Method for manufacturing flexible circuit board with high-precision solder resist pattern

Abstract

The invention discloses a method for manufacturing a flexible circuit board with a high-precision solder resist pattern, which comprises the following steps of: taking a first single-sided flexible copper-clad plate, manufacturing a first windowing pattern, manufacturing a solder resist pattern and a rear circuit pattern which comprise an IC (integrated circuit) bonding pad pattern and are positioned between opposite bonding pads of the IC bonding pad pattern, taking a second single-sided flexible copper-clad plate and a second circuit pattern, and manufacturing a second windowing pattern and a rear circuit pattern which are positioned between the bonding pads of the IC bonding pad pattern; making discontinuous through grooves along the edge of the second circuit pattern, forming a connecting position, aligning, pressing, cutting off the connecting position, and uncovering to form the flexible circuit board; through a mode of firstly manufacturing the solder resist pattern before manufacturing the circuit pattern and then manufacturing the first circuit pattern, the solder resist pattern is high in precision, thickness and flatness, the second single-sided flexible copper-clad plate is used for manufacturing the second circuit pattern, protection and release effects on the solder resist pattern are achieved, pressing damage is prevented, the processing precision of the cover film is improved, and the production efficiency is improved. The whole processing flow is matched before and after, and the manufacturing quality of the high-precision flexible circuit board is improved.

Description

Technical Field

[0001] The invention relates to the field of circuit board processing, and in particular to a method for manufacturing a flexible circuit board with a high-precision solder resist pattern. Background Art

[0002] When some IC chips are soldered, the height of the chip body is higher than the height of the pins, while the height of the IC pad corresponding to the circuit board surface is higher than the height of the empty space in the middle of the IC pad (corresponding to the chip body). Therefore, after soldering, there is a large gap between the chip body and the empty space, and the chip body is in an overhead state. This affects the stability of the chip when used and is prone to problems such as solder joint cracking. Therefore, it is necessary to make a filling layer in the empty space so that the chip body can be "lifted up" after soldering to improve the stability of the chip.

[0003] For high-precision flexible circuit boards with the above characteristics, there are currently two methods for making the filling layer: A covering film is made for the area and attached together with the covering film on the surface to form a filling layer.

[0004] The problem with this production method is that the covering film at the empty space is in an independent state and generally needs to be attached independently, which makes it difficult to form a reference for alignment. In addition, due to its small size and high precision, it is easy to cause problems such as deviation and displacement during attachment.

[0005] After the flexible circuit board is manufactured, a filling layer is formed by manufacturing a solder resist layer at the position.

[0006] The problem with this production method is that for high-precision flexible circuit boards, on the one hand, the space in the middle of the high-precision IC pads is small, and the production of the solder mask requires high processing accuracy such as alignment, exposure, and cover film lamination; on the other hand, the flexible circuit board is relatively soft, and the production of the solder mask is prone to problems such as deviation and unevenness.

[0007] Based on the above background and problems, it is necessary to provide a method for manufacturing a flexible circuit board with a high-precision solder mask pattern. Summary of the invention

[0008] The present invention aims at the problem that the flexible circuit board in the middle of the IC pad in the prior art has the problem that when the filling layer is made of a covering film layer, there is a problem that it is easy to deviate and shift. When the filling layer is made of a solder mask layer, there is a problem that it is easy to deviate and be uneven. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern is proposed: S10: Take a first single-sided flexible copper-clad laminate, make a first window pattern on the copper layer, make ink at the position of the first window pattern, and bake and solidify it to form a solder resist pattern; then make a first circuit pattern, including making an IC pad pattern; the formation range of the solder resist pattern and the IC pad pattern is the surface pattern area, and the solder resist pattern is located between the opposite pads of the IC pad pattern; the circuit pattern core board is formed as a whole; S20: Take a second single-sided flexible copper-clad laminate, and make a second circuit pattern on the copper layer, wherein the size of the second circuit pattern covers the surface pattern area; make discontinuous through grooves on the insulating dielectric layer of the second single-sided flexible copper-clad laminate along the edge of the second circuit pattern, wherein the non-through groove positions of the discontinuous through grooves form connection positions; and form a covering film pattern board as a whole; S30: aligning the circuit pattern core board and the cover film pattern board, wherein the second circuit pattern corresponds to and is arranged relative to the surface pattern area; and then laminating them to form a pressed board; S40: cutting off the connection position of the pressing plate and removing the cover to form the flexible circuit board.

