxide solution.

Preferably, the degreasing time in the step 4) is 2-6 h.

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

the invention discloses a processing method of a circuit flush printed board, which bonds a copper foil needing to be manufactured with a process copper-clad layer through specific resin, processes a needed printed pattern, then carries out glue filling in the reverse direction to realize the embedding of a printed conductor, then carries out etching to remove the process copper-clad layer, removes the resin by alkali liquor, and can expose the embedded conductor to achieve the function of circuit flushing. The copper thickness of the outer layer has no special requirement, the adaptable products have more varieties, and the coplanarity consistency of the products is higher. The polishing process in the traditional processing method is avoided, the manufacturing difficulty of the product is reduced, and the application field of the flush printed board is improved.

Furthermore, the thickness of the coating layer is used for ensuring the integrity of acrylic resin coating, reducing overflow in the bonding process and facilitating subsequent removal; the thickness of the copper foil depends on the design requirement of a printed pattern, and the thickness of the general copper foil is more than or equal to 18 mu m so as to ensure enough rigidity and operability in the pasting process.

Further, the copper foil of the same thickness is selected to maintain overall symmetry and reduce bending due to differential expansion of the material.

Further, the copper chloride is etched in an acid mode, the copper-clad layer is a protective layer in the pressing process and plays a role in buffering and supporting, and the printed pattern is a circuit pattern needing to be embedded into the base material.

Furthermore, the pressing process and parameters are consistent with those of the conventional printed board product.

Drawings

Fig. 1 is a view showing a structure of a process for manufacturing a printed board with a flush circuit as mentioned in the background art;

FIG. 2 is a flow chart of the present invention before lamination of the printed circuit boards with flush circuits;

FIG. 3 is a flow chart of the manufacturing process of laminating and degreasing the printed circuit boards with flush lines according to the present invention;

wherein: 101-copper foil; 102-a resin; 103-dry film; 104-a prepreg; 105-an insulating substrate.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the 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.

It should be noted that the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover non-exclusive inclusions, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed, but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The invention is described in further detail below with reference to the accompanying drawings:

example 1

step 1) preparing two copper foils 101 with the thickness of 25 micrometers as shown in figure 2, covering acrylic resin 102 with the thickness of 20 micrometers on the surface of one copper foil 101 to obtain a resin copper foil, and carrying out fast pressing on the resin copper foil and the other copper foil 101 together, wherein the fast pressing condition is at the temperature of 120 ℃; a pressure of 15 Psi; the time is 5 min. And then baking and curing, wherein the baking and curing condition parameters are as follows: the temperature is 130 ℃; the time is 1.5 h. Obtaining a substrate;

step 2) completely covering one surface of the substrate with the dry film 103, pasting the dry film 103 on the other surface of the substrate according to a preset printed pattern, and etching the substrate covered with the dry film 103 to obtain a sheet with the printed pattern;

step 3) as shown in fig. 3, laminating and laminating the sheet, the prepreg 104 and the insulating base material 105 according to the product requirement, and etching by using a copper chloride solution to obtain a printing plate preform;

and 4) placing the printing plate preform in a sodium hydroxide solution with the mass fraction of 25% for degreasing for 2.5h to obtain the printed plate with the flush circuit.

Example 2

as shown in fig. 2, in the step (1), one surface of a copper foil 101 is coated with a layer of acrylic resin 102 with a total thickness of 15 μm by spraying, the thickness of the coating layer is to ensure the coating integrity of the acrylic resin 102, reduce overflow in the bonding process and facilitate subsequent removal, the thickness of the copper foil 101 depends on the design requirement of a printed pattern, the thickness of a general copper foil 101 is more than or equal to 18 μm, in the embodiment, the thickness of the copper foil 101 is 18 μm to ensure sufficient rigidity and operability in the bonding process.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is at a temperature of 150 ℃; a pressure of 15 Psi; the time period is 4 min. And baking at 120 ℃ for 2h after fast pressing to cure the resin layer.

