Method for manufacturing printed circuit board

Abstract

Even for a printed circuit board having through-hole specifications that are difficult to fill with holes by conventional methods, a filling material can be appropriately filled in these through-holes. A sealing film (12) is attached to the lower surface of the printed circuit board (10), and a filling material (16) is pressed into the through-hole (11) from the upper surface side of the printed circuit board (10) by screen printing in a vacuum atmosphere. Then, the film (12) is peeled off from the printed circuit board (10), and an auxiliary filling process is performed in which the filling material (16) is gently supplied again to make the filling material (16) protrude from the lower surface side of the through-hole (11) while overlapping on a fixture plate (18) having a recess (17) formed at a position corresponding to the through-hole (11).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a printed circuit board in which a through hole of the printed circuit board is filled with a resin. Background Art

[0002] As a high-density mounting substrate for electronic devices, a build-up wiring substrate is used. This is a structure in which circuits are overlapped into multiple layers on both sides of a core substrate having through holes with an insulating layer therebetween. The through holes of the core substrate are filled with a resin for hole filling, and after both sides are flattened by polishing, a multi-layer circuit is formed thereon. The core substrate is stacked layer by layer in sequence as described above to form a multi-layer substrate, so when the flatness of the core substrate is poor, it will have an adverse effect on the flatness of the layers overlapped thereon and even the accuracy of the circuit pattern. Therefore, a high degree of flatness is required for the core substrate. In addition, the core substrate is not limited to this kind of build-up wiring substrate. For example, the printed substrate of an IC package carrying a semiconductor chip also becomes a reason for reducing the connection reliability with the semiconductor chip when its flatness is poor, so a high degree of flatness is still required.

[0003] As a method for manufacturing a printed circuit board having a through hole and requiring a high degree of flatness as described above, the methods described in the following patent documents 1 and 2 are known. In these methods, an adhesive film is attached to the lower surface of the printed circuit board to make the through hole a bottomed structure, and then a filling material is placed on the printed circuit board in a vacuum atmosphere and a scraper is slid to press the filling material into the through hole. Then, after the filling material is cured, the adhesive film on the back is peeled off, and the resin remaining on both sides of the printed circuit board is removed by polishing and grinding to make it flat.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2003-188308

[0007] Patent Document 2: Japanese Patent Application Laid-Open No. 2005-57109 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the above method, since the adhesive film is peeled off after the filling material is cured, the adhesive layer of the adhesive film is closely attached to the filling material cured in the through hole, and the adhesive layer and the filling material are peeled off from the adhesive film and remain in the through hole, thereby reducing the characteristics as a printed circuit board.

[0010] However, if the adhesive film is peeled off before the filling material is cured, part of the uncured filling material adheres to the adhesive film side and falls out of the through hole, resulting in insufficient filling material on the back side of the printed circuit board, and a depression of several tens of μm is generated after the filling material is cured. This impairs the flatness of the printed circuit board.

[0011] Therefore, the inventors of this application invented the following method as an undisclosed technology. Figure 1 As shown in (A), a fixture plate 4 having a recess 3 pre-formed at a position corresponding to the through hole 2 of the printed substrate 1 is prepared, and the fixture plate 4 is attached to the back side of the printed substrate 1. Figure 1 As shown in (B), for example, the filling material 7 is filled in the through hole 2 of the printed substrate 1 by screen printing using a screen printing plate 5 and a squeegee 6. In this way, the filling material 7 is filled in the through hole 2, as shown in FIG. Figure 1 As shown in (C), it is possible to form a state protruding from both sides of the printed substrate 1. Therefore, if the filling material 7 is solidified and both sides of the printed substrate 1 are ground by, for example, polishing, the filling material 7 that remains on both sides of the printed substrate 1 and solidifies can be removed, so that both sides of the printed substrate 1 are smoothed.

[0012] With respect to a printed circuit board of conventional specifications, the above-mentioned undisclosed invention allows the filling material 7 to be equally filled into each through hole 2 , and as a result, a sufficiently flat printed circuit board 1 can be manufactured by polishing both the front and back surfaces.

[0013] However, in recent years, as semiconductor chips have become smaller, the pitch of wiring patterns and through holes in the relevant areas have been narrowed, for example, in printed circuit boards on which semiconductor chips are mounted. As a result, areas with densely packed through holes of extremely small diameters have been generated in the printed circuit board, or the opening diameters of through holes in the same substrate have been expanded, that is, the opening diameters of various sizes are mixed.

