A stepped circuit board and its manufacturing method, and double-layer adhesive tape

Abstract

The present invention relates to the field of PCB technology, and discloses a stepped circuit board and its manufacturing method and double-layer tape. The manufacturing method comprises: pasting a double-layer tape on the target area of ​​a designated core board; the designated core board is a core board located at the bottom of the step groove to be manufactured, and the target area is located in the orthographic projection area of ​​the step groove and is smaller than the orthographic projection area by a preset size on one side; the double-layer tape comprises a first PI layer, a first adhesive layer, a second PI layer and a second adhesive layer stacked in sequence from top to bottom, and the first adhesive layer has a greater adhesive strength than the second adhesive layer; the double-layer tape is pressed at high temperature to make the first adhesive layer melt and flow to seal the outer edges of the second PI layer and the second adhesive layer; the designated core board is pressed with other core boards to form a multi-layer board by using an adhesive sheet; after controlled depth milling, the cover is opened and the double-layer tape is removed. The present invention can effectively avoid the risks of glue overflow, liquid medicine infiltration and tape falling off, and greatly reduce the difficulty of removing the tape.

Description

Technical Field

[0001] The present invention relates to the technical field of PCB (Printed Circuit Board), and in particular to a stepped circuit board and a manufacturing method thereof, and a double-layer adhesive tape. Background Art

[0002] With the upgrading of market demand, PCB is developing towards thinness, high density, three-dimensional structure and other design directions under the premise of meeting the good electrical and thermal performance of electronic products. Stepped circuit board has become an important development direction, which has a wide range of applications in three-dimensional assembly, reducing the assembly volume of electrical equipment and special electrical performance.

[0003] At present, tape is usually used to make stepped circuit boards. The production method is as follows:

[0004] On the core board with the groove bottom pattern made, a protective tape is pasted on the surface of the groove bottom pattern area; then the core board pasted with the protective tape is laminated with other core boards to form a multi-layer board; then the step groove making area of ​​the multi-layer board is depth-controlled milling, and finally the cover is opened and the protective tape on the groove bottom is removed.

[0005] This manufacturing process is a highly applicable process. The protective tape used is used to protect the bottom pattern of the groove to prevent the adhesive sheet from melting and flowing to the surface of the bottom pattern of the groove during high-temperature lamination. However, there are currently two types of protective tapes commonly used: low-viscosity tape and high-viscosity tape. These two types of tapes each have their own scope of application, and at the same time have certain limitations, making it difficult to promote their use in large quantities, as follows:

[0006] Low-viscosity tape is only suitable for thin copper circuit patterns, but not for thick copper circuit patterns. This is because when the circuit pattern is thick, low-viscosity tape is prone to insufficient filling of the circuit, resulting in the risk of glue overflow, solution infiltration, and tape falling off. High-viscosity tape, however, is difficult to open due to its strong viscosity and is difficult to clean. Summary of the invention

[0007] The object of the present invention is to provide a stepped circuit board and a manufacturing method thereof, and a double-layer adhesive tape, so as to simultaneously overcome the defects of the existing adhesive tape, namely, insufficient filling and difficulty in removal.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] A method for manufacturing a stepped circuit board, comprising:

[0010] Apply double-layer tape to the target area of ​​the designated core board after the groove bottom pattern is made;

[0011] Wherein, the designated core board is the first core board located at the bottom layer of the step groove to be made, the target area is located within the orthographic projection area of ​​the step groove and is smaller than the orthographic projection area by a preset size on one side; the double-layer adhesive tape includes a first PI layer, a first bonding layer, a second PI layer and a second bonding layer stacked in sequence from top to bottom, and the bonding strength of the first bonding layer is greater than the bonding strength of the second bonding layer;

[0012] Pressing the double-layer adhesive tape at high temperature to make the first adhesive layer melt and flow to seal the second PI layer and the outer edge of the second adhesive layer;

[0013] By utilizing the melting flow of the bonding sheet under high temperature and high pressure, the designated core board and other core boards constituting the circuit board are laminated and pressed in a preset order to form a multilayer board with preset layers;

[0014] After depth-controlled milling is performed on the step groove manufacturing area of ​​the multilayer board, the cover is opened and the double-layer adhesive tape is removed.