And (3) completely sticking a dry film 103 on one surface of the quickly pressed material for protection, sticking a dry film 103 on the other surface for protection according to a required printed pattern, removing the unprotected part of the copper clad through copper chloride acidic etching until the copper clad on the surface is completely removed, and manufacturing the sheet with one surface being copper clad and one surface being printed with the pattern. The copper-clad layer is a protective layer in the pressing process and plays a role in buffering and supporting, and the printed pattern is a circuit pattern which needs to be embedded into the insulating substrate.

Step (4) as shown in fig. 3, the sheets, the prepreg 104 and the insulating substrate 105 are laminated according to the product requirements, and the laminating process and parameters are consistent with those of a conventional printed board product.

And (5) removing the copper clad on the outer surface of the laminated printed board through copper chloride acidic etching until the copper clad on the surface is completely removed.

And (6) immersing the product into 25 mass percent of sodium hydroxide solution at the temperature of 60 ℃ for 4 hours under the ultrasonic condition until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

And (7) the subsequent processing of the step is consistent with the processing method of the traditional flush printed board.

Example 3

in the step (1), one surface of the copper foil 101 is coated with a layer of acrylic resin 102 with a total thickness of 5 μm by spraying or rolling, and the thickness of the copper foil 101 is 20 μm.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is 100 ℃; a pressure of 10 Psi; the time is 1 min. And (4) after fast pressing, baking for 1h at 100 ℃ to cure the resin layer. The copper foil 101 of the same thickness is selected to maintain overall symmetry and reduce bending due to differential expansion of the material.

And (4) laminating the sheets, the prepreg 104 and the insulating base material 105 according to the product requirements, wherein the laminating process and parameters are consistent with those of a conventional printed board product.

And (6) immersing the product into a sodium hydroxide solution with the mass percent of 20% and the temperature of 40 ℃ under the ultrasonic condition for 2 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

Example 4

in the step (1), one surface of a copper foil 101 is coated with a layer of acrylic resin 102 with a total thickness of 25 μm by spraying or rolling, and the thickness of the copper foil 101 is 30 μm.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is 180 ℃; a pressure of 20 Psi; the time is 10 min. And (4) baking for 4 hours at 180 ℃ after fast pressing to solidify the resin layer. The copper foil 101 of the same thickness is selected in order to maintain the overall symmetry and reduce the bending caused by the different expansion of the material.

And (6) immersing the product into a potassium hydroxide solution with the mass percent of 30% and the temperature of 70 ℃ under the ultrasonic condition for 6 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

Example 5

in the step (1), one surface of the copper foil 101 is coated with a layer of acrylic resin 102 with the total thickness of 10 mu m by spraying or rolling coating, and the thickness of the copper foil 101 is 24 mu m.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is 160 ℃; a pressure of 12 Psi; the time is 3 min. And (4) after fast pressing, baking for 2.5 hours at 160 ℃ to solidify the resin layer. The copper foil 101 of the same thickness is selected to maintain overall symmetry and reduce bending due to differential expansion of the material.

And (6) immersing the product into a sodium hydroxide solution with the mass percent of 22% and the temperature of 50 ℃ under the ultrasonic condition for 3 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

Example 6

in the step (1), one surface of a copper foil 101 is coated with a layer of acrylic resin 102 with the total thickness of 8 μm by spraying or rolling, and the thickness of the copper foil 101 is 19 μm.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is at a temperature of 130 ℃; a pressure of 11 Psi; the time is 8 min. And (4) after fast pressing, baking for 3 hours at 150 ℃ to solidify the resin layer. The copper foil 101 of the same thickness is selected in order to maintain the overall symmetry and reduce the bending caused by the different expansion of the material.

And (3) completely sticking a dry film 103 on one surface of the quickly pressed material for protection, sticking a dry film 103 on the other surface for protection according to a required printed pattern, removing the unprotected part of the copper clad through copper chloride acidic etching until the copper clad on the surface is completely removed, and manufacturing the sheet with one surface being copper clad and one surface being printed with the pattern. The copper-clad layer is a protective layer in the pressing process and plays a role in buffering and supporting, and the printed pattern is a circuit pattern which needs to be embedded into the insulating substrate 105.