[0014] When the filling material 7 is filled into the through hole 2 by the above-mentioned screen printing, the smaller the opening diameter of the through hole 2 is, the greater the filling resistance of the filling material 7 to the through hole 2 is. Therefore, if the above-mentioned undisclosed invention is used to fill the holes of a printed substrate in which the opening diameter of the through hole 2 is within a large range in the same substrate, for example, the filling material is easier to be pressed into the through hole 2 with a large opening diameter than the through hole 2 with a small opening diameter. Therefore, Figure 1As shown in (C), the following phenomenon occurs: the protrusion of the filling material 7 on the back side of the printed substrate 1 increases significantly in the through hole 2 with a large opening diameter compared to the through hole 2 with a small opening diameter. The protruding portion of the filling material 7 is polished and ground after the filling material 7 is solidified. Therefore, if you want to fully grind the protruding portion of the filling material 7 in the through hole 2 on the large diameter side, excessive grinding is performed on the through hole 2 side with a small opening diameter, and the copper foil of the printed substrate 1 may also be cut off. In addition, since the grinding burden is large, the consumption of abrasives is also high, which will waste a lot of expensive filling materials. However, if the printing conditions are determined in a manner that makes the protrusion of the filling material 7 from the through hole 2 on the large diameter side appropriate in consideration of the grinding ability, the problem of insufficient filling of the through hole 2 on the small diameter side will occur.

[0015] In addition, there are various opening diameters that are mixed together, not limited to the case where the opening diameters are not limited to the case where various opening diameters are mixed together. For example, in a printed substrate having a region where through holes of extremely small diameters are densely arranged in a grid shape, such as directly below a large semiconductor chip, there is the following problem. That is, on the fixture plate 4 that supports the printed substrate having such a highly dense through hole state, a wide recess 3 that reaches the entire through hole region has to be formed. Therefore, during screen printing, the outer peripheral edge of the through hole dense region in the printed substrate 1 is supported by the fixture plate 4 and the printed substrate 1 is less flexed, but in the central part of the region, the printed substrate 1 is flexed in a concave manner due to the pressing force of the scraper 1. Such unevenness in the amount of deflection becomes significant as the thickness of the printed substrate 1 becomes thinner, resulting in uneven filling of the filling material. Moreover, in a printed substrate having a large diameter through hole with an opening diameter of about 0.5 mm or more, for example, the large diameter through hole originally has extremely small filling resistance of the filling material, so there is a situation where it is difficult to adjust the various conditions of screen printing to make the filling amount equal.

[0016] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a method for manufacturing a printed circuit board, which can appropriately fill a filling material into through holes even in a printed circuit board having through hole specifications that are difficult to fill with a conventional method.

[0017] Technical solutions to solve problems

[0018] The present invention is a method for manufacturing a printed circuit board having a through hole that penetrates the substrate and in which a filling material is filled in the through hole, wherein the method performs the following steps: a filling material filling step, in which the opening end surface of the through hole on one side of the printed circuit board is blocked to a state where the filling material cannot escape, and the filling material is pressed into the through hole from the other side of the printed circuit board to fill the through hole with the filling material; and an auxiliary filling step, after the filling material filling step and before the filling material is cured, the filling material is supplied again from the other side of the printed circuit board with the opening end surface of the through hole open.

[0019] In the filling material filling process, the filling material is filled deep into the through hole while blocking the open end surface of one side of the through hole, and then before the filling material solidifies, the auxiliary filling process is performed while leaving the open end surface of the through hole open, so that the filling material can also protrude outward from the open end surface of one side of the through hole.

[0020] Compared with the filling material filling process, the auxiliary filling process can adopt a filling method with a small pressing force of the filling material. Therefore, even in the case where the opening diameters of the through holes are different, when the through holes with extremely small diameters are densely packed, or even when the through holes include large diameters, the additional filling amounts of the filling materials for each through hole will not be very different, and an appropriate amount of filling material can be supplied from each through hole.

[0021] Furthermore, in the filling material filling process, the opening end face of the through hole can be blocked to prevent the filling material from coming out by pasting a film having an adhesive layer formed on the surface of the film substrate on one surface of the printed substrate, and on this basis, the printed substrate is placed on a flat fixture, and the filling material is pressed into the through hole from the other side of the printed substrate. In this way, even in the case of poor flatness of the printed substrate, the opening end face of the through hole can be reliably blocked. Although the film needs to be peeled off before the auxiliary filling process, even if a part of the filling material filled in the through hole is attached to the film and removed at this time, since the filling material is replenished through the auxiliary filling process, it is possible to supply an amount suitable for replenishing the filling material to each through hole. In addition, even in the case where an excess amount exceeding the amount removed is supplied and the filling material protrudes to the back side, it is possible to make the protruding amount approximately equal for each through hole.