[0015] Optionally, the method further comprises: before laminating the stacked plates, making a groove for filling the flow glue on the surface of the double-layer tape, wherein the depth of the groove does not exceed the depth of the second PI layer;

[0016] When the cover is opened, the substrate in the step groove manufacturing area and the double-layer adhesive tape adhered to the bottom of the substrate are removed together.

[0017] Optionally, the cross section of the groove is a cross-shaped structure.

[0018] Optionally, the method of applying a double layer of adhesive tape to a target area of ​​a designated core board comprises:

[0019] Firstly, a low-viscosity tape is pasted on the designated core board, and then a high-viscosity tape is pasted on the surface of the low-viscosity tape;

[0020] The covering sizes of the low-viscosity tape and the high-viscosity tape are both larger than the size of the target area, the low-viscosity tape includes the second PI layer and the second adhesive layer stacked together; the high-viscosity tape includes the first PI layer and the first adhesive layer stacked together;

[0021] After the lamination is completed, the low-viscosity tape and the high-viscosity tape are subjected to laser ablation to remove the redundant portions of the low-viscosity tape and the high-viscosity tape outside the target area.

[0022] Optionally, the thickness of the high-viscosity tape is greater than the thickness of the low-viscosity tape.

[0023] Optionally, the method further includes: before laminating the stacked boards, performing a slit treatment on the adhesive sheet stacked between the double-layer tape and other adjacent core boards, wherein the slit is located above the edge of the first PI layer.

[0024] A double-layer adhesive tape comprises: a first PI layer, a first adhesive layer, a second PI layer and a second adhesive layer stacked in sequence from top to bottom;

[0025] The bonding strength of the first bonding layer is greater than that of the second bonding layer, and outer edges of the second PI layer and the second bonding layer are sealed by the first bonding layer.

[0026] Optionally, a groove for filling the flowing glue is made on the surface of the double-layer tape, and the depth of the groove does not exceed the depth of the second PI layer.

[0027] Optionally, the cross section of the groove is a cross-shaped structure.

[0028] A stepped circuit board is manufactured according to any of the above methods for manufacturing a stepped circuit board.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] In the embodiment of the present invention, a double-layer tape with a special structure is realized by combining a traditional low-viscosity tape and a high-viscosity tape, and the double-layer tape is applied to the surface of the groove bottom pattern. Since the first adhesive layer of the high-viscosity tape covers the entire groove bottom area, and the edge area around the groove bottom area is attached to the high-viscosity tape, and the high-viscosity tape has a strong filling ability, compared with the traditional method of covering the entire groove bottom with a low-viscosity tape, regardless of whether the thickness of the groove bottom pattern is thin or thick, the risks of glue overflow, liquid medicine infiltration and tape falling off can be effectively avoided;

[0031] At the same time, after opening the cover, the high-viscosity tape in the double-layer tape is only adhered to the edge areas around the bottom of the groove, and the low-viscosity tape is adhered to the larger middle area of ​​the bottom of the groove. The low-viscosity tape is easy to remove due to its low viscosity. Therefore, compared with the traditional method of covering the entire bottom of the groove with high-viscosity tape, the difficulty of removing the tape can be greatly reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0033] Figure 1A flow chart of a method for manufacturing a stepped circuit board provided by an embodiment of the present invention;

[0034] Figures 2 to 8 A schematic diagram of the manufacturing process of a stepped circuit board provided in an embodiment of the present invention;

[0035] Fig. 9 A schematic cross-sectional view of a groove provided in an embodiment of the present invention;

[0036] Fig.10 A schematic structural diagram of a double-layer adhesive tape provided in an embodiment of the present invention.

[0037] Figure numerals: designated core board 1, double-layer adhesive tape 2, first PI layer 21, first bonding layer 22, second PI layer 23, second bonding layer 24, groove 25, bonding sheet 3, slit 31, other core board 4. DETAILED DESCRIPTION

[0038] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] To solve the defects of both traditional low-viscosity tape and high-viscosity tape, please refer to Figure 1 As shown, an embodiment of the present invention provides a method for manufacturing a stepped circuit board, comprising:

[0040] Step 101 , affixing a double-layer adhesive tape 2 to a target area of ​​a designated core board 1 where the groove bottom pattern is completed.