And (6) immersing the product into a potassium hydroxide solution with the mass percentage of 24% and the temperature of 65 ℃ under the ultrasonic condition for 3.5 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

Example 7

in the step (1), one surface of a copper foil 101 is coated with a layer of acrylic resin 102 with a total thickness of 17 μm by spraying or rolling, and the thickness of the copper foil 101 is 23 μm.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is at a temperature of 165 ℃; a pressure of 7 Psi; the time period is 7 min. After the rapid pressing, the resin layer was cured by baking at 175 ℃ for 2 hours. The copper foil 101 of the same thickness is selected to maintain overall symmetry and reduce bending due to differential expansion of the material.

And (6) immersing the product into a sodium hydroxide solution with the mass percent of 22% and the temperature of 55 ℃ under the ultrasonic condition for 5 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

Example 8

in the step (1), one surface of a copper foil 101 is coated with a layer of acrylic resin 102 with a total thickness of 22 μm by spraying or rolling, and the thickness of the copper foil is 27 μm.

Step (2) using copper foil 101 with the same thickness, and carrying out fast pressing on the copper foil 101 coated with acrylic resin 102 under a vacuum condition, wherein the fast pressing condition is at a temperature of 110 ℃; a pressure of 18 Psi; the time period is 6 min. And after fast pressing, baking for 3.5 hours at 145 ℃ to solidify the resin layer. The copper foil 101 of the same thickness is selected to maintain overall symmetry and reduce bending due to differential expansion of the material.

And (6) immersing the product into a sodium hydroxide solution with the mass percent of 27% and the temperature of 65 ℃ under the ultrasonic condition for 4.5 hours until the acrylic resin 102 is removed. Thus, a product in which the conductive line is embedded in the insulating base material 105 and the conductive line is flush with the surface of the substrate can be obtained.

The copper foil used in the present invention is a copper foil having a smooth surface and a rough surface, and the two smooth surfaces are bonded to each other when the copper foil is pressed quickly. The dry film used in the examples is a dry film commonly used by those skilled in the art, and may be used, for example, a dry film of a brand such as dupont or hitachi.

In conclusion, compared with the traditional processing method of the flush printed board, the method provided by the invention does not need surface polishing, and has the problems of low polishing efficiency and polishing coplanarity difference. The method adopts a reverse glue filling method to realize the embedding of the printed conductor, namely, in the traditional method, a circuit is firstly processed, then a prepreg is pressed on the circuit, and the resin of the prepreg after pressing is also adhered to the surface of the circuit, so the conductor can be exposed only by polishing and removing the resin covering the circuit, and in the method, the conductor is adhered on the removable resin, the prepreg is filled from the reverse direction, the condition that the resin is pressed into the surface of the circuit does not exist, and the processed product has higher consistency.

The above-mentioned contents are only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited thereby, and any modification made on the basis of the technical idea of the present invention falls within the protection scope of the claims of the present invention.

Claims

1. A processing method of a circuit flush printed board is characterized by comprising the following steps:

2. The method for processing the printed circuit board with the flush printed circuit according to claim 1, wherein in the step 1), the copper foil has a thickness of at least 18 μm in the step 1);

the thickness of the resin is 5 to 25 μm.

3. The method for processing the printed board with the flush circuit as claimed in claim 1, wherein in step 1), the two copper foils have the same thickness and size.

4. The method for processing a printed circuit board with flush wires as claimed in claim 1, wherein in step 1), the resin is acrylic resin.

5. The method for processing the printed board with the flush circuit as claimed in claim 1, wherein in the step 1), the condition parameters of the quick pressing are as follows: the temperature is 100-180 ℃; the pressure is 10-20 Psi; the time is 1-10 min.

6. The method for processing the printed circuit board with the flush printed circuit board according to claim 1, wherein in the step 1), the baking and curing condition parameters are as follows: the temperature is 100-180 ℃; the time is 1-4 h.

7. The processing method of the printed circuit board with the flush printed circuit board according to claim 1, wherein the mass percent of the strong base in the strong base solution in the step 4) is 20-30%; the temperature of the strong alkali solution is 40-70 ℃.

8. The method for processing a printed circuit board having a flat surface according to claim 1 or 7, wherein the alkali solution is a sodium hydroxide solution or a potassium hydroxide solution.

9. The method for processing the printed circuit board with the flush printed circuit board as claimed in claim 1, wherein the degreasing time in the step 4) is 2-6 h.