BGA (ball grid array) area flatness PCB (printed circuit board) and preparation method thereof

Abstract

The invention discloses a BGA (Ball Grid Array) area flatness PCB (Printed Circuit Board) and a preparation method thereof in the technical field of PCB production processes, and aims to solve the problem that the flatness cannot meet the actual production requirement in the prior art. The preparation method comprises the following steps: obtaining a carrier, a prepreg and a peelable copper foil; sequentially laminating the carrier, the prepreg and the peelable copper foil to form an upper, middle and lower laminated structure; laminating and pre-curing the upper, middle and lower laminated structure by adopting a laminating machine to form a false layer; laminating the false layer with a preset inner-layer core plate, a press steel plate and a buffer material to form a multi-layer PCB structure; and stripping the strippable copper foil from the multi-layer PCB structure, and removing the false layer to obtain the BGA area PCB with the preset flatness. According to the method, the flatness range of the BGA area can be controlled within 50 # imgabs0 #.

Description

Technical Field

[0001] The invention relates to a BGA area flatness PCB and a preparation method thereof, belonging to the technical field of PCB board production process. Background Art

[0002] PCB (Printed Circuit Board) is the core component of electronic products and is known as the "mother of electronic products". It is responsible for interconnection and signal transmission between electronic components and provides support for various electronic components. A variety of electronic components can be installed on PCB, including resistors, capacitors, inductors, crystal oscillators, relays and various types of chips. Among these components, chips play a core role and are usually packaged in the form of BGA (Ball Grid Array) and fixed to a specific area of ​​the PCB using solder paste through SMT (Surface Mount Technology).

[0003] With the rapid development of new technologies such as new energy vehicles, 5G, and artificial intelligence, the requirements for chip performance are getting higher and higher, the amount of data and processing requirements are increasing, the chip structure is becoming more complex, and the size is increasing. This directly leads to higher performance requirements for PCBs, especially the flatness requirements for the BGA area are becoming more and more stringent. Usually, the flatness is required to be controlled within 50 microns, otherwise larger chips may warp after packaging. The heat effect during the SMT process may further cause deformation, making the ball pins not in the same plane. If the BGA area of ​​the PCB is not flat enough, it will increase the risk of cold soldering and poor contact.

[0004] In the traditional PCB manufacturing process, different inner layer patterns in the BGA area may cause the area with more copper to bulge out more than the area with less copper after lamination, affecting the flatness. For example, a typical sandwich structure is made up of multiple layers of materials, including an outer copper foil, filler, an inner core layer, and more filler and copper foil. During the manufacturing process, in order to ensure a good fit between the outer copper foil and the steel plate and prevent the copper foil from wrinkling during lamination, copper foil is placed on both sides of the steel plate, and a buffer layer and steel plate are stacked on the outside. The press transmits temperature and pressure through these steel plates to melt the PP material and fill the gaps. However, due to the elasticity of the buffer material and the possible inconsistency caused by the multi-layer stacking, this may cause the PCB to fail to achieve a highly consistent board thickness after lamination, thus affecting the flatness of the BGA area.

[0005] At present, the general level of the PCB manufacturing industry is a flatness of more than 100 microns, which cannot meet the needs of high-performance chip development. In order to solve these problems, it is necessary to innovate and improve the existing PCB pressing processing methods to achieve higher flatness standards and better electronic performance. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and provide a BGA area flatness PCB and a preparation method thereof, which can achieve the BGA area flatness on the PCB board that cannot meet the requirement of <=50 To solve the above technical problems, the present invention is implemented by adopting the following technical solutions: A method for preparing a PCB with a flat BGA area, comprising: Obtaining a carrier, a prepreg, and a strippable copper foil; The carrier, the prepreg and the peelable copper foil are stacked in sequence to form an upper, middle and lower stacking structure; Using a laminator to press and pre-cure the upper, middle and lower stacked structures to form a false layer; The dummy layer is pressed together with a preset inner core plate, a press steel plate, and a buffer material to form a multi-layer PCB structure; The strippable copper foil is stripped from the multi-layer PCB structure, and the dummy layer is removed to obtain a BGA area PCB with a predetermined flatness.