[0009] Furthermore, before making the ink, the first window pattern position is subjected to plasma treatment.

[0010] Furthermore, the circuit pattern forming core board further includes: after the baking and curing, laser ablation of the solder resist pattern along the edge of the first window pattern is performed to ablate the solder resist pattern that overflows the first window pattern.

[0011] Furthermore, after the laser ablation, alkali washing and water washing are performed.

[0012] Furthermore, after the laser ablation is performed, micro-etching is performed.

[0013] Furthermore, the micro-etched copper layer has a thickness of 5 μm to 8 μm.

[0014] Furthermore, the width of the connection site is 50 μm to 2.0 mm.

[0015] Furthermore, the second single-sided flexible copper-clad laminate comprises an adhesive layer, and the adhesive layer is located between the copper layer and the insulating medium layer.

[0016] Furthermore, the copper layer of the second single-sided flexible copper clad laminate has a thickness of 5 μm to 15 μm.

[0017] Furthermore, the connection position of the pressed plate is cut off by laser ablation, and the laser ablation is followed by alkali washing and water washing.

[0018] The technical solution of the present invention makes a solder resist pattern before making a circuit pattern, and then makes the first circuit pattern, so that the solder resist pattern can be limited to the range of the first window pattern without the need for alignment, exposure, development and other processes, and the thickness of the solder resist pattern can be limited to the thickness of the copper layer, and a smoother surface effect is formed, which effectively improves the processing accuracy and effect of the solder resist pattern; by using the second single-sided flexible copper-clad laminate to make the covering film, it can protect the surface pattern area during the pressing process, and at the same time play a more important release role to prevent the solder resist layer from being adhered or damaged during pressing, and the second circuit pattern can be used to form a more high-precision alignment effect, forming an overall covering film layer alignment accuracy higher than the alignment accuracy of the window covering film, thereby improving the processing quality of the high-precision circuit board; the overall production process forms a high-precision production of the solder resist pattern, and the processing process of using the second circuit pattern to protect the solder resist pattern to press the covering film layer forms a front-to-back processing flow, forming an innovation in the overall process flow, and improving the production quality of the high-precision flexible circuit board. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] 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 the structures shown in these drawings without paying creative work.

[0020] Figure 1 The main process flow chart of the embodiment of the present invention is included; Figure 2 Schematic diagram of the cross-sectional structure of the windowed flexible core panel of this embodiment; Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of the AA surface; Figure 4 Schematic diagram of the cross-sectional structure of the ink layer core plate of this embodiment; Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure of the BB surface; Figure 6 Schematic diagram of the planar structure of the laser ablation solder resist pattern of this embodiment; Figure 7 is a schematic diagram of the planar structure of another ink layer core plate of this embodiment; Figure 8 for Figure 7 Schematic diagram of the cross-sectional structure of the CC surface; Fig. 9 Schematic diagram of the planar structure of the circuit pattern core board of this embodiment; Fig.10 for Fig. 9 Schematic diagram of the cross-sectional structure of the DD surface; Fig.11 is a schematic diagram of the planar structure of the graphic cover film of this embodiment; Fig.12 for Fig.11 Schematic diagram of the cross-sectional structure of the EE surface; Fig.13 is a schematic diagram of the cross-sectional structure of the pressed plate of this embodiment; Fig.14 is a schematic diagram of the planar structure of the flexible circuit board of this embodiment; Fig.15 for Fig.14 Schematic diagram of the cross-sectional structure of the FF surface.

[0021] Description of Figure Numbers:

[0022] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0023] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments 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.

[0024] It should be noted that all directional indications in the embodiments of the present invention (such as up, down, left, right, front, back, inside, outside...) are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0025] In addition, in the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0026] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0027] See also Figure 1 ; Figure 1 The main process flow chart included in the embodiment of the present invention.

