Circuit board pattern manufacturing method based on mSAP process improvement and PCB manufactured by circuit board pattern manufacturing method

Abstract

The invention discloses a circuit board pattern manufacturing method based on mSAP process improvement and a PCB manufactured by the circuit board pattern manufacturing method, and relates to the technical field of PCB manufacturing. According to the method provided by the invention, when a conventional mSAP flow pattern is exposed, the linear edge of a required pattern is extended towards the outside of a PCB contour in parallel and exceeds a contour line, and after a first edge pattern is formed, the extended part exceeding the contour is milled away in advance along the edge of the PCB contour; a second edge pattern (the first edge pattern does not exceed the remaining part of the contour line) of which one straight line edge coincides (is tangent) with the contour edge of the PCB can be formed, and finally, a copper layer of the second edge pattern is etched away through small etching amount of flash etching to expose a base material; therefore, the requirements that the distance between the required pattern edge and the PCB contour edge is smaller than 0.025 mm and the pattern edge and the PCB contour edge are not tangent (copper is not exposed) can be met.

Description

Technical Field

[0001] This invention relates to the field of PCB manufacturing technology, specifically to a method for fabricating circuit board patterns based on an improved mSAP process and the PCB board manufactured therefrom. Background Technology

[0002] mSAP (Modified Semi-Additive Process) is a high-precision PCB (Printed Circuit Board) circuit pattern fabrication process, mainly including the following steps: Substrate preparation: Depositing a thin copper layer (1-3μm) on an insulating substrate through chemical or electroplating methods → Pattern transfer: Forming a precise circuit pattern through laser direct imaging (LDI) or photolithography → Selective thickening: Electroplating a thicker copper layer (up to 25μm) only in areas requiring conductivity → Etching removal: Dissolving the unprotected thin copper layer, preserving the high-precision circuitry. Typically, mSAP is performed on large-size substrates. After the pattern is formed using mSAP, the large substrate needs to be cut to the appropriate size to obtain the finished patterned PCB board. However, the current process for cutting large-size substrates mainly involves edge routing. The instruments used in edge routing have limited precision. To avoid damaging the patterns on the circuit board during routing, technicians typically leave a safety distance of at least 0.125mm between the edge of the pattern formed by mSAP and the location on the large-size substrate to be cut (the cutting location will later become the outline edge of the finished PCB board, generally referred to as the outer edge). Even when using a high-precision CCD optical router (which uses pattern target point positioning processing, reducing the alignment tolerance to + / -0.050mm) instead of a conventional router, a safety distance of at least 0.075mm is still required in this process (based on the router's alignment tolerance of + / -0.050mm, the pattern itself formed by mSAP also has a dimensional tolerance of + / -0.025mm from its center to its edge). Given the increasingly refined nature of current PCB manufacturing processes, meeting the requirement of small-pitch, high-precision spacing of less than 0.025mm between the edge of the circuit pattern and the outer edge of the circuit board is a pressing problem that needs to be solved. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a circuit board pattern fabrication method based on an improved mSAP process.

[0004] The above-mentioned objective of this invention is achieved through the following technical solution: A method for fabricating circuit board patterns based on an improved mSAP process includes the following steps: S1. Mark the finished PCB outline on a large-size copper-clad laminate, such that the finished PCB outline contains at least one straight edge; cover the copper surface of the large-size copper-clad laminate with a photosensitive dry film, and crosslink the photosensitive dry film at specific locations through exposure, so that the other part of the dry film that is not crosslinked forms a first pattern; the first pattern includes a required pattern and a first edge pattern, wherein the side of the required pattern closest to the straight edge of the finished PCB outline forms a required pattern edge, the required pattern edge is a straight line and parallel to the straight edge of the finished PCB outline; the first edge pattern is rectangular and one of its rectangular sides coincides with the edge of the required pattern, the rectangular side is an overlapping side, and two parallel rectangular sides perpendicular to the overlapping side intersect perpendicularly with the straight edge in the finished PCB outline, so that the first edge pattern extends beyond the finished PCB outline; wash away the uncrosslinked dry film to expose the underlying copper surface, and deposit a first copper layer on the exposed copper surface, the pattern formed by the first copper layer being consistent with the first pattern; S2. Using a CCD router, perform the first router along the straight edge that intersects the two straight edges of the first edge graphic in the finished PCB board outline. After routerting the corresponding straight edge in the finished PCB board outline, the first router ends, resulting in a substrate to be cut with a second graphic on its surface. The second graphic includes a required graphic and a second edge graphic. The second edge graphic is a rectangle, one of which coincides with the edge of the required graphic, and the other rectangular edge parallel to this rectangular edge coincides with the straight edge of the finished PCB board outline that has been routerted. S3. Remove the photosensitive dry film on the substrate to be cut, remove the second edge pattern by flash etching, and then use a regular router to perform a second router, router out the remaining edge according to the outline of the finished PCB board, and you can get a circuit board with the required pattern printed on the surface.