[0022] When the filling material is formed to protrude from each through hole approximately evenly by an appropriate amount through the auxiliary filling process, a filling material curing process is then performed to cure the filling material, and the protruding portion is polished through a polishing process as needed, thereby manufacturing a printed circuit board with both sides flattened.

[0023] If the filling material filling process and the auxiliary filling process are performed by screen printing, the filling material can be selectively buried in a part of the through-hole group in the printed substrate. Not only is there no waste, but the holes can be buried by dividing the through-hole group into multiple groups and performing multiple screen printing. Therefore, the printing conditions of the screen printing can be made most suitable for each through-hole group to fill the holes.

[0024] As a film used in the film lamination process, if a structure is used in which an area with an adhesive layer formed in the entire area and a non-formation area without an adhesive layer coexist, air discharge from the through-hole becomes better, so it is easy to fill the filling material deep into the through-hole, which is effective in the case of a printed substrate with a through-hole with a high aspect ratio (depth / opening diameter) and a particularly small opening diameter.

[0025] As the film used in the film lamination process, if a film substrate having multiple pores for air permeability formed therethrough or a film substrate having multiple ventilation grooves formed in depressions on the surface is used, the air discharge from the through holes will be better, so it is effective in printed circuit boards with through holes with a high aspect ratio.

[0026] Effects of the Invention

[0027] According to the present invention, even in a printed circuit board having through-hole specifications that are difficult to fill with a conventional method, these through-holes can be appropriately filled with a filling material. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is an enlarged schematic cross-sectional view showing a hole filling method of an undisclosed invention.

[0029] Figure 2 is a cross-sectional view of an IC package.

[0030] Figure 3 It is a cross-sectional view of a printed circuit board.

[0031] Figure 4 It is a cross-sectional view showing the printed circuit board after the film lamination step.

[0032] Figure 5 is an enlarged top view of the sealing film.

[0033] Figure 6 It is a cross-sectional view showing a state where a printed circuit board is set on a jig plate.

[0034] Figure 7 It is a cross-sectional view showing the state of the filling material filling process.

[0035] Figure 8 It is a top view showing the flow of air in the filling material filling step.

[0036] Fig. 9 It is a cross-sectional view showing the flow of air in the filling material filling step.

[0037] Fig.10 It is a cross-sectional view showing the state of the film stripping step.

[0038] Fig.11 It is a cross-sectional view showing the printed circuit board after the film stripping step.

[0039] Fig.12 This is a cross-sectional view showing a state where a printed circuit board is set on a countersinking jig plate.

[0040] Fig.13 It is a cross-sectional view showing the state of the auxiliary filling process.

[0041] Fig.14 It is a cross-sectional view showing the printed circuit board after the auxiliary filling step.

[0042] Fig.15 It is a cross-sectional view showing the printed circuit board after the planarization step. DETAILED DESCRIPTION

[0043] <Implementation method 1>

[0044] pass Figures 2 to 15 Embodiment 1 of the present invention will be described.

[0045] In this embodiment, an example of applying the present invention to a printed circuit board of an integrated circuit package having a ball grid array is shown. The printed circuit board 10 manufactured in this embodiment has a plurality of through holes 11, such as Figure 2 As shown, a semiconductor chip 20 is mounted on the upper surface of the printed substrate 10 and electrically connected to pads (not shown) formed on the upper surface of the printed substrate 10 via a plurality of solder balls 21. The semiconductor chip 20 is also fixed to the printed substrate 10 via an adhesive 22, and a heat sink 23 is bonded to the upper surface of the semiconductor chip 20 via an adhesive 24.

[0046] In addition, as the starting material of the printed circuit board 10, for example, a double-sided copper-clad printed circuit board with a thickness of about 0.1 mm to 8.0 mm is recommended. A through hole with an inner diameter of about 0.1 mm to 5.0 mm is pre-formed in the printed circuit board 10, and an inner surface plating is performed on the inner wall surface to conduct the copper foils on both sides to form a through hole 11 that electrically conducts the copper foils on both sides. Figure 3 As shown, the through hole 11 has opening end faces opened on the upper and lower surfaces of the printed substrate 10. In this embodiment, through holes 11 with different opening diameters can be mixed in the printed substrate 10, and their aspect ratios (plate thickness of the printed substrate 10 / opening diameter of the through hole 11) vary. For example, Figure 3(The drawings have different vertical and horizontal scales.) The aspect ratio of the through hole 11A with a small opening diameter shown is, for example, greater than 10, and the aspect ratio of the through hole 11B with a large opening diameter is, for example, about 5.