[0028] The method for manufacturing a flexible circuit board with a high-precision solder mask pattern according to an embodiment of the present invention comprises: Figure 1 The main production process is described in detail step by step as follows.

[0029] See also Figures 2 to 10 ; Figure 2 Schematic diagram of the cross-sectional structure of the windowed flexible core panel of this embodiment; Figure 3 for Figure 2 Schematic diagram of the cross-sectional structure of the AA surface; Figure 4 Schematic diagram of the cross-sectional structure of the ink layer core plate of this embodiment; Figure 5 for Figure 4 Schematic diagram of the cross-sectional structure of the BB surface; Figure 6 Schematic diagram of the planar structure of the laser ablation solder resist pattern of this embodiment; Figure 7 is a schematic diagram of the planar structure of another ink layer core plate of this embodiment; Figure 8 for Figure 7 Schematic diagram of the cross-sectional structure of the CC surface; Fig. 9 Schematic diagram of the planar structure of the circuit pattern core board of this embodiment; Fig.10 for Fig. 9 Schematic diagram of the cross-sectional structure of the DD surface.

[0030] Step S10: Take a first single-sided flexible copper-clad laminate, which is composed of a copper layer and a first flexible dielectric layer 130, make a first window pattern 110 on the copper layer, form a window copper layer 120 on the copper layer, and form a window flexible core board 10 ( Figure 2 , Figure 3 ); Ink is made toward the first window opening pattern 110, and is baked and cured to form a solder resist pattern 210, and the ink layer core board 20 is formed as a whole ( Figure 4 , Figure 5 ); then make the first circuit pattern 310, including making IC pad pattern 3110; the range of formation of solder resist pattern 210 and IC pad pattern 3110 is surface pattern area 320, solder resist pattern 310 is located between the opposite pads of IC pad pattern 3110; the circuit pattern core board 30 is formed as a whole.

[0031] The first window pattern 110 is first made, and then ink is directly made in the area to form a solder resist pattern 210. There is no process processing such as alignment, exposure, and development, which avoids the superposition of factors such as alignment error, exposure error, and material expansion and contraction error when making the solder resist pattern 210 (after making the first circuit pattern 310), resulting in problems such as solder resist deviation. That is, this method adopts the method of first making the solder resist pattern 210 and then making the first circuit pattern 310, which is different from the method of first making the first circuit pattern 310 and then making the solder resist pattern 210 in the prior art; and the solder resist pattern 210 is made between the opposite pads of the IC pad pattern 3110, that is, corresponding to the area where the chip body is located after the IC chip is welded, so as to support the IC chip body.

[0032] In this embodiment, before the ink is prepared, the position of the first window pattern 110 is subjected to plasma treatment.

[0033] The position of the first window pattern 110, that is, the position where the copper layer is removed to expose the insulating dielectric layer of the first single-sided flexible copper-clad laminate, that is, the first flexible dielectric layer 130 (generally a polyimide material) is exposed, is subjected to plasma treatment, which can effectively improve the material activity of the first flexible dielectric layer 130 at the position of the first window pattern 110, and improve the uniform roughness of the material surface, thereby improving the bonding force between the ink and the material, and preventing problems such as ink falling off.

[0034] Please continue reading Figure 6 and Figure 7 .

[0035] In this embodiment, forming the circuit pattern core board further includes: after baking and curing, laser ablation of the solder resist pattern 210 along the edge of the first window pattern 110 is performed to ablate the solder resist pattern 210 that overflows the first window pattern 110.

[0036] The ink is generally produced by silk screen printing. In the present embodiment, the ink can be produced by producing a dot screen, and a screen window pattern is produced at a position of the screen corresponding to the first window pattern 110. During silk screen printing, the ink leaks from the screen window pattern to the position of the first window pattern 110, and the ink generally diffuses and overflows to a range outside the first window pattern 110 by silk screen printing. Therefore, laser ablation can be optionally used to cut off the overflowed solder resist pattern 210, and only the solder resist pattern 210 in the first window pattern 110 is retained. Since there is a copper layer under the overflowed ink, the laser ablation energy can be adjusted to an energy range that burns the solder resist pattern 210 without damaging the copper layer.