[0041] Among them, Figure 2 As shown, the designated core board 1 is the first core board located at the bottom layer of the step groove to be made according to the preset stacking order, and the local board area of ​​the core board will form the groove bottom of the step groove. The target area is located in the orthographic projection area of ​​the step groove to be made, and is slightly smaller than the orthographic projection area on one side (for example, 0-4 mil smaller on one side).

[0042] The double-layer adhesive tape 2 includes a first PI layer 21, a first adhesive layer 22, a second PI layer 23, and a second adhesive layer 24 stacked in sequence from top to bottom, and the bonding strength of the first adhesive layer 22 is greater than the bonding strength of the second adhesive layer 24. Figure 3 shown.

[0043] The stacked first PI layer 21 and the first adhesive layer 22 can be regarded as high-viscosity tapes, and the stacked second PI layer 23 and the second adhesive layer 24 can be regarded as low-viscosity tapes.

[0044] Step 102 : Press the double-layer adhesive tape 2 at high temperature to make the first adhesive layer 22 melt and flow to seal the outer edges of the second PI layer 23 and the second adhesive layer 24 .

[0045] Specifically, high-temperature rapid pressing is performed under vacuum, the pressing time can be selected to be 2-5 minutes, and the pressing temperature can be selected to be 150-200 degrees Celsius.

[0046] Under the action of high temperature and high pressure, the first adhesive layer 22 with high viscosity is in a molten state and flows to the surrounding gaps under the action of gravity, thereby gradually covering the outer edge of the low-viscosity tape located below it; finally, after the first adhesive layer 22 is cured, the low-viscosity tape will be completely wrapped between the high-viscosity tape and the designated core board 1 to achieve a sealing effect, such as Figure 5 shown.

[0047] At the same time, it can be understood that after the first adhesive layer 22 is cured, the area of ​​the double-sided tape on the designated core board 1 will slightly exceed the target area and be basically consistent with the preset groove bottom area size. At this time, the edge area around the groove bottom is bonded with the high-viscosity tape, and the middle area is bonded with the low-viscosity tape.

[0048] Step 103, using the melt flow of the bonding sheet 3 under high temperature and high pressure, the designated core board 1 and other core boards 4 constituting the circuit board are laminated in a preset order to form a multilayer board with preset layers. The states before and after lamination are as follows: Figure 6 and Figure 7 shown.

[0049] During the high-temperature pressing process of this step, since the first adhesive layer 22 of the high-viscosity tape covers the entire bottom area of ​​the groove, and the edge areas around the bottom area of ​​the groove are attached to the high-viscosity tape, and the high-viscosity tape has a strong filling ability, no matter whether the thickness of the bottom pattern of the groove is thin or thick, the risks of glue overflow, drug penetration and tape falling off can be effectively avoided.

[0050] Step 104: After depth-controlled milling is performed on the step groove production area of ​​the multilayer board, the cover is opened and the double-layer tape 2 is removed. The obtained step-type circuit board is as follows: Figure 8 shown.

[0051] In this step, the depth of the controlled milling can be above the double-layer tape 2. After opening the cover, the high-viscosity tape in the double-layer tape 2 is only attached to the edge areas around the bottom of the groove, and the low-viscosity tape is attached to the larger middle area of ​​the bottom of the groove. The low-viscosity tape is easy to remove due to its low viscosity. Therefore, compared with the traditional method of covering the entire bottom of the groove with high-viscosity tape, the difficulty of removing the tape can be greatly reduced.

[0052] In summary, in the embodiment of the present invention, a double-layer tape 2 with a special structure is realized by combining traditional low-viscosity tape and high-viscosity tape. The double-layer tape 2 is applied to the surface of the groove bottom pattern, which can not only effectively reduce the risks of glue overflow, drug penetration and tape falling off, but also can be easily removed after opening the cover to avoid residual glue on the surface of the pattern.