[0005] Conventional mSAP processes first form patterns through exposure and copper plating, then directly remove the base copper on the substrate that does not need to form patterns through flash etching, and finally, the PCB board is obtained by routing along the outline marked on the large-size substrate. The circuit board patterning method based on the improved mSAP process provided by this invention, on the basis of conventional mSAP processes, extends the straight edges of the desired pattern outwards parallel to obtain a rectangular first edge pattern, forming a first pattern (including the desired pattern and the first edge pattern) that partially extends beyond the outline of the finished PCB board. Then, a high-precision CCD router is introduced to perform the first routing along the straight edges of the aforementioned outline. The routing stops after the straight edges are formed. At this point, the edge pattern in the second pattern contains a rectangular edge that coincides with the straight edge, which can serve a positioning function. After the first routing, the remaining processes (film removal, flash etching, and routing) are performed according to conventional procedures to obtain a circuit board with the desired pattern printed on its surface. The distance between the edge of the desired pattern on the circuit board and the edge of the circuit board outline is entirely determined by the flash etching step, i.e., removing the second edge pattern, thereby significantly reducing the distance between the pattern edge and the PCB outline edge. If the order of the first router and the formation of the first pattern is reversed, and the straight edge of the finished PCB board outline is routerd first, and then the corresponding pattern is exposed and deposited along the straight edge, the instruments used for exposure and deposition will still have alignment tolerance with the large-size copper-clad substrate (this is a defect of the instrument itself and cannot be avoided). Therefore, the effect of reducing the distance between the edge of the pattern and the edge of the PCB board outline of this invention cannot be obtained.

[0006] The method provided by this invention is applicable to any PCB board that requires reducing the distance between the straight edge of the required graphic and the outer contour edge of the straight PCB board.

[0007] It should be noted that the straight lines that overlap between the required graphic and the first edge graphic in this invention are not physical graphics, but rather boundaries that are artificially defined during the design of the first graphic.

[0008] Preferably, the rectangular side of the first edge graphic that coincides with the edge of the required graphic has a side length > 50 μm.

[0009] Preferably, the thickness of the first copper layer in step S1 is 18-26 μm.

[0010] In some embodiments, the deposition in step S1 can be performed by electroplating, chemical deposition, or other methods.

[0011] In some implementations, the required graphic may be a rectangle.

[0012] Preferably, in step S1, the first edge graphic portion that extends beyond the outline of the finished PCB board has a rectangular edge that does not intersect with the straight edge of the finished PCB board outline, and the distance between the rectangular edge of the first edge graphic portion that extends beyond the outline and the straight edge of the finished PCB board outline is ≥0.075 mm.

[0013] Preferably, step S1 further includes a positioning target in the first pattern.

[0014] More preferably, the positioning target is set at the edge of the SET or in the waste area.

[0015] More preferably, the positioning target is circular with a diameter of 1-2 mm.

[0016] By avoiding the set position of the positioning target during exposure, the photosensitive dry film at the target position is not cross-linked. The uncross-linked dry film is washed away to expose the copper surface below. The first copper layer is deposited on the exposed copper surface, so that a positioning target that can be recognized by the CCD can be further introduced into the first pattern.

[0017] Preferably, the photosensitive dry film in step S1 is a positive film dry film.

[0018] Preferably, the deposition in step S1 is performed by electroplating. The deposited patterned copper layer is formed by electroplating to create a copper layer pattern.

[0019] Preferably, the first milling step S2 is performed by first rough milling at a cutting speed of 0.1-0.3 m / min, followed by fine milling at a cutting speed of 0.5-0.7 m / min.

[0020] More preferably, the roughing is done with a milling cutter with a diameter of 0.6-0.8 mm, and the finishing is done with a milling cutter with a diameter of 0.5-0.7 mm.

[0021] Burrs and copper wires may remain on the edge of the PCB after routing, affecting the alignment accuracy of subsequent flash etching. Using the specific process flow of this invention for routing helps to further reduce the distance between the edge of the graphic and the outer contour of the PCB.