[0037] Furthermore, after laser ablation, alkali washing and water washing are performed.

[0038] After laser ablation, impurities such as carbon powder will be produced, which can be cleaned with alkaline solutions such as KOH or NaOH and washed with DI water.

[0039] Furthermore, after laser ablation, micro-etching is performed, and further, the thickness of the micro-etched copper layer is 5 μm to 8 μm, forming another ink layer core board 20A.

[0040] After laser ablation, there may be solder resist pattern 210 still covering the surface of the copper layer in a microscopic state. The copper layer of a certain thickness is etched away by micro-etching to completely remove the solder resist pattern 210 covering the surface of the copper layer.

[0041] Therefore, it can be understood that the copper layer of the first single-sided flexible copper-clad laminate in this embodiment needs to be pre-increased by the thickness to be etched away at that location relative to the prior art, that is, pre-increased by 5μm to 8μm. The thickness is pre-increased first, and then etched at that location to form the copper thickness required for the first circuit pattern 310. The reason why laser ablation is used for processing is that the flexible circuit board is relatively soft and inconvenient to be polished and removed.

[0042] In this embodiment, the ink may preferably be a flexible solder resist ink, which is easy to match with the material of the flexible circuit board.

[0043] See also Figures 11 to 13 ; Fig.11 is a schematic diagram of the planar structure of the graphic cover film of this embodiment; Fig.12 for Fig.11 Schematic diagram of the cross-sectional structure of the EE surface.

[0044] Step S20: Take a second single-sided flexible copper-clad laminate, and make a second circuit pattern 410 on the copper layer, the size of which covers the surface pattern area 320; make discontinuous through grooves 430 on the insulating dielectric layer (i.e., the covering film layer 420) of the second single-sided flexible copper-clad laminate along the edge of the second circuit pattern 410, and form connecting positions 440 at the non-through groove positions of the discontinuous through grooves 430; and form a covering film pattern board 40 as a whole.

[0045] This embodiment adopts a second single-sided flexible copper-clad laminate to produce graphics, instead of directly using a covering film (with windows) for lamination, and uses the second circuit pattern 410 to protect the surface pattern area during the lamination process, and at the same time plays a more important release role to prevent the solder mask from being adhered or damaged during lamination. The second circuit pattern 410 can be used to form a more precise alignment effect, forming a higher alignment accuracy of the overall covering film layer 420 than the alignment accuracy of the covering film with windows, thereby improving the processing quality of high-precision circuit boards.

[0046] First, an intermittent through groove 430 is made to form a partial cut of the covering film layer corresponding to the second circuit pattern 410 to prevent subsequent simultaneous cutting, which would produce large laser ablation carbon powder and impurities, pollute the surface of the flexible circuit board, and cause short circuit and other hidden dangers. At the same time, a number of connection positions 440 are reserved to ensure the effective connection of the second circuit pattern 410 during pressing.

[0047] In this embodiment, the width of the connection position 440 is 50 μm to 2.0 mm; the connection position 440 is set to a suitable size according to the size of the pattern and application requirements to ensure that it can be connected.

[0048] In this embodiment, the second single-sided flexible copper-clad laminate comprises an adhesive layer, which is located between the copper layer and the insulating medium layer and is an acrylic adhesive layer or an epoxy resin adhesive layer.

[0049] The glue layer can effectively play a bonding role and form a difference in adhesion performance with the second circuit pattern 410, so that under the lamination condition, the glue layer effectively adheres while the second circuit pattern 410 does not adhere.

[0050] In this embodiment, the copper layer of the second single-sided flexible copper clad laminate (also the second circuit pattern 410 ) is 5 μm to 15 μm; the copper layer is only used for release and auxiliary alignment, so a thinner copper layer can meet application requirements.

[0051] See also Fig.13 ; Fig.13 It is a schematic diagram of the cross-sectional structure of the pressed plate of this embodiment.