[0047] (Film pasting process)

[0048] On one surface of the printed circuit board 10 (in Figure 3 The lower surface (hereinafter referred to as the "back surface") side is firstly pasted with a sealing film 12 (refer to Figure 4 The sealing film 12 is made of synthetic resin with a thickness of 35 μm to 100 μm, for example, and is formed by printing an adhesive layer 12B on a film substrate 12A having a smooth surface. Figure 5 As shown, the adhesive layer 12B is in a scattered dot configuration in which circular dots are placed in a staggered grid, that is, the adhesive layer 12B is formed by dividing the region of the film substrate 12A into a plurality of small regions, and the formation region and non-formation region of the adhesive layer 12B coexist in the entire region of the film substrate 12A. In addition, since the film substrate 12A and the adhesive layer 12B are both transparent, dots are marked in the circular region representing the adhesive layer 12B to be drawn in a manner that is easy to observe.

[0049] The diameter of the adhesive layer 12B may be smaller or larger than the diameter of the through hole 11 indicated by the two-dot chain line in the figure, and is preferably in the range of 100 μm to 500 μm, and is arranged at intervals of 10 μm to 400 μm.

[0050] In addition, in the film substrate 12A, as Figure 5 As shown in the figure, minute air-permeable pores 12C with a diameter of about 10 μm to 100 μm are arranged in a scattered manner in advance in a grid or staggered grid shape at a pitch of, for example, 2 mm to 4 mm over the entire surface area of ​​the film substrate 12A. These pores 12C are formed by pressing a needle with a sharp tip from the side opposite to the surface where the adhesive layer 12B is formed after the adhesive layer 12B is formed on the film substrate 12A, and minute burrs generated when the needle penetrates the film substrate 12A sometimes protrude to the surface on the adhesive layer 12B side.

[0051] As described above, after the hole-opening process for forming the fine pores 12C (for example, after several seconds), the sealing film 12 is pressed at a relatively low pressure so that the surface on the adhesive layer 12B side faces the back of the printed substrate 10, thereby performing a film-attaching process for attaching the sealing film 12 to the printed substrate 10. As a result, the open end surface on the lower surface side of the through hole 11 is blocked in a state where the filling material does not escape. That is, the open end surface on the lower surface side of the through hole 11 is roughly sealed by the viscous liquid. However, since the sealing film 12 is pressed at a low pressure in the film-attaching process, or the tiny burrs generated by the hole-opening process slightly protrude toward the printed substrate 10 side, the entire area of ​​each adhesive layer 12B is not tightly attached to the printed substrate 10, but only the irregularly shaped tiny area is tightly attached to the printed substrate 10, so there is a tiny gap at the interface between the printed substrate 10 and the sealing film 12, and the gap is connected to the air-permeable fine pores 12C. Therefore, the opening end surface on the lower surface side of the through hole 11 is sealed by the viscous liquid as described above, but is in a state of being communicated with the outside by gas.

[0052] (Filling material filling process)

[0053] Then, if Figure 6 and Figure 7 As shown, the printed substrate 10 to which the sealing film 12 is attached is filled with a filling material using a vacuum printer in a manner such that the sealing film 12 is placed on a flat fixture 13. The vacuum printer is a well-known structure in which a screen printing plate 14 and a scraper 15 that slides on the screen printing plate 14 are provided in a vacuum chamber maintained at a pressure sufficiently lower than the atmospheric pressure (e.g., 50 Pa to 100 Pa), and when a filling material 16 such as a synthetic resin for hole filling is supplied to the screen printing plate 14, the scraper 15 is lowered onto the screen printing plate 14 and made to slide on the screen printing plate 14, thereby pressing the filling material 16 downward through the screen printing plate 14. As shown in FIG. Figure 7 As shown, the printed circuit board 10 with the sealing film 12 attached thereto is arranged so that the sealing film 12 side contacts the flat jig 13 and the other side (hereinafter referred to as the “front side”) opposite thereto is located below the screen printing plate 14 .

[0054] The screen printing plate 14 is provided with through holes (not shown) at positions corresponding to the through holes 11 of the printed substrate 10. The printed substrate 10 is accurately positioned relative to the screen printing plate 14 so that the through holes formed in the screen printing plate 14 are connected to the through holes 11 of the printed substrate 10, and the filling material 16 is pressed into the through holes 11.