[0022] Preferably, the flash etching in step S3 is performed using a flash etchant, which includes a sulfuric acid-hydrogen peroxide etchant solution.

[0023] In this invention, one of the rectangular edges of the second edge pattern coincides with the straight edge of the finished PCB board outline that has been etched. Therefore, the first copper layer thickness edge of the second edge pattern directly contacts the flash etchant, resulting in a faster exchange rate of the flash etchant at this edge position and a better flash etch effect than other positions.

[0024] Preferably, the second milling step S3 is performed as follows: first, a first rough milling is performed at a speed of 5-20 mm / s, followed by a second rough milling at a speed of 0.1-1 mm / s, then a first fine milling is performed at a speed of 10-30 mm / s, and finally a second fine milling is performed at a speed of 1-5 mm / s.

[0025] More preferably, the second gong edge described in step S3 satisfies at least one of the following (a)-(d); (a) The first rough gonging is done using a gong cutter with a diameter of 1-1.5 mm; (b) The second roughing is done using a gong cutter with a diameter of 0.3-1 mm; (c) The first fine gonging is performed using a gong cutter with a diameter of 0.8-1.2 mm; (d) The second fine gonging is performed using a gong cutter with a diameter of 0.1-0.8 mm.

[0026] This invention also protects products made by the above method.

[0027] Compared with the prior art, the present invention has the following beneficial effects: In the conventional mSAP process for pattern exposure, this invention extends the straight edge of the desired pattern parallel to the outside of the PCB outline to form the first edge pattern. After forming the first edge pattern, the extended portion is pre-riveted along the edge of the PCB outline to form a second edge pattern in which one of the straight edges coincides with (is tangent to) the edge of the PCB outline. Finally, the copper layer of the second edge pattern is etched away by a small amount of flash etching to expose the substrate. This achieves the requirement that the distance from the edge of the desired pattern to the edge of the PCB outline is <0.025mm and that they are not tangent (no copper is exposed). Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the PCB prepared according to the present invention. The red part in the figure represents the required pattern.

[0029] Figure 2 This is a schematic diagram of a large-size copper-clad substrate with a first pattern on its surface obtained in step S1 of the present invention.

[0030] Figure 3 This is a schematic diagram of a large-size copper-clad substrate with corresponding straight lines in the finished product outline obtained in step S2 of the present invention.

[0031] Figure 4 This is a schematic diagram of a circuit board with a pattern printed on its surface, obtained in step S3 of the present invention.

[0032] Figure 5 This is a magnified image of the circuit board with printed patterns on its surface obtained in step S3 of the present invention under a 500x optical microscope. Detailed Implementation

[0033] The present invention will be further described below with reference to specific embodiments, but the embodiments do not limit the present invention in any way. Unless otherwise stated, the raw materials and reagents used in the embodiments of the present invention are conventionally purchased raw materials and reagents.

[0034] Example 1 A method for fabricating circuit board patterns based on an improved mSAP process includes the following steps: S1. Mark the finished PCB outline on a large-size copper-clad laminate, such that the finished PCB outline contains at least one straight edge; cover the copper surface of the large-size copper-clad laminate with a photosensitive dry film, and crosslink the photosensitive dry film at specific locations through exposure, so that the uncrosslinked portion of the dry film forms a first pattern; the first pattern includes a required pattern and a first edge pattern, wherein the required pattern is a rectangle with a size of 150×55μm, wherein a required pattern edge with a side length of 55μm is formed on the side closest to the straight edge of the finished PCB outline, and the required pattern edge is parallel to the straight edge of the finished PCB outline; the first edge pattern is a rectangle, and one of its rectangular sides coincides with the 55μm side length of the required pattern edge (the first edge pattern and the required pattern together form the first rectangular pattern), the rectangular side is the overlapping side, and two parallel rectangular sides perpendicular to the overlapping side intersect perpendicularly with the straight edge in the finished PCB outline, such that the first edge pattern extends beyond the finished PCB outline, and the distance between the rectangular side of the extended portion of the first edge pattern that does not intersect with the straight edge of the finished PCB outline and the straight edge is ≥0.075. mm; the first pattern also includes four positioning targets with a diameter of 1.5 mm at the four corners of the SET edge on the substrate; the uncrosslinked dry film is washed away to expose the copper surface below, and a first copper layer with a thickness of 25 μm is electroplated and deposited on the exposed copper surface, the pattern formed by the first copper layer is consistent with the first pattern; S2. Using a CCD router, with the four positioning targets of the SET edge, the board surface is fixed on the router table using negative pressure. The first router is performed along the straight edge that intersects the two straight edges of the first edge pattern in the finished PCB board outline: after drilling the cutting hole with a 0.5mm drill bit, rough router is performed with a 0.7mm keyway cutter at a speed of 0.2m / min, followed by fine router with a 0.6mm double-edged cutter at a speed of 0.6m / min; after routerting the corresponding straight edge in the finished PCB board outline, the first router is completed, and a substrate with a second pattern on the surface is obtained to be cut; the second pattern includes the required pattern and the second edge pattern. The second edge pattern is a rectangle, one of which coincides with the edge of the required pattern, and the other rectangular edge parallel to the required pattern coincides with the straight edge of the finished PCB board outline that has been routerted; S3. Remove the photosensitive dry film on the substrate to be cut, and use a sulfuric acid-hydrogen peroxide etching solution to flash-etch away the second edge pattern (flash etching amount is ~5μm). Then, use a regular router to perform a second edge routing: first, perform a rough routing at a speed of 10 mm / s and a 1.2 mm router cutter, then perform a second rough routing at a speed of 0.5 mm / s and a 0.6 mm regular router cutter, then perform a first fine routing at a speed of 20 mm / s and a 1.0 mm diameter router cutter, and finally perform a second fine routing at a speed of 2 mm / s and a 0.4 mm router cutter. The remaining edges are routerd according to the outline of the finished PCB board to obtain a circuit board with the required pattern printed on the surface.