[0052] Step S30: Align the circuit pattern core board 30 and the cover film pattern board 40, and arrange the second circuit pattern 410 correspondingly and opposite to the surface pattern area 320; and then press them together to form a press board 50; See also Fig.14 and Fig.15 ; Fig.14 is a schematic diagram of the planar structure of the flexible circuit board of this embodiment; Fig.15 for Fig.14 Schematic diagram of the cross-sectional structure of the FF surface.

[0053] Step S40: The connection position 440 of the pressing plate 50 is cut off, and the cover is opened, so that the surface pattern area 320 forms a pattern window 610, and the flexible circuit board 60 is formed.

[0054] In this embodiment, the connection position 440 of the pressing plate 50 is cut off by laser ablation, and then alkali washing and water washing are performed.

[0055] After the pressing is completed, the connection position 440 is cut off through post-processing, and the cover can be removed to remove the second single-sided flexible copper clad board covering the surface of the surface pattern area to expose the solder mask pattern 210 and the IC pad pattern 3110.

[0056] It is worth noting that due to the actual design and processing of circuit boards, the actual structure diagram and the thickness of each layer, line width and other dimensions are all in the micron level. For example, the thickness of each layer is generally 5μm to 50μm. If the drawings in the specification are made according to the actual proportion, there will be a problem of unclear drawings. Therefore, in order to more clearly show the implementation process of the manufacturing method, the drawings of this embodiment are all schematic diagrams that enlarge the technical features, which do not represent the size of the actual structure diagram, nor do they represent enlarged views of the actual structure diagram in proportion.

[0057] The above are only preferred embodiments of the present invention, and are not intended to limit the patent scope of the present invention. All equivalent structural changes made using the contents of the present invention's specification and drawings, or directly / indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern, characterized in that: S10: Take a first single-sided flexible copper-clad laminate, make a first window pattern on the copper layer, make ink at the position of the first window pattern, and bake and solidify it to form a solder resist pattern; then make a first circuit pattern, including making an IC pad pattern; the formation range of the solder resist pattern and the IC pad pattern is the surface pattern area, and the solder resist pattern is located between the opposite pads of the IC pad pattern; the circuit pattern core board is formed as a whole; S20: Take a second single-sided flexible copper-clad laminate, and make a second circuit pattern on the copper layer, wherein the size of the second circuit pattern covers the surface pattern area; make discontinuous through grooves on the insulating dielectric layer of the second single-sided flexible copper-clad laminate along the edge of the second circuit pattern, wherein the non-through groove positions of the discontinuous through grooves form connection positions; and form a covering film pattern board as a whole; S30: aligning the circuit pattern core board with the cover film pattern board, wherein the second circuit pattern corresponds to and is arranged relative to the surface pattern area; Then press together to form a pressed board; S40: cutting off the connection position of the pressing plate and removing the cover to form the flexible circuit board.

2. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1, characterized in that: Before making the ink, the first window pattern position is subjected to plasma treatment.

3. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1, characterized in that: The circuit pattern forming core board further includes: after the baking and curing, laser ablation of the solder resist pattern along the edge of the first window pattern is performed to ablate the solder resist pattern that overflows the first window pattern.

4. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 3, characterized in that: After the laser ablation, alkali washing and water washing are performed.

5. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 3 or 4, characterized in that: After the laser ablation is performed, micro-etching is performed.

6. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1, characterized in that: The micro-etched copper layer has a thickness of 5 μm to 8 μm.

7. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1, characterized in that: The width of the connection site is 50 μm to 2.0 mm.

8. The method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1, characterized in that: The second single-sided flexible copper-clad laminate comprises an adhesive layer, and the adhesive layer is located between the copper layer and the insulating medium layer.

9. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1 or 8, characterized in that: The copper layer of the second single-sided flexible copper clad laminate has a thickness of 5 μm to 15 μm.

10. A method for manufacturing a flexible circuit board with a high-precision solder mask pattern as claimed in claim 1 or 8, characterized in that: The connection position of the pressing plate is cut off by laser ablation, and the laser ablation is followed by alkali washing and water washing.

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