[0055] The flat jig 13 is formed into a flat surface not only in the area corresponding to the through hole 11 but also in the entire area, and supports the sealing film 12 from the bottom side to maintain a state in which the open end surface on the back side of the through hole 11 is blocked by the sealing film 12. Thus, the filling material 16 pressed into the through hole 11 can be prevented from leaking from the gap between the sealing film 12 and the printed circuit board 10.

[0056] The scraper 15 is a synthetic resin plate as known. By adjusting the pressing angle or pressing pressure relative to the screen plate 14, the force of pressing the filling material 16 downwardly of the screen plate 14 can be adjusted, and the amount of the filling material 16 pressed can be adjusted.

[0057] Since the adhesive layer 12B is formed in a scattered pattern on the sealing film 12 and a plurality of fine holes 12C are formed on the sealing film 12, when the printed substrate 10 is screen-printed in a vacuum printer, when the filling material 16 is pressed into the through hole 11, the minute gas remaining in the through hole 11 is Figure 8 and Fig. 9 As shown by the dotted line in the figure, the filling material 16 is discharged into the vacuum chamber through the gaps between the scattered adhesive layers 12B, the fine holes 12C, and the small gaps between the sealing film 12 and the flat jig 13. Therefore, the filling material 16 is smoothly filled in the through hole 11 until it reaches the sealing film 12.

[0058] On the other hand, on the front side of the screen printing plate 14 on the opposite side from the sealing film 12, as shown in FIG. Figure 7 As shown, after the squeegee 15 passes, a protrusion 16A is formed in which the filling material 16 slightly protrudes from the opening end face of the through hole 11. Since the protrusion 16A is formed by the filling material 16 leaking out of the through hole of the screen printing plate 14 when the screen printing plate 14 leaves the front side of the printed substrate 10, the protrusion size from the opening end face of the through hole 11 is independent of the diameter size of the through hole 11, and is substantially equal for any through hole 11.

[0059] (Stripping process)

[0060] Next, the printed substrate 10 is taken out from the vacuum printer. Fig.10 As shown, the sealing film 12 is peeled off from the printed substrate 10. In the present embodiment, the filling material 16 uses a filling material that has the property of being completely cured by heating or ultraviolet irradiation. After the above-mentioned filling material filling step, before the curing of the filling material 16 begins, the sealing film 12 is peeled off from the printed substrate 10. Therefore, a part of the filling material 16 in the through hole 11 may be removed from the through hole 11 while being attached to the adhesive layer 12B. As a result, a depression 16B of about 10 μm is generated in the small-diameter through hole 11A, and a depression 16C of about 30 μm is generated in the large-diameter through hole 11B (see Fig.11 ).

[0061] (Auxiliary filling process)

[0062] Next, the printed substrate 10 from which the sealing film 12 has been peeled off is placed again on the vacuum printer. In this case, a support jig 18 having recesses 17 formed at positions corresponding to the through holes 11 of the printed substrate 10 is provided in advance in the vacuum printer instead of the flat jig 13, and the printed substrate 10 is placed on the support jig 18 in such a manner that the through holes 11 correspond to the recesses 17. Fig.12 As shown in FIG. 1 , the recess 17 may be an independent recess 17A having an inner diameter slightly larger than the opening diameter of the through hole 11A and corresponding one-to-one to each through hole 11A, or may be a combined recess 17B in which one recess corresponds to the formation area of ​​a plurality of through holes 11B. The area other than the recesses 17A and 17B on the upper surface of the support jig 18 is flat, and is in close contact with the back surface of the printed substrate 10 to support the printed substrate 10.

[0063] In this state where the printed substrate 10 is positioned and placed on the support fixture 18 in the vacuum printer, if needed again, the vacuum atmosphere is returned and the screen printing of the filling material 16 is performed from the front side of the printed substrate 10. In the screen printing in this case, the filling material 16 is already filled in the through hole 11 in almost the entirety, that is, in the portion other than the recesses 16B and 16C. Since the open end surface of the back of each through hole 11 is in a state of communication with the recesses 17A and 17B of the support fixture 18, the filling resistance of the filling material 16 is extremely small. Therefore, for example, even if the pressing dimension when the scraper 15 is brought into contact with the screen printing plate 14 is reduced and the filling force of the filling material 16 is extremely small, the filling material 16 is replenished and supplied to the through hole 11, as shown in FIG. Fig.13 As shown, the filling material 16 is in a state of protruding from the opening end surface on the back side of the through hole 11, and a protruding portion 16D is formed.