[0053] In order to further simplify the removal operation of the double-sided tape, the method for manufacturing a stepped circuit board provided in an embodiment of the present invention may also include: before laminating the stacked boards, making a groove 25 for filling the flow glue on the surface of the double-layer tape 2, and the depth of the groove 25 does not exceed the depth of the second PI layer 23; when opening the cover, the substrate in the step groove manufacturing area and the double-layer tape 2 adhered to the bottom of the substrate are removed.

[0054] Since a groove 25 is provided on the surface of the double-sided tape in the overlapping area of ​​the low-viscosity tape and the high-viscosity tape, during the lamination process, the adhesive sheet 3 between the double-sided tape and the other core boards 4 immediately above it will melt and flow into the groove 25, thereby enhancing the bonding strength between the substrate and the double-sided tape in the step groove manufacturing area, so that the substrate and the double-layer tape 2 can be removed together during the opening process, simplifying the removal operation and reducing the difficulty.

[0055] In this embodiment, the groove 25 can be any shape. For example, Fig. 9 As shown, the cross section of the groove 25 is a cross-shaped structure. Since the cross-shaped structure is a cross structure, it is easier to improve the bonding strength between the two compared with a strip-shaped structure.

[0056] It should be noted that in the above step 101, a double-sided tape of appropriate size can be pre-made and applied to the target area, or a larger double-sided tape can be applied to the target area and then the excess part can be removed. Compared with the former, the latter method can be more conducive to improving control accuracy.

[0057] Exemplarily, a method for applying a double-layer adhesive tape 2 to a target area of ​​a designated core board 1 includes:

[0058] First, a low-viscosity tape is applied to the designated core board 1, and then a high-viscosity tape is applied to the surface of the low-viscosity tape; wherein, the covering sizes of the low-viscosity tape and the high-viscosity tape are both larger than the size of the target area; to ensure the sealing effect, preferably, the thickness of the high-viscosity tape is greater than the thickness of the low-viscosity tape.

[0059] After the lamination is completed, the low-viscosity tape and the high-viscosity tape are laser ablated to remove the excess portions of the low-viscosity tape and the high-viscosity tape outside the target area.

[0060] This method can effectively ensure the accuracy of the laminating position and size of the low-viscosity tape and the high-viscosity tape, and ultimately obtain low-viscosity tape and high-viscosity tape of the same size as the target area.

[0061] In other embodiments, a laser ablation method may be used in stages to obtain low-viscosity tape and high-viscosity tape with slightly different sizes. However, in order to ensure the lamination effect and avoid the phenomenon of uneven lamination due to the first PI layer 21 of the high-viscosity tape being suspended (when the size of the high-viscosity tape is slightly larger than that of the low-viscosity tape, the edge portion will be suspended), it is preferred that the size of the high-viscosity tape does not exceed that of the low-viscosity tape.

[0062] In this embodiment, the overall thickness of the double-sided tape selected is set according to the thickness of the medium (adhesive sheet 3) between the groove bottom pattern and the upper core plate. Generally, the overall thickness of the double-sided tape = the medium thickness + 25 microns. Based on this, for example, the thickness of the high-viscosity tape is 80-150 microns (the first PI layer 21 is 55-120 microns, and the first adhesive layer 22 is 25-30 microns), and the thickness of the low-viscosity tape is 35 microns (the second PI layer 23 is 25 microns, and the second adhesive layer 24 is 10 microns).

[0063] In addition, before laminating the stacked boards, the bonding sheet 3 stacked between the double-layer adhesive tape 2 and other adjacent core boards 4 is pre-slit, and the slit 31 is located above the edge of the first PI layer 21. This slit operation can effectively reduce the difficulty of opening the cover.

[0064] like Fig.10 As shown, an embodiment of the present invention also provides a double-layer tape 2, comprising: a first PI layer 21, a first adhesive layer 22, a second PI layer 23 and a second adhesive layer 24 stacked in sequence from top to bottom; the bonding strength of the first adhesive layer 22 is greater than the bonding strength of the second adhesive layer 24, and the outer edges of the second PI layer 23 and the second adhesive layer 24 are sealed by the first adhesive layer 22.