[0007] Preferably, the medium parameters of the carrier include: Withstand temperature 200℃-800℃; Withstand pressure 300 psi -1000psi; Surface smoothness: 0-5 .

[0008] Preferably, the curing parameters of the prepreg include: Thickness: 0.05-0.1mm; Curing temperature: 80℃-180℃; Curing pressure: 50 psi -260psi.

[0009] Preferably, the strippable copper foil comprises a first copper foil, a separation layer and a second copper foil, and the first copper foil and the second copper foil are separated by the separation layer in between.

[0010] Preferably, the pressing and pre-curing treatments meet the following conditions: Temperature: 80℃-180℃; Pressure: 50 psi -260psi.

[0011] Preferably, the stripping copper foil is stripped from the multi-layer PCB structure, comprising: The first copper foil and the separation layer are peeled off, and the second copper foil remains.

[0012] Preferably, removing the dummy layer further comprises: The removed dummy layer is sequentially etched, ground and cleaned to obtain the carrier, which is used to repeatedly prepare the dummy layer.

[0013] Preferably, the BGA area PCB with a predetermined flatness is a symmetrical structure.

[0014] Preferably, the BGA area PCB with a predetermined flatness comprises an inner core board, a prepreg and a second copper foil, wherein the prepreg is located on both sides of the inner core board, and the second copper foil covers the prepreg.

[0015] In a second aspect, a BGA area flatness PCB is manufactured using the method for preparing a BGA area flatness PCB described in the first aspect.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The present invention forms a stable upper, middle and lower stacked structure by obtaining a carrier, a prepreg and a strippable copper foil and stacking them in sequence. The stability of this structure lays a foundation for subsequent lamination and pre-curing treatment. Subsequently, a laminator is used to laminate and pre-cure the laminated structure to form a dummy layer. The dummy layer is used to replace the traditional laminate for lamination, which not only improves production efficiency, but also ensures the flatness of the dummy layer due to the absolute flatness and non-deformation characteristics of the carrier, thereby directly affecting the flatness of the BGA area of ​​the final PCB.

[0017] The dummy layer is pressed together with the inner core board, press steel plate and buffer material to form a multi-layer PCB structure, which not only enhances the overall structural stability of the PCB, but also further improves the quality and performance of the PCB by precisely controlling the pressing conditions, such as temperature and pressure. Finally, by peeling off the strippable copper foil and removing the dummy layer, a BGA area PCB with high flatness is finally obtained, meeting the requirements of high-precision electronic component assembly.

[0018] In addition, this method also has the advantage of material recycling. After completing its function, the dummy layer can be restored to a carrier through etching, grinding and cleaning, and can be reused. This not only reduces production costs, but also complies with the concepts of environmental protection and sustainable development. Overall, this preparation method improves the quality and performance of PCBs through innovative process flows, while also improving production efficiency and material utilization, which plays an important role in promoting the electronics manufacturing industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of a peelable copper foil provided by an embodiment of the present invention; Figure 2 is a schematic diagram of the structure of a dummy layer provided in an embodiment of the present invention; Figure 3is a schematic diagram of the structure after lamination and pre-curing treatment provided by an embodiment of the present invention; Figure 4 is a schematic diagram of the structure of a final product provided by an embodiment of the present invention; In the figure: 1, carrier; 2, semi-cured sheet; 3, peelable copper foil; 301, first copper foil; 302, separation layer; 303, second copper foil; 4, dummy layer; 5, press steel plate; 6, buffer material; 7, inner core board. DETAILED DESCRIPTION

[0020] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0021] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0022] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances. Example 1

[0023] See also Figure 3 A method for preparing a BGA area flatness PCB comprises the following steps: Step S1, obtain carrier 1, and carrier 1 meets the following conditions: 1) The carrier 1 material can maintain flatness and does not deform during the manufacturing process and when subjected to temperature and pressure changes; 2) The carrier 1 material evenly transmits temperature and pressure during the manufacturing process to ensure that all parts can reach the required curing conditions during the lamination process.