[0064] The screen printing is performed when the filling force of the filling material 16 is extremely small. Therefore, regardless of the size of the opening diameter of the through hole 11, whether it is a small-diameter through hole 11A or a large-diameter through hole 11B, the protruding volume of each protrusion 16D from the opening end surface can be suppressed to a smaller deviation than before.

[0065] (Filling material curing process)

[0066] Next, the printed substrate 10 after the auxiliary filling step is taken out from the vacuum printer, and the filling material 16 is completely cured by heating or ultraviolet irradiation.

[0067] (Planarization process)

[0068] After the filling material 16 is completely cured, the two sides of the printed substrate 10 are ground by, for example, polishing, and the protrusions 16A and 16D protruding from the two opening end surfaces of the through hole 11 are removed from the two sides of the printed substrate 10. Fig.15 As shown, the entire areas of both surfaces of the printed circuit board 10 are flattened.

[0069] Here, although the polishing grinder is not shown in the figure, it is equipped with a plurality of polishing wheels, which place the printed substrate 10 on a roller and convey it in a predetermined direction, and have a rotation axis extending along the surface of the printed substrate 10 and in a direction orthogonal to the conveying direction. The polishing wheels are arranged on the upper and lower sides sandwiching the printed substrate 10, and on each single side, a plurality of, for example, two each, are arranged at intervals in the conveying direction of the printed substrate 10. In the present embodiment, the printed substrate 10 is first polished by the first polishing wheel on the back side, then polished by the first polishing wheel on the front side, then polished by the second polishing wheel on the front side, and finally polished by the second polishing wheel on the back side. When polishing by each polishing wheel, an abrasive is supplied, and the printed substrate 10 is supported by a support roller provided on the side opposite to the polishing wheel.

[0070] In the initial grinding by the polishing wheel, on the back side of the printed substrate 10, the volume of the protrusion 16D of the filling material 16 has little deviation regardless of the diameter size of the through hole 11, so the grinding of the protrusion 16D can be performed evenly over the entire area of ​​the back side of the printed substrate 10.

[0071] Furthermore, when the polishing is transferred to the front side of the printed circuit board 10 , since the volume of the protrusion 16A of the filling material 16 is independent of the diameter of the through hole 11 and has little deviation, the polishing of the protrusion 16A can be performed evenly over the entire area of ​​the front side of the printed circuit board 10 .

[0072] Therefore, the back side and the front side are ground in the same manner, and local grinding residues caused by volume deviation of the protrusions 16A and 16D are not generated. When the grinding is transferred to the opposite side, the printed substrate 10 is not strongly pressed against the polishing wheel due to the grinding residues partially remaining on the back side, and both sides are ground equally. Thus, it is possible to prevent the copper foil from being excessively cut or the filler material 16 from being excessively remaining locally on both the front and back sides of the printed substrate 10.

[0073] Thus, according to the present embodiment, when the filling material 16 is filled into the through hole 11 of the printed substrate 10, even if the opening diameter of the through hole 11 varies in size, the protruding volume of the protruding portion of the filling material 16 on the upper and lower surfaces of the printed substrate 10 can be suppressed to a small deviation regardless of the opening diameter of the through hole 11, so that in the subsequent flattening process, the protruding portions 16A and 16D of the filling material 16 can be evenly ground over the entire area.

[0074] In particular, in the present embodiment, in the filling material filling process, the filling material 16 is filled by screen printing, so that the filling material 16 can be selectively filled only in the target through hole 11. Therefore, the following multi-division filling material filling process can also be adopted, for example, all through holes to be filled are divided into two types according to their aspect ratios, and only the hole filling of the through hole group with a high aspect ratio is performed in the first screen printing, and only the hole filling of the through hole group with a low aspect ratio is performed in the second screen printing. In this way, it is possible to adopt printing conditions suitable for the through hole group as the target in each screen printing, and it is particularly suitable for hole filling of a printed substrate including through holes with a high aspect ratio.

[0075] In addition, in this embodiment, since the adhesive layer 12B of the sealing film 12 is formed by a collection of multiple points scattered in the area of ​​the film substrate 12A, the residual air in the through hole 11 is easily discharged through the gaps between the points (the non-forming area of ​​the adhesive layer), and the filling material can be smoothly filled.

[0076] <Other embodiments>

[0077] The present invention is not limited to the embodiments described with reference to the drawings, and for example, the following embodiments are also included in the technical scope of the present invention.