[0035] Examples 2-5 A circuit board pattern fabrication method based on an improved mSAP process differs from Example 1 only in that: The operating parameters of the CCD milling machine in step S2 are different, as shown in Table 1 below.

[0036] Table 1. Comparative Example 1 An mSAP process includes the following steps: S1. Mark the finished PCB outline on a large-size copper-clad laminate, such that the finished PCB outline contains at least one straight edge; cover the copper surface of the large-size copper-clad laminate with a photosensitive dry film, and crosslink the photosensitive dry film at specific locations through exposure, so that the other part of the dry film that is not crosslinked forms a desired pattern, the desired pattern being a rectangle with a size of 150×55μm; the side of the desired pattern closest to the straight edge of the finished PCB outline forms the edge of the desired pattern, and the distance between the edge of the desired pattern and the straight edge of the finished PCB outline is 0.125mm; wash away the uncrosslinked dry film to expose the underlying copper surface, and electroplate a copper layer with a thickness of 26μm on the exposed copper surface, the pattern formed by the copper layer being consistent with the desired pattern; S2. Remove the photosensitive dry film from the substrate to be cut and perform flash etching (flash etching amount is ~5μm). Then, use a regular router to perform edge routing: first, perform the first rough routing at a speed of 10 mm / s and a 1.2 mm router cutter, then perform the second rough routing at a speed of 0.5 mm / s and a 0.6 mm regular router cutter, then perform the first fine routing at a speed of 20 mm / s and a 1.0 mm diameter router cutter, and finally perform the second fine routing at a speed of 2 mm / s and a 0.4 mm router cutter. Rout all edges according to the finished PCB board outline to obtain a circuit board with the required pattern printed on the surface.

[0037] Performance testing Example of minimum distance test from graphic edge to outline edge: Take the finished board with the final engraved outline, and use a digital microscope (focus on and acquire images of different parts at different heights, perform high-quality depth synthesis, and construct and display 3D images) to collect the length of the copper-free area from the graphic edge to the outline edge of the finished board. The minimum length measured is the minimum distance from the graphic edge to the outline edge when made in this way (this method will not damage the pattern).

[0038] The minimum distance test method for the graphic edge to the outline edge is as follows: Take the finished board with the final engraved outline, and use a digital microscope (which focuses on and acquires images of different parts at different heights, performs high-quality depth synthesis, and constructs and displays 3D images) to collect the length X of the copper-free area from the graphic edge to the outline edge of the finished board. The maximum value obtained by subtracting X from 0.125mm is the critical value that the engraving will not damage the pattern in this way. This critical value is the minimum safe distance from the graphic edge to the outline edge in this way.

[0039] The test results are shown in Table 2 below: Table 2. As can be seen from Table 2 above, the method provided by this invention determines the distance between the edge of the graphic and the edge of the outline solely by the flash etching step, which can achieve the requirement that the distance from the edge of the graphic to the edge of the PCB outline is <0.025mm and that they are not tangent (no exposed copper).