[0065] Furthermore, a groove 25 for filling the flowing glue is made on the surface of the double-layer tape 2, and the depth of the groove 25 does not exceed the depth of the second PI layer 23. The groove 25 can be specifically any shape. Exemplarily, the cross section of the groove 25 is a cross-shaped structure, which is easier to improve the bonding strength compared with the strip structure.

[0066] The double-layer adhesive tape 2 is made by combining a traditional low-viscosity adhesive tape and a high-viscosity adhesive tape in a special way, which can ensure good bonding strength and reduce the difficulty of removing the adhesive tape due to its strong viscosity.

[0067] Correspondingly, an embodiment of the present invention further provides a stepped circuit board, which is manufactured according to the above step circuit board manufacturing method. The stepped circuit board has a good-quality groove bottom pattern due to the use of a special double-sided tape.

[0068] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for manufacturing a stepped circuit board, characterized in that: include: Apply double-layer tape to the target area of ​​the designated core board after the groove bottom pattern is made; Wherein, the designated core board is the first core board located at the bottom layer of the step groove to be made, the target area is located within the orthographic projection area of ​​the step groove and is smaller than the orthographic projection area by a preset size on one side; the double-layer adhesive tape includes a first PI layer, a first bonding layer, a second PI layer and a second bonding layer stacked in sequence from top to bottom, and the bonding strength of the first bonding layer is greater than the bonding strength of the second bonding layer; Pressing the double-layer adhesive tape at high temperature to make the first adhesive layer melt and flow to seal the second PI layer and the outer edge of the second adhesive layer; By utilizing the melting flow of the bonding sheet under high temperature and high pressure, the designated core board and other core boards constituting the circuit board are laminated and pressed in a preset order to form a multilayer board with preset layers; After depth-controlled milling is performed on the step groove production area of ​​the multilayer board, the cover is opened and the double-layer tape is removed; It also includes: before laminating the stacked boards, making a groove for filling the flow glue on the surface of the double-layer tape, wherein the depth of the groove does not exceed the depth of the second PI layer; When the cover is opened, the substrate in the step groove manufacturing area and the double-layer adhesive tape adhered to the bottom of the substrate are removed together.

2. The method for manufacturing a stepped circuit board according to claim 1, characterized in that: The cross section of the groove is a cross-shaped structure.

3. The method for manufacturing a stepped circuit board according to claim 1, characterized in that: The method of applying a double-layer adhesive tape to a target area of ​​a designated core board after the groove bottom pattern is produced comprises: Firstly, a low-viscosity tape is pasted on the designated core board, and then a high-viscosity tape is pasted on the surface of the low-viscosity tape; The covering sizes of the low-viscosity tape and the high-viscosity tape are both larger than the size of the target area, the low-viscosity tape includes the second PI layer and the second adhesive layer stacked together; the high-viscosity tape includes the first PI layer and the first adhesive layer stacked together; After the lamination is completed, the low-viscosity tape and the high-viscosity tape are subjected to laser ablation to remove the redundant portions of the low-viscosity tape and the high-viscosity tape outside the target area.

4. The method for manufacturing a stepped circuit board according to claim 1, characterized in that: The thickness of the first adhesive layer is greater than the thickness of the second adhesive layer.

5. The method for manufacturing a stepped circuit board according to claim 1, characterized in that: Also includes: Before the laminated boards are pressed together, the adhesive sheet stacked between the double-layer adhesive tape and other adjacent core boards is subjected to a slit process, wherein the slit is located above the edge of the first PI layer.

6. A double-layer adhesive tape, characterized in that: include: A first PI layer, a first bonding layer, a second PI layer and a second bonding layer are stacked in sequence from top to bottom; The bonding strength of the first bonding layer is greater than the bonding strength of the second bonding layer, and the outer edges of the second PI layer and the second bonding layer are sealed by the first bonding layer; A groove for filling the flowing glue is made on the surface of the double-layer tape, and the depth of the groove does not exceed the depth of the second PI layer.

7. The double-layer adhesive tape according to claim 6, characterized in that: The cross section of the groove is a cross-shaped structure.

8. A stepped circuit board, characterized in that: The stepped circuit board is manufactured according to the method for manufacturing a stepped circuit board according to any one of claims 1 to 5.

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