[0078] (1) In the above-mentioned embodiment, an example of a printed substrate used for an IC package body carrying an IC chip is shown, but it is not limited to this. The hole filling method is applicable to a printed substrate with through holes having a high aspect ratio, for example, and of course it can also be applied to a core substrate of a laminated substrate.

[0079] (2) In the above embodiment, an example of performing the filling material filling process and the auxiliary filling process by screen printing is shown, but it is also possible to supply the filling material to the entire surface of the printed substrate without using a screen printing plate, for example, by pressing the filling material into the through hole by a scraper or the like, or by generating a pressure difference on both sides of the printed substrate and using the pressure difference to press the filling material. In addition, when the filling material filling process and the auxiliary filling process are performed by screen printing, it is not limited to being performed by the same vacuum printer as in the above embodiment, and the two processes may be performed by different vacuum printers. In this case, the flat jig and the support jig can be pre-set in each vacuum printer, and there is no need to replace each jig in one vacuum printer, thereby improving productivity.

[0080] (3) In the above embodiment, when the filling material filling process is performed, a sealing film is attached to one side of the printed substrate to block the open end surface of one side of the through hole, but the film is not necessarily required. In the case where the flatness of the printed substrate is good, the printed substrate can be placed on a flat fixture plate to perform the filling of the filling material. In addition, when the open end surface of the through hole is blocked by the film, in this embodiment, the adhesive layer is closely attached to the printed substrate, but the adhesive layer is divided into a plurality of small areas within the area of ​​the film base material and is formed to coexist with the non-formation area where the adhesive layer is not formed, so that air is allowed to flow through the non-formation area where the adhesive layer is not formed, thereby allowing the air in the through hole to be discharged, and the filling of the filling material is performed smoothly.

[0081] (4) In the above embodiment, by forming a plurality of air-permeable pores on the film substrate of the sealing film, degassing from the through holes is promoted when the filling material is printed in a vacuum atmosphere, and the filling material is smoothly filled. However, it is not necessary to form pores on the film substrate. For example, as the film substrate, a porous film (for example, made of ultra-high molecular weight polyethylene) having air permeability based on continuous pores can be used. In addition, even if an air vent through the film substrate is not necessarily formed, for example, by using a film substrate having a plurality of grooves of a small depth in a grid or irregular shape on the surface on which the adhesive is attached to the printed substrate, an air vent connected to the outside can be formed at the interface of the two when the sealing film is attached to the printed substrate. Therefore, when the filling material is printed in a vacuum atmosphere, degassing from the through holes can be promoted, and the filling material can be smoothly filled.

[0082] (5) In the above-mentioned embodiment, the auxiliary filling process is performed before the solidification of the filling material begins, but it is not limited to this. It can also be performed after the solidification begins inevitably or intentionally. In short, as long as the filling material is additionally supplied to the through hole through the auxiliary filling process, the process can be performed when a part of the filled filling material protrudes from the open end surface of the through hole.

[0083] (6) In the above embodiment, an example of forming a conductive copper plating layer on the inner wall surface of the through hole is shown, but the present invention is not limited to this. It is also possible to form a resin layer containing a functional material having desired properties selected among conductivity, magnetism or dielectricity. In addition, it is also possible to use a functional material having desired properties selected among conductivity, magnetism or dielectricity as a filling material.

[0084] (7) In the above-mentioned embodiment, an example is shown in which the through holes with different hole diameters are formed on the printed circuit board, but the present invention is not limited to this. The present invention can also be applied to hole filling of the printed circuit board having a region where through holes with extremely small diameters are densely arranged in a lattice or staggered lattice, such as directly below a large semiconductor chip (for example, a rectangular region with a narrow pitch of 0.5 mm or less between through holes and a single side of 20 mm or more). This is because, in the filling material filling step of filling the filling material with the sealing film blocking the lower surface of the through hole, the filling material is filled into the entire through hole, and the filling material is slowly replenished in the subsequent auxiliary filling step, so that the bending of the printed circuit board can be suppressed as much as possible, and the filling material on the lower side can be protruded roughly evenly.

[0085] In addition, for example, even in the case of a relatively large diameter through hole with an opening diameter of more than 0.5 mm, the filling material is first filled into the entire through hole in the filling material filling process, and then the filling material is slowly replenished in the subsequent auxiliary filling process. This makes it easy to control the amount of protrusion to the lower side of the filling material, so that the protrusion can be uniform.