[0024] Furthermore, the medium parameters of the carrier 1 are as follows: It can withstand temperatures of 200°C-800°C, and the temperature of the embodiment of the present invention is set to 800°C; The pressure can be 300 psi -1000 psi, and the pressure value of the embodiment of the present invention is set to 1000 psi; Surface smoothness: 0-5 ; The surface flatness of the embodiment of the present invention is set to 3um.

[0025] Obtain a prepreg 2, and the size and model of the prepreg 2 must be consistent with the requirements of the final PCB product to ensure that the required electrical connection and mechanical support can be achieved during the manufacturing process. The curing parameters of the prepreg 2 include: Thickness: 0.05 mm -0.1 mm, the thickness of the embodiment of the present invention is set to 0.1 mm; Curing temperature: 80℃-180℃; Curing pressure: 50 psi -260psi.

[0026] See also Figure 2 , obtaining a peelable copper foil 3, wherein the peelable copper foil 3 comprises a first copper foil 301, a separation layer 302, and a second copper foil 303, and the first copper foil 301 and the second copper foil 303 are isolated by the separation layer 302 in the middle.

[0027] Furthermore, the size of the strippable copper foil 3 is completely consistent with the size of the PCB board to be finally produced, that is, the size of the copper foil can cover the entire surface of the PCB board to ensure that the copper foil can be evenly applied to every part of the PCB during the manufacturing process.

[0028] It should be noted that the peelable copper foil 3 is a special copper foil material that can be peeled off or removed during the manufacturing process, for example, to provide flatness during the lamination process, and can be easily peeled off from the PCB, leaving the desired circuit pattern.

[0029] Step S2, stacking the carrier 1, the prepreg 2 and the peelable copper foil 3 in sequence to form an upper, middle and lower stacking structure, and pressing and pre-curing the upper, middle and lower stacking structure with a laminator to form a dummy layer 4.

[0030] See also Figure 2The dummy layer 4 is a temporary laminate structure used to provide additional flatness and support during the PCB manufacturing process. The carrier 1 plays a role in supporting and transferring heat and pressure in the dummy layer 4; the prepreg 2 is used as an intermediate layer in the dummy layer 4 to provide certain structural strength and adhesion; the peelable copper foil 3 is placed above or below the prepreg 2 to provide external flatness during the lamination process.

[0031] It should be noted that the laminator can be a vacuum high temperature press, a vacuum laminator or a fast press.

[0032] Furthermore, the lamination and pre-curing process meet the following conditions: Temperature: 80°C-180°C, the curing temperature of the embodiment of the present invention is set to 180°C; Pressure: 50 psi -260 psi, the pressure temperature of the embodiment of the present invention is set to 200 psi.

[0033] It should be noted that the temperature and pressure conditions satisfied by the lamination and pre-curing treatment are the same as the curing temperature and curing pressure range experienced by the semi-cured sheet 2 during the lamination process, that is, the temperature and pressure range after lamination and pre-curing treatment is equal to the curing temperature and curing pressure of the semi-cured sheet 2 itself.

[0034] Step S3, pressing the dummy layer 4 with other materials, namely the inner core board 7, the press steel plate 5, and the buffer material 6, to form a multi-layer PCB structure.

[0035] Step S4, peeling off the peelable copper foil 3 from the multi-layer PCB structure, and removing the dummy layer (4), to obtain a BGA area PCB with a predetermined flatness.

[0036] For details, see Figure 4 , the first copper foil 301 and the separation layer 302 in the peelable copper foil 3 are peeled off, and the second copper foil 303 is retained; since the dummy layer 4 plays a role in ensuring flatness during the lamination process, once the lamination is completed, the dummy layer 4 will be removed, thereby obtaining a BGA area PCB with a predetermined flatness. The BGA area flatness PCB includes an inner core board 7, a prepreg 2, and a second copper foil 303, the prepreg 2 is located on both sides of the inner core board 7, and the second copper foil 303 covers the prepreg 2.