[0040] according to Figure 1 It is evident that the graphic creation method provided by this invention is applicable to any graphic requiring straight edges.

[0041] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A method for fabricating circuit board patterns based on an improved mSAP process, characterized in that, Includes the following steps: S1. Mark the finished PCB outline on a large-size copper-clad laminate, such that the finished PCB outline contains at least one straight edge; cover the copper surface of the large-size copper-clad laminate with a photosensitive dry film, and crosslink the photosensitive dry film at specific locations through exposure, so that the other part of the dry film that is not crosslinked forms a first pattern; the first pattern includes a required pattern and a first edge pattern, wherein the side of the required pattern closest to the straight edge of the finished PCB outline forms a required pattern edge, the required pattern edge is a straight line and parallel to the straight edge of the finished PCB outline; the first edge pattern is rectangular and one of its rectangular sides coincides with the edge of the required pattern, the rectangular side is an overlapping side, and two parallel rectangular sides perpendicular to the overlapping side intersect perpendicularly with the straight edge in the finished PCB outline, so that the first edge pattern extends beyond the finished PCB outline; wash away the uncrosslinked dry film to expose the underlying copper surface, and deposit a first copper layer on the exposed copper surface, the pattern formed by the first copper layer being consistent with the first pattern; S2. Using a CCD router, perform the first router along the straight edge that intersects the two straight edges of the first edge graphic in the finished PCB board outline. After routerting the corresponding straight edge in the finished PCB board outline, the first router ends, resulting in a substrate to be cut with a second graphic on its surface. The second graphic includes a required graphic and a second edge graphic. The second edge graphic is a rectangle, one of which coincides with the edge of the required graphic, and the other rectangular edge parallel to this rectangular edge coincides with the straight edge of the finished PCB board outline that has been routerted. S3. Remove the photosensitive dry film on the substrate to be cut, remove the second edge pattern by flash etching, and then use a regular router to perform a second router, router out the remaining edge according to the outline of the finished PCB board, and you can get a circuit board with the required pattern printed on the surface.

2. The circuit board pattern fabrication method based on improved mSAP process as described in claim 1, characterized in that, In step S1, the first edge graphic portion that extends beyond the outline of the finished PCB board has a rectangular edge that does not intersect with the straight edge of the finished PCB board outline, and the distance between the rectangular edge of the first edge graphic portion that extends beyond the outline and the straight edge of the finished PCB board outline is ≥0.075 mm.

3. The circuit board pattern fabrication method based on mSAP process improvement as described in claim 1, characterized in that, Step S1 The first graphic also includes a positioning target.

4. The circuit board pattern fabrication method based on improved mSAP process as described in claim 3, characterized in that, The positioning target is circular with a diameter of 1-2 mm.

5. The circuit board pattern fabrication method based on mSAP process improvement as described in claim 1, characterized in that, The first milling step S2 involves: first, rough milling at a cutting speed of 0.1-0.3 m / min, followed by fine milling at a cutting speed of 0.5-0.7 m / min.

6. The circuit board pattern fabrication method based on improved mSAP process as described in claim 5, characterized in that, The roughing process is performed using a gong cutter with a diameter of 0.6-0.8 mm; And / or, the precision gonging is performed using a gong cutter with a diameter of 0.5-0.7 mm.

7. The circuit board pattern fabrication method based on improved mSAP process as described in claim 1, characterized in that, The flash etching in step S3 is performed using a flash etchant, which includes a sulfuric acid-hydrogen peroxide system etching solution.

8. The circuit board pattern fabrication method based on the improved mSAP process as described in claim 1, characterized in that, The second milling step S3 is as follows: first, perform the first rough milling at a speed of 5-20 mm / s, then perform the second rough milling at a speed of 0.1-1 mm / s, then perform the first fine milling at a speed of 10-30 mm / s, and finally perform the second fine milling at a speed of 1-5 mm / s.

9. The circuit board pattern fabrication method based on improved mSAP process as described in claim 8, characterized in that, The second gong edge described in step S3 satisfies at least one of the following (a)-(d); (a) The first rough gonging is done using a gong cutter with a diameter of 1-1.5 mm; (b) The second roughing is done using a gong cutter with a diameter of 0.3-1 mm; (c) The first fine gonging is performed using a gong cutter with a diameter of 0.8-1.2 mm; (d) The second fine gonging is performed using a gong cutter with a diameter of 0.1-0.8 mm.

10. A product manufactured by the circuit board patterning method based on the improved mSAP process as described in any one of claims 1-9.

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