[0086] (8) In the above embodiment, an example of filling the filling material by screen printing is shown, but the present invention is not limited thereto, and other filling methods that do not use a screen printing plate may be used, such as a filling method using only a scraper or a filling method that presses the filling material from one surface of the printed substrate without using a scraper. It should be noted that the filling material filling step and the auxiliary filling step of the present invention are performed by various filling material filling methods or a filling method combining these methods, so that the filling material is supplied to the through hole in two stages.

[0087] (9) In the above-mentioned embodiment, an example is shown in which the adhesive layer 12B scatters circular dots, but the shape of the dots is not limited to a circle, and of course, it can also be a non-circular shape such as a rectangle, a polygon, or an oval. In addition, the adhesive layer can also be formed by dividing it into a plurality of strip-shaped areas. In other words, it is preferred that the adhesive layer is not formed in the entire area to be pasted to the printed substrate, but rather a form in which a formation area and a non-formation area of ​​the adhesive layer coexist in the area to be pasted to the printed substrate.

[0088] Description of symbols

[0089] 10: Printed substrate

[0090] 11: Through hole

[0091] 12: Sealing film (film)

[0092] 12A: Film substrate

[0093] 12B: Adhesive layer

[0094] 12C: Fine Pores

[0095] 13: Flat fixture

[0096] 18: Support fixture

[0097] 14: Screen printing plate

[0098] 15: Scraper

[0099] 16: Filling material

[0100] 16A, 16D: protrusion

Claims

1. A method for manufacturing a printed circuit board, the method comprising: manufacturing a printed circuit board having a through hole penetrating the substrate and having the through hole filled with a filling material, wherein: The method for manufacturing the printed circuit board performs the following steps: a filling material filling step of, in a state where an opening end surface of the through hole on one surface side of the printed substrate is blocked so that the filling material cannot escape, pressing the filling material from the other surface side of the printed substrate to fill the through hole with the filling material; and an auxiliary filling step of supplying the filling material again from the other surface side of the printed circuit board while leaving the opening end surface of the through hole open after the filling material filling step and before the filling material is cured, The method for manufacturing a printed circuit board performs a film pasting step, wherein a film having an adhesive layer formed on a surface of a film substrate is pasted on one surface of the printed circuit board, thereby blocking the opening end surface of the through hole on the one surface side so that the filling material cannot escape. Then, the printed circuit board is placed on a flat jig having a flat surface at least at a position corresponding to the through hole to perform the filling material filling step, and a film stripping step of stripping the film is performed before supplying the filling material into the through hole in the auxiliary filling step.

2. The method for manufacturing a printed circuit board according to claim 1, wherein: In the auxiliary filling step, the filling material is supplied from the other surface side of the printed substrate while the printed substrate is positioned so that the one surface side contacts and overlaps on the supporting jig, and the supporting jig has a recess formed at a position corresponding to the through hole.

3. The method for manufacturing a printed circuit board according to claim 1, wherein: In the auxiliary filling step, the filling material is supplied from the other surface side of the printed circuit board so that the filling material protrudes from the opening end surface on the one surface side of the through hole.

4. The method for manufacturing a printed circuit board according to claim 1, wherein: The filling material filling process is carried out by screen printing, and the screen printing is a process as follows: a screen printing plate is overlapped on the other side of the printed substrate, and a scraper is slid along the screen printing plate while supplying the filling material to the screen printing plate, so as to fill the filling material from the pores formed in the screen printing plate into the through hole.

5. The method for manufacturing a printed circuit board according to claim 4, wherein: The filling material filling step is performed by multiple screen printing processes with different printing conditions.

6. The method for manufacturing a printed circuit board according to claim 1, wherein: The film substrate having the adhesive layer formed on one side thereof is subjected to a hole-forming step, wherein a needle with a sharp tip is pressed against the film substrate from a side opposite to the adhesive layer to form a plurality of air-permeable fine holes on the film substrate. Then, the film attaching process is performed.

7. The method for manufacturing a printed circuit board according to any one of claims 1 to 6, wherein: In the film laminating step, a sealing film for printing a filling material of a printed substrate is used. When the through hole of the printed substrate is filled with the filling material by printing in a vacuum atmosphere, the sealing film is attached to the printed substrate from the side opposite to the side to which the filling material is supplied. The sealing film comprises a film substrate, an adhesive layer formed on the surface of the film substrate, and a vent path that connects the interface between the printed substrate and the film substrate to the outside, wherein the adhesive layer is formed by dividing the area to be attached to the printed substrate into a plurality of small areas and coexists with a non-formation area where the adhesive layer is not formed. The ventilation path is formed by a plurality of air-permeable pores penetrating the membrane substrate or a plurality of ventilation grooves formed indented on the surface of the membrane substrate.

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