[0037] Furthermore, the BGA area PCB is a symmetrical structure, and the flatness of the BGA area satisfies <=50 requirements.

[0038] Furthermore, the removed dummy layer 4 can be reused, and the specific processing process includes: The unnecessary parts of the material are removed by etching in sequence to form the desired pattern or structure; Next, the dummy layer 4 is ground to remove the rough edges or uneven surfaces left after etching, in preparation for the next step of cleaning and reuse; Finally, the dummy layer 4 is cleaned to remove the residues on the surface of the material, ensuring that the surface of the carrier is clean and free of residual chemicals.

[0039] The processed carrier is stored and used for subsequent PCB manufacturing, thereby achieving resource recycling and cost savings. Example 2

[0040] A BGA area flatness PCB is manufactured by the method for manufacturing the BGA area flatness PCB described in Example 1.

[0041] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a PCB with high flatness in a BGA area, characterized in that: include: Obtaining a carrier (1), a prepreg (2), and a peelable copper foil (3); The carrier (1), the prepreg (2) and the peelable copper foil (3) are stacked in sequence to form an upper, middle and lower stacked structure; Using a laminator to press and pre-cure the upper, middle and lower stacked structures to form a dummy layer (4); The dummy layer (4) is pressed together with a preset inner core plate (7), a press steel plate (5), and a buffer material (6) to form a multi-layer PCB structure; The strippable copper foil (3) is stripped from the multi-layer PCB structure, and the dummy layer (4) is removed to obtain a BGA area PCB with a predetermined flatness.

2. The method for preparing a BGA area flatness PCB according to claim 1, characterized in that: The medium parameters of the carrier (1) include: Withstand temperature 200℃-800℃; Withstand pressure 300 psi -1000psi; Surface smoothness: 0-5 .

3. The method for preparing a BGA area flatness PCB according to claim 1, characterized in that: The curing parameters of the prepreg (2) include: Thickness: 0.05-0.1mm; Curing temperature: 80℃-180℃; Curing pressure: 50 psi -260psi.

4. The method for preparing a BGA area flatness PCB according to claim 1, characterized in that: The strippable copper foil (3) comprises a first copper foil (301), a separation layer (302) and a second copper foil (303); the first copper foil (301) and the second copper foil (303) are isolated by the separation layer (302) in the middle.

5. The method for preparing a BGA area flatness PCB according to claim 1, characterized in that: The pressing and pre-curing treatment meets the following conditions: Temperature: 80℃-180℃; Pressure: 50 psi -260psi.

6. The method for preparing a PCB with BGA area flatness according to claim 4, characterized in that: The strippable copper foil (3) is stripped from the multi-layer PCB structure, comprising: The first copper foil (301) and the separation layer (302) are peeled off, and the second copper foil (303) is retained.

7. The method for preparing a PCB with BGA area flatness according to claim 1, characterized in that: Removing the fake layer (4), further comprising: The removed dummy layer (4) is sequentially etched, ground, and cleaned to obtain the carrier (1), and the carrier (1) is used to repeatedly prepare the dummy layer (4).

8. The BGA area flatness PCB according to claim 1, characterized in that: The BGA area PCB with a predetermined flatness is a symmetrical structure, and the flatness range is 0-50 between.

9. The BGA area flatness PCB according to claim 8, characterized in that: A BGA area PCB with a predetermined flatness comprises an inner core board (7), a prepreg (2) and a second copper foil (303), wherein the prepreg (2) is located on both sides of the inner core board (7), and the second copper foil (303) covers the prepreg (2).

10. A BGA area flatness PCB, characterized in that: The PCB is manufactured by the method for preparing a BGA area flatness PCB according to any one of claims 1 to 9.

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